/src/postgres/src/backend/optimizer/util/clauses.c

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/*-------------------------------------------------------------------------
 *
 * clauses.c
 *    routines to manipulate qualification clauses
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/optimizer/util/clauses.c
 *
 * HISTORY
 *    AUTHOR      DATE      MAJOR EVENT
 *    Andrew Yu     Nov 3, 1994   clause.c and clauses.c combined
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "access/htup_details.h"
#include "catalog/pg_language.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_type.h"
#include "executor/executor.h"
#include "executor/functions.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/multibitmapset.h"
#include "nodes/nodeFuncs.h"
#include "nodes/subscripting.h"
#include "nodes/supportnodes.h"
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/optimizer.h"
#include "optimizer/plancat.h"
#include "optimizer/planmain.h"
#include "parser/analyze.h"
#include "parser/parse_coerce.h"
#include "parser/parse_collate.h"
#include "parser/parse_func.h"
#include "parser/parse_oper.h"
#include "rewrite/rewriteHandler.h"
#include "rewrite/rewriteManip.h"
#include "tcop/tcopprot.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/datum.h"
#include "utils/fmgroids.h"
#include "utils/json.h"
#include "utils/jsonb.h"
#include "utils/jsonpath.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/syscache.h"
#include "utils/typcache.h"

typedef struct
{
  ParamListInfo boundParams;
  PlannerInfo *root;
  List     *active_fns;
  Node     *case_val;
  bool    estimate;
} eval_const_expressions_context;

typedef struct
{
  int     nargs;
  List     *args;
  int      *usecounts;
} substitute_actual_parameters_context;

typedef struct
{
  int     nargs;
  List     *args;
  int     sublevels_up;
} substitute_actual_srf_parameters_context;

typedef struct
{
  char     *proname;
  char     *prosrc;
} inline_error_callback_arg;

typedef struct
{
  char    max_hazard;   /* worst proparallel hazard found so far */
  char    max_interesting;  /* worst proparallel hazard of interest */
  List     *safe_param_ids; /* PARAM_EXEC Param IDs to treat as safe */
} max_parallel_hazard_context;

static bool contain_agg_clause_walker(Node *node, void *context);
static bool find_window_functions_walker(Node *node, WindowFuncLists *lists);
static bool contain_subplans_walker(Node *node, void *context);
static bool contain_mutable_functions_walker(Node *node, void *context);
static bool contain_volatile_functions_walker(Node *node, void *context);
static bool contain_volatile_functions_not_nextval_walker(Node *node, void *context);
static bool max_parallel_hazard_walker(Node *node,
                     max_parallel_hazard_context *context);
static bool contain_nonstrict_functions_walker(Node *node, void *context);
static bool contain_exec_param_walker(Node *node, List *param_ids);
static bool contain_context_dependent_node(Node *clause);
static bool contain_context_dependent_node_walker(Node *node, int *flags);
static bool contain_leaked_vars_walker(Node *node, void *context);
static Relids find_nonnullable_rels_walker(Node *node, bool top_level);
static List *find_nonnullable_vars_walker(Node *node, bool top_level);
static bool is_strict_saop(ScalarArrayOpExpr *expr, bool falseOK);
static bool convert_saop_to_hashed_saop_walker(Node *node, void *context);
static Node *eval_const_expressions_mutator(Node *node,
                      eval_const_expressions_context *context);
static bool contain_non_const_walker(Node *node, void *context);
static bool ece_function_is_safe(Oid funcid,
                 eval_const_expressions_context *context);
static List *simplify_or_arguments(List *args,
                   eval_const_expressions_context *context,
                   bool *haveNull, bool *forceTrue);
static List *simplify_and_arguments(List *args,
                  eval_const_expressions_context *context,
                  bool *haveNull, bool *forceFalse);
static Node *simplify_boolean_equality(Oid opno, List *args);
static Expr *simplify_function(Oid funcid,
                 Oid result_type, int32 result_typmod,
                 Oid result_collid, Oid input_collid, List **args_p,
                 bool funcvariadic, bool process_args, bool allow_non_const,
                 eval_const_expressions_context *context);
static List *reorder_function_arguments(List *args, int pronargs,
                    HeapTuple func_tuple);
static List *add_function_defaults(List *args, int pronargs,
                   HeapTuple func_tuple);
static List *fetch_function_defaults(HeapTuple func_tuple);
static void recheck_cast_function_args(List *args, Oid result_type,
                     Oid *proargtypes, int pronargs,
                     HeapTuple func_tuple);
static Expr *evaluate_function(Oid funcid, Oid result_type, int32 result_typmod,
                 Oid result_collid, Oid input_collid, List *args,
                 bool funcvariadic,
                 HeapTuple func_tuple,
                 eval_const_expressions_context *context);
static Expr *inline_function(Oid funcid, Oid result_type, Oid result_collid,
               Oid input_collid, List *args,
               bool funcvariadic,
               HeapTuple func_tuple,
               eval_const_expressions_context *context);
static Node *substitute_actual_parameters(Node *expr, int nargs, List *args,
                      int *usecounts);
static Node *substitute_actual_parameters_mutator(Node *node,
                          substitute_actual_parameters_context *context);
static void sql_inline_error_callback(void *arg);
static Query *substitute_actual_srf_parameters(Query *expr,
                         int nargs, List *args);
static Node *substitute_actual_srf_parameters_mutator(Node *node,
                            substitute_actual_srf_parameters_context *context);
static bool pull_paramids_walker(Node *node, Bitmapset **context);


/*****************************************************************************
 *    Aggregate-function clause manipulation
 *****************************************************************************/

/*
 * contain_agg_clause
 *    Recursively search for Aggref/GroupingFunc nodes within a clause.
 *
 *    Returns true if any aggregate found.
 *
 * This does not descend into subqueries, and so should be used only after
 * reduction of sublinks to subplans, or in contexts where it's known there
 * are no subqueries.  There mustn't be outer-aggregate references either.
 *
 * (If you want something like this but able to deal with subqueries,
 * see rewriteManip.c's contain_aggs_of_level().)
 */
bool
contain_agg_clause(Node *clause)
{
  return contain_agg_clause_walker(clause, NULL);
}

static bool
contain_agg_clause_walker(Node *node, void *context)
{
  if (node == NULL)
    return false;
  if (IsA(node, Aggref))
  {
    Assert(((Aggref *) node)->agglevelsup == 0);
    return true;      /* abort the tree traversal and return true */
  }
  if (IsA(node, GroupingFunc))
  {
    Assert(((GroupingFunc *) node)->agglevelsup == 0);
    return true;      /* abort the tree traversal and return true */
  }
  Assert(!IsA(node, SubLink));
  return expression_tree_walker(node, contain_agg_clause_walker, context);
}

/*****************************************************************************
 *    Window-function clause manipulation
 *****************************************************************************/

/*
 * contain_window_function
 *    Recursively search for WindowFunc nodes within a clause.
 *
 * Since window functions don't have level fields, but are hard-wired to
 * be associated with the current query level, this is just the same as
 * rewriteManip.c's function.
 */
bool
contain_window_function(Node *clause)
{
  return contain_windowfuncs(clause);
}

/*
 * find_window_functions
 *    Locate all the WindowFunc nodes in an expression tree, and organize
 *    them by winref ID number.
 *
 * Caller must provide an upper bound on the winref IDs expected in the tree.
 */
WindowFuncLists *
find_window_functions(Node *clause, Index maxWinRef)
{
  WindowFuncLists *lists = palloc(sizeof(WindowFuncLists));

  lists->numWindowFuncs = 0;
  lists->maxWinRef = maxWinRef;
  lists->windowFuncs = (List **) palloc0((maxWinRef + 1) * sizeof(List *));
  (void) find_window_functions_walker(clause, lists);
  return lists;
}

static bool
find_window_functions_walker(Node *node, WindowFuncLists *lists)
{
  if (node == NULL)
    return false;
  if (IsA(node, WindowFunc))
  {
    WindowFunc *wfunc = (WindowFunc *) node;

    /* winref is unsigned, so one-sided test is OK */
    if (wfunc->winref > lists->maxWinRef)
      elog(ERROR, "WindowFunc contains out-of-range winref %u",
         wfunc->winref);
    /* eliminate duplicates, so that we avoid repeated computation */
    if (!list_member(lists->windowFuncs[wfunc->winref], wfunc))
    {
      lists->windowFuncs[wfunc->winref] =
        lappend(lists->windowFuncs[wfunc->winref], wfunc);
      lists->numWindowFuncs++;
    }

    /*
     * We assume that the parser checked that there are no window
     * functions in the arguments or filter clause.  Hence, we need not
     * recurse into them.  (If either the parser or the planner screws up
     * on this point, the executor will still catch it; see ExecInitExpr.)
     */
    return false;
  }
  Assert(!IsA(node, SubLink));
  return expression_tree_walker(node, find_window_functions_walker, lists);
}


/*****************************************************************************
 *    Support for expressions returning sets
 *****************************************************************************/

/*
 * expression_returns_set_rows
 *    Estimate the number of rows returned by a set-returning expression.
 *    The result is 1 if it's not a set-returning expression.
 *
 * We should only examine the top-level function or operator; it used to be
 * appropriate to recurse, but not anymore.  (Even if there are more SRFs in
 * the function's inputs, their multipliers are accounted for separately.)
 *
 * Note: keep this in sync with expression_returns_set() in nodes/nodeFuncs.c.
 */
double
expression_returns_set_rows(PlannerInfo *root, Node *clause)
{
  if (clause == NULL)
    return 1.0;
  if (IsA(clause, FuncExpr))
  {
    FuncExpr   *expr = (FuncExpr *) clause;

    if (expr->funcretset)
      return clamp_row_est(get_function_rows(root, expr->funcid, clause));
  }
  if (IsA(clause, OpExpr))
  {
    OpExpr     *expr = (OpExpr *) clause;

    if (expr->opretset)
    {
      set_opfuncid(expr);
      return clamp_row_est(get_function_rows(root, expr->opfuncid, clause));
    }
  }
  return 1.0;
}


/*****************************************************************************
 *    Subplan clause manipulation
 *****************************************************************************/

/*
 * contain_subplans
 *    Recursively search for subplan nodes within a clause.
 *
 * If we see a SubLink node, we will return true.  This is only possible if
 * the expression tree hasn't yet been transformed by subselect.c.  We do not
 * know whether the node will produce a true subplan or just an initplan,
 * but we make the conservative assumption that it will be a subplan.
 *
 * Returns true if any subplan found.
 */
bool
contain_subplans(Node *clause)
{
  return contain_subplans_walker(clause, NULL);
}

static bool
contain_subplans_walker(Node *node, void *context)
{
  if (node == NULL)
    return false;
  if (IsA(node, SubPlan) ||
    IsA(node, AlternativeSubPlan) ||
    IsA(node, SubLink))
    return true;     /* abort the tree traversal and return true */
  return expression_tree_walker(node, contain_subplans_walker, context);
}


/*****************************************************************************
 *    Check clauses for mutable functions
 *****************************************************************************/

/*
 * contain_mutable_functions
 *    Recursively search for mutable functions within a clause.
 *
 * Returns true if any mutable function (or operator implemented by a
 * mutable function) is found.  This test is needed so that we don't
 * mistakenly think that something like "WHERE random() < 0.5" can be treated
 * as a constant qualification.
 *
 * This will give the right answer only for clauses that have been put
 * through expression preprocessing.  Callers outside the planner typically
 * should use contain_mutable_functions_after_planning() instead, for the
 * reasons given there.
 *
 * We will recursively look into Query nodes (i.e., SubLink sub-selects)
 * but not into SubPlans.  See comments for contain_volatile_functions().
 */
bool
contain_mutable_functions(Node *clause)
{
  return contain_mutable_functions_walker(clause, NULL);
}

static bool
contain_mutable_functions_checker(Oid func_id, void *context)
{
  return (func_volatile(func_id) != PROVOLATILE_IMMUTABLE);
}

static bool
contain_mutable_functions_walker(Node *node, void *context)
{
  if (node == NULL)
    return false;
  /* Check for mutable functions in node itself */
  if (check_functions_in_node(node, contain_mutable_functions_checker,
                context))
    return true;

  if (IsA(node, JsonConstructorExpr))
  {
    const JsonConstructorExpr *ctor = (JsonConstructorExpr *) node;
    ListCell   *lc;
    bool    is_jsonb;

    is_jsonb = ctor->returning->format->format_type == JS_FORMAT_JSONB;

    /*
     * Check argument_type => json[b] conversions specifically.  We still
     * recurse to check 'args' below, but here we want to specifically
     * check whether or not the emitted clause would fail to be immutable
     * because of TimeZone, for example.
     */
    foreach(lc, ctor->args)
    {
      Oid     typid = exprType(lfirst(lc));

      if (is_jsonb ?
        !to_jsonb_is_immutable(typid) :
        !to_json_is_immutable(typid))
        return true;
    }

    /* Check all subnodes */
  }

  if (IsA(node, JsonExpr))
  {
    JsonExpr   *jexpr = castNode(JsonExpr, node);
    Const    *cnst;

    if (!IsA(jexpr->path_spec, Const))
      return true;

    cnst = castNode(Const, jexpr->path_spec);

    Assert(cnst->consttype == JSONPATHOID);
    if (cnst->constisnull)
      return false;

    if (jspIsMutable(DatumGetJsonPathP(cnst->constvalue),
             jexpr->passing_names, jexpr->passing_values))
      return true;
  }

  if (IsA(node, SQLValueFunction))
  {
    /* all variants of SQLValueFunction are stable */
    return true;
  }

  if (IsA(node, NextValueExpr))
  {
    /* NextValueExpr is volatile */
    return true;
  }

  /*
   * It should be safe to treat MinMaxExpr as immutable, because it will
   * depend on a non-cross-type btree comparison function, and those should
   * always be immutable.  Treating XmlExpr as immutable is more dubious,
   * and treating CoerceToDomain as immutable is outright dangerous.  But we
   * have done so historically, and changing this would probably cause more
   * problems than it would fix.  In practice, if you have a non-immutable
   * domain constraint you are in for pain anyhow.
   */

  /* Recurse to check arguments */
  if (IsA(node, Query))
  {
    /* Recurse into subselects */
    return query_tree_walker((Query *) node,
                 contain_mutable_functions_walker,
                 context, 0);
  }
  return expression_tree_walker(node, contain_mutable_functions_walker,
                  context);
}

/*
 * contain_mutable_functions_after_planning
 *    Test whether given expression contains mutable functions.
 *
 * This is a wrapper for contain_mutable_functions() that is safe to use from
 * outside the planner.  The difference is that it first runs the expression
 * through expression_planner().  There are two key reasons why we need that:
 *
 * First, function default arguments will get inserted, which may affect
 * volatility (consider "default now()").
 *
 * Second, inline-able functions will get inlined, which may allow us to
 * conclude that the function is really less volatile than it's marked.
 * As an example, polymorphic functions must be marked with the most volatile
 * behavior that they have for any input type, but once we inline the
 * function we may be able to conclude that it's not so volatile for the
 * particular input type we're dealing with.
 */
bool
contain_mutable_functions_after_planning(Expr *expr)
{
  /* We assume here that expression_planner() won't scribble on its input */
  expr = expression_planner(expr);

  /* Now we can search for non-immutable functions */
  return contain_mutable_functions((Node *) expr);
}


/*****************************************************************************
 *    Check clauses for volatile functions
 *****************************************************************************/

/*
 * contain_volatile_functions
 *    Recursively search for volatile functions within a clause.
 *
 * Returns true if any volatile function (or operator implemented by a
 * volatile function) is found. This test prevents, for example,
 * invalid conversions of volatile expressions into indexscan quals.
 *
 * This will give the right answer only for clauses that have been put
 * through expression preprocessing.  Callers outside the planner typically
 * should use contain_volatile_functions_after_planning() instead, for the
 * reasons given there.
 *
 * We will recursively look into Query nodes (i.e., SubLink sub-selects)
 * but not into SubPlans.  This is a bit odd, but intentional.  If we are
 * looking at a SubLink, we are probably deciding whether a query tree
 * transformation is safe, and a contained sub-select should affect that;
 * for example, duplicating a sub-select containing a volatile function
 * would be bad.  However, once we've got to the stage of having SubPlans,
 * subsequent planning need not consider volatility within those, since
 * the executor won't change its evaluation rules for a SubPlan based on
 * volatility.
 *
 * For some node types, for example, RestrictInfo and PathTarget, we cache
 * whether we found any volatile functions or not and reuse that value in any
 * future checks for that node.  All of the logic for determining if the
 * cached value should be set to VOLATILITY_NOVOLATILE or VOLATILITY_VOLATILE
 * belongs in this function.  Any code which makes changes to these nodes
 * which could change the outcome this function must set the cached value back
 * to VOLATILITY_UNKNOWN.  That allows this function to redetermine the
 * correct value during the next call, should we need to redetermine if the
 * node contains any volatile functions again in the future.
 */
bool
contain_volatile_functions(Node *clause)
{
  return contain_volatile_functions_walker(clause, NULL);
}

static bool
contain_volatile_functions_checker(Oid func_id, void *context)
{
  return (func_volatile(func_id) == PROVOLATILE_VOLATILE);
}

static bool
contain_volatile_functions_walker(Node *node, void *context)
{
  if (node == NULL)
    return false;
  /* Check for volatile functions in node itself */
  if (check_functions_in_node(node, contain_volatile_functions_checker,
                context))
    return true;

  if (IsA(node, NextValueExpr))
  {
    /* NextValueExpr is volatile */
    return true;
  }

  if (IsA(node, RestrictInfo))
  {
    RestrictInfo *rinfo = (RestrictInfo *) node;

    /*
     * For RestrictInfo, check if we've checked the volatility of it
     * before.  If so, we can just use the cached value and not bother
     * checking it again.  Otherwise, check it and cache if whether we
     * found any volatile functions.
     */
    if (rinfo->has_volatile == VOLATILITY_NOVOLATILE)
      return false;
    else if (rinfo->has_volatile == VOLATILITY_VOLATILE)
      return true;
    else
    {
      bool    hasvolatile;

      hasvolatile = contain_volatile_functions_walker((Node *) rinfo->clause,
                              context);
      if (hasvolatile)
        rinfo->has_volatile = VOLATILITY_VOLATILE;
      else
        rinfo->has_volatile = VOLATILITY_NOVOLATILE;

      return hasvolatile;
    }
  }

  if (IsA(node, PathTarget))
  {
    PathTarget *target = (PathTarget *) node;

    /*
     * We also do caching for PathTarget the same as we do above for
     * RestrictInfos.
     */
    if (target->has_volatile_expr == VOLATILITY_NOVOLATILE)
      return false;
    else if (target->has_volatile_expr == VOLATILITY_VOLATILE)
      return true;
    else
    {
      bool    hasvolatile;

      hasvolatile = contain_volatile_functions_walker((Node *) target->exprs,
                              context);

      if (hasvolatile)
        target->has_volatile_expr = VOLATILITY_VOLATILE;
      else
        target->has_volatile_expr = VOLATILITY_NOVOLATILE;

      return hasvolatile;
    }
  }

  /*
   * See notes in contain_mutable_functions_walker about why we treat
   * MinMaxExpr, XmlExpr, and CoerceToDomain as immutable, while
   * SQLValueFunction is stable.  Hence, none of them are of interest here.
   */

  /* Recurse to check arguments */
  if (IsA(node, Query))
  {
    /* Recurse into subselects */
    return query_tree_walker((Query *) node,
                 contain_volatile_functions_walker,
                 context, 0);
  }
  return expression_tree_walker(node, contain_volatile_functions_walker,
                  context);
}

/*
 * contain_volatile_functions_after_planning
 *    Test whether given expression contains volatile functions.
 *
 * This is a wrapper for contain_volatile_functions() that is safe to use from
 * outside the planner.  The difference is that it first runs the expression
 * through expression_planner().  There are two key reasons why we need that:
 *
 * First, function default arguments will get inserted, which may affect
 * volatility (consider "default random()").
 *
 * Second, inline-able functions will get inlined, which may allow us to
 * conclude that the function is really less volatile than it's marked.
 * As an example, polymorphic functions must be marked with the most volatile
 * behavior that they have for any input type, but once we inline the
 * function we may be able to conclude that it's not so volatile for the
 * particular input type we're dealing with.
 */
bool
contain_volatile_functions_after_planning(Expr *expr)
{
  /* We assume here that expression_planner() won't scribble on its input */
  expr = expression_planner(expr);

  /* Now we can search for volatile functions */
  return contain_volatile_functions((Node *) expr);
}

/*
 * Special purpose version of contain_volatile_functions() for use in COPY:
 * ignore nextval(), but treat all other functions normally.
 */
bool
contain_volatile_functions_not_nextval(Node *clause)
{
  return contain_volatile_functions_not_nextval_walker(clause, NULL);
}

static bool
contain_volatile_functions_not_nextval_checker(Oid func_id, void *context)
{
  return (func_id != F_NEXTVAL &&
      func_volatile(func_id) == PROVOLATILE_VOLATILE);
}

static bool
contain_volatile_functions_not_nextval_walker(Node *node, void *context)
{
  if (node == NULL)
    return false;
  /* Check for volatile functions in node itself */
  if (check_functions_in_node(node,
                contain_volatile_functions_not_nextval_checker,
                context))
    return true;

  /*
   * See notes in contain_mutable_functions_walker about why we treat
   * MinMaxExpr, XmlExpr, and CoerceToDomain as immutable, while
   * SQLValueFunction is stable.  Hence, none of them are of interest here.
   * Also, since we're intentionally ignoring nextval(), presumably we
   * should ignore NextValueExpr.
   */

  /* Recurse to check arguments */
  if (IsA(node, Query))
  {
    /* Recurse into subselects */
    return query_tree_walker((Query *) node,
                 contain_volatile_functions_not_nextval_walker,
                 context, 0);
  }
  return expression_tree_walker(node,
                  contain_volatile_functions_not_nextval_walker,
                  context);
}


/*****************************************************************************
 *    Check queries for parallel unsafe and/or restricted constructs
 *****************************************************************************/

/*
 * max_parallel_hazard
 *    Find the worst parallel-hazard level in the given query
 *
 * Returns the worst function hazard property (the earliest in this list:
 * PROPARALLEL_UNSAFE, PROPARALLEL_RESTRICTED, PROPARALLEL_SAFE) that can
 * be found in the given parsetree.  We use this to find out whether the query
 * can be parallelized at all.  The caller will also save the result in
 * PlannerGlobal so as to short-circuit checks of portions of the querytree
 * later, in the common case where everything is SAFE.
 */
char
max_parallel_hazard(Query *parse)
{
  max_parallel_hazard_context context;

  context.max_hazard = PROPARALLEL_SAFE;
  context.max_interesting = PROPARALLEL_UNSAFE;
  context.safe_param_ids = NIL;
  (void) max_parallel_hazard_walker((Node *) parse, &context);
  return context.max_hazard;
}

/*
 * is_parallel_safe
 *    Detect whether the given expr contains only parallel-safe functions
 *
 * root->glob->maxParallelHazard must previously have been set to the
 * result of max_parallel_hazard() on the whole query.
 */
bool
is_parallel_safe(PlannerInfo *root, Node *node)
{
  max_parallel_hazard_context context;
  PlannerInfo *proot;
  ListCell   *l;

  /*
   * Even if the original querytree contained nothing unsafe, we need to
   * search the expression if we have generated any PARAM_EXEC Params while
   * planning, because those are parallel-restricted and there might be one
   * in this expression.  But otherwise we don't need to look.
   */
  if (root->glob->maxParallelHazard == PROPARALLEL_SAFE &&
    root->glob->paramExecTypes == NIL)
    return true;
  /* Else use max_parallel_hazard's search logic, but stop on RESTRICTED */
  context.max_hazard = PROPARALLEL_SAFE;
  context.max_interesting = PROPARALLEL_RESTRICTED;
  context.safe_param_ids = NIL;

  /*
   * The params that refer to the same or parent query level are considered
   * parallel-safe.  The idea is that we compute such params at Gather or
   * Gather Merge node and pass their value to workers.
   */
  for (proot = root; proot != NULL; proot = proot->parent_root)
  {
    foreach(l, proot->init_plans)
    {
      SubPlan    *initsubplan = (SubPlan *) lfirst(l);

      context.safe_param_ids = list_concat(context.safe_param_ids,
                         initsubplan->setParam);
    }
  }

  return !max_parallel_hazard_walker(node, &context);
}

/* core logic for all parallel-hazard checks */
static bool
max_parallel_hazard_test(char proparallel, max_parallel_hazard_context *context)
{
  switch (proparallel)
  {
    case PROPARALLEL_SAFE:
      /* nothing to see here, move along */
      break;
    case PROPARALLEL_RESTRICTED:
      /* increase max_hazard to RESTRICTED */
      Assert(context->max_hazard != PROPARALLEL_UNSAFE);
      context->max_hazard = proparallel;
      /* done if we are not expecting any unsafe functions */
      if (context->max_interesting == proparallel)
        return true;
      break;
    case PROPARALLEL_UNSAFE:
      context->max_hazard = proparallel;
      /* we're always done at the first unsafe construct */
      return true;
    default:
      elog(ERROR, "unrecognized proparallel value \"%c\"", proparallel);
      break;
  }
  return false;
}

/* check_functions_in_node callback */
static bool
max_parallel_hazard_checker(Oid func_id, void *context)
{
  return max_parallel_hazard_test(func_parallel(func_id),
                  (max_parallel_hazard_context *) context);
}

static bool
max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
{
  if (node == NULL)
    return false;

  /* Check for hazardous functions in node itself */
  if (check_functions_in_node(node, max_parallel_hazard_checker,
                context))
    return true;

  /*
   * It should be OK to treat MinMaxExpr as parallel-safe, since btree
   * opclass support functions are generally parallel-safe.  XmlExpr is a
   * bit more dubious but we can probably get away with it.  We err on the
   * side of caution by treating CoerceToDomain as parallel-restricted.
   * (Note: in principle that's wrong because a domain constraint could
   * contain a parallel-unsafe function; but useful constraints probably
   * never would have such, and assuming they do would cripple use of
   * parallel query in the presence of domain types.)  SQLValueFunction
   * should be safe in all cases.  NextValueExpr is parallel-unsafe.
   */
  if (IsA(node, CoerceToDomain))
  {
    if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
      return true;
  }

  else if (IsA(node, NextValueExpr))
  {
    if (max_parallel_hazard_test(PROPARALLEL_UNSAFE, context))
      return true;
  }

  /*
   * Treat window functions as parallel-restricted because we aren't sure
   * whether the input row ordering is fully deterministic, and the output
   * of window functions might vary across workers if not.  (In some cases,
   * like where the window frame orders by a primary key, we could relax
   * this restriction.  But it doesn't currently seem worth expending extra
   * effort to do so.)
   */
  else if (IsA(node, WindowFunc))
  {
    if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
      return true;
  }

  /*
   * As a notational convenience for callers, look through RestrictInfo.
   */
  else if (IsA(node, RestrictInfo))
  {
    RestrictInfo *rinfo = (RestrictInfo *) node;

    return max_parallel_hazard_walker((Node *) rinfo->clause, context);
  }

  /*
   * Really we should not see SubLink during a max_interesting == restricted
   * scan, but if we do, return true.
   */
  else if (IsA(node, SubLink))
  {
    if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
      return true;
  }

  /*
   * Only parallel-safe SubPlans can be sent to workers.  Within the
   * testexpr of the SubPlan, Params representing the output columns of the
   * subplan can be treated as parallel-safe, so temporarily add their IDs
   * to the safe_param_ids list while examining the testexpr.
   */
  else if (IsA(node, SubPlan))
  {
    SubPlan    *subplan = (SubPlan *) node;
    List     *save_safe_param_ids;

    if (!subplan->parallel_safe &&
      max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
      return true;
    save_safe_param_ids = context->safe_param_ids;
    context->safe_param_ids = list_concat_copy(context->safe_param_ids,
                           subplan->paramIds);
    if (max_parallel_hazard_walker(subplan->testexpr, context))
      return true;   /* no need to restore safe_param_ids */
    list_free(context->safe_param_ids);
    context->safe_param_ids = save_safe_param_ids;
    /* we must also check args, but no special Param treatment there */
    if (max_parallel_hazard_walker((Node *) subplan->args, context))
      return true;
    /* don't want to recurse normally, so we're done */
    return false;
  }

  /*
   * We can't pass Params to workers at the moment either, so they are also
   * parallel-restricted, unless they are PARAM_EXTERN Params or are
   * PARAM_EXEC Params listed in safe_param_ids, meaning they could be
   * either generated within workers or can be computed by the leader and
   * then their value can be passed to workers.
   */
  else if (IsA(node, Param))
  {
    Param    *param = (Param *) node;

    if (param->paramkind == PARAM_EXTERN)
      return false;

    if (param->paramkind != PARAM_EXEC ||
      !list_member_int(context->safe_param_ids, param->paramid))
    {
      if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED, context))
        return true;
    }
    return false;     /* nothing to recurse to */
  }

  /*
   * When we're first invoked on a completely unplanned tree, we must
   * recurse into subqueries so to as to locate parallel-unsafe constructs
   * anywhere in the tree.
   */
  else if (IsA(node, Query))
  {
    Query    *query = (Query *) node;

    /* SELECT FOR UPDATE/SHARE must be treated as unsafe */
    if (query->rowMarks != NULL)
    {
      context->max_hazard = PROPARALLEL_UNSAFE;
      return true;
    }

    /* Recurse into subselects */
    return query_tree_walker(query,
                 max_parallel_hazard_walker,
                 context, 0);
  }

  /* Recurse to check arguments */
  return expression_tree_walker(node,
                  max_parallel_hazard_walker,
                  context);
}


/*****************************************************************************
 *    Check clauses for nonstrict functions
 *****************************************************************************/

/*
 * contain_nonstrict_functions
 *    Recursively search for nonstrict functions within a clause.
 *
 * Returns true if any nonstrict construct is found --- ie, anything that
 * could produce non-NULL output with a NULL input.
 *
 * The idea here is that the caller has verified that the expression contains
 * one or more Var or Param nodes (as appropriate for the caller's need), and
 * now wishes to prove that the expression result will be NULL if any of these
 * inputs is NULL.  If we return false, then the proof succeeded.
 */
bool
contain_nonstrict_functions(Node *clause)
{
  return contain_nonstrict_functions_walker(clause, NULL);
}

static bool
contain_nonstrict_functions_checker(Oid func_id, void *context)
{
  return !func_strict(func_id);
}

static bool
contain_nonstrict_functions_walker(Node *node, void *context)
{
  if (node == NULL)
    return false;
  if (IsA(node, Aggref))
  {
    /* an aggregate could return non-null with null input */
    return true;
  }
  if (IsA(node, GroupingFunc))
  {
    /*
     * A GroupingFunc doesn't evaluate its arguments, and therefore must
     * be treated as nonstrict.
     */
    return true;
  }
  if (IsA(node, WindowFunc))
  {
    /* a window function could return non-null with null input */
    return true;
  }
  if (IsA(node, SubscriptingRef))
  {
    SubscriptingRef *sbsref = (SubscriptingRef *) node;
    const SubscriptRoutines *sbsroutines;

    /* Subscripting assignment is always presumed nonstrict */
    if (sbsref->refassgnexpr != NULL)
      return true;
    /* Otherwise we must look up the subscripting support methods */
    sbsroutines = getSubscriptingRoutines(sbsref->refcontainertype, NULL);
    if (!(sbsroutines && sbsroutines->fetch_strict))
      return true;
    /* else fall through to check args */
  }
  if (IsA(node, DistinctExpr))
  {
    /* IS DISTINCT FROM is inherently non-strict */
    return true;
  }
  if (IsA(node, NullIfExpr))
  {
    /* NULLIF is inherently non-strict */
    return true;
  }
  if (IsA(node, BoolExpr))
  {
    BoolExpr   *expr = (BoolExpr *) node;

    switch (expr->boolop)
    {
      case AND_EXPR:
      case OR_EXPR:
        /* AND, OR are inherently non-strict */
        return true;
      default:
        break;
    }
  }
  if (IsA(node, SubLink))
  {
    /* In some cases a sublink might be strict, but in general not */
    return true;
  }
  if (IsA(node, SubPlan))
    return true;
  if (IsA(node, AlternativeSubPlan))
    return true;
  if (IsA(node, FieldStore))
    return true;
  if (IsA(node, CoerceViaIO))
  {
    /*
     * CoerceViaIO is strict regardless of whether the I/O functions are,
     * so just go look at its argument; asking check_functions_in_node is
     * useless expense and could deliver the wrong answer.
     */
    return contain_nonstrict_functions_walker((Node *) ((CoerceViaIO *) node)->arg,
                          context);
  }
  if (IsA(node, ArrayCoerceExpr))
  {
    /*
     * ArrayCoerceExpr is strict at the array level, regardless of what
     * the per-element expression is; so we should ignore elemexpr and
     * recurse only into the arg.
     */
    return contain_nonstrict_functions_walker((Node *) ((ArrayCoerceExpr *) node)->arg,
                          context);
  }
  if (IsA(node, CaseExpr))
    return true;
  if (IsA(node, ArrayExpr))
    return true;
  if (IsA(node, RowExpr))
    return true;
  if (IsA(node, RowCompareExpr))
    return true;
  if (IsA(node, CoalesceExpr))
    return true;
  if (IsA(node, MinMaxExpr))
    return true;
  if (IsA(node, XmlExpr))
    return true;
  if (IsA(node, NullTest))
    return true;
  if (IsA(node, BooleanTest))
    return true;

  /* Check other function-containing nodes */
  if (check_functions_in_node(node, contain_nonstrict_functions_checker,
                context))
    return true;

  return expression_tree_walker(node, contain_nonstrict_functions_walker,
                  context);
}

/*****************************************************************************
 *    Check clauses for Params
 *****************************************************************************/

/*
 * contain_exec_param
 *    Recursively search for PARAM_EXEC Params within a clause.
 *
 * Returns true if the clause contains any PARAM_EXEC Param with a paramid
 * appearing in the given list of Param IDs.  Does not descend into
 * subqueries!
 */
bool
contain_exec_param(Node *clause, List *param_ids)
{
  return contain_exec_param_walker(clause, param_ids);
}

static bool
contain_exec_param_walker(Node *node, List *param_ids)
{
  if (node == NULL)
    return false;
  if (IsA(node, Param))
  {
    Param    *p = (Param *) node;

    if (p->paramkind == PARAM_EXEC &&
      list_member_int(param_ids, p->paramid))
      return true;
  }
  return expression_tree_walker(node, contain_exec_param_walker, param_ids);
}

/*****************************************************************************
 *    Check clauses for context-dependent nodes
 *****************************************************************************/

/*
 * contain_context_dependent_node
 *    Recursively search for context-dependent nodes within a clause.
 *
 * CaseTestExpr nodes must appear directly within the corresponding CaseExpr,
 * not nested within another one, or they'll see the wrong test value.  If one
 * appears "bare" in the arguments of a SQL function, then we can't inline the
 * SQL function for fear of creating such a situation.  The same applies for
 * CaseTestExpr used within the elemexpr of an ArrayCoerceExpr.
 *
 * CoerceToDomainValue would have the same issue if domain CHECK expressions
 * could get inlined into larger expressions, but presently that's impossible.
 * Still, it might be allowed in future, or other node types with similar
 * issues might get invented.  So give this function a generic name, and set
 * up the recursion state to allow multiple flag bits.
 */
static bool
contain_context_dependent_node(Node *clause)
{
  int     flags = 0;

  return contain_context_dependent_node_walker(clause, &flags);
}

#define CCDN_CASETESTEXPR_OK  0x0001  /* CaseTestExpr okay here? */

static bool
contain_context_dependent_node_walker(Node *node, int *flags)
{
  if (node == NULL)
    return false;
  if (IsA(node, CaseTestExpr))
    return !(*flags & CCDN_CASETESTEXPR_OK);
  else if (IsA(node, CaseExpr))
  {
    CaseExpr   *caseexpr = (CaseExpr *) node;

    /*
     * If this CASE doesn't have a test expression, then it doesn't create
     * a context in which CaseTestExprs should appear, so just fall
     * through and treat it as a generic expression node.
     */
    if (caseexpr->arg)
    {
      int     save_flags = *flags;
      bool    res;

      /*
       * Note: in principle, we could distinguish the various sub-parts
       * of a CASE construct and set the flag bit only for some of them,
       * since we are only expecting CaseTestExprs to appear in the
       * "expr" subtree of the CaseWhen nodes.  But it doesn't really
       * seem worth any extra code.  If there are any bare CaseTestExprs
       * elsewhere in the CASE, something's wrong already.
       */
      *flags |= CCDN_CASETESTEXPR_OK;
      res = expression_tree_walker(node,
                     contain_context_dependent_node_walker,
                     flags);
      *flags = save_flags;
      return res;
    }
  }
  else if (IsA(node, ArrayCoerceExpr))
  {
    ArrayCoerceExpr *ac = (ArrayCoerceExpr *) node;
    int     save_flags;
    bool    res;

    /* Check the array expression */
    if (contain_context_dependent_node_walker((Node *) ac->arg, flags))
      return true;

    /* Check the elemexpr, which is allowed to contain CaseTestExpr */
    save_flags = *flags;
    *flags |= CCDN_CASETESTEXPR_OK;
    res = contain_context_dependent_node_walker((Node *) ac->elemexpr,
                          flags);
    *flags = save_flags;
    return res;
  }
  return expression_tree_walker(node, contain_context_dependent_node_walker,
                  flags);
}

/*****************************************************************************
 *      Check clauses for Vars passed to non-leakproof functions
 *****************************************************************************/

/*
 * contain_leaked_vars
 *    Recursively scan a clause to discover whether it contains any Var
 *    nodes (of the current query level) that are passed as arguments to
 *    leaky functions.
 *
 * Returns true if the clause contains any non-leakproof functions that are
 * passed Var nodes of the current query level, and which might therefore leak
 * data.  Such clauses must be applied after any lower-level security barrier
 * clauses.
 */
bool
contain_leaked_vars(Node *clause)
{
  return contain_leaked_vars_walker(clause, NULL);
}

static bool
contain_leaked_vars_checker(Oid func_id, void *context)
{
  return !get_func_leakproof(func_id);
}

static bool
contain_leaked_vars_walker(Node *node, void *context)
{
  if (node == NULL)
    return false;

  switch (nodeTag(node))
  {
    case T_Var:
    case T_Const:
    case T_Param:
    case T_ArrayExpr:
    case T_FieldSelect:
    case T_FieldStore:
    case T_NamedArgExpr:
    case T_BoolExpr:
    case T_RelabelType:
    case T_CollateExpr:
    case T_CaseExpr:
    case T_CaseTestExpr:
    case T_RowExpr:
    case T_SQLValueFunction:
    case T_NullTest:
    case T_BooleanTest:
    case T_NextValueExpr:
    case T_ReturningExpr:
    case T_List:

      /*
       * We know these node types don't contain function calls; but
       * something further down in the node tree might.
       */
      break;

    case T_FuncExpr:
    case T_OpExpr:
    case T_DistinctExpr:
    case T_NullIfExpr:
    case T_ScalarArrayOpExpr:
    case T_CoerceViaIO:
    case T_ArrayCoerceExpr:

      /*
       * If node contains a leaky function call, and there's any Var
       * underneath it, reject.
       */
      if (check_functions_in_node(node, contain_leaked_vars_checker,
                    context) &&
        contain_var_clause(node))
        return true;
      break;

    case T_SubscriptingRef:
      {
        SubscriptingRef *sbsref = (SubscriptingRef *) node;
        const SubscriptRoutines *sbsroutines;

        /* Consult the subscripting support method info */
        sbsroutines = getSubscriptingRoutines(sbsref->refcontainertype,
                            NULL);
        if (!sbsroutines ||
          !(sbsref->refassgnexpr != NULL ?
            sbsroutines->store_leakproof :
            sbsroutines->fetch_leakproof))
        {
          /* Node is leaky, so reject if it contains Vars */
          if (contain_var_clause(node))
            return true;
        }
      }
      break;

    case T_RowCompareExpr:
      {
        /*
         * It's worth special-casing this because a leaky comparison
         * function only compromises one pair of row elements, which
         * might not contain Vars while others do.
         */
        RowCompareExpr *rcexpr = (RowCompareExpr *) node;
        ListCell   *opid;
        ListCell   *larg;
        ListCell   *rarg;

        forthree(opid, rcexpr->opnos,
             larg, rcexpr->largs,
             rarg, rcexpr->rargs)
        {
          Oid     funcid = get_opcode(lfirst_oid(opid));

          if (!get_func_leakproof(funcid) &&
            (contain_var_clause((Node *) lfirst(larg)) ||
             contain_var_clause((Node *) lfirst(rarg))))
            return true;
        }
      }
      break;

    case T_MinMaxExpr:
      {
        /*
         * MinMaxExpr is leakproof if the comparison function it calls
         * is leakproof.
         */
        MinMaxExpr *minmaxexpr = (MinMaxExpr *) node;
        TypeCacheEntry *typentry;
        bool    leakproof;

        /* Look up the btree comparison function for the datatype */
        typentry = lookup_type_cache(minmaxexpr->minmaxtype,
                       TYPECACHE_CMP_PROC);
        if (OidIsValid(typentry->cmp_proc))
          leakproof = get_func_leakproof(typentry->cmp_proc);
        else
        {
          /*
           * The executor will throw an error, but here we just
           * treat the missing function as leaky.
           */
          leakproof = false;
        }

        if (!leakproof &&
          contain_var_clause((Node *) minmaxexpr->args))
          return true;
      }
      break;

    case T_CurrentOfExpr:

      /*
       * WHERE CURRENT OF doesn't contain leaky function calls.
       * Moreover, it is essential that this is considered non-leaky,
       * since the planner must always generate a TID scan when CURRENT
       * OF is present -- cf. cost_tidscan.
       */
      return false;

    default:

      /*
       * If we don't recognize the node tag, assume it might be leaky.
       * This prevents an unexpected security hole if someone adds a new
       * node type that can call a function.
       */
      return true;
  }
  return expression_tree_walker(node, contain_leaked_vars_walker,
                  context);
}

/*
 * find_nonnullable_rels
 *    Determine which base rels are forced nonnullable by given clause.
 *
 * Returns the set of all Relids that are referenced in the clause in such
 * a way that the clause cannot possibly return TRUE if any of these Relids
 * is an all-NULL row.  (It is OK to err on the side of conservatism; hence
 * the analysis here is simplistic.)
 *
 * The semantics here are subtly different from contain_nonstrict_functions:
 * that function is concerned with NULL results from arbitrary expressions,
 * but here we assume that the input is a Boolean expression, and wish to
 * see if NULL inputs will provably cause a FALSE-or-NULL result.  We expect
 * the expression to have been AND/OR flattened and converted to implicit-AND
 * format.
 *
 * Note: this function is largely duplicative of find_nonnullable_vars().
 * The reason not to simplify this function into a thin wrapper around
 * find_nonnullable_vars() is that the tested conditions really are different:
 * a clause like "t1.v1 IS NOT NULL OR t1.v2 IS NOT NULL" does not prove
 * that either v1 or v2 can't be NULL, but it does prove that the t1 row
 * as a whole can't be all-NULL.  Also, the behavior for PHVs is different.
 *
 * top_level is true while scanning top-level AND/OR structure; here, showing
 * the result is either FALSE or NULL is good enough.  top_level is false when
 * we have descended below a NOT or a strict function: now we must be able to
 * prove that the subexpression goes to NULL.
 *
 * We don't use expression_tree_walker here because we don't want to descend
 * through very many kinds of nodes; only the ones we can be sure are strict.
 */
Relids
find_nonnullable_rels(Node *clause)
{
  return find_nonnullable_rels_walker(clause, true);
}

static Relids
find_nonnullable_rels_walker(Node *node, bool top_level)
{
  Relids    result = NULL;
  ListCell   *l;

  if (node == NULL)
    return NULL;
  if (IsA(node, Var))
  {
    Var      *var = (Var *) node;

    if (var->varlevelsup == 0)
      result = bms_make_singleton(var->varno);
  }
  else if (IsA(node, List))
  {
    /*
     * At top level, we are examining an implicit-AND list: if any of the
     * arms produces FALSE-or-NULL then the result is FALSE-or-NULL. If
     * not at top level, we are examining the arguments of a strict
     * function: if any of them produce NULL then the result of the
     * function must be NULL.  So in both cases, the set of nonnullable
     * rels is the union of those found in the arms, and we pass down the
     * top_level flag unmodified.
     */
    foreach(l, (List *) node)
    {
      result = bms_join(result,
                find_nonnullable_rels_walker(lfirst(l),
                               top_level));
    }
  }
  else if (IsA(node, FuncExpr))
  {
    FuncExpr   *expr = (FuncExpr *) node;

    if (func_strict(expr->funcid))
      result = find_nonnullable_rels_walker((Node *) expr->args, false);
  }
  else if (IsA(node, OpExpr))
  {
    OpExpr     *expr = (OpExpr *) node;

    set_opfuncid(expr);
    if (func_strict(expr->opfuncid))
      result = find_nonnullable_rels_walker((Node *) expr->args, false);
  }
  else if (IsA(node, ScalarArrayOpExpr))
  {
    ScalarArrayOpExpr *expr = (ScalarArrayOpExpr *) node;

    if (is_strict_saop(expr, true))
      result = find_nonnullable_rels_walker((Node *) expr->args, false);
  }
  else if (IsA(node, BoolExpr))
  {
    BoolExpr   *expr = (BoolExpr *) node;

    switch (expr->boolop)
    {
      case AND_EXPR:
        /* At top level we can just recurse (to the List case) */
        if (top_level)
        {
          result = find_nonnullable_rels_walker((Node *) expr->args,
                              top_level);
          break;
        }

        /*
         * Below top level, even if one arm produces NULL, the result
         * could be FALSE (hence not NULL).  However, if *all* the
         * arms produce NULL then the result is NULL, so we can take
         * the intersection of the sets of nonnullable rels, just as
         * for OR.  Fall through to share code.
         */
        /* FALL THRU */
      case OR_EXPR:

        /*
         * OR is strict if all of its arms are, so we can take the
         * intersection of the sets of nonnullable rels for each arm.
         * This works for both values of top_level.
         */
        foreach(l, expr->args)
        {
          Relids    subresult;

          subresult = find_nonnullable_rels_walker(lfirst(l),
                               top_level);
          if (result == NULL) /* first subresult? */
            result = subresult;
          else
            result = bms_int_members(result, subresult);

          /*
           * If the intersection is empty, we can stop looking. This
           * also justifies the test for first-subresult above.
           */
          if (bms_is_empty(result))
            break;
        }
        break;
      case NOT_EXPR:
        /* NOT will return null if its arg is null */
        result = find_nonnullable_rels_walker((Node *) expr->args,
                            false);
        break;
      default:
        elog(ERROR, "unrecognized boolop: %d", (int) expr->boolop);
        break;
    }
  }
  else if (IsA(node, RelabelType))
  {
    RelabelType *expr = (RelabelType *) node;

    result = find_nonnullable_rels_walker((Node *) expr->arg, top_level);
  }
  else if (IsA(node, CoerceViaIO))
  {
    /* not clear this is useful, but it can't hurt */
    CoerceViaIO *expr = (CoerceViaIO *) node;

    result = find_nonnullable_rels_walker((Node *) expr->arg, top_level);
  }
  else if (IsA(node, ArrayCoerceExpr))
  {
    /* ArrayCoerceExpr is strict at the array level; ignore elemexpr */
    ArrayCoerceExpr *expr = (ArrayCoerceExpr *) node;

    result = find_nonnullable_rels_walker((Node *) expr->arg, top_level);
  }
  else if (IsA(node, ConvertRowtypeExpr))
  {
    /* not clear this is useful, but it can't hurt */
    ConvertRowtypeExpr *expr = (ConvertRowtypeExpr *) node;

    result = find_nonnullable_rels_walker((Node *) expr->arg, top_level);
  }
  else if (IsA(node, CollateExpr))
  {
    CollateExpr *expr = (CollateExpr *) node;

    result = find_nonnullable_rels_walker((Node *) expr->arg, top_level);
  }
  else if (IsA(node, NullTest))
  {
    /* IS NOT NULL can be considered strict, but only at top level */
    NullTest   *expr = (NullTest *) node;

    if (top_level && expr->nulltesttype == IS_NOT_NULL && !expr->argisrow)
      result = find_nonnullable_rels_walker((Node *) expr->arg, false);
  }
  else if (IsA(node, BooleanTest))
  {
    /* Boolean tests that reject NULL are strict at top level */
    BooleanTest *expr = (BooleanTest *) node;

    if (top_level &&
      (expr->booltesttype == IS_TRUE ||
       expr->booltesttype == IS_FALSE ||
       expr->booltesttype == IS_NOT_UNKNOWN))
      result = find_nonnullable_rels_walker((Node *) expr->arg, false);
  }
  else if (IsA(node, SubPlan))
  {
    SubPlan    *splan = (SubPlan *) node;

    /*
     * For some types of SubPlan, we can infer strictness from Vars in the
     * testexpr (the LHS of the original SubLink).
     *
     * For ANY_SUBLINK, if the subquery produces zero rows, the result is
     * always FALSE.  If the subquery produces more than one row, the
     * per-row results of the testexpr are combined using OR semantics.
     * Hence ANY_SUBLINK can be strict only at top level, but there it's
     * as strict as the testexpr is.
     *
     * For ROWCOMPARE_SUBLINK, if the subquery produces zero rows, the
     * result is always NULL.  Otherwise, the result is as strict as the
     * testexpr is.  So we can check regardless of top_level.
     *
     * We can't prove anything for other sublink types (in particular,
     * note that ALL_SUBLINK will return TRUE if the subquery is empty).
     */
    if ((top_level && splan->subLinkType == ANY_SUBLINK) ||
      splan->subLinkType == ROWCOMPARE_SUBLINK)
      result = find_nonnullable_rels_walker(splan->testexpr, top_level);
  }
  else if (IsA(node, PlaceHolderVar))
  {
    PlaceHolderVar *phv = (PlaceHolderVar *) node;

    /*
     * If the contained expression forces any rels non-nullable, so does
     * the PHV.
     */
    result = find_nonnullable_rels_walker((Node *) phv->phexpr, top_level);

    /*
     * If the PHV's syntactic scope is exactly one rel, it will be forced
     * to be evaluated at that rel, and so it will behave like a Var of
     * that rel: if the rel's entire output goes to null, so will the PHV.
     * (If the syntactic scope is a join, we know that the PHV will go to
     * null if the whole join does; but that is AND semantics while we
     * need OR semantics for find_nonnullable_rels' result, so we can't do
     * anything with the knowledge.)
     */
    if (phv->phlevelsup == 0 &&
      bms_membership(phv->phrels) == BMS_SINGLETON)
      result = bms_add_members(result, phv->phrels);
  }
  return result;
}

/*
 * find_nonnullable_vars
 *    Determine which Vars are forced nonnullable by given clause.
 *
 * Returns the set of all level-zero Vars that are referenced in the clause in
 * such a way that the clause cannot possibly return TRUE if any of these Vars
 * is NULL.  (It is OK to err on the side of conservatism; hence the analysis
 * here is simplistic.)
 *
 * The semantics here are subtly different from contain_nonstrict_functions:
 * that function is concerned with NULL results from arbitrary expressions,
 * but here we assume that the input is a Boolean expression, and wish to
 * see if NULL inputs will provably cause a FALSE-or-NULL result.  We expect
 * the expression to have been AND/OR flattened and converted to implicit-AND
 * format.
 *
 * Attnos of the identified Vars are returned in a multibitmapset (a List of
 * Bitmapsets).  List indexes correspond to relids (varnos), while the per-rel
 * Bitmapsets hold varattnos offset by FirstLowInvalidHeapAttributeNumber.
 *
 * top_level is true while scanning top-level AND/OR structure; here, showing
 * the result is either FALSE or NULL is good enough.  top_level is false when
 * we have descended below a NOT or a strict function: now we must be able to
 * prove that the subexpression goes to NULL.
 *
 * We don't use expression_tree_walker here because we don't want to descend
 * through very many kinds of nodes; only the ones we can be sure are strict.
 */
List *
find_nonnullable_vars(Node *clause)
{
  return find_nonnullable_vars_walker(clause, true);
}

static List *
find_nonnullable_vars_walker(Node *node, bool top_level)
{
  List     *result = NIL;
  ListCell   *l;

  if (node == NULL)
    return NIL;
  if (IsA(node, Var))
  {
    Var      *var = (Var *) node;

    if (var->varlevelsup == 0)
      result = mbms_add_member(result,
                   var->varno,
                   var->varattno - FirstLowInvalidHeapAttributeNumber);
  }
  else if (IsA(node, List))
  {
    /*
     * At top level, we are examining an implicit-AND list: if any of the
     * arms produces FALSE-or-NULL then the result is FALSE-or-NULL. If
     * not at top level, we are examining the arguments of a strict
     * function: if any of them produce NULL then the result of the
     * function must be NULL.  So in both cases, the set of nonnullable
     * vars is the union of those found in the arms, and we pass down the
     * top_level flag unmodified.
     */
    foreach(l, (List *) node)
    {
      result = mbms_add_members(result,
                    find_nonnullable_vars_walker(lfirst(l),
                                   top_level));
    }
  }
  else if (IsA(node, FuncExpr))
  {
    FuncExpr   *expr = (FuncExpr *) node;

    if (func_strict(expr->funcid))
      result = find_nonnullable_vars_walker((Node *) expr->args, false);
  }
  else if (IsA(node, OpExpr))
  {
    OpExpr     *expr = (OpExpr *) node;

    set_opfuncid(expr);
    if (func_strict(expr->opfuncid))
      result = find_nonnullable_vars_walker((Node *) expr->args, false);
  }
  else if (IsA(node, ScalarArrayOpExpr))
  {
    ScalarArrayOpExpr *expr = (ScalarArrayOpExpr *) node;

    if (is_strict_saop(expr, true))
      result = find_nonnullable_vars_walker((Node *) expr->args, false);
  }
  else if (IsA(node, BoolExpr))
  {
    BoolExpr   *expr = (BoolExpr *) node;

    switch (expr->boolop)
    {
      case AND_EXPR:

        /*
         * At top level we can just recurse (to the List case), since
         * the result should be the union of what we can prove in each
         * arm.
         */
        if (top_level)
        {
          result = find_nonnullable_vars_walker((Node *) expr->args,
                              top_level);
          break;
        }

        /*
         * Below top level, even if one arm produces NULL, the result
         * could be FALSE (hence not NULL).  However, if *all* the
         * arms produce NULL then the result is NULL, so we can take
         * the intersection of the sets of nonnullable vars, just as
         * for OR.  Fall through to share code.
         */
        /* FALL THRU */
      case OR_EXPR:

        /*
         * OR is strict if all of its arms are, so we can take the
         * intersection of the sets of nonnullable vars for each arm.
         * This works for both values of top_level.
         */
        foreach(l, expr->args)
        {
          List     *subresult;

          subresult = find_nonnullable_vars_walker(lfirst(l),
                               top_level);
          if (result == NIL) /* first subresult? */
            result = subresult;
          else
            result = mbms_int_members(result, subresult);

          /*
           * If the intersection is empty, we can stop looking. This
           * also justifies the test for first-subresult above.
           */
          if (result == NIL)
            break;
        }
        break;
      case NOT_EXPR:
        /* NOT will return null if its arg is null */
        result = find_nonnullable_vars_walker((Node *) expr->args,
                            false);
        break;
      default:
        elog(ERROR, "unrecognized boolop: %d", (int) expr->boolop);
        break;
    }
  }
  else if (IsA(node, RelabelType))
  {
    RelabelType *expr = (RelabelType *) node;

    result = find_nonnullable_vars_walker((Node *) expr->arg, top_level);
  }
  else if (IsA(node, CoerceViaIO))
  {
    /* not clear this is useful, but it can't hurt */
    CoerceViaIO *expr = (CoerceViaIO *) node;

    result = find_nonnullable_vars_walker((Node *) expr->arg, false);
  }
  else if (IsA(node, ArrayCoerceExpr))
  {
    /* ArrayCoerceExpr is strict at the array level; ignore elemexpr */
    ArrayCoerceExpr *expr = (ArrayCoerceExpr *) node;

    result = find_nonnullable_vars_walker((Node *) expr->arg, top_level);
  }
  else if (IsA(node, ConvertRowtypeExpr))
  {
    /* not clear this is useful, but it can't hurt */
    ConvertRowtypeExpr *expr = (ConvertRowtypeExpr *) node;

    result = find_nonnullable_vars_walker((Node *) expr->arg, top_level);
  }
  else if (IsA(node, CollateExpr))
  {
    CollateExpr *expr = (CollateExpr *) node;

    result = find_nonnullable_vars_walker((Node *) expr->arg, top_level);
  }
  else if (IsA(node, NullTest))
  {
    /* IS NOT NULL can be considered strict, but only at top level */
    NullTest   *expr = (NullTest *) node;

    if (top_level && expr->nulltesttype == IS_NOT_NULL && !expr->argisrow)
      result = find_nonnullable_vars_walker((Node *) expr->arg, false);
  }
  else if (IsA(node, BooleanTest))
  {
    /* Boolean tests that reject NULL are strict at top level */
    BooleanTest *expr = (BooleanTest *) node;

    if (top_level &&
      (expr->booltesttype == IS_TRUE ||
       expr->booltesttype == IS_FALSE ||
       expr->booltesttype == IS_NOT_UNKNOWN))
      result = find_nonnullable_vars_walker((Node *) expr->arg, false);
  }
  else if (IsA(node, SubPlan))
  {
    SubPlan    *splan = (SubPlan *) node;

    /* See analysis in find_nonnullable_rels_walker */
    if ((top_level && splan->subLinkType == ANY_SUBLINK) ||
      splan->subLinkType == ROWCOMPARE_SUBLINK)
      result = find_nonnullable_vars_walker(splan->testexpr, top_level);
  }
  else if (IsA(node, PlaceHolderVar))
  {
    PlaceHolderVar *phv = (PlaceHolderVar *) node;

    result = find_nonnullable_vars_walker((Node *) phv->phexpr, top_level);
  }
  return result;
}

/*
 * find_forced_null_vars
 *    Determine which Vars must be NULL for the given clause to return TRUE.
 *
 * This is the complement of find_nonnullable_vars: find the level-zero Vars
 * that must be NULL for the clause to return TRUE.  (It is OK to err on the
 * side of conservatism; hence the analysis here is simplistic.  In fact,
 * we only detect simple "var IS NULL" tests at the top level.)
 *
 * As with find_nonnullable_vars, we return the varattnos of the identified
 * Vars in a multibitmapset.
 */
List *
find_forced_null_vars(Node *node)
{
  List     *result = NIL;
  Var      *var;
  ListCell   *l;

  if (node == NULL)
    return NIL;
  /* Check single-clause cases using subroutine */
  var = find_forced_null_var(node);
  if (var)
  {
    result = mbms_add_member(result,
                 var->varno,
                 var->varattno - FirstLowInvalidHeapAttributeNumber);
  }
  /* Otherwise, handle AND-conditions */
  else if (IsA(node, List))
  {
    /*
     * At top level, we are examining an implicit-AND list: if any of the
     * arms produces FALSE-or-NULL then the result is FALSE-or-NULL.
     */
    foreach(l, (List *) node)
    {
      result = mbms_add_members(result,
                    find_forced_null_vars((Node *) lfirst(l)));
    }
  }
  else if (IsA(node, BoolExpr))
  {
    BoolExpr   *expr = (BoolExpr *) node;

    /*
     * We don't bother considering the OR case, because it's fairly
     * unlikely anyone would write "v1 IS NULL OR v1 IS NULL". Likewise,
     * the NOT case isn't worth expending code on.
     */
    if (expr->boolop == AND_EXPR)
    {
      /* At top level we can just recurse (to the List case) */
      result = find_forced_null_vars((Node *) expr->args);
    }
  }
  return result;
}

/*
 * find_forced_null_var
 *    Return the Var forced null by the given clause, or NULL if it's
 *    not an IS NULL-type clause.  For success, the clause must enforce
 *    *only* nullness of the particular Var, not any other conditions.
 *
 * This is just the single-clause case of find_forced_null_vars(), without
 * any allowance for AND conditions.  It's used by initsplan.c on individual
 * qual clauses.  The reason for not just applying find_forced_null_vars()
 * is that if an AND of an IS NULL clause with something else were to somehow
 * survive AND/OR flattening, initsplan.c might get fooled into discarding
 * the whole clause when only the IS NULL part of it had been proved redundant.
 */
Var *
find_forced_null_var(Node *node)
{
  if (node == NULL)
    return NULL;
  if (IsA(node, NullTest))
  {
    /* check for var IS NULL */
    NullTest   *expr = (NullTest *) node;

    if (expr->nulltesttype == IS_NULL && !expr->argisrow)
    {
      Var      *var = (Var *) expr->arg;

      if (var && IsA(var, Var) &&
        var->varlevelsup == 0)
        return var;
    }
  }
  else if (IsA(node, BooleanTest))
  {
    /* var IS UNKNOWN is equivalent to var IS NULL */
    BooleanTest *expr = (BooleanTest *) node;

    if (expr->booltesttype == IS_UNKNOWN)
    {
      Var      *var = (Var *) expr->arg;

      if (var && IsA(var, Var) &&
        var->varlevelsup == 0)
        return var;
    }
  }
  return NULL;
}

/*
 * Can we treat a ScalarArrayOpExpr as strict?
 *
 * If "falseOK" is true, then a "false" result can be considered strict,
 * else we need to guarantee an actual NULL result for NULL input.
 *
 * "foo op ALL array" is strict if the op is strict *and* we can prove
 * that the array input isn't an empty array.  We can check that
 * for the cases of an array constant and an ARRAY[] construct.
 *
 * "foo op ANY array" is strict in the falseOK sense if the op is strict.
 * If not falseOK, the test is the same as for "foo op ALL array".
 */
static bool
is_strict_saop(ScalarArrayOpExpr *expr, bool falseOK)
{
  Node     *rightop;

  /* The contained operator must be strict. */
  set_sa_opfuncid(expr);
  if (!func_strict(expr->opfuncid))
    return false;
  /* If ANY and falseOK, that's all we need to check. */
  if (expr->useOr && falseOK)
    return true;
  /* Else, we have to see if the array is provably non-empty. */
  Assert(list_length(expr->args) == 2);
  rightop = (Node *) lsecond(expr->args);
  if (rightop && IsA(rightop, Const))
  {
    Datum   arraydatum = ((Const *) rightop)->constvalue;
    bool    arrayisnull = ((Const *) rightop)->constisnull;
    ArrayType  *arrayval;
    int     nitems;

    if (arrayisnull)
      return false;
    arrayval = DatumGetArrayTypeP(arraydatum);
    nitems = ArrayGetNItems(ARR_NDIM(arrayval), ARR_DIMS(arrayval));
    if (nitems > 0)
      return true;
  }
  else if (rightop && IsA(rightop, ArrayExpr))
  {
    ArrayExpr  *arrayexpr = (ArrayExpr *) rightop;

    if (arrayexpr->elements != NIL && !arrayexpr->multidims)
      return true;
  }
  return false;
}


/*****************************************************************************
 *    Check for "pseudo-constant" clauses
 *****************************************************************************/

/*
 * is_pseudo_constant_clause
 *    Detect whether an expression is "pseudo constant", ie, it contains no
 *    variables of the current query level and no uses of volatile functions.
 *    Such an expr is not necessarily a true constant: it can still contain
 *    Params and outer-level Vars, not to mention functions whose results
 *    may vary from one statement to the next.  However, the expr's value
 *    will be constant over any one scan of the current query, so it can be
 *    used as, eg, an indexscan key.  (Actually, the condition for indexscan
 *    keys is weaker than this; see is_pseudo_constant_for_index().)
 *
 * CAUTION: this function omits to test for one very important class of
 * not-constant expressions, namely aggregates (Aggrefs).  In current usage
 * this is only applied to WHERE clauses and so a check for Aggrefs would be
 * a waste of cycles; but be sure to also check contain_agg_clause() if you
 * want to know about pseudo-constness in other contexts.  The same goes
 * for window functions (WindowFuncs).
 */
bool
is_pseudo_constant_clause(Node *clause)
{
  /*
   * We could implement this check in one recursive scan.  But since the
   * check for volatile functions is both moderately expensive and unlikely
   * to fail, it seems better to look for Vars first and only check for
   * volatile functions if we find no Vars.
   */
  if (!contain_var_clause(clause) &&
    !contain_volatile_functions(clause))
    return true;
  return false;
}

/*
 * is_pseudo_constant_clause_relids
 *    Same as above, except caller already has available the var membership
 *    of the expression; this lets us avoid the contain_var_clause() scan.
 */
bool
is_pseudo_constant_clause_relids(Node *clause, Relids relids)
{
  if (bms_is_empty(relids) &&
    !contain_volatile_functions(clause))
    return true;
  return false;
}


/*****************************************************************************
 *                                       *
 *    General clause-manipulating routines                 *
 *                                       *
 *****************************************************************************/

/*
 * NumRelids
 *    (formerly clause_relids)
 *
 * Returns the number of different base relations referenced in 'clause'.
 */
int
NumRelids(PlannerInfo *root, Node *clause)
{
  int     result;
  Relids    varnos = pull_varnos(root, clause);

  varnos = bms_del_members(varnos, root->outer_join_rels);
  result = bms_num_members(varnos);
  bms_free(varnos);
  return result;
}

/*
 * CommuteOpExpr: commute a binary operator clause
 *
 * XXX the clause is destructively modified!
 */
void
CommuteOpExpr(OpExpr *clause)
{
  Oid     opoid;
  Node     *temp;

  /* Sanity checks: caller is at fault if these fail */
  if (!is_opclause(clause) ||
    list_length(clause->args) != 2)
    elog(ERROR, "cannot commute non-binary-operator clause");

  opoid = get_commutator(clause->opno);

  if (!OidIsValid(opoid))
    elog(ERROR, "could not find commutator for operator %u",
       clause->opno);

  /*
   * modify the clause in-place!
   */
  clause->opno = opoid;
  clause->opfuncid = InvalidOid;
  /* opresulttype, opretset, opcollid, inputcollid need not change */

  temp = linitial(clause->args);
  linitial(clause->args) = lsecond(clause->args);
  lsecond(clause->args) = temp;
}

/*
 * Helper for eval_const_expressions: check that datatype of an attribute
 * is still what it was when the expression was parsed.  This is needed to
 * guard against improper simplification after ALTER COLUMN TYPE.  (XXX we
 * may well need to make similar checks elsewhere?)
 *
 * rowtypeid may come from a whole-row Var, and therefore it can be a domain
 * over composite, but for this purpose we only care about checking the type
 * of a contained field.
 */
static bool
rowtype_field_matches(Oid rowtypeid, int fieldnum,
            Oid expectedtype, int32 expectedtypmod,
            Oid expectedcollation)
{
  TupleDesc tupdesc;
  Form_pg_attribute attr;

  /* No issue for RECORD, since there is no way to ALTER such a type */
  if (rowtypeid == RECORDOID)
    return true;
  tupdesc = lookup_rowtype_tupdesc_domain(rowtypeid, -1, false);
  if (fieldnum <= 0 || fieldnum > tupdesc->natts)
  {
    ReleaseTupleDesc(tupdesc);
    return false;
  }
  attr = TupleDescAttr(tupdesc, fieldnum - 1);
  if (attr->attisdropped ||
    attr->atttypid != expectedtype ||
    attr->atttypmod != expectedtypmod ||
    attr->attcollation != expectedcollation)
  {
    ReleaseTupleDesc(tupdesc);
    return false;
  }
  ReleaseTupleDesc(tupdesc);
  return true;
}


/*--------------------
 * eval_const_expressions
 *
 * Reduce any recognizably constant subexpressions of the given
 * expression tree, for example "2 + 2" => "4".  More interestingly,
 * we can reduce certain boolean expressions even when they contain
 * non-constant subexpressions: "x OR true" => "true" no matter what
 * the subexpression x is.  (XXX We assume that no such subexpression
 * will have important side-effects, which is not necessarily a good
 * assumption in the presence of user-defined functions; do we need a
 * pg_proc flag that prevents discarding the execution of a function?)
 *
 * We do understand that certain functions may deliver non-constant
 * results even with constant inputs, "nextval()" being the classic
 * example.  Functions that are not marked "immutable" in pg_proc
 * will not be pre-evaluated here, although we will reduce their
 * arguments as far as possible.
 *
 * Whenever a function is eliminated from the expression by means of
 * constant-expression evaluation or inlining, we add the function to
 * root->glob->invalItems.  This ensures the plan is known to depend on
 * such functions, even though they aren't referenced anymore.
 *
 * We assume that the tree has already been type-checked and contains
 * only operators and functions that are reasonable to try to execute.
 *
 * NOTE: "root" can be passed as NULL if the caller never wants to do any
 * Param substitutions nor receive info about inlined functions.
 *
 * NOTE: the planner assumes that this will always flatten nested AND and
 * OR clauses into N-argument form.  See comments in prepqual.c.
 *
 * NOTE: another critical effect is that any function calls that require
 * default arguments will be expanded, and named-argument calls will be
 * converted to positional notation.  The executor won't handle either.
 *--------------------
 */
Node *
eval_const_expressions(PlannerInfo *root, Node *node)
{
  eval_const_expressions_context context;

  if (root)
    context.boundParams = root->glob->boundParams; /* bound Params */
  else
    context.boundParams = NULL;
  context.root = root;    /* for inlined-function dependencies */
  context.active_fns = NIL; /* nothing being recursively simplified */
  context.case_val = NULL;  /* no CASE being examined */
  context.estimate = false; /* safe transformations only */
  return eval_const_expressions_mutator(node, &context);
}

#define MIN_ARRAY_SIZE_FOR_HASHED_SAOP 9
/*--------------------
 * convert_saop_to_hashed_saop
 *
 * Recursively search 'node' for ScalarArrayOpExprs and fill in the hash
 * function for any ScalarArrayOpExpr that looks like it would be useful to
 * evaluate using a hash table rather than a linear search.
 *
 * We'll use a hash table if all of the following conditions are met:
 * 1. The 2nd argument of the array contain only Consts.
 * 2. useOr is true or there is a valid negator operator for the
 *    ScalarArrayOpExpr's opno.
 * 3. There's valid hash function for both left and righthand operands and
 *    these hash functions are the same.
 * 4. If the array contains enough elements for us to consider it to be
 *    worthwhile using a hash table rather than a linear search.
 */
void
convert_saop_to_hashed_saop(Node *node)
{
  (void) convert_saop_to_hashed_saop_walker(node, NULL);
}

static bool
convert_saop_to_hashed_saop_walker(Node *node, void *context)
{
  if (node == NULL)
    return false;

  if (IsA(node, ScalarArrayOpExpr))
  {
    ScalarArrayOpExpr *saop = (ScalarArrayOpExpr *) node;
    Expr     *arrayarg = (Expr *) lsecond(saop->args);
    Oid     lefthashfunc;
    Oid     righthashfunc;

    if (arrayarg && IsA(arrayarg, Const) &&
      !((Const *) arrayarg)->constisnull)
    {
      if (saop->useOr)
      {
        if (get_op_hash_functions(saop->opno, &lefthashfunc, &righthashfunc) &&
          lefthashfunc == righthashfunc)
        {
          Datum   arrdatum = ((Const *) arrayarg)->constvalue;
          ArrayType  *arr = (ArrayType *) DatumGetPointer(arrdatum);
          int     nitems;

          /*
           * Only fill in the hash functions if the array looks
           * large enough for it to be worth hashing instead of
           * doing a linear search.
           */
          nitems = ArrayGetNItems(ARR_NDIM(arr), ARR_DIMS(arr));

          if (nitems >= MIN_ARRAY_SIZE_FOR_HASHED_SAOP)
          {
            /* Looks good. Fill in the hash functions */
            saop->hashfuncid = lefthashfunc;
          }
          return false;
        }
      }
      else        /* !saop->useOr */
      {
        Oid     negator = get_negator(saop->opno);

        /*
         * Check if this is a NOT IN using an operator whose negator
         * is hashable.  If so we can still build a hash table and
         * just ensure the lookup items are not in the hash table.
         */
        if (OidIsValid(negator) &&
          get_op_hash_functions(negator, &lefthashfunc, &righthashfunc) &&
          lefthashfunc == righthashfunc)
        {
          Datum   arrdatum = ((Const *) arrayarg)->constvalue;
          ArrayType  *arr = (ArrayType *) DatumGetPointer(arrdatum);
          int     nitems;

          /*
           * Only fill in the hash functions if the array looks
           * large enough for it to be worth hashing instead of
           * doing a linear search.
           */
          nitems = ArrayGetNItems(ARR_NDIM(arr), ARR_DIMS(arr));

          if (nitems >= MIN_ARRAY_SIZE_FOR_HASHED_SAOP)
          {
            /* Looks good. Fill in the hash functions */
            saop->hashfuncid = lefthashfunc;

            /*
             * Also set the negfuncid.  The executor will need
             * that to perform hashtable lookups.
             */
            saop->negfuncid = get_opcode(negator);
          }
          return false;
        }
      }
    }
  }

  return expression_tree_walker(node, convert_saop_to_hashed_saop_walker, NULL);
}


/*--------------------
 * estimate_expression_value
 *
 * This function attempts to estimate the value of an expression for
 * planning purposes.  It is in essence a more aggressive version of
 * eval_const_expressions(): we will perform constant reductions that are
 * not necessarily 100% safe, but are reasonable for estimation purposes.
 *
 * Currently the extra steps that are taken in this mode are:
 * 1. Substitute values for Params, where a bound Param value has been made
 *    available by the caller of planner(), even if the Param isn't marked
 *    constant.  This effectively means that we plan using the first supplied
 *    value of the Param.
 * 2. Fold stable, as well as immutable, functions to constants.
 * 3. Reduce PlaceHolderVar nodes to their contained expressions.
 *--------------------
 */
Node *
estimate_expression_value(PlannerInfo *root, Node *node)
{
  eval_const_expressions_context context;

  context.boundParams = root->glob->boundParams;  /* bound Params */
  /* we do not need to mark the plan as depending on inlined functions */
  context.root = NULL;
  context.active_fns = NIL; /* nothing being recursively simplified */
  context.case_val = NULL;  /* no CASE being examined */
  context.estimate = true;  /* unsafe transformations OK */
  return eval_const_expressions_mutator(node, &context);
}

/*
 * The generic case in eval_const_expressions_mutator is to recurse using
 * expression_tree_mutator, which will copy the given node unchanged but
 * const-simplify its arguments (if any) as far as possible.  If the node
 * itself does immutable processing, and each of its arguments were reduced
 * to a Const, we can then reduce it to a Const using evaluate_expr.  (Some
 * node types need more complicated logic; for example, a CASE expression
 * might be reducible to a constant even if not all its subtrees are.)
 */
#define ece_generic_processing(node) \
  expression_tree_mutator((Node *) (node), eval_const_expressions_mutator, \
              context)

/*
 * Check whether all arguments of the given node were reduced to Consts.
 * By going directly to expression_tree_walker, contain_non_const_walker
 * is not applied to the node itself, only to its children.
 */
#define ece_all_arguments_const(node) \
  (!expression_tree_walker((Node *) (node), contain_non_const_walker, NULL))

/* Generic macro for applying evaluate_expr */
#define ece_evaluate_expr(node) \
  ((Node *) evaluate_expr((Expr *) (node), \
              exprType((Node *) (node)), \
              exprTypmod((Node *) (node)), \
              exprCollation((Node *) (node))))

/*
 * Recursive guts of eval_const_expressions/estimate_expression_value
 */
static Node *
eval_const_expressions_mutator(Node *node,
                 eval_const_expressions_context *context)
{

  /* since this function recurses, it could be driven to stack overflow */
  check_stack_depth();

  if (node == NULL)
    return NULL;
  switch (nodeTag(node))
  {
    case T_Param:
      {
        Param    *param = (Param *) node;
        ParamListInfo paramLI = context->boundParams;

        /* Look to see if we've been given a value for this Param */
        if (param->paramkind == PARAM_EXTERN &&
          paramLI != NULL &&
          param->paramid > 0 &&
          param->paramid <= paramLI->numParams)
        {
          ParamExternData *prm;
          ParamExternData prmdata;

          /*
           * Give hook a chance in case parameter is dynamic.  Tell
           * it that this fetch is speculative, so it should avoid
           * erroring out if parameter is unavailable.
           */
          if (paramLI->paramFetch != NULL)
            prm = paramLI->paramFetch(paramLI, param->paramid,
                          true, &prmdata);
          else
            prm = &paramLI->params[param->paramid - 1];

          /*
           * We don't just check OidIsValid, but insist that the
           * fetched type match the Param, just in case the hook did
           * something unexpected.  No need to throw an error here
           * though; leave that for runtime.
           */
          if (OidIsValid(prm->ptype) &&
            prm->ptype == param->paramtype)
          {
            /* OK to substitute parameter value? */
            if (context->estimate ||
              (prm->pflags & PARAM_FLAG_CONST))
            {
              /*
               * Return a Const representing the param value.
               * Must copy pass-by-ref datatypes, since the
               * Param might be in a memory context
               * shorter-lived than our output plan should be.
               */
              int16   typLen;
              bool    typByVal;
              Datum   pval;
              Const    *con;

              get_typlenbyval(param->paramtype,
                      &typLen, &typByVal);
              if (prm->isnull || typByVal)
                pval = prm->value;
              else
                pval = datumCopy(prm->value, typByVal, typLen);
              con = makeConst(param->paramtype,
                      param->paramtypmod,
                      param->paramcollid,
                      (int) typLen,
                      pval,
                      prm->isnull,
                      typByVal);
              con->location = param->location;
              return (Node *) con;
            }
          }
        }

        /*
         * Not replaceable, so just copy the Param (no need to
         * recurse)
         */
        return (Node *) copyObject(param);
      }
    case T_WindowFunc:
      {
        WindowFunc *expr = (WindowFunc *) node;
        Oid     funcid = expr->winfnoid;
        List     *args;
        Expr     *aggfilter;
        HeapTuple func_tuple;
        WindowFunc *newexpr;

        /*
         * We can't really simplify a WindowFunc node, but we mustn't
         * just fall through to the default processing, because we
         * have to apply expand_function_arguments to its argument
         * list.  That takes care of inserting default arguments and
         * expanding named-argument notation.
         */
        func_tuple = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
        if (!HeapTupleIsValid(func_tuple))
          elog(ERROR, "cache lookup failed for function %u", funcid);

        args = expand_function_arguments(expr->args,
                         false, expr->wintype,
                         func_tuple);

        ReleaseSysCache(func_tuple);

        /* Now, recursively simplify the args (which are a List) */
        args = (List *)
          expression_tree_mutator((Node *) args,
                      eval_const_expressions_mutator,
                      context);
        /* ... and the filter expression, which isn't */
        aggfilter = (Expr *)
          eval_const_expressions_mutator((Node *) expr->aggfilter,
                           context);

        /* And build the replacement WindowFunc node */
        newexpr = makeNode(WindowFunc);
        newexpr->winfnoid = expr->winfnoid;
        newexpr->wintype = expr->wintype;
        newexpr->wincollid = expr->wincollid;
        newexpr->inputcollid = expr->inputcollid;
        newexpr->args = args;
        newexpr->aggfilter = aggfilter;
        newexpr->runCondition = expr->runCondition;
        newexpr->winref = expr->winref;
        newexpr->winstar = expr->winstar;
        newexpr->winagg = expr->winagg;
        newexpr->location = expr->location;

        return (Node *) newexpr;
      }
    case T_FuncExpr:
      {
        FuncExpr   *expr = (FuncExpr *) node;
        List     *args = expr->args;
        Expr     *simple;
        FuncExpr   *newexpr;

        /*
         * Code for op/func reduction is pretty bulky, so split it out
         * as a separate function.  Note: exprTypmod normally returns
         * -1 for a FuncExpr, but not when the node is recognizably a
         * length coercion; we want to preserve the typmod in the
         * eventual Const if so.
         */
        simple = simplify_function(expr->funcid,
                       expr->funcresulttype,
                       exprTypmod(node),
                       expr->funccollid,
                       expr->inputcollid,
                       &args,
                       expr->funcvariadic,
                       true,
                       true,
                       context);
        if (simple)   /* successfully simplified it */
          return (Node *) simple;

        /*
         * The expression cannot be simplified any further, so build
         * and return a replacement FuncExpr node using the
         * possibly-simplified arguments.  Note that we have also
         * converted the argument list to positional notation.
         */
        newexpr = makeNode(FuncExpr);
        newexpr->funcid = expr->funcid;
        newexpr->funcresulttype = expr->funcresulttype;
        newexpr->funcretset = expr->funcretset;
        newexpr->funcvariadic = expr->funcvariadic;
        newexpr->funcformat = expr->funcformat;
        newexpr->funccollid = expr->funccollid;
        newexpr->inputcollid = expr->inputcollid;
        newexpr->args = args;
        newexpr->location = expr->location;
        return (Node *) newexpr;
      }
    case T_OpExpr:
      {
        OpExpr     *expr = (OpExpr *) node;
        List     *args = expr->args;
        Expr     *simple;
        OpExpr     *newexpr;

        /*
         * Need to get OID of underlying function.  Okay to scribble
         * on input to this extent.
         */
        set_opfuncid(expr);

        /*
         * Code for op/func reduction is pretty bulky, so split it out
         * as a separate function.
         */
        simple = simplify_function(expr->opfuncid,
                       expr->opresulttype, -1,
                       expr->opcollid,
                       expr->inputcollid,
                       &args,
                       false,
                       true,
                       true,
                       context);
        if (simple)   /* successfully simplified it */
          return (Node *) simple;

        /*
         * If the operator is boolean equality or inequality, we know
         * how to simplify cases involving one constant and one
         * non-constant argument.
         */
        if (expr->opno == BooleanEqualOperator ||
          expr->opno == BooleanNotEqualOperator)
        {
          simple = (Expr *) simplify_boolean_equality(expr->opno,
                                args);
          if (simple) /* successfully simplified it */
            return (Node *) simple;
        }

        /*
         * The expression cannot be simplified any further, so build
         * and return a replacement OpExpr node using the
         * possibly-simplified arguments.
         */
        newexpr = makeNode(OpExpr);
        newexpr->opno = expr->opno;
        newexpr->opfuncid = expr->opfuncid;
        newexpr->opresulttype = expr->opresulttype;
        newexpr->opretset = expr->opretset;
        newexpr->opcollid = expr->opcollid;
        newexpr->inputcollid = expr->inputcollid;
        newexpr->args = args;
        newexpr->location = expr->location;
        return (Node *) newexpr;
      }
    case T_DistinctExpr:
      {
        DistinctExpr *expr = (DistinctExpr *) node;
        List     *args;
        ListCell   *arg;
        bool    has_null_input = false;
        bool    all_null_input = true;
        bool    has_nonconst_input = false;
        Expr     *simple;
        DistinctExpr *newexpr;

        /*
         * Reduce constants in the DistinctExpr's arguments.  We know
         * args is either NIL or a List node, so we can call
         * expression_tree_mutator directly rather than recursing to
         * self.
         */
        args = (List *) expression_tree_mutator((Node *) expr->args,
                            eval_const_expressions_mutator,
                            context);

        /*
         * We must do our own check for NULLs because DistinctExpr has
         * different results for NULL input than the underlying
         * operator does.
         */
        foreach(arg, args)
        {
          if (IsA(lfirst(arg), Const))
          {
            has_null_input |= ((Const *) lfirst(arg))->constisnull;
            all_null_input &= ((Const *) lfirst(arg))->constisnull;
          }
          else
            has_nonconst_input = true;
        }

        /* all constants? then can optimize this out */
        if (!has_nonconst_input)
        {
          /* all nulls? then not distinct */
          if (all_null_input)
            return makeBoolConst(false, false);

          /* one null? then distinct */
          if (has_null_input)
            return makeBoolConst(true, false);

          /* otherwise try to evaluate the '=' operator */
          /* (NOT okay to try to inline it, though!) */

          /*
           * Need to get OID of underlying function.  Okay to
           * scribble on input to this extent.
           */
          set_opfuncid((OpExpr *) expr);  /* rely on struct
                           * equivalence */

          /*
           * Code for op/func reduction is pretty bulky, so split it
           * out as a separate function.
           */
          simple = simplify_function(expr->opfuncid,
                         expr->opresulttype, -1,
                         expr->opcollid,
                         expr->inputcollid,
                         &args,
                         false,
                         false,
                         false,
                         context);
          if (simple) /* successfully simplified it */
          {
            /*
             * Since the underlying operator is "=", must negate
             * its result
             */
            Const    *csimple = castNode(Const, simple);

            csimple->constvalue =
              BoolGetDatum(!DatumGetBool(csimple->constvalue));
            return (Node *) csimple;
          }
        }

        /*
         * The expression cannot be simplified any further, so build
         * and return a replacement DistinctExpr node using the
         * possibly-simplified arguments.
         */
        newexpr = makeNode(DistinctExpr);
        newexpr->opno = expr->opno;
        newexpr->opfuncid = expr->opfuncid;
        newexpr->opresulttype = expr->opresulttype;
        newexpr->opretset = expr->opretset;
        newexpr->opcollid = expr->opcollid;
        newexpr->inputcollid = expr->inputcollid;
        newexpr->args = args;
        newexpr->location = expr->location;
        return (Node *) newexpr;
      }
    case T_NullIfExpr:
      {
        NullIfExpr *expr;
        ListCell   *arg;
        bool    has_nonconst_input = false;

        /* Copy the node and const-simplify its arguments */
        expr = (NullIfExpr *) ece_generic_processing(node);

        /* If either argument is NULL they can't be equal */
        foreach(arg, expr->args)
        {
          if (!IsA(lfirst(arg), Const))
            has_nonconst_input = true;
          else if (((Const *) lfirst(arg))->constisnull)
            return (Node *) linitial(expr->args);
        }

        /*
         * Need to get OID of underlying function before checking if
         * the function is OK to evaluate.
         */
        set_opfuncid((OpExpr *) expr);

        if (!has_nonconst_input &&
          ece_function_is_safe(expr->opfuncid, context))
          return ece_evaluate_expr(expr);

        return (Node *) expr;
      }
    case T_ScalarArrayOpExpr:
      {
        ScalarArrayOpExpr *saop;

        /* Copy the node and const-simplify its arguments */
        saop = (ScalarArrayOpExpr *) ece_generic_processing(node);

        /* Make sure we know underlying function */
        set_sa_opfuncid(saop);

        /*
         * If all arguments are Consts, and it's a safe function, we
         * can fold to a constant
         */
        if (ece_all_arguments_const(saop) &&
          ece_function_is_safe(saop->opfuncid, context))
          return ece_evaluate_expr(saop);
        return (Node *) saop;
      }
    case T_BoolExpr:
      {
        BoolExpr   *expr = (BoolExpr *) node;

        switch (expr->boolop)
        {
          case OR_EXPR:
            {
              List     *newargs;
              bool    haveNull = false;
              bool    forceTrue = false;

              newargs = simplify_or_arguments(expr->args,
                              context,
                              &haveNull,
                              &forceTrue);
              if (forceTrue)
                return makeBoolConst(true, false);
              if (haveNull)
                newargs = lappend(newargs,
                          makeBoolConst(false, true));
              /* If all the inputs are FALSE, result is FALSE */
              if (newargs == NIL)
                return makeBoolConst(false, false);

              /*
               * If only one nonconst-or-NULL input, it's the
               * result
               */
              if (list_length(newargs) == 1)
                return (Node *) linitial(newargs);
              /* Else we still need an OR node */
              return (Node *) make_orclause(newargs);
            }
          case AND_EXPR:
            {
              List     *newargs;
              bool    haveNull = false;
              bool    forceFalse = false;

              newargs = simplify_and_arguments(expr->args,
                               context,
                               &haveNull,
                               &forceFalse);
              if (forceFalse)
                return makeBoolConst(false, false);
              if (haveNull)
                newargs = lappend(newargs,
                          makeBoolConst(false, true));
              /* If all the inputs are TRUE, result is TRUE */
              if (newargs == NIL)
                return makeBoolConst(true, false);

              /*
               * If only one nonconst-or-NULL input, it's the
               * result
               */
              if (list_length(newargs) == 1)
                return (Node *) linitial(newargs);
              /* Else we still need an AND node */
              return (Node *) make_andclause(newargs);
            }
          case NOT_EXPR:
            {
              Node     *arg;

              Assert(list_length(expr->args) == 1);
              arg = eval_const_expressions_mutator(linitial(expr->args),
                                 context);

              /*
               * Use negate_clause() to see if we can simplify
               * away the NOT.
               */
              return negate_clause(arg);
            }
          default:
            elog(ERROR, "unrecognized boolop: %d",
               (int) expr->boolop);
            break;
        }
        break;
      }

    case T_JsonValueExpr:
      {
        JsonValueExpr *jve = (JsonValueExpr *) node;
        Node     *raw_expr = (Node *) jve->raw_expr;
        Node     *formatted_expr = (Node *) jve->formatted_expr;

        /*
         * If we can fold formatted_expr to a constant, we can elide
         * the JsonValueExpr altogether.  Otherwise we must process
         * raw_expr too.  But JsonFormat is a flat node and requires
         * no simplification, only copying.
         */
        formatted_expr = eval_const_expressions_mutator(formatted_expr,
                                context);
        if (formatted_expr && IsA(formatted_expr, Const))
          return formatted_expr;

        raw_expr = eval_const_expressions_mutator(raw_expr, context);

        return (Node *) makeJsonValueExpr((Expr *) raw_expr,
                          (Expr *) formatted_expr,
                          copyObject(jve->format));
      }

    case T_SubPlan:
    case T_AlternativeSubPlan:

      /*
       * Return a SubPlan unchanged --- too late to do anything with it.
       *
       * XXX should we ereport() here instead?  Probably this routine
       * should never be invoked after SubPlan creation.
       */
      return node;
    case T_RelabelType:
      {
        RelabelType *relabel = (RelabelType *) node;
        Node     *arg;

        /* Simplify the input ... */
        arg = eval_const_expressions_mutator((Node *) relabel->arg,
                           context);
        /* ... and attach a new RelabelType node, if needed */
        return applyRelabelType(arg,
                    relabel->resulttype,
                    relabel->resulttypmod,
                    relabel->resultcollid,
                    relabel->relabelformat,
                    relabel->location,
                    true);
      }
    case T_CoerceViaIO:
      {
        CoerceViaIO *expr = (CoerceViaIO *) node;
        List     *args;
        Oid     outfunc;
        bool    outtypisvarlena;
        Oid     infunc;
        Oid     intypioparam;
        Expr     *simple;
        CoerceViaIO *newexpr;

        /* Make a List so we can use simplify_function */
        args = list_make1(expr->arg);

        /*
         * CoerceViaIO represents calling the source type's output
         * function then the result type's input function.  So, try to
         * simplify it as though it were a stack of two such function
         * calls.  First we need to know what the functions are.
         *
         * Note that the coercion functions are assumed not to care
         * about input collation, so we just pass InvalidOid for that.
         */
        getTypeOutputInfo(exprType((Node *) expr->arg),
                  &outfunc, &outtypisvarlena);
        getTypeInputInfo(expr->resulttype,
                 &infunc, &intypioparam);

        simple = simplify_function(outfunc,
                       CSTRINGOID, -1,
                       InvalidOid,
                       InvalidOid,
                       &args,
                       false,
                       true,
                       true,
                       context);
        if (simple)   /* successfully simplified output fn */
        {
          /*
           * Input functions may want 1 to 3 arguments.  We always
           * supply all three, trusting that nothing downstream will
           * complain.
           */
          args = list_make3(simple,
                    makeConst(OIDOID,
                        -1,
                        InvalidOid,
                        sizeof(Oid),
                        ObjectIdGetDatum(intypioparam),
                        false,
                        true),
                    makeConst(INT4OID,
                        -1,
                        InvalidOid,
                        sizeof(int32),
                        Int32GetDatum(-1),
                        false,
                        true));

          simple = simplify_function(infunc,
                         expr->resulttype, -1,
                         expr->resultcollid,
                         InvalidOid,
                         &args,
                         false,
                         false,
                         true,
                         context);
          if (simple) /* successfully simplified input fn */
            return (Node *) simple;
        }

        /*
         * The expression cannot be simplified any further, so build
         * and return a replacement CoerceViaIO node using the
         * possibly-simplified argument.
         */
        newexpr = makeNode(CoerceViaIO);
        newexpr->arg = (Expr *) linitial(args);
        newexpr->resulttype = expr->resulttype;
        newexpr->resultcollid = expr->resultcollid;
        newexpr->coerceformat = expr->coerceformat;
        newexpr->location = expr->location;
        return (Node *) newexpr;
      }
    case T_ArrayCoerceExpr:
      {
        ArrayCoerceExpr *ac = makeNode(ArrayCoerceExpr);
        Node     *save_case_val;

        /*
         * Copy the node and const-simplify its arguments.  We can't
         * use ece_generic_processing() here because we need to mess
         * with case_val only while processing the elemexpr.
         */
        memcpy(ac, node, sizeof(ArrayCoerceExpr));
        ac->arg = (Expr *)
          eval_const_expressions_mutator((Node *) ac->arg,
                           context);

        /*
         * Set up for the CaseTestExpr node contained in the elemexpr.
         * We must prevent it from absorbing any outer CASE value.
         */
        save_case_val = context->case_val;
        context->case_val = NULL;

        ac->elemexpr = (Expr *)
          eval_const_expressions_mutator((Node *) ac->elemexpr,
                           context);

        context->case_val = save_case_val;

        /*
         * If constant argument and the per-element expression is
         * immutable, we can simplify the whole thing to a constant.
         * Exception: although contain_mutable_functions considers
         * CoerceToDomain immutable for historical reasons, let's not
         * do so here; this ensures coercion to an array-over-domain
         * does not apply the domain's constraints until runtime.
         */
        if (ac->arg && IsA(ac->arg, Const) &&
          ac->elemexpr && !IsA(ac->elemexpr, CoerceToDomain) &&
          !contain_mutable_functions((Node *) ac->elemexpr))
          return ece_evaluate_expr(ac);

        return (Node *) ac;
      }
    case T_CollateExpr:
      {
        /*
         * We replace CollateExpr with RelabelType, so as to improve
         * uniformity of expression representation and thus simplify
         * comparison of expressions.  Hence this looks very nearly
         * the same as the RelabelType case, and we can apply the same
         * optimizations to avoid unnecessary RelabelTypes.
         */
        CollateExpr *collate = (CollateExpr *) node;
        Node     *arg;

        /* Simplify the input ... */
        arg = eval_const_expressions_mutator((Node *) collate->arg,
                           context);
        /* ... and attach a new RelabelType node, if needed */
        return applyRelabelType(arg,
                    exprType(arg),
                    exprTypmod(arg),
                    collate->collOid,
                    COERCE_IMPLICIT_CAST,
                    collate->location,
                    true);
      }
    case T_CaseExpr:
      {
        /*----------
         * CASE expressions can be simplified if there are constant
         * condition clauses:
         *    FALSE (or NULL): drop the alternative
         *    TRUE: drop all remaining alternatives
         * If the first non-FALSE alternative is a constant TRUE,
         * we can simplify the entire CASE to that alternative's
         * expression.  If there are no non-FALSE alternatives,
         * we simplify the entire CASE to the default result (ELSE).
         *
         * If we have a simple-form CASE with constant test
         * expression, we substitute the constant value for contained
         * CaseTestExpr placeholder nodes, so that we have the
         * opportunity to reduce constant test conditions.  For
         * example this allows
         *    CASE 0 WHEN 0 THEN 1 ELSE 1/0 END
         * to reduce to 1 rather than drawing a divide-by-0 error.
         * Note that when the test expression is constant, we don't
         * have to include it in the resulting CASE; for example
         *    CASE 0 WHEN x THEN y ELSE z END
         * is transformed by the parser to
         *    CASE 0 WHEN CaseTestExpr = x THEN y ELSE z END
         * which we can simplify to
         *    CASE WHEN 0 = x THEN y ELSE z END
         * It is not necessary for the executor to evaluate the "arg"
         * expression when executing the CASE, since any contained
         * CaseTestExprs that might have referred to it will have been
         * replaced by the constant.
         *----------
         */
        CaseExpr   *caseexpr = (CaseExpr *) node;
        CaseExpr   *newcase;
        Node     *save_case_val;
        Node     *newarg;
        List     *newargs;
        bool    const_true_cond;
        Node     *defresult = NULL;
        ListCell   *arg;

        /* Simplify the test expression, if any */
        newarg = eval_const_expressions_mutator((Node *) caseexpr->arg,
                            context);

        /* Set up for contained CaseTestExpr nodes */
        save_case_val = context->case_val;
        if (newarg && IsA(newarg, Const))
        {
          context->case_val = newarg;
          newarg = NULL;  /* not needed anymore, see above */
        }
        else
          context->case_val = NULL;

        /* Simplify the WHEN clauses */
        newargs = NIL;
        const_true_cond = false;
        foreach(arg, caseexpr->args)
        {
          CaseWhen   *oldcasewhen = lfirst_node(CaseWhen, arg);
          Node     *casecond;
          Node     *caseresult;

          /* Simplify this alternative's test condition */
          casecond = eval_const_expressions_mutator((Node *) oldcasewhen->expr,
                                context);

          /*
           * If the test condition is constant FALSE (or NULL), then
           * drop this WHEN clause completely, without processing
           * the result.
           */
          if (casecond && IsA(casecond, Const))
          {
            Const    *const_input = (Const *) casecond;

            if (const_input->constisnull ||
              !DatumGetBool(const_input->constvalue))
              continue; /* drop alternative with FALSE cond */
            /* Else it's constant TRUE */
            const_true_cond = true;
          }

          /* Simplify this alternative's result value */
          caseresult = eval_const_expressions_mutator((Node *) oldcasewhen->result,
                                context);

          /* If non-constant test condition, emit a new WHEN node */
          if (!const_true_cond)
          {
            CaseWhen   *newcasewhen = makeNode(CaseWhen);

            newcasewhen->expr = (Expr *) casecond;
            newcasewhen->result = (Expr *) caseresult;
            newcasewhen->location = oldcasewhen->location;
            newargs = lappend(newargs, newcasewhen);
            continue;
          }

          /*
           * Found a TRUE condition, so none of the remaining
           * alternatives can be reached.  We treat the result as
           * the default result.
           */
          defresult = caseresult;
          break;
        }

        /* Simplify the default result, unless we replaced it above */
        if (!const_true_cond)
          defresult = eval_const_expressions_mutator((Node *) caseexpr->defresult,
                                 context);

        context->case_val = save_case_val;

        /*
         * If no non-FALSE alternatives, CASE reduces to the default
         * result
         */
        if (newargs == NIL)
          return defresult;
        /* Otherwise we need a new CASE node */
        newcase = makeNode(CaseExpr);
        newcase->casetype = caseexpr->casetype;
        newcase->casecollid = caseexpr->casecollid;
        newcase->arg = (Expr *) newarg;
        newcase->args = newargs;
        newcase->defresult = (Expr *) defresult;
        newcase->location = caseexpr->location;
        return (Node *) newcase;
      }
    case T_CaseTestExpr:
      {
        /*
         * If we know a constant test value for the current CASE
         * construct, substitute it for the placeholder.  Else just
         * return the placeholder as-is.
         */
        if (context->case_val)
          return copyObject(context->case_val);
        else
          return copyObject(node);
      }
    case T_SubscriptingRef:
    case T_ArrayExpr:
    case T_RowExpr:
    case T_MinMaxExpr:
      {
        /*
         * Generic handling for node types whose own processing is
         * known to be immutable, and for which we need no smarts
         * beyond "simplify if all inputs are constants".
         *
         * Treating SubscriptingRef this way assumes that subscripting
         * fetch and assignment are both immutable.  This constrains
         * type-specific subscripting implementations; maybe we should
         * relax it someday.
         *
         * Treating MinMaxExpr this way amounts to assuming that the
         * btree comparison function it calls is immutable; see the
         * reasoning in contain_mutable_functions_walker.
         */

        /* Copy the node and const-simplify its arguments */
        node = ece_generic_processing(node);
        /* If all arguments are Consts, we can fold to a constant */
        if (ece_all_arguments_const(node))
          return ece_evaluate_expr(node);
        return node;
      }
    case T_CoalesceExpr:
      {
        CoalesceExpr *coalesceexpr = (CoalesceExpr *) node;
        CoalesceExpr *newcoalesce;
        List     *newargs;
        ListCell   *arg;

        newargs = NIL;
        foreach(arg, coalesceexpr->args)
        {
          Node     *e;

          e = eval_const_expressions_mutator((Node *) lfirst(arg),
                             context);

          /*
           * We can remove null constants from the list. For a
           * non-null constant, if it has not been preceded by any
           * other non-null-constant expressions then it is the
           * result. Otherwise, it's the next argument, but we can
           * drop following arguments since they will never be
           * reached.
           */
          if (IsA(e, Const))
          {
            if (((Const *) e)->constisnull)
              continue; /* drop null constant */
            if (newargs == NIL)
              return e; /* first expr */
            newargs = lappend(newargs, e);
            break;
          }
          newargs = lappend(newargs, e);
        }

        /*
         * If all the arguments were constant null, the result is just
         * null
         */
        if (newargs == NIL)
          return (Node *) makeNullConst(coalesceexpr->coalescetype,
                          -1,
                          coalesceexpr->coalescecollid);

        newcoalesce = makeNode(CoalesceExpr);
        newcoalesce->coalescetype = coalesceexpr->coalescetype;
        newcoalesce->coalescecollid = coalesceexpr->coalescecollid;
        newcoalesce->args = newargs;
        newcoalesce->location = coalesceexpr->location;
        return (Node *) newcoalesce;
      }
    case T_SQLValueFunction:
      {
        /*
         * All variants of SQLValueFunction are stable, so if we are
         * estimating the expression's value, we should evaluate the
         * current function value.  Otherwise just copy.
         */
        SQLValueFunction *svf = (SQLValueFunction *) node;

        if (context->estimate)
          return (Node *) evaluate_expr((Expr *) svf,
                          svf->type,
                          svf->typmod,
                          InvalidOid);
        else
          return copyObject((Node *) svf);
      }
    case T_FieldSelect:
      {
        /*
         * We can optimize field selection from a whole-row Var into a
         * simple Var.  (This case won't be generated directly by the
         * parser, because ParseComplexProjection short-circuits it.
         * But it can arise while simplifying functions.)  Also, we
         * can optimize field selection from a RowExpr construct, or
         * of course from a constant.
         *
         * However, replacing a whole-row Var in this way has a
         * pitfall: if we've already built the rel targetlist for the
         * source relation, then the whole-row Var is scheduled to be
         * produced by the relation scan, but the simple Var probably
         * isn't, which will lead to a failure in setrefs.c.  This is
         * not a problem when handling simple single-level queries, in
         * which expression simplification always happens first.  It
         * is a risk for lateral references from subqueries, though.
         * To avoid such failures, don't optimize uplevel references.
         *
         * We must also check that the declared type of the field is
         * still the same as when the FieldSelect was created --- this
         * can change if someone did ALTER COLUMN TYPE on the rowtype.
         * If it isn't, we skip the optimization; the case will
         * probably fail at runtime, but that's not our problem here.
         */
        FieldSelect *fselect = (FieldSelect *) node;
        FieldSelect *newfselect;
        Node     *arg;

        arg = eval_const_expressions_mutator((Node *) fselect->arg,
                           context);
        if (arg && IsA(arg, Var) &&
          ((Var *) arg)->varattno == InvalidAttrNumber &&
          ((Var *) arg)->varlevelsup == 0)
        {
          if (rowtype_field_matches(((Var *) arg)->vartype,
                        fselect->fieldnum,
                        fselect->resulttype,
                        fselect->resulttypmod,
                        fselect->resultcollid))
          {
            Var      *newvar;

            newvar = makeVar(((Var *) arg)->varno,
                     fselect->fieldnum,
                     fselect->resulttype,
                     fselect->resulttypmod,
                     fselect->resultcollid,
                     ((Var *) arg)->varlevelsup);
            /* New Var has same OLD/NEW returning as old one */
            newvar->varreturningtype = ((Var *) arg)->varreturningtype;
            /* New Var is nullable by same rels as the old one */
            newvar->varnullingrels = ((Var *) arg)->varnullingrels;
            return (Node *) newvar;
          }
        }
        if (arg && IsA(arg, RowExpr))
        {
          RowExpr    *rowexpr = (RowExpr *) arg;

          if (fselect->fieldnum > 0 &&
            fselect->fieldnum <= list_length(rowexpr->args))
          {
            Node     *fld = (Node *) list_nth(rowexpr->args,
                              fselect->fieldnum - 1);

            if (rowtype_field_matches(rowexpr->row_typeid,
                          fselect->fieldnum,
                          fselect->resulttype,
                          fselect->resulttypmod,
                          fselect->resultcollid) &&
              fselect->resulttype == exprType(fld) &&
              fselect->resulttypmod == exprTypmod(fld) &&
              fselect->resultcollid == exprCollation(fld))
              return fld;
          }
        }
        newfselect = makeNode(FieldSelect);
        newfselect->arg = (Expr *) arg;
        newfselect->fieldnum = fselect->fieldnum;
        newfselect->resulttype = fselect->resulttype;
        newfselect->resulttypmod = fselect->resulttypmod;
        newfselect->resultcollid = fselect->resultcollid;
        if (arg && IsA(arg, Const))
        {
          Const    *con = (Const *) arg;

          if (rowtype_field_matches(con->consttype,
                        newfselect->fieldnum,
                        newfselect->resulttype,
                        newfselect->resulttypmod,
                        newfselect->resultcollid))
            return ece_evaluate_expr(newfselect);
        }
        return (Node *) newfselect;
      }
    case T_NullTest:
      {
        NullTest   *ntest = (NullTest *) node;
        NullTest   *newntest;
        Node     *arg;

        arg = eval_const_expressions_mutator((Node *) ntest->arg,
                           context);
        if (ntest->argisrow && arg && IsA(arg, RowExpr))
        {
          /*
           * We break ROW(...) IS [NOT] NULL into separate tests on
           * its component fields.  This form is usually more
           * efficient to evaluate, as well as being more amenable
           * to optimization.
           */
          RowExpr    *rarg = (RowExpr *) arg;
          List     *newargs = NIL;
          ListCell   *l;

          foreach(l, rarg->args)
          {
            Node     *relem = (Node *) lfirst(l);

            /*
             * A constant field refutes the whole NullTest if it's
             * of the wrong nullness; else we can discard it.
             */
            if (relem && IsA(relem, Const))
            {
              Const    *carg = (Const *) relem;

              if (carg->constisnull ?
                (ntest->nulltesttype == IS_NOT_NULL) :
                (ntest->nulltesttype == IS_NULL))
                return makeBoolConst(false, false);
              continue;
            }

            /*
             * Else, make a scalar (argisrow == false) NullTest
             * for this field.  Scalar semantics are required
             * because IS [NOT] NULL doesn't recurse; see comments
             * in ExecEvalRowNullInt().
             */
            newntest = makeNode(NullTest);
            newntest->arg = (Expr *) relem;
            newntest->nulltesttype = ntest->nulltesttype;
            newntest->argisrow = false;
            newntest->location = ntest->location;
            newargs = lappend(newargs, newntest);
          }
          /* If all the inputs were constants, result is TRUE */
          if (newargs == NIL)
            return makeBoolConst(true, false);
          /* If only one nonconst input, it's the result */
          if (list_length(newargs) == 1)
            return (Node *) linitial(newargs);
          /* Else we need an AND node */
          return (Node *) make_andclause(newargs);
        }
        if (!ntest->argisrow && arg && IsA(arg, Const))
        {
          Const    *carg = (Const *) arg;
          bool    result;

          switch (ntest->nulltesttype)
          {
            case IS_NULL:
              result = carg->constisnull;
              break;
            case IS_NOT_NULL:
              result = !carg->constisnull;
              break;
            default:
              elog(ERROR, "unrecognized nulltesttype: %d",
                 (int) ntest->nulltesttype);
              result = false; /* keep compiler quiet */
              break;
          }

          return makeBoolConst(result, false);
        }

        newntest = makeNode(NullTest);
        newntest->arg = (Expr *) arg;
        newntest->nulltesttype = ntest->nulltesttype;
        newntest->argisrow = ntest->argisrow;
        newntest->location = ntest->location;
        return (Node *) newntest;
      }
    case T_BooleanTest:
      {
        /*
         * This case could be folded into the generic handling used
         * for ArrayExpr etc.  But because the simplification logic is
         * so trivial, applying evaluate_expr() to perform it would be
         * a heavy overhead.  BooleanTest is probably common enough to
         * justify keeping this bespoke implementation.
         */
        BooleanTest *btest = (BooleanTest *) node;
        BooleanTest *newbtest;
        Node     *arg;

        arg = eval_const_expressions_mutator((Node *) btest->arg,
                           context);
        if (arg && IsA(arg, Const))
        {
          Const    *carg = (Const *) arg;
          bool    result;

          switch (btest->booltesttype)
          {
            case IS_TRUE:
              result = (!carg->constisnull &&
                    DatumGetBool(carg->constvalue));
              break;
            case IS_NOT_TRUE:
              result = (carg->constisnull ||
                    !DatumGetBool(carg->constvalue));
              break;
            case IS_FALSE:
              result = (!carg->constisnull &&
                    !DatumGetBool(carg->constvalue));
              break;
            case IS_NOT_FALSE:
              result = (carg->constisnull ||
                    DatumGetBool(carg->constvalue));
              break;
            case IS_UNKNOWN:
              result = carg->constisnull;
              break;
            case IS_NOT_UNKNOWN:
              result = !carg->constisnull;
              break;
            default:
              elog(ERROR, "unrecognized booltesttype: %d",
                 (int) btest->booltesttype);
              result = false; /* keep compiler quiet */
              break;
          }

          return makeBoolConst(result, false);
        }

        newbtest = makeNode(BooleanTest);
        newbtest->arg = (Expr *) arg;
        newbtest->booltesttype = btest->booltesttype;
        newbtest->location = btest->location;
        return (Node *) newbtest;
      }
    case T_CoerceToDomain:
      {
        /*
         * If the domain currently has no constraints, we replace the
         * CoerceToDomain node with a simple RelabelType, which is
         * both far faster to execute and more amenable to later
         * optimization.  We must then mark the plan as needing to be
         * rebuilt if the domain's constraints change.
         *
         * Also, in estimation mode, always replace CoerceToDomain
         * nodes, effectively assuming that the coercion will succeed.
         */
        CoerceToDomain *cdomain = (CoerceToDomain *) node;
        CoerceToDomain *newcdomain;
        Node     *arg;

        arg = eval_const_expressions_mutator((Node *) cdomain->arg,
                           context);
        if (context->estimate ||
          !DomainHasConstraints(cdomain->resulttype))
        {
          /* Record dependency, if this isn't estimation mode */
          if (context->root && !context->estimate)
            record_plan_type_dependency(context->root,
                          cdomain->resulttype);

          /* Generate RelabelType to substitute for CoerceToDomain */
          return applyRelabelType(arg,
                      cdomain->resulttype,
                      cdomain->resulttypmod,
                      cdomain->resultcollid,
                      cdomain->coercionformat,
                      cdomain->location,
                      true);
        }

        newcdomain = makeNode(CoerceToDomain);
        newcdomain->arg = (Expr *) arg;
        newcdomain->resulttype = cdomain->resulttype;
        newcdomain->resulttypmod = cdomain->resulttypmod;
        newcdomain->resultcollid = cdomain->resultcollid;
        newcdomain->coercionformat = cdomain->coercionformat;
        newcdomain->location = cdomain->location;
        return (Node *) newcdomain;
      }
    case T_PlaceHolderVar:

      /*
       * In estimation mode, just strip the PlaceHolderVar node
       * altogether; this amounts to estimating that the contained value
       * won't be forced to null by an outer join.  In regular mode we
       * just use the default behavior (ie, simplify the expression but
       * leave the PlaceHolderVar node intact).
       */
      if (context->estimate)
      {
        PlaceHolderVar *phv = (PlaceHolderVar *) node;

        return eval_const_expressions_mutator((Node *) phv->phexpr,
                            context);
      }
      break;
    case T_ConvertRowtypeExpr:
      {
        ConvertRowtypeExpr *cre = castNode(ConvertRowtypeExpr, node);
        Node     *arg;
        ConvertRowtypeExpr *newcre;

        arg = eval_const_expressions_mutator((Node *) cre->arg,
                           context);

        newcre = makeNode(ConvertRowtypeExpr);
        newcre->resulttype = cre->resulttype;
        newcre->convertformat = cre->convertformat;
        newcre->location = cre->location;

        /*
         * In case of a nested ConvertRowtypeExpr, we can convert the
         * leaf row directly to the topmost row format without any
         * intermediate conversions. (This works because
         * ConvertRowtypeExpr is used only for child->parent
         * conversion in inheritance trees, which works by exact match
         * of column name, and a column absent in an intermediate
         * result can't be present in the final result.)
         *
         * No need to check more than one level deep, because the
         * above recursion will have flattened anything else.
         */
        if (arg != NULL && IsA(arg, ConvertRowtypeExpr))
        {
          ConvertRowtypeExpr *argcre = (ConvertRowtypeExpr *) arg;

          arg = (Node *) argcre->arg;

          /*
           * Make sure an outer implicit conversion can't hide an
           * inner explicit one.
           */
          if (newcre->convertformat == COERCE_IMPLICIT_CAST)
            newcre->convertformat = argcre->convertformat;
        }

        newcre->arg = (Expr *) arg;

        if (arg != NULL && IsA(arg, Const))
          return ece_evaluate_expr((Node *) newcre);
        return (Node *) newcre;
      }
    default:
      break;
  }

  /*
   * For any node type not handled above, copy the node unchanged but
   * const-simplify its subexpressions.  This is the correct thing for node
   * types whose behavior might change between planning and execution, such
   * as CurrentOfExpr.  It's also a safe default for new node types not
   * known to this routine.
   */
  return ece_generic_processing(node);
}

/*
 * Subroutine for eval_const_expressions: check for non-Const nodes.
 *
 * We can abort recursion immediately on finding a non-Const node.  This is
 * critical for performance, else eval_const_expressions_mutator would take
 * O(N^2) time on non-simplifiable trees.  However, we do need to descend
 * into List nodes since expression_tree_walker sometimes invokes the walker
 * function directly on List subtrees.
 */
static bool
contain_non_const_walker(Node *node, void *context)
{
  if (node == NULL)
    return false;
  if (IsA(node, Const))
    return false;
  if (IsA(node, List))
    return expression_tree_walker(node, contain_non_const_walker, context);
  /* Otherwise, abort the tree traversal and return true */
  return true;
}

/*
 * Subroutine for eval_const_expressions: check if a function is OK to evaluate
 */
static bool
ece_function_is_safe(Oid funcid, eval_const_expressions_context *context)
{
  char    provolatile = func_volatile(funcid);

  /*
   * Ordinarily we are only allowed to simplify immutable functions. But for
   * purposes of estimation, we consider it okay to simplify functions that
   * are merely stable; the risk that the result might change from planning
   * time to execution time is worth taking in preference to not being able
   * to estimate the value at all.
   */
  if (provolatile == PROVOLATILE_IMMUTABLE)
    return true;
  if (context->estimate && provolatile == PROVOLATILE_STABLE)
    return true;
  return false;
}

/*
 * Subroutine for eval_const_expressions: process arguments of an OR clause
 *
 * This includes flattening of nested ORs as well as recursion to
 * eval_const_expressions to simplify the OR arguments.
 *
 * After simplification, OR arguments are handled as follows:
 *    non constant: keep
 *    FALSE: drop (does not affect result)
 *    TRUE: force result to TRUE
 *    NULL: keep only one
 * We must keep one NULL input because OR expressions evaluate to NULL when no
 * input is TRUE and at least one is NULL.  We don't actually include the NULL
 * here, that's supposed to be done by the caller.
 *
 * The output arguments *haveNull and *forceTrue must be initialized false
 * by the caller.  They will be set true if a NULL constant or TRUE constant,
 * respectively, is detected anywhere in the argument list.
 */
static List *
simplify_or_arguments(List *args,
            eval_const_expressions_context *context,
            bool *haveNull, bool *forceTrue)
{
  List     *newargs = NIL;
  List     *unprocessed_args;

  /*
   * We want to ensure that any OR immediately beneath another OR gets
   * flattened into a single OR-list, so as to simplify later reasoning.
   *
   * To avoid stack overflow from recursion of eval_const_expressions, we
   * resort to some tenseness here: we keep a list of not-yet-processed
   * inputs, and handle flattening of nested ORs by prepending to the to-do
   * list instead of recursing.  Now that the parser generates N-argument
   * ORs from simple lists, this complexity is probably less necessary than
   * it once was, but we might as well keep the logic.
   */
  unprocessed_args = list_copy(args);
  while (unprocessed_args)
  {
    Node     *arg = (Node *) linitial(unprocessed_args);

    unprocessed_args = list_delete_first(unprocessed_args);

    /* flatten nested ORs as per above comment */
    if (is_orclause(arg))
    {
      List     *subargs = ((BoolExpr *) arg)->args;
      List     *oldlist = unprocessed_args;

      unprocessed_args = list_concat_copy(subargs, unprocessed_args);
      /* perhaps-overly-tense code to avoid leaking old lists */
      list_free(oldlist);
      continue;
    }

    /* If it's not an OR, simplify it */
    arg = eval_const_expressions_mutator(arg, context);

    /*
     * It is unlikely but not impossible for simplification of a non-OR
     * clause to produce an OR.  Recheck, but don't be too tense about it
     * since it's not a mainstream case.  In particular we don't worry
     * about const-simplifying the input twice, nor about list leakage.
     */
    if (is_orclause(arg))
    {
      List     *subargs = ((BoolExpr *) arg)->args;

      unprocessed_args = list_concat_copy(subargs, unprocessed_args);
      continue;
    }

    /*
     * OK, we have a const-simplified non-OR argument.  Process it per
     * comments above.
     */
    if (IsA(arg, Const))
    {
      Const    *const_input = (Const *) arg;

      if (const_input->constisnull)
        *haveNull = true;
      else if (DatumGetBool(const_input->constvalue))
      {
        *forceTrue = true;

        /*
         * Once we detect a TRUE result we can just exit the loop
         * immediately.  However, if we ever add a notion of
         * non-removable functions, we'd need to keep scanning.
         */
        return NIL;
      }
      /* otherwise, we can drop the constant-false input */
      continue;
    }

    /* else emit the simplified arg into the result list */
    newargs = lappend(newargs, arg);
  }

  return newargs;
}

/*
 * Subroutine for eval_const_expressions: process arguments of an AND clause
 *
 * This includes flattening of nested ANDs as well as recursion to
 * eval_const_expressions to simplify the AND arguments.
 *
 * After simplification, AND arguments are handled as follows:
 *    non constant: keep
 *    TRUE: drop (does not affect result)
 *    FALSE: force result to FALSE
 *    NULL: keep only one
 * We must keep one NULL input because AND expressions evaluate to NULL when
 * no input is FALSE and at least one is NULL.  We don't actually include the
 * NULL here, that's supposed to be done by the caller.
 *
 * The output arguments *haveNull and *forceFalse must be initialized false
 * by the caller.  They will be set true if a null constant or false constant,
 * respectively, is detected anywhere in the argument list.
 */
static List *
simplify_and_arguments(List *args,
             eval_const_expressions_context *context,
             bool *haveNull, bool *forceFalse)
{
  List     *newargs = NIL;
  List     *unprocessed_args;

  /* See comments in simplify_or_arguments */
  unprocessed_args = list_copy(args);
  while (unprocessed_args)
  {
    Node     *arg = (Node *) linitial(unprocessed_args);

    unprocessed_args = list_delete_first(unprocessed_args);

    /* flatten nested ANDs as per above comment */
    if (is_andclause(arg))
    {
      List     *subargs = ((BoolExpr *) arg)->args;
      List     *oldlist = unprocessed_args;

      unprocessed_args = list_concat_copy(subargs, unprocessed_args);
      /* perhaps-overly-tense code to avoid leaking old lists */
      list_free(oldlist);
      continue;
    }

    /* If it's not an AND, simplify it */
    arg = eval_const_expressions_mutator(arg, context);

    /*
     * It is unlikely but not impossible for simplification of a non-AND
     * clause to produce an AND.  Recheck, but don't be too tense about it
     * since it's not a mainstream case.  In particular we don't worry
     * about const-simplifying the input twice, nor about list leakage.
     */
    if (is_andclause(arg))
    {
      List     *subargs = ((BoolExpr *) arg)->args;

      unprocessed_args = list_concat_copy(subargs, unprocessed_args);
      continue;
    }

    /*
     * OK, we have a const-simplified non-AND argument.  Process it per
     * comments above.
     */
    if (IsA(arg, Const))
    {
      Const    *const_input = (Const *) arg;

      if (const_input->constisnull)
        *haveNull = true;
      else if (!DatumGetBool(const_input->constvalue))
      {
        *forceFalse = true;

        /*
         * Once we detect a FALSE result we can just exit the loop
         * immediately.  However, if we ever add a notion of
         * non-removable functions, we'd need to keep scanning.
         */
        return NIL;
      }
      /* otherwise, we can drop the constant-true input */
      continue;
    }

    /* else emit the simplified arg into the result list */
    newargs = lappend(newargs, arg);
  }

  return newargs;
}

/*
 * Subroutine for eval_const_expressions: try to simplify boolean equality
 * or inequality condition
 *
 * Inputs are the operator OID and the simplified arguments to the operator.
 * Returns a simplified expression if successful, or NULL if cannot
 * simplify the expression.
 *
 * The idea here is to reduce "x = true" to "x" and "x = false" to "NOT x",
 * or similarly "x <> true" to "NOT x" and "x <> false" to "x".
 * This is only marginally useful in itself, but doing it in constant folding
 * ensures that we will recognize these forms as being equivalent in, for
 * example, partial index matching.
 *
 * We come here only if simplify_function has failed; therefore we cannot
 * see two constant inputs, nor a constant-NULL input.
 */
static Node *
simplify_boolean_equality(Oid opno, List *args)
{
  Node     *leftop;
  Node     *rightop;

  Assert(list_length(args) == 2);
  leftop = linitial(args);
  rightop = lsecond(args);
  if (leftop && IsA(leftop, Const))
  {
    Assert(!((Const *) leftop)->constisnull);
    if (opno == BooleanEqualOperator)
    {
      if (DatumGetBool(((Const *) leftop)->constvalue))
        return rightop; /* true = foo */
      else
        return negate_clause(rightop); /* false = foo */
    }
    else
    {
      if (DatumGetBool(((Const *) leftop)->constvalue))
        return negate_clause(rightop); /* true <> foo */
      else
        return rightop; /* false <> foo */
    }
  }
  if (rightop && IsA(rightop, Const))
  {
    Assert(!((Const *) rightop)->constisnull);
    if (opno == BooleanEqualOperator)
    {
      if (DatumGetBool(((Const *) rightop)->constvalue))
        return leftop; /* foo = true */
      else
        return negate_clause(leftop); /* foo = false */
    }
    else
    {
      if (DatumGetBool(((Const *) rightop)->constvalue))
        return negate_clause(leftop); /* foo <> true */
      else
        return leftop; /* foo <> false */
    }
  }
  return NULL;
}

/*
 * Subroutine for eval_const_expressions: try to simplify a function call
 * (which might originally have been an operator; we don't care)
 *
 * Inputs are the function OID, actual result type OID (which is needed for
 * polymorphic functions), result typmod, result collation, the input
 * collation to use for the function, the original argument list (not
 * const-simplified yet, unless process_args is false), and some flags;
 * also the context data for eval_const_expressions.
 *
 * Returns a simplified expression if successful, or NULL if cannot
 * simplify the function call.
 *
 * This function is also responsible for converting named-notation argument
 * lists into positional notation and/or adding any needed default argument
 * expressions; which is a bit grotty, but it avoids extra fetches of the
 * function's pg_proc tuple.  For this reason, the args list is
 * pass-by-reference.  Conversion and const-simplification of the args list
 * will be done even if simplification of the function call itself is not
 * possible.
 */
static Expr *
simplify_function(Oid funcid, Oid result_type, int32 result_typmod,
          Oid result_collid, Oid input_collid, List **args_p,
          bool funcvariadic, bool process_args, bool allow_non_const,
          eval_const_expressions_context *context)
{
  List     *args = *args_p;
  HeapTuple func_tuple;
  Form_pg_proc func_form;
  Expr     *newexpr;

  /*
   * We have three strategies for simplification: execute the function to
   * deliver a constant result, use a transform function to generate a
   * substitute node tree, or expand in-line the body of the function
   * definition (which only works for simple SQL-language functions, but
   * that is a common case).  Each case needs access to the function's
   * pg_proc tuple, so fetch it just once.
   *
   * Note: the allow_non_const flag suppresses both the second and third
   * strategies; so if !allow_non_const, simplify_function can only return a
   * Const or NULL.  Argument-list rewriting happens anyway, though.
   */
  func_tuple = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
  if (!HeapTupleIsValid(func_tuple))
    elog(ERROR, "cache lookup failed for function %u", funcid);
  func_form = (Form_pg_proc) GETSTRUCT(func_tuple);

  /*
   * Process the function arguments, unless the caller did it already.
   *
   * Here we must deal with named or defaulted arguments, and then
   * recursively apply eval_const_expressions to the whole argument list.
   */
  if (process_args)
  {
    args = expand_function_arguments(args, false, result_type, func_tuple);
    args = (List *) expression_tree_mutator((Node *) args,
                        eval_const_expressions_mutator,
                        context);
    /* Argument processing done, give it back to the caller */
    *args_p = args;
  }

  /* Now attempt simplification of the function call proper. */

  newexpr = evaluate_function(funcid, result_type, result_typmod,
                result_collid, input_collid,
                args, funcvariadic,
                func_tuple, context);

  if (!newexpr && allow_non_const && OidIsValid(func_form->prosupport))
  {
    /*
     * Build a SupportRequestSimplify node to pass to the support
     * function, pointing to a dummy FuncExpr node containing the
     * simplified arg list.  We use this approach to present a uniform
     * interface to the support function regardless of how the target
     * function is actually being invoked.
     */
    SupportRequestSimplify req;
    FuncExpr  fexpr;

    fexpr.xpr.type = T_FuncExpr;
    fexpr.funcid = funcid;
    fexpr.funcresulttype = result_type;
    fexpr.funcretset = func_form->proretset;
    fexpr.funcvariadic = funcvariadic;
    fexpr.funcformat = COERCE_EXPLICIT_CALL;
    fexpr.funccollid = result_collid;
    fexpr.inputcollid = input_collid;
    fexpr.args = args;
    fexpr.location = -1;

    req.type = T_SupportRequestSimplify;
    req.root = context->root;
    req.fcall = &fexpr;

    newexpr = (Expr *)
      DatumGetPointer(OidFunctionCall1(func_form->prosupport,
                       PointerGetDatum(&req)));

    /* catch a possible API misunderstanding */
    Assert(newexpr != (Expr *) &fexpr);
  }

  if (!newexpr && allow_non_const)
    newexpr = inline_function(funcid, result_type, result_collid,
                  input_collid, args, funcvariadic,
                  func_tuple, context);

  ReleaseSysCache(func_tuple);

  return newexpr;
}

/*
 * expand_function_arguments: convert named-notation args to positional args
 * and/or insert default args, as needed
 *
 * Returns a possibly-transformed version of the args list.
 *
 * If include_out_arguments is true, then the args list and the result
 * include OUT arguments.
 *
 * The expected result type of the call must be given, for sanity-checking
 * purposes.  Also, we ask the caller to provide the function's actual
 * pg_proc tuple, not just its OID.
 *
 * If we need to change anything, the input argument list is copied, not
 * modified.
 *
 * Note: this gets applied to operator argument lists too, even though the
 * cases it handles should never occur there.  This should be OK since it
 * will fall through very quickly if there's nothing to do.
 */
List *
expand_function_arguments(List *args, bool include_out_arguments,
              Oid result_type, HeapTuple func_tuple)
{
  Form_pg_proc funcform = (Form_pg_proc) GETSTRUCT(func_tuple);
  Oid      *proargtypes = funcform->proargtypes.values;
  int     pronargs = funcform->pronargs;
  bool    has_named_args = false;
  ListCell   *lc;

  /*
   * If we are asked to match to OUT arguments, then use the proallargtypes
   * array (which includes those); otherwise use proargtypes (which
   * doesn't).  Of course, if proallargtypes is null, we always use
   * proargtypes.  (Fetching proallargtypes is annoyingly expensive
   * considering that we may have nothing to do here, but fortunately the
   * common case is include_out_arguments == false.)
   */
  if (include_out_arguments)
  {
    Datum   proallargtypes;
    bool    isNull;

    proallargtypes = SysCacheGetAttr(PROCOID, func_tuple,
                     Anum_pg_proc_proallargtypes,
                     &isNull);
    if (!isNull)
    {
      ArrayType  *arr = DatumGetArrayTypeP(proallargtypes);

      pronargs = ARR_DIMS(arr)[0];
      if (ARR_NDIM(arr) != 1 ||
        pronargs < 0 ||
        ARR_HASNULL(arr) ||
        ARR_ELEMTYPE(arr) != OIDOID)
        elog(ERROR, "proallargtypes is not a 1-D Oid array or it contains nulls");
      Assert(pronargs >= funcform->pronargs);
      proargtypes = (Oid *) ARR_DATA_PTR(arr);
    }
  }

  /* Do we have any named arguments? */
  foreach(lc, args)
  {
    Node     *arg = (Node *) lfirst(lc);

    if (IsA(arg, NamedArgExpr))
    {
      has_named_args = true;
      break;
    }
  }

  /* If so, we must apply reorder_function_arguments */
  if (has_named_args)
  {
    args = reorder_function_arguments(args, pronargs, func_tuple);
    /* Recheck argument types and add casts if needed */
    recheck_cast_function_args(args, result_type,
                   proargtypes, pronargs,
                   func_tuple);
  }
  else if (list_length(args) < pronargs)
  {
    /* No named args, but we seem to be short some defaults */
    args = add_function_defaults(args, pronargs, func_tuple);
    /* Recheck argument types and add casts if needed */
    recheck_cast_function_args(args, result_type,
                   proargtypes, pronargs,
                   func_tuple);
  }

  return args;
}

/*
 * reorder_function_arguments: convert named-notation args to positional args
 *
 * This function also inserts default argument values as needed, since it's
 * impossible to form a truly valid positional call without that.
 */
static List *
reorder_function_arguments(List *args, int pronargs, HeapTuple func_tuple)
{
  Form_pg_proc funcform = (Form_pg_proc) GETSTRUCT(func_tuple);
  int     nargsprovided = list_length(args);
  Node     *argarray[FUNC_MAX_ARGS];
  ListCell   *lc;
  int     i;

  Assert(nargsprovided <= pronargs);
  if (pronargs < 0 || pronargs > FUNC_MAX_ARGS)
    elog(ERROR, "too many function arguments");
  memset(argarray, 0, pronargs * sizeof(Node *));

  /* Deconstruct the argument list into an array indexed by argnumber */
  i = 0;
  foreach(lc, args)
  {
    Node     *arg = (Node *) lfirst(lc);

    if (!IsA(arg, NamedArgExpr))
    {
      /* positional argument, assumed to precede all named args */
      Assert(argarray[i] == NULL);
      argarray[i++] = arg;
    }
    else
    {
      NamedArgExpr *na = (NamedArgExpr *) arg;

      Assert(na->argnumber >= 0 && na->argnumber < pronargs);
      Assert(argarray[na->argnumber] == NULL);
      argarray[na->argnumber] = (Node *) na->arg;
    }
  }

  /*
   * Fetch default expressions, if needed, and insert into array at proper
   * locations (they aren't necessarily consecutive or all used)
   */
  if (nargsprovided < pronargs)
  {
    List     *defaults = fetch_function_defaults(func_tuple);

    i = pronargs - funcform->pronargdefaults;
    foreach(lc, defaults)
    {
      if (argarray[i] == NULL)
        argarray[i] = (Node *) lfirst(lc);
      i++;
    }
  }

  /* Now reconstruct the args list in proper order */
  args = NIL;
  for (i = 0; i < pronargs; i++)
  {
    Assert(argarray[i] != NULL);
    args = lappend(args, argarray[i]);
  }

  return args;
}

/*
 * add_function_defaults: add missing function arguments from its defaults
 *
 * This is used only when the argument list was positional to begin with,
 * and so we know we just need to add defaults at the end.
 */
static List *
add_function_defaults(List *args, int pronargs, HeapTuple func_tuple)
{
  int     nargsprovided = list_length(args);
  List     *defaults;
  int     ndelete;

  /* Get all the default expressions from the pg_proc tuple */
  defaults = fetch_function_defaults(func_tuple);

  /* Delete any unused defaults from the list */
  ndelete = nargsprovided + list_length(defaults) - pronargs;
  if (ndelete < 0)
    elog(ERROR, "not enough default arguments");
  if (ndelete > 0)
    defaults = list_delete_first_n(defaults, ndelete);

  /* And form the combined argument list, not modifying the input list */
  return list_concat_copy(args, defaults);
}

/*
 * fetch_function_defaults: get function's default arguments as expression list
 */
static List *
fetch_function_defaults(HeapTuple func_tuple)
{
  List     *defaults;
  Datum   proargdefaults;
  char     *str;

  proargdefaults = SysCacheGetAttrNotNull(PROCOID, func_tuple,
                      Anum_pg_proc_proargdefaults);
  str = TextDatumGetCString(proargdefaults);
  defaults = castNode(List, stringToNode(str));
  pfree(str);
  return defaults;
}

/*
 * recheck_cast_function_args: recheck function args and typecast as needed
 * after adding defaults.
 *
 * It is possible for some of the defaulted arguments to be polymorphic;
 * therefore we can't assume that the default expressions have the correct
 * data types already.  We have to re-resolve polymorphics and do coercion
 * just like the parser did.
 *
 * This should be a no-op if there are no polymorphic arguments,
 * but we do it anyway to be sure.
 *
 * Note: if any casts are needed, the args list is modified in-place;
 * caller should have already copied the list structure.
 */
static void
recheck_cast_function_args(List *args, Oid result_type,
               Oid *proargtypes, int pronargs,
               HeapTuple func_tuple)
{
  Form_pg_proc funcform = (Form_pg_proc) GETSTRUCT(func_tuple);
  int     nargs;
  Oid     actual_arg_types[FUNC_MAX_ARGS];
  Oid     declared_arg_types[FUNC_MAX_ARGS];
  Oid     rettype;
  ListCell   *lc;

  if (list_length(args) > FUNC_MAX_ARGS)
    elog(ERROR, "too many function arguments");
  nargs = 0;
  foreach(lc, args)
  {
    actual_arg_types[nargs++] = exprType((Node *) lfirst(lc));
  }
  Assert(nargs == pronargs);
  memcpy(declared_arg_types, proargtypes, pronargs * sizeof(Oid));
  rettype = enforce_generic_type_consistency(actual_arg_types,
                         declared_arg_types,
                         nargs,
                         funcform->prorettype,
                         false);
  /* let's just check we got the same answer as the parser did ... */
  if (rettype != result_type)
    elog(ERROR, "function's resolved result type changed during planning");

  /* perform any necessary typecasting of arguments */
  make_fn_arguments(NULL, args, actual_arg_types, declared_arg_types);
}

/*
 * evaluate_function: try to pre-evaluate a function call
 *
 * We can do this if the function is strict and has any constant-null inputs
 * (just return a null constant), or if the function is immutable and has all
 * constant inputs (call it and return the result as a Const node).  In
 * estimation mode we are willing to pre-evaluate stable functions too.
 *
 * Returns a simplified expression if successful, or NULL if cannot
 * simplify the function.
 */
static Expr *
evaluate_function(Oid funcid, Oid result_type, int32 result_typmod,
          Oid result_collid, Oid input_collid, List *args,
          bool funcvariadic,
          HeapTuple func_tuple,
          eval_const_expressions_context *context)
{
  Form_pg_proc funcform = (Form_pg_proc) GETSTRUCT(func_tuple);
  bool    has_nonconst_input = false;
  bool    has_null_input = false;
  ListCell   *arg;
  FuncExpr   *newexpr;

  /*
   * Can't simplify if it returns a set.
   */
  if (funcform->proretset)
    return NULL;

  /*
   * Can't simplify if it returns RECORD.  The immediate problem is that it
   * will be needing an expected tupdesc which we can't supply here.
   *
   * In the case where it has OUT parameters, we could build an expected
   * tupdesc from those, but there may be other gotchas lurking.  In
   * particular, if the function were to return NULL, we would produce a
   * null constant with no remaining indication of which concrete record
   * type it is.  For now, seems best to leave the function call unreduced.
   */
  if (funcform->prorettype == RECORDOID)
    return NULL;

  /*
   * Check for constant inputs and especially constant-NULL inputs.
   */
  foreach(arg, args)
  {
    if (IsA(lfirst(arg), Const))
      has_null_input |= ((Const *) lfirst(arg))->constisnull;
    else
      has_nonconst_input = true;
  }

  /*
   * If the function is strict and has a constant-NULL input, it will never
   * be called at all, so we can replace the call by a NULL constant, even
   * if there are other inputs that aren't constant, and even if the
   * function is not otherwise immutable.
   */
  if (funcform->proisstrict && has_null_input)
    return (Expr *) makeNullConst(result_type, result_typmod,
                    result_collid);

  /*
   * Otherwise, can simplify only if all inputs are constants. (For a
   * non-strict function, constant NULL inputs are treated the same as
   * constant non-NULL inputs.)
   */
  if (has_nonconst_input)
    return NULL;

  /*
   * Ordinarily we are only allowed to simplify immutable functions. But for
   * purposes of estimation, we consider it okay to simplify functions that
   * are merely stable; the risk that the result might change from planning
   * time to execution time is worth taking in preference to not being able
   * to estimate the value at all.
   */
  if (funcform->provolatile == PROVOLATILE_IMMUTABLE)
     /* okay */ ;
  else if (context->estimate && funcform->provolatile == PROVOLATILE_STABLE)
     /* okay */ ;
  else
    return NULL;

  /*
   * OK, looks like we can simplify this operator/function.
   *
   * Build a new FuncExpr node containing the already-simplified arguments.
   */
  newexpr = makeNode(FuncExpr);
  newexpr->funcid = funcid;
  newexpr->funcresulttype = result_type;
  newexpr->funcretset = false;
  newexpr->funcvariadic = funcvariadic;
  newexpr->funcformat = COERCE_EXPLICIT_CALL; /* doesn't matter */
  newexpr->funccollid = result_collid;  /* doesn't matter */
  newexpr->inputcollid = input_collid;
  newexpr->args = args;
  newexpr->location = -1;

  return evaluate_expr((Expr *) newexpr, result_type, result_typmod,
             result_collid);
}

/*
 * inline_function: try to expand a function call inline
 *
 * If the function is a sufficiently simple SQL-language function
 * (just "SELECT expression"), then we can inline it and avoid the rather
 * high per-call overhead of SQL functions.  Furthermore, this can expose
 * opportunities for constant-folding within the function expression.
 *
 * We have to beware of some special cases however.  A directly or
 * indirectly recursive function would cause us to recurse forever,
 * so we keep track of which functions we are already expanding and
 * do not re-expand them.  Also, if a parameter is used more than once
 * in the SQL-function body, we require it not to contain any volatile
 * functions (volatiles might deliver inconsistent answers) nor to be
 * unreasonably expensive to evaluate.  The expensiveness check not only
 * prevents us from doing multiple evaluations of an expensive parameter
 * at runtime, but is a safety value to limit growth of an expression due
 * to repeated inlining.
 *
 * We must also beware of changing the volatility or strictness status of
 * functions by inlining them.
 *
 * Also, at the moment we can't inline functions returning RECORD.  This
 * doesn't work in the general case because it discards information such
 * as OUT-parameter declarations.
 *
 * Also, context-dependent expression nodes in the argument list are trouble.
 *
 * Returns a simplified expression if successful, or NULL if cannot
 * simplify the function.
 */
static Expr *
inline_function(Oid funcid, Oid result_type, Oid result_collid,
        Oid input_collid, List *args,
        bool funcvariadic,
        HeapTuple func_tuple,
        eval_const_expressions_context *context)
{
  Form_pg_proc funcform = (Form_pg_proc) GETSTRUCT(func_tuple);
  char     *src;
  Datum   tmp;
  bool    isNull;
  MemoryContext oldcxt;
  MemoryContext mycxt;
  inline_error_callback_arg callback_arg;
  ErrorContextCallback sqlerrcontext;
  FuncExpr   *fexpr;
  SQLFunctionParseInfoPtr pinfo;
  TupleDesc rettupdesc;
  ParseState *pstate;
  List     *raw_parsetree_list;
  List     *querytree_list;
  Query    *querytree;
  Node     *newexpr;
  int      *usecounts;
  ListCell   *arg;
  int     i;

  /*
   * Forget it if the function is not SQL-language or has other showstopper
   * properties.  (The prokind and nargs checks are just paranoia.)
   */
  if (funcform->prolang != SQLlanguageId ||
    funcform->prokind != PROKIND_FUNCTION ||
    funcform->prosecdef ||
    funcform->proretset ||
    funcform->prorettype == RECORDOID ||
    !heap_attisnull(func_tuple, Anum_pg_proc_proconfig, NULL) ||
    funcform->pronargs != list_length(args))
    return NULL;

  /* Check for recursive function, and give up trying to expand if so */
  if (list_member_oid(context->active_fns, funcid))
    return NULL;

  /* Check permission to call function (fail later, if not) */
  if (object_aclcheck(ProcedureRelationId, funcid, GetUserId(), ACL_EXECUTE) != ACLCHECK_OK)
    return NULL;

  /* Check whether a plugin wants to hook function entry/exit */
  if (FmgrHookIsNeeded(funcid))
    return NULL;

  /*
   * Make a temporary memory context, so that we don't leak all the stuff
   * that parsing might create.
   */
  mycxt = AllocSetContextCreate(CurrentMemoryContext,
                  "inline_function",
                  ALLOCSET_DEFAULT_SIZES);
  oldcxt = MemoryContextSwitchTo(mycxt);

  /*
   * We need a dummy FuncExpr node containing the already-simplified
   * arguments.  (In some cases we don't really need it, but building it is
   * cheap enough that it's not worth contortions to avoid.)
   */
  fexpr = makeNode(FuncExpr);
  fexpr->funcid = funcid;
  fexpr->funcresulttype = result_type;
  fexpr->funcretset = false;
  fexpr->funcvariadic = funcvariadic;
  fexpr->funcformat = COERCE_EXPLICIT_CALL; /* doesn't matter */
  fexpr->funccollid = result_collid;  /* doesn't matter */
  fexpr->inputcollid = input_collid;
  fexpr->args = args;
  fexpr->location = -1;

  /* Fetch the function body */
  tmp = SysCacheGetAttrNotNull(PROCOID, func_tuple, Anum_pg_proc_prosrc);
  src = TextDatumGetCString(tmp);

  /*
   * Setup error traceback support for ereport().  This is so that we can
   * finger the function that bad information came from.
   */
  callback_arg.proname = NameStr(funcform->proname);
  callback_arg.prosrc = src;

  sqlerrcontext.callback = sql_inline_error_callback;
  sqlerrcontext.arg = &callback_arg;
  sqlerrcontext.previous = error_context_stack;
  error_context_stack = &sqlerrcontext;

  /* If we have prosqlbody, pay attention to that not prosrc */
  tmp = SysCacheGetAttr(PROCOID,
              func_tuple,
              Anum_pg_proc_prosqlbody,
              &isNull);
  if (!isNull)
  {
    Node     *n;
    List     *query_list;

    n = stringToNode(TextDatumGetCString(tmp));
    if (IsA(n, List))
      query_list = linitial_node(List, castNode(List, n));
    else
      query_list = list_make1(n);
    if (list_length(query_list) != 1)
      goto fail;
    querytree = linitial(query_list);

    /*
     * Because we'll insist below that the querytree have an empty rtable
     * and no sublinks, it cannot have any relation references that need
     * to be locked or rewritten.  So we can omit those steps.
     */
  }
  else
  {
    /* Set up to handle parameters while parsing the function body. */
    pinfo = prepare_sql_fn_parse_info(func_tuple,
                      (Node *) fexpr,
                      input_collid);

    /*
     * We just do parsing and parse analysis, not rewriting, because
     * rewriting will not affect table-free-SELECT-only queries, which is
     * all that we care about.  Also, we can punt as soon as we detect
     * more than one command in the function body.
     */
    raw_parsetree_list = pg_parse_query(src);
    if (list_length(raw_parsetree_list) != 1)
      goto fail;

    pstate = make_parsestate(NULL);
    pstate->p_sourcetext = src;
    sql_fn_parser_setup(pstate, pinfo);

    querytree = transformTopLevelStmt(pstate, linitial(raw_parsetree_list));

    free_parsestate(pstate);
  }

  /*
   * The single command must be a simple "SELECT expression".
   *
   * Note: if you change the tests involved in this, see also plpgsql's
   * exec_simple_check_plan().  That generally needs to have the same idea
   * of what's a "simple expression", so that inlining a function that
   * previously wasn't inlined won't change plpgsql's conclusion.
   */
  if (!IsA(querytree, Query) ||
    querytree->commandType != CMD_SELECT ||
    querytree->hasAggs ||
    querytree->hasWindowFuncs ||
    querytree->hasTargetSRFs ||
    querytree->hasSubLinks ||
    querytree->cteList ||
    querytree->rtable ||
    querytree->jointree->fromlist ||
    querytree->jointree->quals ||
    querytree->groupClause ||
    querytree->groupingSets ||
    querytree->havingQual ||
    querytree->windowClause ||
    querytree->distinctClause ||
    querytree->sortClause ||
    querytree->limitOffset ||
    querytree->limitCount ||
    querytree->setOperations ||
    list_length(querytree->targetList) != 1)
    goto fail;

  /* If the function result is composite, resolve it */
  (void) get_expr_result_type((Node *) fexpr,
                NULL,
                &rettupdesc);

  /*
   * Make sure the function (still) returns what it's declared to.  This
   * will raise an error if wrong, but that's okay since the function would
   * fail at runtime anyway.  Note that check_sql_fn_retval will also insert
   * a coercion if needed to make the tlist expression match the declared
   * type of the function.
   *
   * Note: we do not try this until we have verified that no rewriting was
   * needed; that's probably not important, but let's be careful.
   */
  querytree_list = list_make1(querytree);
  if (check_sql_fn_retval(list_make1(querytree_list),
              result_type, rettupdesc,
              funcform->prokind,
              false))
    goto fail;       /* reject whole-tuple-result cases */

  /*
   * Given the tests above, check_sql_fn_retval shouldn't have decided to
   * inject a projection step, but let's just make sure.
   */
  if (querytree != linitial(querytree_list))
    goto fail;

  /* Now we can grab the tlist expression */
  newexpr = (Node *) ((TargetEntry *) linitial(querytree->targetList))->expr;

  /*
   * If the SQL function returns VOID, we can only inline it if it is a
   * SELECT of an expression returning VOID (ie, it's just a redirection to
   * another VOID-returning function).  In all non-VOID-returning cases,
   * check_sql_fn_retval should ensure that newexpr returns the function's
   * declared result type, so this test shouldn't fail otherwise; but we may
   * as well cope gracefully if it does.
   */
  if (exprType(newexpr) != result_type)
    goto fail;

  /*
   * Additional validity checks on the expression.  It mustn't be more
   * volatile than the surrounding function (this is to avoid breaking hacks
   * that involve pretending a function is immutable when it really ain't).
   * If the surrounding function is declared strict, then the expression
   * must contain only strict constructs and must use all of the function
   * parameters (this is overkill, but an exact analysis is hard).
   */
  if (funcform->provolatile == PROVOLATILE_IMMUTABLE &&
    contain_mutable_functions(newexpr))
    goto fail;
  else if (funcform->provolatile == PROVOLATILE_STABLE &&
       contain_volatile_functions(newexpr))
    goto fail;

  if (funcform->proisstrict &&
    contain_nonstrict_functions(newexpr))
    goto fail;

  /*
   * If any parameter expression contains a context-dependent node, we can't
   * inline, for fear of putting such a node into the wrong context.
   */
  if (contain_context_dependent_node((Node *) args))
    goto fail;

  /*
   * We may be able to do it; there are still checks on parameter usage to
   * make, but those are most easily done in combination with the actual
   * substitution of the inputs.  So start building expression with inputs
   * substituted.
   */
  usecounts = (int *) palloc0(funcform->pronargs * sizeof(int));
  newexpr = substitute_actual_parameters(newexpr, funcform->pronargs,
                       args, usecounts);

  /* Now check for parameter usage */
  i = 0;
  foreach(arg, args)
  {
    Node     *param = lfirst(arg);

    if (usecounts[i] == 0)
    {
      /* Param not used at all: uncool if func is strict */
      if (funcform->proisstrict)
        goto fail;
    }
    else if (usecounts[i] != 1)
    {
      /* Param used multiple times: uncool if expensive or volatile */
      QualCost  eval_cost;

      /*
       * We define "expensive" as "contains any subplan or more than 10
       * operators".  Note that the subplan search has to be done
       * explicitly, since cost_qual_eval() will barf on unplanned
       * subselects.
       */
      if (contain_subplans(param))
        goto fail;
      cost_qual_eval(&eval_cost, list_make1(param), NULL);
      if (eval_cost.startup + eval_cost.per_tuple >
        10 * cpu_operator_cost)
        goto fail;

      /*
       * Check volatility last since this is more expensive than the
       * above tests
       */
      if (contain_volatile_functions(param))
        goto fail;
    }
    i++;
  }

  /*
   * Whew --- we can make the substitution.  Copy the modified expression
   * out of the temporary memory context, and clean up.
   */
  MemoryContextSwitchTo(oldcxt);

  newexpr = copyObject(newexpr);

  MemoryContextDelete(mycxt);

  /*
   * If the result is of a collatable type, force the result to expose the
   * correct collation.  In most cases this does not matter, but it's
   * possible that the function result is used directly as a sort key or in
   * other places where we expect exprCollation() to tell the truth.
   */
  if (OidIsValid(result_collid))
  {
    Oid     exprcoll = exprCollation(newexpr);

    if (OidIsValid(exprcoll) && exprcoll != result_collid)
    {
      CollateExpr *newnode = makeNode(CollateExpr);

      newnode->arg = (Expr *) newexpr;
      newnode->collOid = result_collid;
      newnode->location = -1;

      newexpr = (Node *) newnode;
    }
  }

  /*
   * Since there is now no trace of the function in the plan tree, we must
   * explicitly record the plan's dependency on the function.
   */
  if (context->root)
    record_plan_function_dependency(context->root, funcid);

  /*
   * Recursively try to simplify the modified expression.  Here we must add
   * the current function to the context list of active functions.
   */
  context->active_fns = lappend_oid(context->active_fns, funcid);
  newexpr = eval_const_expressions_mutator(newexpr, context);
  context->active_fns = list_delete_last(context->active_fns);

  error_context_stack = sqlerrcontext.previous;

  return (Expr *) newexpr;

  /* Here if func is not inlinable: release temp memory and return NULL */
fail:
  MemoryContextSwitchTo(oldcxt);
  MemoryContextDelete(mycxt);
  error_context_stack = sqlerrcontext.previous;

  return NULL;
}

/*
 * Replace Param nodes by appropriate actual parameters
 */
static Node *
substitute_actual_parameters(Node *expr, int nargs, List *args,
               int *usecounts)
{
  substitute_actual_parameters_context context;

  context.nargs = nargs;
  context.args = args;
  context.usecounts = usecounts;

  return substitute_actual_parameters_mutator(expr, &context);
}

static Node *
substitute_actual_parameters_mutator(Node *node,
                   substitute_actual_parameters_context *context)
{
  if (node == NULL)
    return NULL;
  if (IsA(node, Param))
  {
    Param    *param = (Param *) node;

    if (param->paramkind != PARAM_EXTERN)
      elog(ERROR, "unexpected paramkind: %d", (int) param->paramkind);
    if (param->paramid <= 0 || param->paramid > context->nargs)
      elog(ERROR, "invalid paramid: %d", param->paramid);

    /* Count usage of parameter */
    context->usecounts[param->paramid - 1]++;

    /* Select the appropriate actual arg and replace the Param with it */
    /* We don't need to copy at this time (it'll get done later) */
    return list_nth(context->args, param->paramid - 1);
  }
  return expression_tree_mutator(node, substitute_actual_parameters_mutator, context);
}

/*
 * error context callback to let us supply a call-stack traceback
 */
static void
sql_inline_error_callback(void *arg)
{
  inline_error_callback_arg *callback_arg = (inline_error_callback_arg *) arg;
  int     syntaxerrposition;

  /* If it's a syntax error, convert to internal syntax error report */
  syntaxerrposition = geterrposition();
  if (syntaxerrposition > 0)
  {
    errposition(0);
    internalerrposition(syntaxerrposition);
    internalerrquery(callback_arg->prosrc);
  }

  errcontext("SQL function \"%s\" during inlining", callback_arg->proname);
}

/*
 * evaluate_expr: pre-evaluate a constant expression
 *
 * We use the executor's routine ExecEvalExpr() to avoid duplication of
 * code and ensure we get the same result as the executor would get.
 */
Expr *
evaluate_expr(Expr *expr, Oid result_type, int32 result_typmod,
        Oid result_collation)
{
  EState     *estate;
  ExprState  *exprstate;
  MemoryContext oldcontext;
  Datum   const_val;
  bool    const_is_null;
  int16   resultTypLen;
  bool    resultTypByVal;

  /*
   * To use the executor, we need an EState.
   */
  estate = CreateExecutorState();

  /* We can use the estate's working context to avoid memory leaks. */
  oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);

  /* Make sure any opfuncids are filled in. */
  fix_opfuncids((Node *) expr);

  /*
   * Prepare expr for execution.  (Note: we can't use ExecPrepareExpr
   * because it'd result in recursively invoking eval_const_expressions.)
   */
  exprstate = ExecInitExpr(expr, NULL);

  /*
   * And evaluate it.
   *
   * It is OK to use a default econtext because none of the ExecEvalExpr()
   * code used in this situation will use econtext.  That might seem
   * fortuitous, but it's not so unreasonable --- a constant expression does
   * not depend on context, by definition, n'est ce pas?
   */
  const_val = ExecEvalExprSwitchContext(exprstate,
                      GetPerTupleExprContext(estate),
                      &const_is_null);

  /* Get info needed about result datatype */
  get_typlenbyval(result_type, &resultTypLen, &resultTypByVal);

  /* Get back to outer memory context */
  MemoryContextSwitchTo(oldcontext);

  /*
   * Must copy result out of sub-context used by expression eval.
   *
   * Also, if it's varlena, forcibly detoast it.  This protects us against
   * storing TOAST pointers into plans that might outlive the referenced
   * data.  (makeConst would handle detoasting anyway, but it's worth a few
   * extra lines here so that we can do the copy and detoast in one step.)
   */
  if (!const_is_null)
  {
    if (resultTypLen == -1)
      const_val = PointerGetDatum(PG_DETOAST_DATUM_COPY(const_val));
    else
      const_val = datumCopy(const_val, resultTypByVal, resultTypLen);
  }

  /* Release all the junk we just created */
  FreeExecutorState(estate);

  /*
   * Make the constant result node.
   */
  return (Expr *) makeConst(result_type, result_typmod, result_collation,
                resultTypLen,
                const_val, const_is_null,
                resultTypByVal);
}


/*
 * inline_set_returning_function
 *    Attempt to "inline" a set-returning function in the FROM clause.
 *
 * "rte" is an RTE_FUNCTION rangetable entry.  If it represents a call of a
 * set-returning SQL function that can safely be inlined, expand the function
 * and return the substitute Query structure.  Otherwise, return NULL.
 *
 * We assume that the RTE's expression has already been put through
 * eval_const_expressions(), which among other things will take care of
 * default arguments and named-argument notation.
 *
 * This has a good deal of similarity to inline_function(), but that's
 * for the non-set-returning case, and there are enough differences to
 * justify separate functions.
 */
Query *
inline_set_returning_function(PlannerInfo *root, RangeTblEntry *rte)
{
  RangeTblFunction *rtfunc;
  FuncExpr   *fexpr;
  Oid     func_oid;
  HeapTuple func_tuple;
  Form_pg_proc funcform;
  char     *src;
  Datum   tmp;
  bool    isNull;
  MemoryContext oldcxt;
  MemoryContext mycxt;
  inline_error_callback_arg callback_arg;
  ErrorContextCallback sqlerrcontext;
  SQLFunctionParseInfoPtr pinfo;
  TypeFuncClass functypclass;
  TupleDesc rettupdesc;
  List     *raw_parsetree_list;
  List     *querytree_list;
  Query    *querytree;

  Assert(rte->rtekind == RTE_FUNCTION);

  /*
   * It doesn't make a lot of sense for a SQL SRF to refer to itself in its
   * own FROM clause, since that must cause infinite recursion at runtime.
   * It will cause this code to recurse too, so check for stack overflow.
   * (There's no need to do more.)
   */
  check_stack_depth();

  /* Fail if the RTE has ORDINALITY - we don't implement that here. */
  if (rte->funcordinality)
    return NULL;

  /* Fail if RTE isn't a single, simple FuncExpr */
  if (list_length(rte->functions) != 1)
    return NULL;
  rtfunc = (RangeTblFunction *) linitial(rte->functions);

  if (!IsA(rtfunc->funcexpr, FuncExpr))
    return NULL;
  fexpr = (FuncExpr *) rtfunc->funcexpr;

  func_oid = fexpr->funcid;

  /*
   * The function must be declared to return a set, else inlining would
   * change the results if the contained SELECT didn't return exactly one
   * row.
   */
  if (!fexpr->funcretset)
    return NULL;

  /*
   * Refuse to inline if the arguments contain any volatile functions or
   * sub-selects.  Volatile functions are rejected because inlining may
   * result in the arguments being evaluated multiple times, risking a
   * change in behavior.  Sub-selects are rejected partly for implementation
   * reasons (pushing them down another level might change their behavior)
   * and partly because they're likely to be expensive and so multiple
   * evaluation would be bad.
   */
  if (contain_volatile_functions((Node *) fexpr->args) ||
    contain_subplans((Node *) fexpr->args))
    return NULL;

  /* Check permission to call function (fail later, if not) */
  if (object_aclcheck(ProcedureRelationId, func_oid, GetUserId(), ACL_EXECUTE) != ACLCHECK_OK)
    return NULL;

  /* Check whether a plugin wants to hook function entry/exit */
  if (FmgrHookIsNeeded(func_oid))
    return NULL;

  /*
   * OK, let's take a look at the function's pg_proc entry.
   */
  func_tuple = SearchSysCache1(PROCOID, ObjectIdGetDatum(func_oid));
  if (!HeapTupleIsValid(func_tuple))
    elog(ERROR, "cache lookup failed for function %u", func_oid);
  funcform = (Form_pg_proc) GETSTRUCT(func_tuple);

  /*
   * Forget it if the function is not SQL-language or has other showstopper
   * properties.  In particular it mustn't be declared STRICT, since we
   * couldn't enforce that.  It also mustn't be VOLATILE, because that is
   * supposed to cause it to be executed with its own snapshot, rather than
   * sharing the snapshot of the calling query.  We also disallow returning
   * SETOF VOID, because inlining would result in exposing the actual result
   * of the function's last SELECT, which should not happen in that case.
   * (Rechecking prokind, proretset, and pronargs is just paranoia.)
   */
  if (funcform->prolang != SQLlanguageId ||
    funcform->prokind != PROKIND_FUNCTION ||
    funcform->proisstrict ||
    funcform->provolatile == PROVOLATILE_VOLATILE ||
    funcform->prorettype == VOIDOID ||
    funcform->prosecdef ||
    !funcform->proretset ||
    list_length(fexpr->args) != funcform->pronargs ||
    !heap_attisnull(func_tuple, Anum_pg_proc_proconfig, NULL))
  {
    ReleaseSysCache(func_tuple);
    return NULL;
  }

  /*
   * Make a temporary memory context, so that we don't leak all the stuff
   * that parsing might create.
   */
  mycxt = AllocSetContextCreate(CurrentMemoryContext,
                  "inline_set_returning_function",
                  ALLOCSET_DEFAULT_SIZES);
  oldcxt = MemoryContextSwitchTo(mycxt);

  /* Fetch the function body */
  tmp = SysCacheGetAttrNotNull(PROCOID, func_tuple, Anum_pg_proc_prosrc);
  src = TextDatumGetCString(tmp);

  /*
   * Setup error traceback support for ereport().  This is so that we can
   * finger the function that bad information came from.
   */
  callback_arg.proname = NameStr(funcform->proname);
  callback_arg.prosrc = src;

  sqlerrcontext.callback = sql_inline_error_callback;
  sqlerrcontext.arg = &callback_arg;
  sqlerrcontext.previous = error_context_stack;
  error_context_stack = &sqlerrcontext;

  /* If we have prosqlbody, pay attention to that not prosrc */
  tmp = SysCacheGetAttr(PROCOID,
              func_tuple,
              Anum_pg_proc_prosqlbody,
              &isNull);
  if (!isNull)
  {
    Node     *n;

    n = stringToNode(TextDatumGetCString(tmp));
    if (IsA(n, List))
      querytree_list = linitial_node(List, castNode(List, n));
    else
      querytree_list = list_make1(n);
    if (list_length(querytree_list) != 1)
      goto fail;
    querytree = linitial(querytree_list);

    /* Acquire necessary locks, then apply rewriter. */
    AcquireRewriteLocks(querytree, true, false);
    querytree_list = pg_rewrite_query(querytree);
    if (list_length(querytree_list) != 1)
      goto fail;
    querytree = linitial(querytree_list);
  }
  else
  {
    /*
     * Set up to handle parameters while parsing the function body.  We
     * can use the FuncExpr just created as the input for
     * prepare_sql_fn_parse_info.
     */
    pinfo = prepare_sql_fn_parse_info(func_tuple,
                      (Node *) fexpr,
                      fexpr->inputcollid);

    /*
     * Parse, analyze, and rewrite (unlike inline_function(), we can't
     * skip rewriting here).  We can fail as soon as we find more than one
     * query, though.
     */
    raw_parsetree_list = pg_parse_query(src);
    if (list_length(raw_parsetree_list) != 1)
      goto fail;

    querytree_list = pg_analyze_and_rewrite_withcb(linitial(raw_parsetree_list),
                             src,
                             (ParserSetupHook) sql_fn_parser_setup,
                             pinfo, NULL);
    if (list_length(querytree_list) != 1)
      goto fail;
    querytree = linitial(querytree_list);
  }

  /*
   * Also resolve the actual function result tupdesc, if composite.  If we
   * have a coldeflist, believe that; otherwise use get_expr_result_type.
   * (This logic should match ExecInitFunctionScan.)
   */
  if (rtfunc->funccolnames != NIL)
  {
    functypclass = TYPEFUNC_RECORD;
    rettupdesc = BuildDescFromLists(rtfunc->funccolnames,
                    rtfunc->funccoltypes,
                    rtfunc->funccoltypmods,
                    rtfunc->funccolcollations);
  }
  else
    functypclass = get_expr_result_type((Node *) fexpr, NULL, &rettupdesc);

  /*
   * The single command must be a plain SELECT.
   */
  if (!IsA(querytree, Query) ||
    querytree->commandType != CMD_SELECT)
    goto fail;

  /*
   * Make sure the function (still) returns what it's declared to.  This
   * will raise an error if wrong, but that's okay since the function would
   * fail at runtime anyway.  Note that check_sql_fn_retval will also insert
   * coercions if needed to make the tlist expression(s) match the declared
   * type of the function.  We also ask it to insert dummy NULL columns for
   * any dropped columns in rettupdesc, so that the elements of the modified
   * tlist match up to the attribute numbers.
   *
   * If the function returns a composite type, don't inline unless the check
   * shows it's returning a whole tuple result; otherwise what it's
   * returning is a single composite column which is not what we need.
   */
  if (!check_sql_fn_retval(list_make1(querytree_list),
               fexpr->funcresulttype, rettupdesc,
               funcform->prokind,
               true) &&
    (functypclass == TYPEFUNC_COMPOSITE ||
     functypclass == TYPEFUNC_COMPOSITE_DOMAIN ||
     functypclass == TYPEFUNC_RECORD))
    goto fail;       /* reject not-whole-tuple-result cases */

  /*
   * check_sql_fn_retval might've inserted a projection step, but that's
   * fine; just make sure we use the upper Query.
   */
  querytree = linitial_node(Query, querytree_list);

  /*
   * Looks good --- substitute parameters into the query.
   */
  querytree = substitute_actual_srf_parameters(querytree,
                         funcform->pronargs,
                         fexpr->args);

  /*
   * Copy the modified query out of the temporary memory context, and clean
   * up.
   */
  MemoryContextSwitchTo(oldcxt);

  querytree = copyObject(querytree);

  MemoryContextDelete(mycxt);
  error_context_stack = sqlerrcontext.previous;
  ReleaseSysCache(func_tuple);

  /*
   * We don't have to fix collations here because the upper query is already
   * parsed, ie, the collations in the RTE are what count.
   */

  /*
   * Since there is now no trace of the function in the plan tree, we must
   * explicitly record the plan's dependency on the function.
   */
  record_plan_function_dependency(root, func_oid);

  /*
   * We must also notice if the inserted query adds a dependency on the
   * calling role due to RLS quals.
   */
  if (querytree->hasRowSecurity)
    root->glob->dependsOnRole = true;

  return querytree;

  /* Here if func is not inlinable: release temp memory and return NULL */
fail:
  MemoryContextSwitchTo(oldcxt);
  MemoryContextDelete(mycxt);
  error_context_stack = sqlerrcontext.previous;
  ReleaseSysCache(func_tuple);

  return NULL;
}

/*
 * Replace Param nodes by appropriate actual parameters
 *
 * This is just enough different from substitute_actual_parameters()
 * that it needs its own code.
 */
static Query *
substitute_actual_srf_parameters(Query *expr, int nargs, List *args)
{
  substitute_actual_srf_parameters_context context;

  context.nargs = nargs;
  context.args = args;
  context.sublevels_up = 1;

  return query_tree_mutator(expr,
                substitute_actual_srf_parameters_mutator,
                &context,
                0);
}

static Node *
substitute_actual_srf_parameters_mutator(Node *node,
                     substitute_actual_srf_parameters_context *context)
{
  Node     *result;

  if (node == NULL)
    return NULL;
  if (IsA(node, Query))
  {
    context->sublevels_up++;
    result = (Node *) query_tree_mutator((Query *) node,
                       substitute_actual_srf_parameters_mutator,
                       context,
                       0);
    context->sublevels_up--;
    return result;
  }
  if (IsA(node, Param))
  {
    Param    *param = (Param *) node;

    if (param->paramkind == PARAM_EXTERN)
    {
      if (param->paramid <= 0 || param->paramid > context->nargs)
        elog(ERROR, "invalid paramid: %d", param->paramid);

      /*
       * Since the parameter is being inserted into a subquery, we must
       * adjust levels.
       */
      result = copyObject(list_nth(context->args, param->paramid - 1));
      IncrementVarSublevelsUp(result, context->sublevels_up, 0);
      return result;
    }
  }
  return expression_tree_mutator(node,
                   substitute_actual_srf_parameters_mutator,
                   context);
}

/*
 * pull_paramids
 *    Returns a Bitmapset containing the paramids of all Params in 'expr'.
 */
Bitmapset *
pull_paramids(Expr *expr)
{
  Bitmapset  *result = NULL;

  (void) pull_paramids_walker((Node *) expr, &result);

  return result;
}

static bool
pull_paramids_walker(Node *node, Bitmapset **context)
{
  if (node == NULL)
    return false;
  if (IsA(node, Param))
  {
    Param    *param = (Param *) node;

    *context = bms_add_member(*context, param->paramid);
    return false;
  }
  return expression_tree_walker(node, pull_paramids_walker, context);
}

/*
 * Build ScalarArrayOpExpr on top of 'exprs.' 'haveNonConst' indicates
 * whether at least one of the expressions is not Const.  When it's false,
 * the array constant is built directly; otherwise, we have to build a child
 * ArrayExpr. The 'exprs' list gets freed if not directly used in the output
 * expression tree.
 */
ScalarArrayOpExpr *
make_SAOP_expr(Oid oper, Node *leftexpr, Oid coltype, Oid arraycollid,
         Oid inputcollid, List *exprs, bool haveNonConst)
{
  Node     *arrayNode = NULL;
  ScalarArrayOpExpr *saopexpr = NULL;
  Oid     arraytype = get_array_type(coltype);

  if (!OidIsValid(arraytype))
    return NULL;

  /*
   * Assemble an array from the list of constants.  It seems more profitable
   * to build a const array.  But in the presence of other nodes, we don't
   * have a specific value here and must employ an ArrayExpr instead.
   */
  if (haveNonConst)
  {
    ArrayExpr  *arrayExpr = makeNode(ArrayExpr);

    /* array_collid will be set by parse_collate.c */
    arrayExpr->element_typeid = coltype;
    arrayExpr->array_typeid = arraytype;
    arrayExpr->multidims = false;
    arrayExpr->elements = exprs;
    arrayExpr->location = -1;

    arrayNode = (Node *) arrayExpr;
  }
  else
  {
    int16   typlen;
    bool    typbyval;
    char    typalign;
    Datum    *elems;
    bool     *nulls;
    int     i = 0;
    ArrayType  *arrayConst;
    int     dims[1] = {list_length(exprs)};
    int     lbs[1] = {1};

    get_typlenbyvalalign(coltype, &typlen, &typbyval, &typalign);

    elems = (Datum *) palloc(sizeof(Datum) * list_length(exprs));
    nulls = (bool *) palloc(sizeof(bool) * list_length(exprs));
    foreach_node(Const, value, exprs)
    {
      elems[i] = value->constvalue;
      nulls[i++] = value->constisnull;
    }

    arrayConst = construct_md_array(elems, nulls, 1, dims, lbs,
                    coltype, typlen, typbyval, typalign);
    arrayNode = (Node *) makeConst(arraytype, -1, arraycollid,
                     -1, PointerGetDatum(arrayConst),
                     false, false);

    pfree(elems);
    pfree(nulls);
    list_free(exprs);
  }

  /* Build the SAOP expression node */
  saopexpr = makeNode(ScalarArrayOpExpr);
  saopexpr->opno = oper;
  saopexpr->opfuncid = get_opcode(oper);
  saopexpr->hashfuncid = InvalidOid;
  saopexpr->negfuncid = InvalidOid;
  saopexpr->useOr = true;
  saopexpr->inputcollid = inputcollid;
  saopexpr->args = list_make2(leftexpr, arrayNode);
  saopexpr->location = -1;

  return saopexpr;
}

Coverage Report

Created: 2025-06-15 06:31