/src/postgres/src/backend/parser/parse_clause.c

Source
/*-------------------------------------------------------------------------
 *
 * parse_clause.c
 *    handle clauses in parser
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/parser/parse_clause.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "access/htup_details.h"
#include "access/nbtree.h"
#include "access/table.h"
#include "access/tsmapi.h"
#include "catalog/catalog.h"
#include "catalog/pg_am.h"
#include "catalog/pg_amproc.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_type.h"
#include "commands/defrem.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/optimizer.h"
#include "parser/analyze.h"
#include "parser/parse_clause.h"
#include "parser/parse_coerce.h"
#include "parser/parse_collate.h"
#include "parser/parse_expr.h"
#include "parser/parse_func.h"
#include "parser/parse_oper.h"
#include "parser/parse_relation.h"
#include "parser/parse_target.h"
#include "parser/parse_type.h"
#include "parser/parser.h"
#include "rewrite/rewriteManip.h"
#include "utils/builtins.h"
#include "utils/catcache.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "utils/syscache.h"


static int  extractRemainingColumns(ParseState *pstate,
                  ParseNamespaceColumn *src_nscolumns,
                  List *src_colnames,
                  List **src_colnos,
                  List **res_colnames, List **res_colvars,
                  ParseNamespaceColumn *res_nscolumns);
static Node *transformJoinUsingClause(ParseState *pstate,
                    List *leftVars, List *rightVars);
static Node *transformJoinOnClause(ParseState *pstate, JoinExpr *j,
                   List *namespace);
static ParseNamespaceItem *transformTableEntry(ParseState *pstate, RangeVar *r);
static ParseNamespaceItem *transformRangeSubselect(ParseState *pstate,
                           RangeSubselect *r);
static ParseNamespaceItem *transformRangeFunction(ParseState *pstate,
                          RangeFunction *r);
static ParseNamespaceItem *transformRangeTableFunc(ParseState *pstate,
                           RangeTableFunc *rtf);
static TableSampleClause *transformRangeTableSample(ParseState *pstate,
                          RangeTableSample *rts);
static ParseNamespaceItem *getNSItemForSpecialRelationTypes(ParseState *pstate,
                              RangeVar *rv);
static Node *transformFromClauseItem(ParseState *pstate, Node *n,
                   ParseNamespaceItem **top_nsitem,
                   List **namespace);
static Var *buildVarFromNSColumn(ParseState *pstate,
                 ParseNamespaceColumn *nscol);
static Node *buildMergedJoinVar(ParseState *pstate, JoinType jointype,
                Var *l_colvar, Var *r_colvar);
static void markRelsAsNulledBy(ParseState *pstate, Node *n, int jindex);
static void setNamespaceColumnVisibility(List *namespace, bool cols_visible);
static void setNamespaceLateralState(List *namespace,
                   bool lateral_only, bool lateral_ok);
static void checkExprIsVarFree(ParseState *pstate, Node *n,
                 const char *constructName);
static TargetEntry *findTargetlistEntrySQL92(ParseState *pstate, Node *node,
                       List **tlist, ParseExprKind exprKind);
static TargetEntry *findTargetlistEntrySQL99(ParseState *pstate, Node *node,
                       List **tlist, ParseExprKind exprKind);
static int  get_matching_location(int sortgroupref,
                  List *sortgrouprefs, List *exprs);
static List *resolve_unique_index_expr(ParseState *pstate, InferClause *infer,
                     Relation heapRel);
static List *addTargetToGroupList(ParseState *pstate, TargetEntry *tle,
                  List *grouplist, List *targetlist, int location);
static WindowClause *findWindowClause(List *wclist, const char *name);
static Node *transformFrameOffset(ParseState *pstate, int frameOptions,
                  Oid rangeopfamily, Oid rangeopcintype, Oid *inRangeFunc,
                  Node *clause);


/*
 * transformFromClause -
 *    Process the FROM clause and add items to the query's range table,
 *    joinlist, and namespace.
 *
 * Note: we assume that the pstate's p_rtable, p_joinlist, and p_namespace
 * lists were initialized to NIL when the pstate was created.
 * We will add onto any entries already present --- this is needed for rule
 * processing, as well as for UPDATE and DELETE.
 */
void
transformFromClause(ParseState *pstate, List *frmList)
{
  ListCell   *fl;

  /*
   * The grammar will have produced a list of RangeVars, RangeSubselects,
   * RangeFunctions, and/or JoinExprs. Transform each one (possibly adding
   * entries to the rtable), check for duplicate refnames, and then add it
   * to the joinlist and namespace.
   *
   * Note we must process the items left-to-right for proper handling of
   * LATERAL references.
   */
  foreach(fl, frmList)
  {
    Node     *n = lfirst(fl);
    ParseNamespaceItem *nsitem;
    List     *namespace;

    n = transformFromClauseItem(pstate, n,
                  &nsitem,
                  &namespace);

    checkNameSpaceConflicts(pstate, pstate->p_namespace, namespace);

    /* Mark the new namespace items as visible only to LATERAL */
    setNamespaceLateralState(namespace, true, true);

    pstate->p_joinlist = lappend(pstate->p_joinlist, n);
    pstate->p_namespace = list_concat(pstate->p_namespace, namespace);
  }

  /*
   * We're done parsing the FROM list, so make all namespace items
   * unconditionally visible.  Note that this will also reset lateral_only
   * for any namespace items that were already present when we were called;
   * but those should have been that way already.
   */
  setNamespaceLateralState(pstate->p_namespace, false, true);
}

/*
 * setTargetTable
 *    Add the target relation of INSERT/UPDATE/DELETE/MERGE to the range table,
 *    and make the special links to it in the ParseState.
 *
 *    We also open the target relation and acquire a write lock on it.
 *    This must be done before processing the FROM list, in case the target
 *    is also mentioned as a source relation --- we want to be sure to grab
 *    the write lock before any read lock.
 *
 *    If alsoSource is true, add the target to the query's joinlist and
 *    namespace.  For INSERT, we don't want the target to be joined to;
 *    it's a destination of tuples, not a source.  MERGE is actually
 *    both, but we'll add it separately to joinlist and namespace, so
 *    doing nothing (like INSERT) is correct here.  For UPDATE/DELETE,
 *    we do need to scan or join the target.  (NOTE: we do not bother
 *    to check for namespace conflict; we assume that the namespace was
 *    initially empty in these cases.)
 *
 *    Finally, we mark the relation as requiring the permissions specified
 *    by requiredPerms.
 *
 *    Returns the rangetable index of the target relation.
 */
int
setTargetTable(ParseState *pstate, RangeVar *relation,
         bool inh, bool alsoSource, AclMode requiredPerms)
{
  ParseNamespaceItem *nsitem;

  /*
   * ENRs hide tables of the same name, so we need to check for them first.
   * In contrast, CTEs don't hide tables (for this purpose).
   */
  if (relation->schemaname == NULL &&
    scanNameSpaceForENR(pstate, relation->relname))
    ereport(ERROR,
        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
         errmsg("relation \"%s\" cannot be the target of a modifying statement",
            relation->relname)));

  /* Close old target; this could only happen for multi-action rules */
  if (pstate->p_target_relation != NULL)
    table_close(pstate->p_target_relation, NoLock);

  /*
   * Open target rel and grab suitable lock (which we will hold till end of
   * transaction).
   *
   * free_parsestate() will eventually do the corresponding table_close(),
   * but *not* release the lock.
   */
  pstate->p_target_relation = parserOpenTable(pstate, relation,
                        RowExclusiveLock);

  /*
   * Now build an RTE and a ParseNamespaceItem.
   */
  nsitem = addRangeTableEntryForRelation(pstate, pstate->p_target_relation,
                       RowExclusiveLock,
                       relation->alias, inh, false);

  /* remember the RTE/nsitem as being the query target */
  pstate->p_target_nsitem = nsitem;

  /*
   * Override addRangeTableEntry's default ACL_SELECT permissions check, and
   * instead mark target table as requiring exactly the specified
   * permissions.
   *
   * If we find an explicit reference to the rel later during parse
   * analysis, we will add the ACL_SELECT bit back again; see
   * markVarForSelectPriv and its callers.
   */
  nsitem->p_perminfo->requiredPerms = requiredPerms;

  /*
   * If UPDATE/DELETE, add table to joinlist and namespace.
   */
  if (alsoSource)
    addNSItemToQuery(pstate, nsitem, true, true, true);

  return nsitem->p_rtindex;
}

/*
 * Extract all not-in-common columns from column lists of a source table
 *
 * src_nscolumns and src_colnames describe the source table.
 *
 * *src_colnos initially contains the column numbers of the already-merged
 * columns.  We add to it the column number of each additional column.
 * Also append to *res_colnames the name of each additional column,
 * append to *res_colvars a Var for each additional column, and copy the
 * columns' nscolumns data into res_nscolumns[] (which is caller-allocated
 * space that had better be big enough).
 *
 * Returns the number of columns added.
 */
static int
extractRemainingColumns(ParseState *pstate,
            ParseNamespaceColumn *src_nscolumns,
            List *src_colnames,
            List **src_colnos,
            List **res_colnames, List **res_colvars,
            ParseNamespaceColumn *res_nscolumns)
{
  int     colcount = 0;
  Bitmapset  *prevcols;
  int     attnum;
  ListCell   *lc;

  /*
   * While we could just test "list_member_int(*src_colnos, attnum)" to
   * detect already-merged columns in the loop below, that would be O(N^2)
   * for a wide input table.  Instead build a bitmapset of just the merged
   * USING columns, which we won't add to within the main loop.
   */
  prevcols = NULL;
  foreach(lc, *src_colnos)
  {
    prevcols = bms_add_member(prevcols, lfirst_int(lc));
  }

  attnum = 0;
  foreach(lc, src_colnames)
  {
    char     *colname = strVal(lfirst(lc));

    attnum++;
    /* Non-dropped and not already merged? */
    if (colname[0] != '\0' && !bms_is_member(attnum, prevcols))
    {
      /* Yes, so emit it as next output column */
      *src_colnos = lappend_int(*src_colnos, attnum);
      *res_colnames = lappend(*res_colnames, lfirst(lc));
      *res_colvars = lappend(*res_colvars,
                   buildVarFromNSColumn(pstate,
                            src_nscolumns + attnum - 1));
      /* Copy the input relation's nscolumn data for this column */
      res_nscolumns[colcount] = src_nscolumns[attnum - 1];
      colcount++;
    }
  }
  return colcount;
}

/*
 * transformJoinUsingClause()
 *    Build a complete ON clause from a partially-transformed USING list.
 *    We are given lists of nodes representing left and right match columns.
 *    Result is a transformed qualification expression.
 */
static Node *
transformJoinUsingClause(ParseState *pstate,
             List *leftVars, List *rightVars)
{
  Node     *result;
  List     *andargs = NIL;
  ListCell   *lvars,
         *rvars;

  /*
   * We cheat a little bit here by building an untransformed operator tree
   * whose leaves are the already-transformed Vars.  This requires collusion
   * from transformExpr(), which normally could be expected to complain
   * about already-transformed subnodes.  However, this does mean that we
   * have to mark the columns as requiring SELECT privilege for ourselves;
   * transformExpr() won't do it.
   */
  forboth(lvars, leftVars, rvars, rightVars)
  {
    Var      *lvar = (Var *) lfirst(lvars);
    Var      *rvar = (Var *) lfirst(rvars);
    A_Expr     *e;

    /* Require read access to the join variables */
    markVarForSelectPriv(pstate, lvar);
    markVarForSelectPriv(pstate, rvar);

    /* Now create the lvar = rvar join condition */
    e = makeSimpleA_Expr(AEXPR_OP, "=",
               (Node *) copyObject(lvar), (Node *) copyObject(rvar),
               -1);

    /* Prepare to combine into an AND clause, if multiple join columns */
    andargs = lappend(andargs, e);
  }

  /* Only need an AND if there's more than one join column */
  if (list_length(andargs) == 1)
    result = (Node *) linitial(andargs);
  else
    result = (Node *) makeBoolExpr(AND_EXPR, andargs, -1);

  /*
   * Since the references are already Vars, and are certainly from the input
   * relations, we don't have to go through the same pushups that
   * transformJoinOnClause() does.  Just invoke transformExpr() to fix up
   * the operators, and we're done.
   */
  result = transformExpr(pstate, result, EXPR_KIND_JOIN_USING);

  result = coerce_to_boolean(pstate, result, "JOIN/USING");

  return result;
}

/*
 * transformJoinOnClause()
 *    Transform the qual conditions for JOIN/ON.
 *    Result is a transformed qualification expression.
 */
static Node *
transformJoinOnClause(ParseState *pstate, JoinExpr *j, List *namespace)
{
  Node     *result;
  List     *save_namespace;

  /*
   * The namespace that the join expression should see is just the two
   * subtrees of the JOIN plus any outer references from upper pstate
   * levels.  Temporarily set this pstate's namespace accordingly.  (We need
   * not check for refname conflicts, because transformFromClauseItem()
   * already did.)  All namespace items are marked visible regardless of
   * LATERAL state.
   */
  setNamespaceLateralState(namespace, false, true);

  save_namespace = pstate->p_namespace;
  pstate->p_namespace = namespace;

  result = transformWhereClause(pstate, j->quals,
                  EXPR_KIND_JOIN_ON, "JOIN/ON");

  pstate->p_namespace = save_namespace;

  return result;
}

/*
 * transformTableEntry --- transform a RangeVar (simple relation reference)
 */
static ParseNamespaceItem *
transformTableEntry(ParseState *pstate, RangeVar *r)
{
  /* addRangeTableEntry does all the work */
  return addRangeTableEntry(pstate, r, r->alias, r->inh, true);
}

/*
 * transformRangeSubselect --- transform a sub-SELECT appearing in FROM
 */
static ParseNamespaceItem *
transformRangeSubselect(ParseState *pstate, RangeSubselect *r)
{
  Query    *query;

  /*
   * Set p_expr_kind to show this parse level is recursing to a subselect.
   * We can't be nested within any expression, so don't need save-restore
   * logic here.
   */
  Assert(pstate->p_expr_kind == EXPR_KIND_NONE);
  pstate->p_expr_kind = EXPR_KIND_FROM_SUBSELECT;

  /*
   * If the subselect is LATERAL, make lateral_only names of this level
   * visible to it.  (LATERAL can't nest within a single pstate level, so we
   * don't need save/restore logic here.)
   */
  Assert(!pstate->p_lateral_active);
  pstate->p_lateral_active = r->lateral;

  /*
   * Analyze and transform the subquery.  Note that if the subquery doesn't
   * have an alias, it can't be explicitly selected for locking, but locking
   * might still be required (if there is an all-tables locking clause).
   */
  query = parse_sub_analyze(r->subquery, pstate, NULL,
                isLockedRefname(pstate,
                        r->alias == NULL ? NULL :
                        r->alias->aliasname),
                true);

  /* Restore state */
  pstate->p_lateral_active = false;
  pstate->p_expr_kind = EXPR_KIND_NONE;

  /*
   * Check that we got a SELECT.  Anything else should be impossible given
   * restrictions of the grammar, but check anyway.
   */
  if (!IsA(query, Query) ||
    query->commandType != CMD_SELECT)
    elog(ERROR, "unexpected non-SELECT command in subquery in FROM");

  /*
   * OK, build an RTE and nsitem for the subquery.
   */
  return addRangeTableEntryForSubquery(pstate,
                     query,
                     r->alias,
                     r->lateral,
                     true);
}


/*
 * transformRangeFunction --- transform a function call appearing in FROM
 */
static ParseNamespaceItem *
transformRangeFunction(ParseState *pstate, RangeFunction *r)
{
  List     *funcexprs = NIL;
  List     *funcnames = NIL;
  List     *coldeflists = NIL;
  bool    is_lateral;
  ListCell   *lc;

  /*
   * We make lateral_only names of this level visible, whether or not the
   * RangeFunction is explicitly marked LATERAL.  This is needed for SQL
   * spec compliance in the case of UNNEST(), and seems useful on
   * convenience grounds for all functions in FROM.
   *
   * (LATERAL can't nest within a single pstate level, so we don't need
   * save/restore logic here.)
   */
  Assert(!pstate->p_lateral_active);
  pstate->p_lateral_active = true;

  /*
   * Transform the raw expressions.
   *
   * While transforming, also save function names for possible use as alias
   * and column names.  We use the same transformation rules as for a SELECT
   * output expression.  For a FuncCall node, the result will be the
   * function name, but it is possible for the grammar to hand back other
   * node types.
   *
   * We have to get this info now, because FigureColname only works on raw
   * parsetrees.  Actually deciding what to do with the names is left up to
   * addRangeTableEntryForFunction.
   *
   * Likewise, collect column definition lists if there were any.  But
   * complain if we find one here and the RangeFunction has one too.
   */
  foreach(lc, r->functions)
  {
    List     *pair = (List *) lfirst(lc);
    Node     *fexpr;
    List     *coldeflist;
    Node     *newfexpr;
    Node     *last_srf;

    /* Disassemble the function-call/column-def-list pairs */
    Assert(list_length(pair) == 2);
    fexpr = (Node *) linitial(pair);
    coldeflist = (List *) lsecond(pair);

    /*
     * If we find a function call unnest() with more than one argument and
     * no special decoration, transform it into separate unnest() calls on
     * each argument.  This is a kluge, for sure, but it's less nasty than
     * other ways of implementing the SQL-standard UNNEST() syntax.
     *
     * If there is any decoration (including a coldeflist), we don't
     * transform, which probably means a no-such-function error later.  We
     * could alternatively throw an error right now, but that doesn't seem
     * tremendously helpful.  If someone is using any such decoration,
     * then they're not using the SQL-standard syntax, and they're more
     * likely expecting an un-tweaked function call.
     *
     * Note: the transformation changes a non-schema-qualified unnest()
     * function name into schema-qualified pg_catalog.unnest().  This
     * choice is also a bit debatable, but it seems reasonable to force
     * use of built-in unnest() when we make this transformation.
     */
    if (IsA(fexpr, FuncCall))
    {
      FuncCall   *fc = (FuncCall *) fexpr;

      if (list_length(fc->funcname) == 1 &&
        strcmp(strVal(linitial(fc->funcname)), "unnest") == 0 &&
        list_length(fc->args) > 1 &&
        fc->agg_order == NIL &&
        fc->agg_filter == NULL &&
        fc->over == NULL &&
        !fc->agg_star &&
        !fc->agg_distinct &&
        !fc->func_variadic &&
        coldeflist == NIL)
      {
        ListCell   *lc2;

        foreach(lc2, fc->args)
        {
          Node     *arg = (Node *) lfirst(lc2);
          FuncCall   *newfc;

          last_srf = pstate->p_last_srf;

          newfc = makeFuncCall(SystemFuncName("unnest"),
                     list_make1(arg),
                     COERCE_EXPLICIT_CALL,
                     fc->location);

          newfexpr = transformExpr(pstate, (Node *) newfc,
                       EXPR_KIND_FROM_FUNCTION);

          /* nodeFunctionscan.c requires SRFs to be at top level */
          if (pstate->p_last_srf != last_srf &&
            pstate->p_last_srf != newfexpr)
            ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("set-returning functions must appear at top level of FROM"),
                 parser_errposition(pstate,
                          exprLocation(pstate->p_last_srf))));

          funcexprs = lappend(funcexprs, newfexpr);

          funcnames = lappend(funcnames,
                    FigureColname((Node *) newfc));

          /* coldeflist is empty, so no error is possible */

          coldeflists = lappend(coldeflists, coldeflist);
        }
        continue;   /* done with this function item */
      }
    }

    /* normal case ... */
    last_srf = pstate->p_last_srf;

    newfexpr = transformExpr(pstate, fexpr,
                 EXPR_KIND_FROM_FUNCTION);

    /* nodeFunctionscan.c requires SRFs to be at top level */
    if (pstate->p_last_srf != last_srf &&
      pstate->p_last_srf != newfexpr)
      ereport(ERROR,
          (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
           errmsg("set-returning functions must appear at top level of FROM"),
           parser_errposition(pstate,
                    exprLocation(pstate->p_last_srf))));

    funcexprs = lappend(funcexprs, newfexpr);

    funcnames = lappend(funcnames,
              FigureColname(fexpr));

    if (coldeflist && r->coldeflist)
      ereport(ERROR,
          (errcode(ERRCODE_SYNTAX_ERROR),
           errmsg("multiple column definition lists are not allowed for the same function"),
           parser_errposition(pstate,
                    exprLocation((Node *) r->coldeflist))));

    coldeflists = lappend(coldeflists, coldeflist);
  }

  pstate->p_lateral_active = false;

  /*
   * We must assign collations now so that the RTE exposes correct collation
   * info for Vars created from it.
   */
  assign_list_collations(pstate, funcexprs);

  /*
   * Install the top-level coldeflist if there was one (we already checked
   * that there was no conflicting per-function coldeflist).
   *
   * We only allow this when there's a single function (even after UNNEST
   * expansion) and no WITH ORDINALITY.  The reason for the latter
   * restriction is that it's not real clear whether the ordinality column
   * should be in the coldeflist, and users are too likely to make mistakes
   * in one direction or the other.  Putting the coldeflist inside ROWS
   * FROM() is much clearer in this case.
   */
  if (r->coldeflist)
  {
    if (list_length(funcexprs) != 1)
    {
      if (r->is_rowsfrom)
        ereport(ERROR,
            (errcode(ERRCODE_SYNTAX_ERROR),
             errmsg("ROWS FROM() with multiple functions cannot have a column definition list"),
             errhint("Put a separate column definition list for each function inside ROWS FROM()."),
             parser_errposition(pstate,
                      exprLocation((Node *) r->coldeflist))));
      else
        ereport(ERROR,
            (errcode(ERRCODE_SYNTAX_ERROR),
             errmsg("UNNEST() with multiple arguments cannot have a column definition list"),
             errhint("Use separate UNNEST() calls inside ROWS FROM(), and attach a column definition list to each one."),
             parser_errposition(pstate,
                      exprLocation((Node *) r->coldeflist))));
    }
    if (r->ordinality)
      ereport(ERROR,
          (errcode(ERRCODE_SYNTAX_ERROR),
           errmsg("WITH ORDINALITY cannot be used with a column definition list"),
           errhint("Put the column definition list inside ROWS FROM()."),
           parser_errposition(pstate,
                    exprLocation((Node *) r->coldeflist))));

    coldeflists = list_make1(r->coldeflist);
  }

  /*
   * Mark the RTE as LATERAL if the user said LATERAL explicitly, or if
   * there are any lateral cross-references in it.
   */
  is_lateral = r->lateral || contain_vars_of_level((Node *) funcexprs, 0);

  /*
   * OK, build an RTE and nsitem for the function.
   */
  return addRangeTableEntryForFunction(pstate,
                     funcnames, funcexprs, coldeflists,
                     r, is_lateral, true);
}

/*
 * transformRangeTableFunc -
 *      Transform a raw RangeTableFunc into TableFunc.
 *
 * Transform the namespace clauses, the document-generating expression, the
 * row-generating expression, the column-generating expressions, and the
 * default value expressions.
 */
static ParseNamespaceItem *
transformRangeTableFunc(ParseState *pstate, RangeTableFunc *rtf)
{
  TableFunc  *tf = makeNode(TableFunc);
  const char *constructName;
  Oid     docType;
  bool    is_lateral;
  ListCell   *col;
  char    **names;
  int     colno;

  /*
   * Currently we only support XMLTABLE here.  See transformJsonTable() for
   * JSON_TABLE support.
   */
  tf->functype = TFT_XMLTABLE;
  constructName = "XMLTABLE";
  docType = XMLOID;

  /*
   * We make lateral_only names of this level visible, whether or not the
   * RangeTableFunc is explicitly marked LATERAL.  This is needed for SQL
   * spec compliance and seems useful on convenience grounds for all
   * functions in FROM.
   *
   * (LATERAL can't nest within a single pstate level, so we don't need
   * save/restore logic here.)
   */
  Assert(!pstate->p_lateral_active);
  pstate->p_lateral_active = true;

  /* Transform and apply typecast to the row-generating expression ... */
  Assert(rtf->rowexpr != NULL);
  tf->rowexpr = coerce_to_specific_type(pstate,
                      transformExpr(pstate, rtf->rowexpr, EXPR_KIND_FROM_FUNCTION),
                      TEXTOID,
                      constructName);
  assign_expr_collations(pstate, tf->rowexpr);

  /* ... and to the document itself */
  Assert(rtf->docexpr != NULL);
  tf->docexpr = coerce_to_specific_type(pstate,
                      transformExpr(pstate, rtf->docexpr, EXPR_KIND_FROM_FUNCTION),
                      docType,
                      constructName);
  assign_expr_collations(pstate, tf->docexpr);

  /* undef ordinality column number */
  tf->ordinalitycol = -1;

  /* Process column specs */
  names = palloc_array(char *, list_length(rtf->columns));

  colno = 0;
  foreach(col, rtf->columns)
  {
    RangeTableFuncCol *rawc = (RangeTableFuncCol *) lfirst(col);
    Oid     typid;
    int32   typmod;
    Node     *colexpr;
    Node     *coldefexpr;
    int     j;

    tf->colnames = lappend(tf->colnames,
                 makeString(pstrdup(rawc->colname)));

    /*
     * Determine the type and typmod for the new column. FOR ORDINALITY
     * columns are INTEGER per spec; the others are user-specified.
     */
    if (rawc->for_ordinality)
    {
      if (tf->ordinalitycol != -1)
        ereport(ERROR,
            (errcode(ERRCODE_SYNTAX_ERROR),
             errmsg("only one FOR ORDINALITY column is allowed"),
             parser_errposition(pstate, rawc->location)));

      typid = INT4OID;
      typmod = -1;
      tf->ordinalitycol = colno;
    }
    else
    {
      if (rawc->typeName->setof)
        ereport(ERROR,
            (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
             errmsg("column \"%s\" cannot be declared SETOF",
                rawc->colname),
             parser_errposition(pstate, rawc->location)));

      typenameTypeIdAndMod(pstate, rawc->typeName,
                 &typid, &typmod);
    }

    tf->coltypes = lappend_oid(tf->coltypes, typid);
    tf->coltypmods = lappend_int(tf->coltypmods, typmod);
    tf->colcollations = lappend_oid(tf->colcollations,
                    get_typcollation(typid));

    /* Transform the PATH and DEFAULT expressions */
    if (rawc->colexpr)
    {
      colexpr = coerce_to_specific_type(pstate,
                        transformExpr(pstate, rawc->colexpr,
                              EXPR_KIND_FROM_FUNCTION),
                        TEXTOID,
                        constructName);
      assign_expr_collations(pstate, colexpr);
    }
    else
      colexpr = NULL;

    if (rawc->coldefexpr)
    {
      coldefexpr = coerce_to_specific_type_typmod(pstate,
                            transformExpr(pstate, rawc->coldefexpr,
                                    EXPR_KIND_FROM_FUNCTION),
                            typid, typmod,
                            constructName);
      assign_expr_collations(pstate, coldefexpr);
    }
    else
      coldefexpr = NULL;

    tf->colexprs = lappend(tf->colexprs, colexpr);
    tf->coldefexprs = lappend(tf->coldefexprs, coldefexpr);

    if (rawc->is_not_null)
      tf->notnulls = bms_add_member(tf->notnulls, colno);

    /* make sure column names are unique */
    for (j = 0; j < colno; j++)
      if (strcmp(names[j], rawc->colname) == 0)
        ereport(ERROR,
            (errcode(ERRCODE_SYNTAX_ERROR),
             errmsg("column name \"%s\" is not unique",
                rawc->colname),
             parser_errposition(pstate, rawc->location)));
    names[colno] = rawc->colname;

    colno++;
  }
  pfree(names);

  /* Namespaces, if any, also need to be transformed */
  if (rtf->namespaces != NIL)
  {
    ListCell   *ns;
    ListCell   *lc2;
    List     *ns_uris = NIL;
    List     *ns_names = NIL;
    bool    default_ns_seen = false;

    foreach(ns, rtf->namespaces)
    {
      ResTarget  *r = (ResTarget *) lfirst(ns);
      Node     *ns_uri;

      Assert(IsA(r, ResTarget));
      ns_uri = transformExpr(pstate, r->val, EXPR_KIND_FROM_FUNCTION);
      ns_uri = coerce_to_specific_type(pstate, ns_uri,
                       TEXTOID, constructName);
      assign_expr_collations(pstate, ns_uri);
      ns_uris = lappend(ns_uris, ns_uri);

      /* Verify consistency of name list: no dupes, only one DEFAULT */
      if (r->name != NULL)
      {
        foreach(lc2, ns_names)
        {
          String     *ns_node = lfirst_node(String, lc2);

          if (ns_node == NULL)
            continue;
          if (strcmp(strVal(ns_node), r->name) == 0)
            ereport(ERROR,
                (errcode(ERRCODE_SYNTAX_ERROR),
                 errmsg("namespace name \"%s\" is not unique",
                    r->name),
                 parser_errposition(pstate, r->location)));
        }
      }
      else
      {
        if (default_ns_seen)
          ereport(ERROR,
              (errcode(ERRCODE_SYNTAX_ERROR),
               errmsg("only one default namespace is allowed"),
               parser_errposition(pstate, r->location)));
        default_ns_seen = true;
      }

      /* We represent DEFAULT by a null pointer */
      ns_names = lappend(ns_names,
                 r->name ? makeString(r->name) : NULL);
    }

    tf->ns_uris = ns_uris;
    tf->ns_names = ns_names;
  }

  tf->location = rtf->location;

  pstate->p_lateral_active = false;

  /*
   * Mark the RTE as LATERAL if the user said LATERAL explicitly, or if
   * there are any lateral cross-references in it.
   */
  is_lateral = rtf->lateral || contain_vars_of_level((Node *) tf, 0);

  return addRangeTableEntryForTableFunc(pstate,
                      tf, rtf->alias, is_lateral, true);
}

/*
 * transformRangeTableSample --- transform a TABLESAMPLE clause
 *
 * Caller has already transformed rts->relation, we just have to validate
 * the remaining fields and create a TableSampleClause node.
 */
static TableSampleClause *
transformRangeTableSample(ParseState *pstate, RangeTableSample *rts)
{
  TableSampleClause *tablesample;
  Oid     handlerOid;
  Oid     funcargtypes[1];
  TsmRoutine *tsm;
  List     *fargs;
  ListCell   *larg,
         *ltyp;

  /*
   * To validate the sample method name, look up the handler function, which
   * has the same name, one dummy INTERNAL argument, and a result type of
   * tsm_handler.  (Note: tablesample method names are not schema-qualified
   * in the SQL standard; but since they are just functions to us, we allow
   * schema qualification to resolve any potential ambiguity.)
   */
  funcargtypes[0] = INTERNALOID;

  handlerOid = LookupFuncName(rts->method, 1, funcargtypes, true);

  /* we want error to complain about no-such-method, not no-such-function */
  if (!OidIsValid(handlerOid))
    ereport(ERROR,
        (errcode(ERRCODE_UNDEFINED_OBJECT),
         errmsg("tablesample method %s does not exist",
            NameListToString(rts->method)),
         parser_errposition(pstate, rts->location)));

  /* check that handler has correct return type */
  if (get_func_rettype(handlerOid) != TSM_HANDLEROID)
    ereport(ERROR,
        (errcode(ERRCODE_WRONG_OBJECT_TYPE),
         errmsg("function %s must return type %s",
            NameListToString(rts->method), "tsm_handler"),
         parser_errposition(pstate, rts->location)));

  /* OK, run the handler to get TsmRoutine, for argument type info */
  tsm = GetTsmRoutine(handlerOid);

  tablesample = makeNode(TableSampleClause);
  tablesample->tsmhandler = handlerOid;

  /* check user provided the expected number of arguments */
  if (list_length(rts->args) != list_length(tsm->parameterTypes))
    ereport(ERROR,
        (errcode(ERRCODE_INVALID_TABLESAMPLE_ARGUMENT),
         errmsg_plural("tablesample method %s requires %d argument, not %d",
                 "tablesample method %s requires %d arguments, not %d",
                 list_length(tsm->parameterTypes),
                 NameListToString(rts->method),
                 list_length(tsm->parameterTypes),
                 list_length(rts->args)),
         parser_errposition(pstate, rts->location)));

  /*
   * Transform the arguments, typecasting them as needed.  Note we must also
   * assign collations now, because assign_query_collations() doesn't
   * examine any substructure of RTEs.
   */
  fargs = NIL;
  forboth(larg, rts->args, ltyp, tsm->parameterTypes)
  {
    Node     *arg = (Node *) lfirst(larg);
    Oid     argtype = lfirst_oid(ltyp);

    arg = transformExpr(pstate, arg, EXPR_KIND_FROM_FUNCTION);
    arg = coerce_to_specific_type(pstate, arg, argtype, "TABLESAMPLE");
    assign_expr_collations(pstate, arg);
    fargs = lappend(fargs, arg);
  }
  tablesample->args = fargs;

  /* Process REPEATABLE (seed) */
  if (rts->repeatable != NULL)
  {
    Node     *arg;

    if (!tsm->repeatable_across_queries)
      ereport(ERROR,
          (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
           errmsg("tablesample method %s does not support REPEATABLE",
              NameListToString(rts->method)),
           parser_errposition(pstate, rts->location)));

    arg = transformExpr(pstate, rts->repeatable, EXPR_KIND_FROM_FUNCTION);
    arg = coerce_to_specific_type(pstate, arg, FLOAT8OID, "REPEATABLE");
    assign_expr_collations(pstate, arg);
    tablesample->repeatable = (Expr *) arg;
  }
  else
    tablesample->repeatable = NULL;

  return tablesample;
}

/*
 * getNSItemForSpecialRelationTypes
 *
 * If given RangeVar refers to a CTE or an EphemeralNamedRelation,
 * build and return an appropriate ParseNamespaceItem, otherwise return NULL
 */
static ParseNamespaceItem *
getNSItemForSpecialRelationTypes(ParseState *pstate, RangeVar *rv)
{
  ParseNamespaceItem *nsitem;
  CommonTableExpr *cte;
  Index   levelsup;

  /*
   * if it is a qualified name, it can't be a CTE or tuplestore reference
   */
  if (rv->schemaname)
    return NULL;

  cte = scanNameSpaceForCTE(pstate, rv->relname, &levelsup);
  if (cte)
    nsitem = addRangeTableEntryForCTE(pstate, cte, levelsup, rv, true);
  else if (scanNameSpaceForENR(pstate, rv->relname))
    nsitem = addRangeTableEntryForENR(pstate, rv, true);
  else
    nsitem = NULL;

  return nsitem;
}

/*
 * transformFromClauseItem -
 *    Transform a FROM-clause item, adding any required entries to the
 *    range table list being built in the ParseState, and return the
 *    transformed item ready to include in the joinlist.  Also build a
 *    ParseNamespaceItem list describing the names exposed by this item.
 *    This routine can recurse to handle SQL92 JOIN expressions.
 *
 * The function return value is the node to add to the jointree (a
 * RangeTblRef or JoinExpr).  Additional output parameters are:
 *
 * *top_nsitem: receives the ParseNamespaceItem directly corresponding to the
 * jointree item.  (This is only used during internal recursion, not by
 * outside callers.)
 *
 * *namespace: receives a List of ParseNamespaceItems for the RTEs exposed
 * as table/column names by this item.  (The lateral_only flags in these items
 * are indeterminate and should be explicitly set by the caller before use.)
 */
static Node *
transformFromClauseItem(ParseState *pstate, Node *n,
            ParseNamespaceItem **top_nsitem,
            List **namespace)
{
  /* Guard against stack overflow due to overly deep subtree */
  check_stack_depth();

  if (IsA(n, RangeVar))
  {
    /* Plain relation reference, or perhaps a CTE reference */
    RangeVar   *rv = (RangeVar *) n;
    RangeTblRef *rtr;
    ParseNamespaceItem *nsitem;

    /* Check if it's a CTE or tuplestore reference */
    nsitem = getNSItemForSpecialRelationTypes(pstate, rv);

    /* if not found above, must be a table reference */
    if (!nsitem)
      nsitem = transformTableEntry(pstate, rv);

    *top_nsitem = nsitem;
    *namespace = list_make1(nsitem);
    rtr = makeNode(RangeTblRef);
    rtr->rtindex = nsitem->p_rtindex;
    return (Node *) rtr;
  }
  else if (IsA(n, RangeSubselect))
  {
    /* sub-SELECT is like a plain relation */
    RangeTblRef *rtr;
    ParseNamespaceItem *nsitem;

    nsitem = transformRangeSubselect(pstate, (RangeSubselect *) n);
    *top_nsitem = nsitem;
    *namespace = list_make1(nsitem);
    rtr = makeNode(RangeTblRef);
    rtr->rtindex = nsitem->p_rtindex;
    return (Node *) rtr;
  }
  else if (IsA(n, RangeFunction))
  {
    /* function is like a plain relation */
    RangeTblRef *rtr;
    ParseNamespaceItem *nsitem;

    nsitem = transformRangeFunction(pstate, (RangeFunction *) n);
    *top_nsitem = nsitem;
    *namespace = list_make1(nsitem);
    rtr = makeNode(RangeTblRef);
    rtr->rtindex = nsitem->p_rtindex;
    return (Node *) rtr;
  }
  else if (IsA(n, RangeTableFunc) || IsA(n, JsonTable))
  {
    /* table function is like a plain relation */
    RangeTblRef *rtr;
    ParseNamespaceItem *nsitem;

    if (IsA(n, JsonTable))
      nsitem = transformJsonTable(pstate, (JsonTable *) n);
    else
      nsitem = transformRangeTableFunc(pstate, (RangeTableFunc *) n);

    *top_nsitem = nsitem;
    *namespace = list_make1(nsitem);
    rtr = makeNode(RangeTblRef);
    rtr->rtindex = nsitem->p_rtindex;
    return (Node *) rtr;
  }
  else if (IsA(n, RangeTableSample))
  {
    /* TABLESAMPLE clause (wrapping some other valid FROM node) */
    RangeTableSample *rts = (RangeTableSample *) n;
    Node     *rel;
    RangeTblEntry *rte;

    /* Recursively transform the contained relation */
    rel = transformFromClauseItem(pstate, rts->relation,
                    top_nsitem, namespace);
    rte = (*top_nsitem)->p_rte;
    /* We only support this on plain relations and matviews */
    if (rte->rtekind != RTE_RELATION ||
      (rte->relkind != RELKIND_RELATION &&
       rte->relkind != RELKIND_MATVIEW &&
       rte->relkind != RELKIND_PARTITIONED_TABLE))
      ereport(ERROR,
          (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
           errmsg("TABLESAMPLE clause can only be applied to tables and materialized views"),
           parser_errposition(pstate, exprLocation(rts->relation))));

    /* Transform TABLESAMPLE details and attach to the RTE */
    rte->tablesample = transformRangeTableSample(pstate, rts);
    return rel;
  }
  else if (IsA(n, JoinExpr))
  {
    /* A newfangled join expression */
    JoinExpr   *j = (JoinExpr *) n;
    ParseNamespaceItem *nsitem;
    ParseNamespaceItem *l_nsitem;
    ParseNamespaceItem *r_nsitem;
    List     *l_namespace,
           *r_namespace,
           *my_namespace,
           *l_colnames,
           *r_colnames,
           *res_colnames,
           *l_colnos,
           *r_colnos,
           *res_colvars;
    ParseNamespaceColumn *l_nscolumns,
           *r_nscolumns,
           *res_nscolumns;
    int     res_colindex;
    bool    lateral_ok;
    int     sv_namespace_length;
    int     k;

    /*
     * Recursively process the left subtree, then the right.  We must do
     * it in this order for correct visibility of LATERAL references.
     */
    j->larg = transformFromClauseItem(pstate, j->larg,
                      &l_nsitem,
                      &l_namespace);

    /*
     * Make the left-side RTEs available for LATERAL access within the
     * right side, by temporarily adding them to the pstate's namespace
     * list.  Per SQL:2008, if the join type is not INNER or LEFT then the
     * left-side names must still be exposed, but it's an error to
     * reference them.  (Stupid design, but that's what it says.)  Hence,
     * we always push them into the namespace, but mark them as not
     * lateral_ok if the jointype is wrong.
     *
     * Notice that we don't require the merged namespace list to be
     * conflict-free.  See the comments for scanNameSpaceForRefname().
     */
    lateral_ok = (j->jointype == JOIN_INNER || j->jointype == JOIN_LEFT);
    setNamespaceLateralState(l_namespace, true, lateral_ok);

    sv_namespace_length = list_length(pstate->p_namespace);
    pstate->p_namespace = list_concat(pstate->p_namespace, l_namespace);

    /* And now we can process the RHS */
    j->rarg = transformFromClauseItem(pstate, j->rarg,
                      &r_nsitem,
                      &r_namespace);

    /* Remove the left-side RTEs from the namespace list again */
    pstate->p_namespace = list_truncate(pstate->p_namespace,
                      sv_namespace_length);

    /*
     * Check for conflicting refnames in left and right subtrees. Must do
     * this because higher levels will assume I hand back a self-
     * consistent namespace list.
     */
    checkNameSpaceConflicts(pstate, l_namespace, r_namespace);

    /*
     * Generate combined namespace info for possible use below.
     */
    my_namespace = list_concat(l_namespace, r_namespace);

    /*
     * We'll work from the nscolumns data and eref alias column names for
     * each of the input nsitems.  Note that these include dropped
     * columns, which is helpful because we can keep track of physical
     * input column numbers more easily.
     */
    l_nscolumns = l_nsitem->p_nscolumns;
    l_colnames = l_nsitem->p_names->colnames;
    r_nscolumns = r_nsitem->p_nscolumns;
    r_colnames = r_nsitem->p_names->colnames;

    /*
     * Natural join does not explicitly specify columns; must generate
     * columns to join. Need to run through the list of columns from each
     * table or join result and match up the column names. Use the first
     * table, and check every column in the second table for a match.
     * (We'll check that the matches were unique later on.) The result of
     * this step is a list of column names just like an explicitly-written
     * USING list.
     */
    if (j->isNatural)
    {
      List     *rlist = NIL;
      ListCell   *lx,
             *rx;

      Assert(j->usingClause == NIL);  /* shouldn't have USING() too */

      foreach(lx, l_colnames)
      {
        char     *l_colname = strVal(lfirst(lx));
        String     *m_name = NULL;

        if (l_colname[0] == '\0')
          continue; /* ignore dropped columns */

        foreach(rx, r_colnames)
        {
          char     *r_colname = strVal(lfirst(rx));

          if (strcmp(l_colname, r_colname) == 0)
          {
            m_name = makeString(l_colname);
            break;
          }
        }

        /* matched a right column? then keep as join column... */
        if (m_name != NULL)
          rlist = lappend(rlist, m_name);
      }

      j->usingClause = rlist;
    }

    /*
     * If a USING clause alias was specified, save the USING columns as
     * its column list.
     */
    if (j->join_using_alias)
      j->join_using_alias->colnames = j->usingClause;

    /*
     * Now transform the join qualifications, if any.
     */
    l_colnos = NIL;
    r_colnos = NIL;
    res_colnames = NIL;
    res_colvars = NIL;

    /* this may be larger than needed, but it's not worth being exact */
    res_nscolumns = palloc0_array(ParseNamespaceColumn,
                    list_length(l_colnames) + list_length(r_colnames));
    res_colindex = 0;

    if (j->usingClause)
    {
      /*
       * JOIN/USING (or NATURAL JOIN, as transformed above). Transform
       * the list into an explicit ON-condition.
       */
      List     *ucols = j->usingClause;
      List     *l_usingvars = NIL;
      List     *r_usingvars = NIL;
      ListCell   *ucol;

      Assert(j->quals == NULL); /* shouldn't have ON() too */

      foreach(ucol, ucols)
      {
        char     *u_colname = strVal(lfirst(ucol));
        ListCell   *col;
        int     ndx;
        int     l_index = -1;
        int     r_index = -1;
        Var      *l_colvar,
               *r_colvar;

        Assert(u_colname[0] != '\0');

        /* Check for USING(foo,foo) */
        foreach(col, res_colnames)
        {
          char     *res_colname = strVal(lfirst(col));

          if (strcmp(res_colname, u_colname) == 0)
            ereport(ERROR,
                (errcode(ERRCODE_DUPLICATE_COLUMN),
                 errmsg("column name \"%s\" appears more than once in USING clause",
                    u_colname)));
        }

        /* Find it in left input */
        ndx = 0;
        foreach(col, l_colnames)
        {
          char     *l_colname = strVal(lfirst(col));

          if (strcmp(l_colname, u_colname) == 0)
          {
            if (l_index >= 0)
              ereport(ERROR,
                  (errcode(ERRCODE_AMBIGUOUS_COLUMN),
                   errmsg("common column name \"%s\" appears more than once in left table",
                      u_colname)));
            l_index = ndx;
          }
          ndx++;
        }
        if (l_index < 0)
          ereport(ERROR,
              (errcode(ERRCODE_UNDEFINED_COLUMN),
               errmsg("column \"%s\" specified in USING clause does not exist in left table",
                  u_colname)));
        l_colnos = lappend_int(l_colnos, l_index + 1);

        /* Find it in right input */
        ndx = 0;
        foreach(col, r_colnames)
        {
          char     *r_colname = strVal(lfirst(col));

          if (strcmp(r_colname, u_colname) == 0)
          {
            if (r_index >= 0)
              ereport(ERROR,
                  (errcode(ERRCODE_AMBIGUOUS_COLUMN),
                   errmsg("common column name \"%s\" appears more than once in right table",
                      u_colname)));
            r_index = ndx;
          }
          ndx++;
        }
        if (r_index < 0)
          ereport(ERROR,
              (errcode(ERRCODE_UNDEFINED_COLUMN),
               errmsg("column \"%s\" specified in USING clause does not exist in right table",
                  u_colname)));
        r_colnos = lappend_int(r_colnos, r_index + 1);

        /* Build Vars to use in the generated JOIN ON clause */
        l_colvar = buildVarFromNSColumn(pstate, l_nscolumns + l_index);
        l_usingvars = lappend(l_usingvars, l_colvar);
        r_colvar = buildVarFromNSColumn(pstate, r_nscolumns + r_index);
        r_usingvars = lappend(r_usingvars, r_colvar);

        /*
         * While we're here, add column names to the res_colnames
         * list.  It's a bit ugly to do this here while the
         * corresponding res_colvars entries are not made till later,
         * but doing this later would require an additional traversal
         * of the usingClause list.
         */
        res_colnames = lappend(res_colnames, lfirst(ucol));
      }

      /* Construct the generated JOIN ON clause */
      j->quals = transformJoinUsingClause(pstate,
                        l_usingvars,
                        r_usingvars);
    }
    else if (j->quals)
    {
      /* User-written ON-condition; transform it */
      j->quals = transformJoinOnClause(pstate, j, my_namespace);
    }
    else
    {
      /* CROSS JOIN: no quals */
    }

    /*
     * If this is an outer join, now mark the appropriate child RTEs as
     * being nulled by this join.  We have finished processing the child
     * join expressions as well as the current join's quals, which deal in
     * non-nulled input columns.  All future references to those RTEs will
     * see possibly-nulled values, and we should mark generated Vars to
     * account for that.  In particular, the join alias Vars that we're
     * about to build should reflect the nulling effects of this join.
     *
     * A difficulty with doing this is that we need the join's RT index,
     * which we don't officially have yet.  However, no other RTE can get
     * made between here and the addRangeTableEntryForJoin call, so we can
     * predict what the assignment will be.  (Alternatively, we could call
     * addRangeTableEntryForJoin before we have all the data computed, but
     * this seems less ugly.)
     */
    j->rtindex = list_length(pstate->p_rtable) + 1;

    switch (j->jointype)
    {
      case JOIN_INNER:
        break;
      case JOIN_LEFT:
        markRelsAsNulledBy(pstate, j->rarg, j->rtindex);
        break;
      case JOIN_FULL:
        markRelsAsNulledBy(pstate, j->larg, j->rtindex);
        markRelsAsNulledBy(pstate, j->rarg, j->rtindex);
        break;
      case JOIN_RIGHT:
        markRelsAsNulledBy(pstate, j->larg, j->rtindex);
        break;
      default:
        /* shouldn't see any other types here */
        elog(ERROR, "unrecognized join type: %d",
           (int) j->jointype);
        break;
    }

    /*
     * Now we can construct join alias expressions for the USING columns.
     */
    if (j->usingClause)
    {
      ListCell   *lc1,
             *lc2;

      /* Scan the colnos lists to recover info from the previous loop */
      forboth(lc1, l_colnos, lc2, r_colnos)
      {
        int     l_index = lfirst_int(lc1) - 1;
        int     r_index = lfirst_int(lc2) - 1;
        Var      *l_colvar,
               *r_colvar;
        Node     *u_colvar;
        ParseNamespaceColumn *res_nscolumn;

        /*
         * Note we re-build these Vars: they might have different
         * varnullingrels than the ones made in the previous loop.
         */
        l_colvar = buildVarFromNSColumn(pstate, l_nscolumns + l_index);
        r_colvar = buildVarFromNSColumn(pstate, r_nscolumns + r_index);

        /* Construct the join alias Var for this column */
        u_colvar = buildMergedJoinVar(pstate,
                        j->jointype,
                        l_colvar,
                        r_colvar);
        res_colvars = lappend(res_colvars, u_colvar);

        /* Construct column's res_nscolumns[] entry */
        res_nscolumn = res_nscolumns + res_colindex;
        res_colindex++;
        if (u_colvar == (Node *) l_colvar)
        {
          /* Merged column is equivalent to left input */
          *res_nscolumn = l_nscolumns[l_index];
        }
        else if (u_colvar == (Node *) r_colvar)
        {
          /* Merged column is equivalent to right input */
          *res_nscolumn = r_nscolumns[r_index];
        }
        else
        {
          /*
           * Merged column is not semantically equivalent to either
           * input, so it needs to be referenced as the join output
           * column.
           */
          res_nscolumn->p_varno = j->rtindex;
          res_nscolumn->p_varattno = res_colindex;
          res_nscolumn->p_vartype = exprType(u_colvar);
          res_nscolumn->p_vartypmod = exprTypmod(u_colvar);
          res_nscolumn->p_varcollid = exprCollation(u_colvar);
          res_nscolumn->p_varnosyn = j->rtindex;
          res_nscolumn->p_varattnosyn = res_colindex;
        }
      }
    }

    /* Add remaining columns from each side to the output columns */
    res_colindex +=
      extractRemainingColumns(pstate,
                  l_nscolumns, l_colnames, &l_colnos,
                  &res_colnames, &res_colvars,
                  res_nscolumns + res_colindex);
    res_colindex +=
      extractRemainingColumns(pstate,
                  r_nscolumns, r_colnames, &r_colnos,
                  &res_colnames, &res_colvars,
                  res_nscolumns + res_colindex);

    /* If join has an alias, it syntactically hides all inputs */
    if (j->alias)
    {
      for (k = 0; k < res_colindex; k++)
      {
        ParseNamespaceColumn *nscol = res_nscolumns + k;

        nscol->p_varnosyn = j->rtindex;
        nscol->p_varattnosyn = k + 1;
      }
    }

    /*
     * Now build an RTE and nsitem for the result of the join.
     */
    nsitem = addRangeTableEntryForJoin(pstate,
                       res_colnames,
                       res_nscolumns,
                       j->jointype,
                       list_length(j->usingClause),
                       res_colvars,
                       l_colnos,
                       r_colnos,
                       j->join_using_alias,
                       j->alias,
                       true);

    /* Verify that we correctly predicted the join's RT index */
    Assert(j->rtindex == nsitem->p_rtindex);
    /* Cross-check number of columns, too */
    Assert(res_colindex == list_length(nsitem->p_names->colnames));

    /*
     * Save a link to the JoinExpr in the proper element of p_joinexprs.
     * Since we maintain that list lazily, it may be necessary to fill in
     * empty entries before we can add the JoinExpr in the right place.
     */
    for (k = list_length(pstate->p_joinexprs) + 1; k < j->rtindex; k++)
      pstate->p_joinexprs = lappend(pstate->p_joinexprs, NULL);
    pstate->p_joinexprs = lappend(pstate->p_joinexprs, j);
    Assert(list_length(pstate->p_joinexprs) == j->rtindex);

    /*
     * If the join has a USING alias, build a ParseNamespaceItem for that
     * and add it to the list of nsitems in the join's input.
     */
    if (j->join_using_alias)
    {
      ParseNamespaceItem *jnsitem;

      jnsitem = palloc_object(ParseNamespaceItem);
      jnsitem->p_names = j->join_using_alias;
      jnsitem->p_rte = nsitem->p_rte;
      jnsitem->p_rtindex = nsitem->p_rtindex;
      jnsitem->p_perminfo = NULL;
      /* no need to copy the first N columns, just use res_nscolumns */
      jnsitem->p_nscolumns = res_nscolumns;
      /* set default visibility flags; might get changed later */
      jnsitem->p_rel_visible = true;
      jnsitem->p_cols_visible = true;
      jnsitem->p_lateral_only = false;
      jnsitem->p_lateral_ok = true;
      jnsitem->p_returning_type = VAR_RETURNING_DEFAULT;
      /* Per SQL, we must check for alias conflicts */
      checkNameSpaceConflicts(pstate, list_make1(jnsitem), my_namespace);
      my_namespace = lappend(my_namespace, jnsitem);
    }

    /*
     * Prepare returned namespace list.  If the JOIN has an alias then it
     * hides the contained RTEs completely; otherwise, the contained RTEs
     * are still visible as table names, but are not visible for
     * unqualified column-name access.
     *
     * Note: if there are nested alias-less JOINs, the lower-level ones
     * will remain in the list although they have neither p_rel_visible
     * nor p_cols_visible set.  We could delete such list items, but it's
     * unclear that it's worth expending cycles to do so.
     */
    if (j->alias != NULL)
      my_namespace = NIL;
    else
      setNamespaceColumnVisibility(my_namespace, false);

    /*
     * The join RTE itself is always made visible for unqualified column
     * names.  It's visible as a relation name only if it has an alias.
     */
    nsitem->p_rel_visible = (j->alias != NULL);
    nsitem->p_cols_visible = true;
    nsitem->p_lateral_only = false;
    nsitem->p_lateral_ok = true;

    *top_nsitem = nsitem;
    *namespace = lappend(my_namespace, nsitem);

    return (Node *) j;
  }
  else
    elog(ERROR, "unrecognized node type: %d", (int) nodeTag(n));
  return NULL;       /* can't get here, keep compiler quiet */
}

/*
 * buildVarFromNSColumn -
 *    build a Var node using ParseNamespaceColumn data
 *
 * This is used to construct joinaliasvars entries.
 * We can assume varlevelsup should be 0, and no location is specified.
 * Note also that no column SELECT privilege is requested here; that would
 * happen only if the column is actually referenced in the query.
 */
static Var *
buildVarFromNSColumn(ParseState *pstate, ParseNamespaceColumn *nscol)
{
  Var      *var;

  Assert(nscol->p_varno > 0); /* i.e., not deleted column */
  var = makeVar(nscol->p_varno,
          nscol->p_varattno,
          nscol->p_vartype,
          nscol->p_vartypmod,
          nscol->p_varcollid,
          0);
  /* makeVar doesn't offer parameters for these, so set by hand: */
  var->varreturningtype = nscol->p_varreturningtype;
  var->varnosyn = nscol->p_varnosyn;
  var->varattnosyn = nscol->p_varattnosyn;

  /* ... and update varnullingrels */
  markNullableIfNeeded(pstate, var);

  return var;
}

/*
 * buildMergedJoinVar -
 *    generate a suitable replacement expression for a merged join column
 */
static Node *
buildMergedJoinVar(ParseState *pstate, JoinType jointype,
           Var *l_colvar, Var *r_colvar)
{
  Oid     outcoltype;
  int32   outcoltypmod;
  Node     *l_node,
         *r_node,
         *res_node;

  outcoltype = select_common_type(pstate,
                  list_make2(l_colvar, r_colvar),
                  "JOIN/USING",
                  NULL);
  outcoltypmod = select_common_typmod(pstate,
                    list_make2(l_colvar, r_colvar),
                    outcoltype);

  /*
   * Insert coercion functions if needed.  Note that a difference in typmod
   * can only happen if input has typmod but outcoltypmod is -1. In that
   * case we insert a RelabelType to clearly mark that result's typmod is
   * not same as input.  We never need coerce_type_typmod.
   */
  if (l_colvar->vartype != outcoltype)
    l_node = coerce_type(pstate, (Node *) l_colvar, l_colvar->vartype,
               outcoltype, outcoltypmod,
               COERCION_IMPLICIT, COERCE_IMPLICIT_CAST, -1);
  else if (l_colvar->vartypmod != outcoltypmod)
    l_node = (Node *) makeRelabelType((Expr *) l_colvar,
                      outcoltype, outcoltypmod,
                      InvalidOid, /* fixed below */
                      COERCE_IMPLICIT_CAST);
  else
    l_node = (Node *) l_colvar;

  if (r_colvar->vartype != outcoltype)
    r_node = coerce_type(pstate, (Node *) r_colvar, r_colvar->vartype,
               outcoltype, outcoltypmod,
               COERCION_IMPLICIT, COERCE_IMPLICIT_CAST, -1);
  else if (r_colvar->vartypmod != outcoltypmod)
    r_node = (Node *) makeRelabelType((Expr *) r_colvar,
                      outcoltype, outcoltypmod,
                      InvalidOid, /* fixed below */
                      COERCE_IMPLICIT_CAST);
  else
    r_node = (Node *) r_colvar;

  /*
   * Choose what to emit
   */
  switch (jointype)
  {
    case JOIN_INNER:

      /*
       * We can use either var; prefer non-coerced one if available.
       */
      if (IsA(l_node, Var))
        res_node = l_node;
      else if (IsA(r_node, Var))
        res_node = r_node;
      else
        res_node = l_node;
      break;
    case JOIN_LEFT:
      /* Always use left var */
      res_node = l_node;
      break;
    case JOIN_RIGHT:
      /* Always use right var */
      res_node = r_node;
      break;
    case JOIN_FULL:
      {
        /*
         * Here we must build a COALESCE expression to ensure that the
         * join output is non-null if either input is.
         */
        CoalesceExpr *c = makeNode(CoalesceExpr);

        c->coalescetype = outcoltype;
        /* coalescecollid will get set below */
        c->args = list_make2(l_node, r_node);
        c->location = -1;
        res_node = (Node *) c;
        break;
      }
    default:
      elog(ERROR, "unrecognized join type: %d", (int) jointype);
      res_node = NULL; /* keep compiler quiet */
      break;
  }

  /*
   * Apply assign_expr_collations to fix up the collation info in the
   * coercion and CoalesceExpr nodes, if we made any.  This must be done now
   * so that the join node's alias vars show correct collation info.
   */
  assign_expr_collations(pstate, res_node);

  return res_node;
}

/*
 * markRelsAsNulledBy -
 *    Mark the given jointree node and its children as nulled by join jindex
 */
static void
markRelsAsNulledBy(ParseState *pstate, Node *n, int jindex)
{
  int     varno;
  ListCell   *lc;

  /* Note: we can't see FromExpr here */
  if (IsA(n, RangeTblRef))
  {
    varno = ((RangeTblRef *) n)->rtindex;
  }
  else if (IsA(n, JoinExpr))
  {
    JoinExpr   *j = (JoinExpr *) n;

    /* recurse to children */
    markRelsAsNulledBy(pstate, j->larg, jindex);
    markRelsAsNulledBy(pstate, j->rarg, jindex);
    varno = j->rtindex;
  }
  else
  {
    elog(ERROR, "unrecognized node type: %d", (int) nodeTag(n));
    varno = 0;        /* keep compiler quiet */
  }

  /*
   * Now add jindex to the p_nullingrels set for relation varno.  Since we
   * maintain the p_nullingrels list lazily, we might need to extend it to
   * make the varno'th entry exist.
   */
  while (list_length(pstate->p_nullingrels) < varno)
    pstate->p_nullingrels = lappend(pstate->p_nullingrels, NULL);
  lc = list_nth_cell(pstate->p_nullingrels, varno - 1);
  lfirst(lc) = bms_add_member((Bitmapset *) lfirst(lc), jindex);
}

/*
 * setNamespaceColumnVisibility -
 *    Convenience subroutine to update cols_visible flags in a namespace list.
 */
static void
setNamespaceColumnVisibility(List *namespace, bool cols_visible)
{
  ListCell   *lc;

  foreach(lc, namespace)
  {
    ParseNamespaceItem *nsitem = (ParseNamespaceItem *) lfirst(lc);

    nsitem->p_cols_visible = cols_visible;
  }
}

/*
 * setNamespaceLateralState -
 *    Convenience subroutine to update LATERAL flags in a namespace list.
 */
static void
setNamespaceLateralState(List *namespace, bool lateral_only, bool lateral_ok)
{
  ListCell   *lc;

  foreach(lc, namespace)
  {
    ParseNamespaceItem *nsitem = (ParseNamespaceItem *) lfirst(lc);

    nsitem->p_lateral_only = lateral_only;
    nsitem->p_lateral_ok = lateral_ok;
  }
}


/*
 * transformWhereClause -
 *    Transform the qualification and make sure it is of type boolean.
 *    Used for WHERE and allied clauses.
 *
 * constructName does not affect the semantics, but is used in error messages
 */
Node *
transformWhereClause(ParseState *pstate, Node *clause,
           ParseExprKind exprKind, const char *constructName)
{
  Node     *qual;

  if (clause == NULL)
    return NULL;

  qual = transformExpr(pstate, clause, exprKind);

  qual = coerce_to_boolean(pstate, qual, constructName);

  return qual;
}


/*
 * transformLimitClause -
 *    Transform the expression and make sure it is of type bigint.
 *    Used for LIMIT and allied clauses.
 *
 * Note: as of Postgres 8.2, LIMIT expressions are expected to yield int8,
 * rather than int4 as before.
 *
 * constructName does not affect the semantics, but is used in error messages
 */
Node *
transformLimitClause(ParseState *pstate, Node *clause,
           ParseExprKind exprKind, const char *constructName,
           LimitOption limitOption)
{
  Node     *qual;

  if (clause == NULL)
    return NULL;

  qual = transformExpr(pstate, clause, exprKind);

  qual = coerce_to_specific_type(pstate, qual, INT8OID, constructName);

  /* LIMIT can't refer to any variables of the current query */
  checkExprIsVarFree(pstate, qual, constructName);

  /*
   * Don't allow NULLs in FETCH FIRST .. WITH TIES.  This test is ugly and
   * extremely simplistic, in that you can pass a NULL anyway by hiding it
   * inside an expression -- but this protects ruleutils against emitting an
   * unadorned NULL that's not accepted back by the grammar.
   */
  if (exprKind == EXPR_KIND_LIMIT && limitOption == LIMIT_OPTION_WITH_TIES &&
    IsA(clause, A_Const) && castNode(A_Const, clause)->isnull)
    ereport(ERROR,
        (errcode(ERRCODE_INVALID_ROW_COUNT_IN_LIMIT_CLAUSE),
         errmsg("row count cannot be null in FETCH FIRST ... WITH TIES clause")));

  return qual;
}

/*
 * checkExprIsVarFree
 *    Check that given expr has no Vars of the current query level
 *    (aggregates and window functions should have been rejected already).
 *
 * This is used to check expressions that have to have a consistent value
 * across all rows of the query, such as a LIMIT.  Arguably it should reject
 * volatile functions, too, but we don't do that --- whatever value the
 * function gives on first execution is what you get.
 *
 * constructName does not affect the semantics, but is used in error messages
 */
static void
checkExprIsVarFree(ParseState *pstate, Node *n, const char *constructName)
{
  if (contain_vars_of_level(n, 0))
  {
    ereport(ERROR,
        (errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
    /* translator: %s is name of a SQL construct, eg LIMIT */
         errmsg("argument of %s must not contain variables",
            constructName),
         parser_errposition(pstate,
                  locate_var_of_level(n, 0))));
  }
}


/*
 * checkTargetlistEntrySQL92 -
 *    Validate a targetlist entry found by findTargetlistEntrySQL92
 *
 * When we select a pre-existing tlist entry as a result of syntax such
 * as "GROUP BY 1", we have to make sure it is acceptable for use in the
 * indicated clause type; transformExpr() will have treated it as a regular
 * targetlist item.
 */
static void
checkTargetlistEntrySQL92(ParseState *pstate, TargetEntry *tle,
              ParseExprKind exprKind)
{
  switch (exprKind)
  {
    case EXPR_KIND_GROUP_BY:
      /* reject aggregates and window functions */
      if (pstate->p_hasAggs &&
        contain_aggs_of_level((Node *) tle->expr, 0))
        ereport(ERROR,
            (errcode(ERRCODE_GROUPING_ERROR),
        /* translator: %s is name of a SQL construct, eg GROUP BY */
             errmsg("aggregate functions are not allowed in %s",
                ParseExprKindName(exprKind)),
             parser_errposition(pstate,
                      locate_agg_of_level((Node *) tle->expr, 0))));
      if (pstate->p_hasWindowFuncs &&
        contain_windowfuncs((Node *) tle->expr))
        ereport(ERROR,
            (errcode(ERRCODE_WINDOWING_ERROR),
        /* translator: %s is name of a SQL construct, eg GROUP BY */
             errmsg("window functions are not allowed in %s",
                ParseExprKindName(exprKind)),
             parser_errposition(pstate,
                      locate_windowfunc((Node *) tle->expr))));
      break;
    case EXPR_KIND_ORDER_BY:
      /* no extra checks needed */
      break;
    case EXPR_KIND_DISTINCT_ON:
      /* no extra checks needed */
      break;
    default:
      elog(ERROR, "unexpected exprKind in checkTargetlistEntrySQL92");
      break;
  }
}

/*
 *  findTargetlistEntrySQL92 -
 *    Returns the targetlist entry matching the given (untransformed) node.
 *    If no matching entry exists, one is created and appended to the target
 *    list as a "resjunk" node.
 *
 * This function supports the old SQL92 ORDER BY interpretation, where the
 * expression is an output column name or number.  If we fail to find a
 * match of that sort, we fall through to the SQL99 rules.  For historical
 * reasons, Postgres also allows this interpretation for GROUP BY, though
 * the standard never did.  However, for GROUP BY we prefer a SQL99 match.
 * This function is *not* used for WINDOW definitions.
 *
 * node   the ORDER BY, GROUP BY, or DISTINCT ON expression to be matched
 * tlist  the target list (passed by reference so we can append to it)
 * exprKind identifies clause type being processed
 */
static TargetEntry *
findTargetlistEntrySQL92(ParseState *pstate, Node *node, List **tlist,
             ParseExprKind exprKind)
{
  ListCell   *tl;

  /*----------
   * Handle two special cases as mandated by the SQL92 spec:
   *
   * 1. Bare ColumnName (no qualifier or subscripts)
   *    For a bare identifier, we search for a matching column name
   *    in the existing target list.  Multiple matches are an error
   *    unless they refer to identical values; for example,
   *    we allow  SELECT a, a FROM table ORDER BY a
   *    but not SELECT a AS b, b FROM table ORDER BY b
   *    If no match is found, we fall through and treat the identifier
   *    as an expression.
   *    For GROUP BY, it is incorrect to match the grouping item against
   *    targetlist entries: according to SQL92, an identifier in GROUP BY
   *    is a reference to a column name exposed by FROM, not to a target
   *    list column.  However, many implementations (including pre-7.0
   *    PostgreSQL) accept this anyway.  So for GROUP BY, we look first
   *    to see if the identifier matches any FROM column name, and only
   *    try for a targetlist name if it doesn't.  This ensures that we
   *    adhere to the spec in the case where the name could be both.
   *    DISTINCT ON isn't in the standard, so we can do what we like there;
   *    we choose to make it work like ORDER BY, on the rather flimsy
   *    grounds that ordinary DISTINCT works on targetlist entries.
   *
   * 2. IntegerConstant
   *    This means to use the n'th item in the existing target list.
   *    Note that it would make no sense to order/group/distinct by an
   *    actual constant, so this does not create a conflict with SQL99.
   *    GROUP BY column-number is not allowed by SQL92, but since
   *    the standard has no other behavior defined for this syntax,
   *    we may as well accept this common extension.
   *
   * Note that pre-existing resjunk targets must not be used in either case,
   * since the user didn't write them in his SELECT list.
   *
   * If neither special case applies, fall through to treat the item as
   * an expression per SQL99.
   *----------
   */
  if (IsA(node, ColumnRef) &&
    list_length(((ColumnRef *) node)->fields) == 1 &&
    IsA(linitial(((ColumnRef *) node)->fields), String))
  {
    char     *name = strVal(linitial(((ColumnRef *) node)->fields));
    int     location = ((ColumnRef *) node)->location;

    if (exprKind == EXPR_KIND_GROUP_BY)
    {
      /*
       * In GROUP BY, we must prefer a match against a FROM-clause
       * column to one against the targetlist.  Look to see if there is
       * a matching column.  If so, fall through to use SQL99 rules.
       * NOTE: if name could refer ambiguously to more than one column
       * name exposed by FROM, colNameToVar will ereport(ERROR). That's
       * just what we want here.
       *
       * Small tweak for 7.4.3: ignore matches in upper query levels.
       * This effectively changes the search order for bare names to (1)
       * local FROM variables, (2) local targetlist aliases, (3) outer
       * FROM variables, whereas before it was (1) (3) (2). SQL92 and
       * SQL99 do not allow GROUPing BY an outer reference, so this
       * breaks no cases that are legal per spec, and it seems a more
       * self-consistent behavior.
       */
      if (colNameToVar(pstate, name, true, location) != NULL)
        name = NULL;
    }

    if (name != NULL)
    {
      TargetEntry *target_result = NULL;

      foreach(tl, *tlist)
      {
        TargetEntry *tle = (TargetEntry *) lfirst(tl);

        if (!tle->resjunk &&
          strcmp(tle->resname, name) == 0)
        {
          if (target_result != NULL)
          {
            if (!equal(target_result->expr, tle->expr))
              ereport(ERROR,
                  (errcode(ERRCODE_AMBIGUOUS_COLUMN),

              /*------
                translator: first %s is name of a SQL construct, eg ORDER BY */
                   errmsg("%s \"%s\" is ambiguous",
                      ParseExprKindName(exprKind),
                      name),
                   parser_errposition(pstate, location)));
          }
          else
            target_result = tle;
          /* Stay in loop to check for ambiguity */
        }
      }
      if (target_result != NULL)
      {
        /* return the first match, after suitable validation */
        checkTargetlistEntrySQL92(pstate, target_result, exprKind);
        return target_result;
      }
    }
  }
  if (IsA(node, A_Const))
  {
    A_Const    *aconst = castNode(A_Const, node);
    int     targetlist_pos = 0;
    int     target_pos;

    if (!IsA(&aconst->val, Integer))
      ereport(ERROR,
          (errcode(ERRCODE_SYNTAX_ERROR),
      /* translator: %s is name of a SQL construct, eg ORDER BY */
           errmsg("non-integer constant in %s",
              ParseExprKindName(exprKind)),
           parser_errposition(pstate, aconst->location)));

    target_pos = intVal(&aconst->val);
    foreach(tl, *tlist)
    {
      TargetEntry *tle = (TargetEntry *) lfirst(tl);

      if (!tle->resjunk)
      {
        if (++targetlist_pos == target_pos)
        {
          /* return the unique match, after suitable validation */
          checkTargetlistEntrySQL92(pstate, tle, exprKind);
          return tle;
        }
      }
    }
    ereport(ERROR,
        (errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
    /* translator: %s is name of a SQL construct, eg ORDER BY */
         errmsg("%s position %d is not in select list",
            ParseExprKindName(exprKind), target_pos),
         parser_errposition(pstate, aconst->location)));
  }

  /*
   * Otherwise, we have an expression, so process it per SQL99 rules.
   */
  return findTargetlistEntrySQL99(pstate, node, tlist, exprKind);
}

/*
 *  findTargetlistEntrySQL99 -
 *    Returns the targetlist entry matching the given (untransformed) node.
 *    If no matching entry exists, one is created and appended to the target
 *    list as a "resjunk" node.
 *
 * This function supports the SQL99 interpretation, wherein the expression
 * is just an ordinary expression referencing input column names.
 *
 * node   the ORDER BY, GROUP BY, etc expression to be matched
 * tlist  the target list (passed by reference so we can append to it)
 * exprKind identifies clause type being processed
 */
static TargetEntry *
findTargetlistEntrySQL99(ParseState *pstate, Node *node, List **tlist,
             ParseExprKind exprKind)
{
  TargetEntry *target_result;
  ListCell   *tl;
  Node     *expr;

  /*
   * Convert the untransformed node to a transformed expression, and search
   * for a match in the tlist.  NOTE: it doesn't really matter whether there
   * is more than one match.  Also, we are willing to match an existing
   * resjunk target here, though the SQL92 cases above must ignore resjunk
   * targets.
   */
  expr = transformExpr(pstate, node, exprKind);

  foreach(tl, *tlist)
  {
    TargetEntry *tle = (TargetEntry *) lfirst(tl);
    Node     *texpr;

    /*
     * Ignore any implicit cast on the existing tlist expression.
     *
     * This essentially allows the ORDER/GROUP/etc item to adopt the same
     * datatype previously selected for a textually-equivalent tlist item.
     * There can't be any implicit cast at top level in an ordinary SELECT
     * tlist at this stage, but the case does arise with ORDER BY in an
     * aggregate function.
     */
    texpr = strip_implicit_coercions((Node *) tle->expr);

    if (equal(expr, texpr))
      return tle;
  }

  /*
   * If no matches, construct a new target entry which is appended to the
   * end of the target list.  This target is given resjunk = true so that it
   * will not be projected into the final tuple.
   */
  target_result = transformTargetEntry(pstate, node, expr, exprKind,
                     NULL, true);

  *tlist = lappend(*tlist, target_result);

  return target_result;
}

/*-------------------------------------------------------------------------
 * Flatten out parenthesized sublists in grouping lists, and some cases
 * of nested grouping sets.
 *
 * Inside a grouping set (ROLLUP, CUBE, or GROUPING SETS), we expect the
 * content to be nested no more than 2 deep: i.e. ROLLUP((a,b),(c,d)) is
 * ok, but ROLLUP((a,(b,c)),d) is flattened to ((a,b,c),d), which we then
 * (later) normalize to ((a,b,c),(d)).
 *
 * CUBE or ROLLUP can be nested inside GROUPING SETS (but not the reverse),
 * and we leave that alone if we find it. But if we see GROUPING SETS inside
 * GROUPING SETS, we can flatten and normalize as follows:
 *   GROUPING SETS (a, (b,c), GROUPING SETS ((c,d),(e)), (f,g))
 * becomes
 *   GROUPING SETS ((a), (b,c), (c,d), (e), (f,g))
 *
 * This is per the spec's syntax transformations, but these are the only such
 * transformations we do in parse analysis, so that queries retain the
 * originally specified grouping set syntax for CUBE and ROLLUP as much as
 * possible when deparsed. (Full expansion of the result into a list of
 * grouping sets is left to the planner.)
 *
 * When we're done, the resulting list should contain only these possible
 * elements:
 *   - an expression
 *   - a CUBE or ROLLUP with a list of expressions nested 2 deep
 *   - a GROUPING SET containing any of:
 *    - expression lists
 *    - empty grouping sets
 *    - CUBE or ROLLUP nodes with lists nested 2 deep
 * The return is a new list, but doesn't deep-copy the old nodes except for
 * GroupingSet nodes.
 *
 * As a side effect, flag whether the list has any GroupingSet nodes.
 *-------------------------------------------------------------------------
 */
static Node *
flatten_grouping_sets(Node *expr, bool toplevel, bool *hasGroupingSets)
{
  /* just in case of pathological input */
  check_stack_depth();

  if (expr == (Node *) NIL)
    return (Node *) NIL;

  switch (expr->type)
  {
    case T_RowExpr:
      {
        RowExpr    *r = (RowExpr *) expr;

        if (r->row_format == COERCE_IMPLICIT_CAST)
          return flatten_grouping_sets((Node *) r->args,
                         false, NULL);
      }
      break;
    case T_GroupingSet:
      {
        GroupingSet *gset = (GroupingSet *) expr;
        ListCell   *l2;
        List     *result_set = NIL;

        if (hasGroupingSets)
          *hasGroupingSets = true;

        /*
         * at the top level, we skip over all empty grouping sets; the
         * caller can supply the canonical GROUP BY () if nothing is
         * left.
         */

        if (toplevel && gset->kind == GROUPING_SET_EMPTY)
          return (Node *) NIL;

        foreach(l2, gset->content)
        {
          Node     *n1 = lfirst(l2);
          Node     *n2 = flatten_grouping_sets(n1, false, NULL);

          if (IsA(n1, GroupingSet) &&
            ((GroupingSet *) n1)->kind == GROUPING_SET_SETS)
            result_set = list_concat(result_set, (List *) n2);
          else
            result_set = lappend(result_set, n2);
        }

        /*
         * At top level, keep the grouping set node; but if we're in a
         * nested grouping set, then we need to concat the flattened
         * result into the outer list if it's simply nested.
         */

        if (toplevel || (gset->kind != GROUPING_SET_SETS))
        {
          return (Node *) makeGroupingSet(gset->kind, result_set, gset->location);
        }
        else
          return (Node *) result_set;
      }
    case T_List:
      {
        List     *result = NIL;
        ListCell   *l;

        foreach(l, (List *) expr)
        {
          Node     *n = flatten_grouping_sets(lfirst(l), toplevel, hasGroupingSets);

          if (n != (Node *) NIL)
          {
            if (IsA(n, List))
              result = list_concat(result, (List *) n);
            else
              result = lappend(result, n);
          }
        }

        return (Node *) result;
      }
    default:
      break;
  }

  return expr;
}

/*
 * Transform a single expression within a GROUP BY clause or grouping set.
 *
 * The expression is added to the targetlist if not already present, and to the
 * flatresult list (which will become the groupClause) if not already present
 * there.  The sortClause is consulted for operator and sort order hints.
 *
 * Returns the ressortgroupref of the expression.
 *
 * flatresult reference to flat list of SortGroupClause nodes
 * seen_local bitmapset of sortgrouprefs already seen at the local level
 * pstate   ParseState
 * gexpr    node to transform
 * targetlist reference to TargetEntry list
 * sortClause ORDER BY clause (SortGroupClause nodes)
 * exprKind   expression kind
 * useSQL99   SQL99 rather than SQL92 syntax
 * toplevel   false if within any grouping set
 */
static Index
transformGroupClauseExpr(List **flatresult, Bitmapset *seen_local,
             ParseState *pstate, Node *gexpr,
             List **targetlist, List *sortClause,
             ParseExprKind exprKind, bool useSQL99, bool toplevel)
{
  TargetEntry *tle;
  bool    found = false;

  if (useSQL99)
    tle = findTargetlistEntrySQL99(pstate, gexpr,
                     targetlist, exprKind);
  else
    tle = findTargetlistEntrySQL92(pstate, gexpr,
                     targetlist, exprKind);

  if (tle->ressortgroupref > 0)
  {
    ListCell   *sl;

    /*
     * Eliminate duplicates (GROUP BY x, x) but only at local level.
     * (Duplicates in grouping sets can affect the number of returned
     * rows, so can't be dropped indiscriminately.)
     *
     * Since we don't care about anything except the sortgroupref, we can
     * use a bitmapset rather than scanning lists.
     */
    if (bms_is_member(tle->ressortgroupref, seen_local))
      return 0;

    /*
     * If we're already in the flat clause list, we don't need to consider
     * adding ourselves again.
     */
    found = targetIsInSortList(tle, InvalidOid, *flatresult);
    if (found)
      return tle->ressortgroupref;

    /*
     * If the GROUP BY tlist entry also appears in ORDER BY, copy operator
     * info from the (first) matching ORDER BY item.  This means that if
     * you write something like "GROUP BY foo ORDER BY foo USING <<<", the
     * GROUP BY operation silently takes on the equality semantics implied
     * by the ORDER BY.  There are two reasons to do this: it improves the
     * odds that we can implement both GROUP BY and ORDER BY with a single
     * sort step, and it allows the user to choose the equality semantics
     * used by GROUP BY, should she be working with a datatype that has
     * more than one equality operator.
     *
     * If we're in a grouping set, though, we force our requested ordering
     * to be NULLS LAST, because if we have any hope of using a sorted agg
     * for the job, we're going to be tacking on generated NULL values
     * after the corresponding groups. If the user demands nulls first,
     * another sort step is going to be inevitable, but that's the
     * planner's problem.
     */

    foreach(sl, sortClause)
    {
      SortGroupClause *sc = (SortGroupClause *) lfirst(sl);

      if (sc->tleSortGroupRef == tle->ressortgroupref)
      {
        SortGroupClause *grpc = copyObject(sc);

        if (!toplevel)
          grpc->nulls_first = false;
        *flatresult = lappend(*flatresult, grpc);
        found = true;
        break;
      }
    }
  }

  /*
   * If no match in ORDER BY, just add it to the result using default
   * sort/group semantics.
   */
  if (!found)
    *flatresult = addTargetToGroupList(pstate, tle,
                       *flatresult, *targetlist,
                       exprLocation(gexpr));

  /*
   * _something_ must have assigned us a sortgroupref by now...
   */

  return tle->ressortgroupref;
}

/*
 * Transform a list of expressions within a GROUP BY clause or grouping set.
 *
 * The list of expressions belongs to a single clause within which duplicates
 * can be safely eliminated.
 *
 * Returns an integer list of ressortgroupref values.
 *
 * flatresult reference to flat list of SortGroupClause nodes
 * pstate   ParseState
 * list     nodes to transform
 * targetlist reference to TargetEntry list
 * sortClause ORDER BY clause (SortGroupClause nodes)
 * exprKind   expression kind
 * useSQL99   SQL99 rather than SQL92 syntax
 * toplevel   false if within any grouping set
 */
static List *
transformGroupClauseList(List **flatresult,
             ParseState *pstate, List *list,
             List **targetlist, List *sortClause,
             ParseExprKind exprKind, bool useSQL99, bool toplevel)
{
  Bitmapset  *seen_local = NULL;
  List     *result = NIL;
  ListCell   *gl;

  foreach(gl, list)
  {
    Node     *gexpr = (Node *) lfirst(gl);

    Index   ref = transformGroupClauseExpr(flatresult,
                           seen_local,
                           pstate,
                           gexpr,
                           targetlist,
                           sortClause,
                           exprKind,
                           useSQL99,
                           toplevel);

    if (ref > 0)
    {
      seen_local = bms_add_member(seen_local, ref);
      result = lappend_int(result, ref);
    }
  }

  return result;
}

/*
 * Transform a grouping set and (recursively) its content.
 *
 * The grouping set might be a GROUPING SETS node with other grouping sets
 * inside it, but SETS within SETS have already been flattened out before
 * reaching here.
 *
 * Returns the transformed node, which now contains SIMPLE nodes with lists
 * of ressortgrouprefs rather than expressions.
 *
 * flatresult reference to flat list of SortGroupClause nodes
 * pstate   ParseState
 * gset     grouping set to transform
 * targetlist reference to TargetEntry list
 * sortClause ORDER BY clause (SortGroupClause nodes)
 * exprKind   expression kind
 * useSQL99   SQL99 rather than SQL92 syntax
 * toplevel   false if within any grouping set
 */
static Node *
transformGroupingSet(List **flatresult,
           ParseState *pstate, GroupingSet *gset,
           List **targetlist, List *sortClause,
           ParseExprKind exprKind, bool useSQL99, bool toplevel)
{
  ListCell   *gl;
  List     *content = NIL;

  Assert(toplevel || gset->kind != GROUPING_SET_SETS);

  foreach(gl, gset->content)
  {
    Node     *n = lfirst(gl);

    if (IsA(n, List))
    {
      List     *l = transformGroupClauseList(flatresult,
                           pstate, (List *) n,
                           targetlist, sortClause,
                           exprKind, useSQL99, false);

      content = lappend(content, makeGroupingSet(GROUPING_SET_SIMPLE,
                             l,
                             exprLocation(n)));
    }
    else if (IsA(n, GroupingSet))
    {
      GroupingSet *gset2 = (GroupingSet *) lfirst(gl);

      content = lappend(content, transformGroupingSet(flatresult,
                              pstate, gset2,
                              targetlist, sortClause,
                              exprKind, useSQL99, false));
    }
    else
    {
      Index   ref = transformGroupClauseExpr(flatresult,
                             NULL,
                             pstate,
                             n,
                             targetlist,
                             sortClause,
                             exprKind,
                             useSQL99,
                             false);

      content = lappend(content, makeGroupingSet(GROUPING_SET_SIMPLE,
                             list_make1_int(ref),
                             exprLocation(n)));
    }
  }

  /* Arbitrarily cap the size of CUBE, which has exponential growth */
  if (gset->kind == GROUPING_SET_CUBE)
  {
    if (list_length(content) > 12)
      ereport(ERROR,
          (errcode(ERRCODE_TOO_MANY_COLUMNS),
           errmsg("CUBE is limited to 12 elements"),
           parser_errposition(pstate, gset->location)));
  }

  return (Node *) makeGroupingSet(gset->kind, content, gset->location);
}


/*
 * transformGroupClause -
 *    transform a GROUP BY clause
 *
 * GROUP BY items will be added to the targetlist (as resjunk columns)
 * if not already present, so the targetlist must be passed by reference.
 *
 * This is also used for window PARTITION BY clauses (which act almost the
 * same, but are always interpreted per SQL99 rules).
 *
 * Grouping sets make this a lot more complex than it was. Our goal here is
 * twofold: we make a flat list of SortGroupClause nodes referencing each
 * distinct expression used for grouping, with those expressions added to the
 * targetlist if needed. At the same time, we build the groupingSets tree,
 * which stores only ressortgrouprefs as integer lists inside GroupingSet nodes
 * (possibly nested, but limited in depth: a GROUPING_SET_SETS node can contain
 * nested SIMPLE, CUBE or ROLLUP nodes, but not more sets - we flatten that
 * out; while CUBE and ROLLUP can contain only SIMPLE nodes).
 *
 * We skip much of the hard work if there are no grouping sets.
 *
 * One subtlety is that the groupClause list can end up empty while the
 * groupingSets list is not; this happens if there are only empty grouping
 * sets, or an explicit GROUP BY (). This has the same effect as specifying
 * aggregates or a HAVING clause with no GROUP BY; the output is one row per
 * grouping set even if the input is empty.
 *
 * Returns the transformed (flat) groupClause.
 *
 * pstate   ParseState
 * grouplist  clause to transform
 * groupingSets reference to list to contain the grouping set tree
 * targetlist reference to TargetEntry list
 * sortClause ORDER BY clause (SortGroupClause nodes)
 * exprKind   expression kind
 * useSQL99   SQL99 rather than SQL92 syntax
 */
List *
transformGroupClause(ParseState *pstate, List *grouplist, List **groupingSets,
           List **targetlist, List *sortClause,
           ParseExprKind exprKind, bool useSQL99)
{
  List     *result = NIL;
  List     *flat_grouplist;
  List     *gsets = NIL;
  ListCell   *gl;
  bool    hasGroupingSets = false;
  Bitmapset  *seen_local = NULL;

  /*
   * Recursively flatten implicit RowExprs. (Technically this is only needed
   * for GROUP BY, per the syntax rules for grouping sets, but we do it
   * anyway.)
   */
  flat_grouplist = (List *) flatten_grouping_sets((Node *) grouplist,
                          true,
                          &hasGroupingSets);

  /*
   * If the list is now empty, but hasGroupingSets is true, it's because we
   * elided redundant empty grouping sets. Restore a single empty grouping
   * set to leave a canonical form: GROUP BY ()
   */

  if (flat_grouplist == NIL && hasGroupingSets)
  {
    flat_grouplist = list_make1(makeGroupingSet(GROUPING_SET_EMPTY,
                          NIL,
                          exprLocation((Node *) grouplist)));
  }

  foreach(gl, flat_grouplist)
  {
    Node     *gexpr = (Node *) lfirst(gl);

    if (IsA(gexpr, GroupingSet))
    {
      GroupingSet *gset = (GroupingSet *) gexpr;

      switch (gset->kind)
      {
        case GROUPING_SET_EMPTY:
          gsets = lappend(gsets, gset);
          break;
        case GROUPING_SET_SIMPLE:
          /* can't happen */
          Assert(false);
          break;
        case GROUPING_SET_SETS:
        case GROUPING_SET_CUBE:
        case GROUPING_SET_ROLLUP:
          gsets = lappend(gsets,
                  transformGroupingSet(&result,
                             pstate, gset,
                             targetlist, sortClause,
                             exprKind, useSQL99, true));
          break;
      }
    }
    else
    {
      Index   ref = transformGroupClauseExpr(&result, seen_local,
                             pstate, gexpr,
                             targetlist, sortClause,
                             exprKind, useSQL99, true);

      if (ref > 0)
      {
        seen_local = bms_add_member(seen_local, ref);
        if (hasGroupingSets)
          gsets = lappend(gsets,
                  makeGroupingSet(GROUPING_SET_SIMPLE,
                          list_make1_int(ref),
                          exprLocation(gexpr)));
      }
    }
  }

  /* parser should prevent this */
  Assert(gsets == NIL || groupingSets != NULL);

  if (groupingSets)
    *groupingSets = gsets;

  return result;
}

/*
 * transformSortClause -
 *    transform an ORDER BY clause
 *
 * ORDER BY items will be added to the targetlist (as resjunk columns)
 * if not already present, so the targetlist must be passed by reference.
 *
 * This is also used for window and aggregate ORDER BY clauses (which act
 * almost the same, but are always interpreted per SQL99 rules).
 */
List *
transformSortClause(ParseState *pstate,
          List *orderlist,
          List **targetlist,
          ParseExprKind exprKind,
          bool useSQL99)
{
  List     *sortlist = NIL;
  ListCell   *olitem;

  foreach(olitem, orderlist)
  {
    SortBy     *sortby = (SortBy *) lfirst(olitem);
    TargetEntry *tle;

    if (useSQL99)
      tle = findTargetlistEntrySQL99(pstate, sortby->node,
                       targetlist, exprKind);
    else
      tle = findTargetlistEntrySQL92(pstate, sortby->node,
                       targetlist, exprKind);

    sortlist = addTargetToSortList(pstate, tle,
                     sortlist, *targetlist, sortby);
  }

  return sortlist;
}

/*
 * transformWindowDefinitions -
 *    transform window definitions (WindowDef to WindowClause)
 */
List *
transformWindowDefinitions(ParseState *pstate,
               List *windowdefs,
               List **targetlist)
{
  List     *result = NIL;
  Index   winref = 0;
  ListCell   *lc;

  foreach(lc, windowdefs)
  {
    WindowDef  *windef = (WindowDef *) lfirst(lc);
    WindowClause *refwc = NULL;
    List     *partitionClause;
    List     *orderClause;
    Oid     rangeopfamily = InvalidOid;
    Oid     rangeopcintype = InvalidOid;
    WindowClause *wc;

    winref++;

    /*
     * Check for duplicate window names.
     */
    if (windef->name &&
      findWindowClause(result, windef->name) != NULL)
      ereport(ERROR,
          (errcode(ERRCODE_WINDOWING_ERROR),
           errmsg("window \"%s\" is already defined", windef->name),
           parser_errposition(pstate, windef->location)));

    /*
     * If it references a previous window, look that up.
     */
    if (windef->refname)
    {
      refwc = findWindowClause(result, windef->refname);
      if (refwc == NULL)
        ereport(ERROR,
            (errcode(ERRCODE_UNDEFINED_OBJECT),
             errmsg("window \"%s\" does not exist",
                windef->refname),
             parser_errposition(pstate, windef->location)));
    }

    /*
     * Transform PARTITION and ORDER specs, if any.  These are treated
     * almost exactly like top-level GROUP BY and ORDER BY clauses,
     * including the special handling of nondefault operator semantics.
     */
    orderClause = transformSortClause(pstate,
                      windef->orderClause,
                      targetlist,
                      EXPR_KIND_WINDOW_ORDER,
                      true /* force SQL99 rules */ );
    partitionClause = transformGroupClause(pstate,
                         windef->partitionClause,
                         NULL,
                         targetlist,
                         orderClause,
                         EXPR_KIND_WINDOW_PARTITION,
                         true /* force SQL99 rules */ );

    /*
     * And prepare the new WindowClause.
     */
    wc = makeNode(WindowClause);
    wc->name = windef->name;
    wc->refname = windef->refname;

    /*
     * Per spec, a windowdef that references a previous one copies the
     * previous partition clause (and mustn't specify its own).  It can
     * specify its own ordering clause, but only if the previous one had
     * none.  It always specifies its own frame clause, and the previous
     * one must not have a frame clause.  Yeah, it's bizarre that each of
     * these cases works differently, but SQL:2008 says so; see 7.11
     * <window clause> syntax rule 10 and general rule 1.  The frame
     * clause rule is especially bizarre because it makes "OVER foo"
     * different from "OVER (foo)", and requires the latter to throw an
     * error if foo has a nondefault frame clause.  Well, ours not to
     * reason why, but we do go out of our way to throw a useful error
     * message for such cases.
     */
    if (refwc)
    {
      if (partitionClause)
        ereport(ERROR,
            (errcode(ERRCODE_WINDOWING_ERROR),
             errmsg("cannot override PARTITION BY clause of window \"%s\"",
                windef->refname),
             parser_errposition(pstate, windef->location)));
      wc->partitionClause = copyObject(refwc->partitionClause);
    }
    else
      wc->partitionClause = partitionClause;
    if (refwc)
    {
      if (orderClause && refwc->orderClause)
        ereport(ERROR,
            (errcode(ERRCODE_WINDOWING_ERROR),
             errmsg("cannot override ORDER BY clause of window \"%s\"",
                windef->refname),
             parser_errposition(pstate, windef->location)));
      if (orderClause)
      {
        wc->orderClause = orderClause;
        wc->copiedOrder = false;
      }
      else
      {
        wc->orderClause = copyObject(refwc->orderClause);
        wc->copiedOrder = true;
      }
    }
    else
    {
      wc->orderClause = orderClause;
      wc->copiedOrder = false;
    }
    if (refwc && refwc->frameOptions != FRAMEOPTION_DEFAULTS)
    {
      /*
       * Use this message if this is a WINDOW clause, or if it's an OVER
       * clause that includes ORDER BY or framing clauses.  (We already
       * rejected PARTITION BY above, so no need to check that.)
       */
      if (windef->name ||
        orderClause || windef->frameOptions != FRAMEOPTION_DEFAULTS)
        ereport(ERROR,
            (errcode(ERRCODE_WINDOWING_ERROR),
             errmsg("cannot copy window \"%s\" because it has a frame clause",
                windef->refname),
             parser_errposition(pstate, windef->location)));
      /* Else this clause is just OVER (foo), so say this: */
      ereport(ERROR,
          (errcode(ERRCODE_WINDOWING_ERROR),
           errmsg("cannot copy window \"%s\" because it has a frame clause",
              windef->refname),
           errhint("Omit the parentheses in this OVER clause."),
           parser_errposition(pstate, windef->location)));
    }
    wc->frameOptions = windef->frameOptions;

    /*
     * RANGE offset PRECEDING/FOLLOWING requires exactly one ORDER BY
     * column; check that and get its sort opfamily info.
     */
    if ((wc->frameOptions & FRAMEOPTION_RANGE) &&
      (wc->frameOptions & (FRAMEOPTION_START_OFFSET |
                 FRAMEOPTION_END_OFFSET)))
    {
      SortGroupClause *sortcl;
      Node     *sortkey;
      CompareType rangecmptype;

      if (list_length(wc->orderClause) != 1)
        ereport(ERROR,
            (errcode(ERRCODE_WINDOWING_ERROR),
             errmsg("RANGE with offset PRECEDING/FOLLOWING requires exactly one ORDER BY column"),
             parser_errposition(pstate, windef->location)));
      sortcl = linitial_node(SortGroupClause, wc->orderClause);
      sortkey = get_sortgroupclause_expr(sortcl, *targetlist);
      /* Find the sort operator in pg_amop */
      if (!get_ordering_op_properties(sortcl->sortop,
                      &rangeopfamily,
                      &rangeopcintype,
                      &rangecmptype))
        elog(ERROR, "operator %u is not a valid ordering operator",
           sortcl->sortop);
      /* Record properties of sort ordering */
      wc->inRangeColl = exprCollation(sortkey);
      wc->inRangeAsc = !sortcl->reverse_sort;
      wc->inRangeNullsFirst = sortcl->nulls_first;
    }

    /* Per spec, GROUPS mode requires an ORDER BY clause */
    if (wc->frameOptions & FRAMEOPTION_GROUPS)
    {
      if (wc->orderClause == NIL)
        ereport(ERROR,
            (errcode(ERRCODE_WINDOWING_ERROR),
             errmsg("GROUPS mode requires an ORDER BY clause"),
             parser_errposition(pstate, windef->location)));
    }

    /* Process frame offset expressions */
    wc->startOffset = transformFrameOffset(pstate, wc->frameOptions,
                         rangeopfamily, rangeopcintype,
                         &wc->startInRangeFunc,
                         windef->startOffset);
    wc->endOffset = transformFrameOffset(pstate, wc->frameOptions,
                       rangeopfamily, rangeopcintype,
                       &wc->endInRangeFunc,
                       windef->endOffset);
    wc->winref = winref;

    result = lappend(result, wc);
  }

  return result;
}

/*
 * transformDistinctClause -
 *    transform a DISTINCT clause
 *
 * Since we may need to add items to the query's targetlist, that list
 * is passed by reference.
 *
 * As with GROUP BY, we absorb the sorting semantics of ORDER BY as much as
 * possible into the distinctClause.  This avoids a possible need to re-sort,
 * and allows the user to choose the equality semantics used by DISTINCT,
 * should she be working with a datatype that has more than one equality
 * operator.
 *
 * is_agg is true if we are transforming an aggregate(DISTINCT ...)
 * function call.  This does not affect any behavior, only the phrasing
 * of error messages.
 */
List *
transformDistinctClause(ParseState *pstate,
            List **targetlist, List *sortClause, bool is_agg)
{
  List     *result = NIL;
  ListCell   *slitem;
  ListCell   *tlitem;

  /*
   * The distinctClause should consist of all ORDER BY items followed by all
   * other non-resjunk targetlist items.  There must not be any resjunk
   * ORDER BY items --- that would imply that we are sorting by a value that
   * isn't necessarily unique within a DISTINCT group, so the results
   * wouldn't be well-defined.  This construction ensures we follow the rule
   * that sortClause and distinctClause match; in fact the sortClause will
   * always be a prefix of distinctClause.
   *
   * Note a corner case: the same TLE could be in the ORDER BY list multiple
   * times with different sortops.  We have to include it in the
   * distinctClause the same way to preserve the prefix property. The net
   * effect will be that the TLE value will be made unique according to both
   * sortops.
   */
  foreach(slitem, sortClause)
  {
    SortGroupClause *scl = (SortGroupClause *) lfirst(slitem);
    TargetEntry *tle = get_sortgroupclause_tle(scl, *targetlist);

    if (tle->resjunk)
      ereport(ERROR,
          (errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
           is_agg ?
           errmsg("in an aggregate with DISTINCT, ORDER BY expressions must appear in argument list") :
           errmsg("for SELECT DISTINCT, ORDER BY expressions must appear in select list"),
           parser_errposition(pstate,
                    exprLocation((Node *) tle->expr))));
    result = lappend(result, copyObject(scl));
  }

  /*
   * Now add any remaining non-resjunk tlist items, using default sort/group
   * semantics for their data types.
   */
  foreach(tlitem, *targetlist)
  {
    TargetEntry *tle = (TargetEntry *) lfirst(tlitem);

    if (tle->resjunk)
      continue;     /* ignore junk */
    result = addTargetToGroupList(pstate, tle,
                    result, *targetlist,
                    exprLocation((Node *) tle->expr));
  }

  /*
   * Complain if we found nothing to make DISTINCT.  Returning an empty list
   * would cause the parsed Query to look like it didn't have DISTINCT, with
   * results that would probably surprise the user.  Note: this case is
   * presently impossible for aggregates because of grammar restrictions,
   * but we check anyway.
   */
  if (result == NIL)
    ereport(ERROR,
        (errcode(ERRCODE_SYNTAX_ERROR),
         is_agg ?
         errmsg("an aggregate with DISTINCT must have at least one argument") :
         errmsg("SELECT DISTINCT must have at least one column")));

  return result;
}

/*
 * transformDistinctOnClause -
 *    transform a DISTINCT ON clause
 *
 * Since we may need to add items to the query's targetlist, that list
 * is passed by reference.
 *
 * As with GROUP BY, we absorb the sorting semantics of ORDER BY as much as
 * possible into the distinctClause.  This avoids a possible need to re-sort,
 * and allows the user to choose the equality semantics used by DISTINCT,
 * should she be working with a datatype that has more than one equality
 * operator.
 */
List *
transformDistinctOnClause(ParseState *pstate, List *distinctlist,
              List **targetlist, List *sortClause)
{
  List     *result = NIL;
  List     *sortgrouprefs = NIL;
  bool    skipped_sortitem;
  ListCell   *lc;
  ListCell   *lc2;

  /*
   * Add all the DISTINCT ON expressions to the tlist (if not already
   * present, they are added as resjunk items).  Assign sortgroupref numbers
   * to them, and make a list of these numbers.  (NB: we rely below on the
   * sortgrouprefs list being one-for-one with the original distinctlist.
   * Also notice that we could have duplicate DISTINCT ON expressions and
   * hence duplicate entries in sortgrouprefs.)
   */
  foreach(lc, distinctlist)
  {
    Node     *dexpr = (Node *) lfirst(lc);
    int     sortgroupref;
    TargetEntry *tle;

    tle = findTargetlistEntrySQL92(pstate, dexpr, targetlist,
                     EXPR_KIND_DISTINCT_ON);
    sortgroupref = assignSortGroupRef(tle, *targetlist);
    sortgrouprefs = lappend_int(sortgrouprefs, sortgroupref);
  }

  /*
   * If the user writes both DISTINCT ON and ORDER BY, adopt the sorting
   * semantics from ORDER BY items that match DISTINCT ON items, and also
   * adopt their column sort order.  We insist that the distinctClause and
   * sortClause match, so throw error if we find the need to add any more
   * distinctClause items after we've skipped an ORDER BY item that wasn't
   * in DISTINCT ON.
   */
  skipped_sortitem = false;
  foreach(lc, sortClause)
  {
    SortGroupClause *scl = (SortGroupClause *) lfirst(lc);

    if (list_member_int(sortgrouprefs, scl->tleSortGroupRef))
    {
      if (skipped_sortitem)
        ereport(ERROR,
            (errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
             errmsg("SELECT DISTINCT ON expressions must match initial ORDER BY expressions"),
             parser_errposition(pstate,
                      get_matching_location(scl->tleSortGroupRef,
                                  sortgrouprefs,
                                  distinctlist))));
      else
        result = lappend(result, copyObject(scl));
    }
    else
      skipped_sortitem = true;
  }

  /*
   * Now add any remaining DISTINCT ON items, using default sort/group
   * semantics for their data types.  (Note: this is pretty questionable; if
   * the ORDER BY list doesn't include all the DISTINCT ON items and more
   * besides, you certainly aren't using DISTINCT ON in the intended way,
   * and you probably aren't going to get consistent results.  It might be
   * better to throw an error or warning here.  But historically we've
   * allowed it, so keep doing so.)
   */
  forboth(lc, distinctlist, lc2, sortgrouprefs)
  {
    Node     *dexpr = (Node *) lfirst(lc);
    int     sortgroupref = lfirst_int(lc2);
    TargetEntry *tle = get_sortgroupref_tle(sortgroupref, *targetlist);

    if (targetIsInSortList(tle, InvalidOid, result))
      continue;     /* already in list (with some semantics) */
    if (skipped_sortitem)
      ereport(ERROR,
          (errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
           errmsg("SELECT DISTINCT ON expressions must match initial ORDER BY expressions"),
           parser_errposition(pstate, exprLocation(dexpr))));
    result = addTargetToGroupList(pstate, tle,
                    result, *targetlist,
                    exprLocation(dexpr));
  }

  /*
   * An empty result list is impossible here because of grammar
   * restrictions.
   */
  Assert(result != NIL);

  return result;
}

/*
 * get_matching_location
 *    Get the exprLocation of the exprs member corresponding to the
 *    (first) member of sortgrouprefs that equals sortgroupref.
 *
 * This is used so that we can point at a troublesome DISTINCT ON entry.
 * (Note that we need to use the original untransformed DISTINCT ON list
 * item, as whatever TLE it corresponds to will very possibly have a
 * parse location pointing to some matching entry in the SELECT list
 * or ORDER BY list.)
 */
static int
get_matching_location(int sortgroupref, List *sortgrouprefs, List *exprs)
{
  ListCell   *lcs;
  ListCell   *lce;

  forboth(lcs, sortgrouprefs, lce, exprs)
  {
    if (lfirst_int(lcs) == sortgroupref)
      return exprLocation((Node *) lfirst(lce));
  }
  /* if no match, caller blew it */
  elog(ERROR, "get_matching_location: no matching sortgroupref");
  return -1;         /* keep compiler quiet */
}

/*
 * resolve_unique_index_expr
 *    Infer a unique index from a list of indexElems, for ON
 *    CONFLICT clause
 *
 * Perform parse analysis of expressions and columns appearing within ON
 * CONFLICT clause.  During planning, the returned list of expressions is used
 * to infer which unique index to use.
 */
static List *
resolve_unique_index_expr(ParseState *pstate, InferClause *infer,
              Relation heapRel)
{
  List     *result = NIL;
  ListCell   *l;

  foreach(l, infer->indexElems)
  {
    IndexElem  *ielem = (IndexElem *) lfirst(l);
    InferenceElem *pInfer = makeNode(InferenceElem);
    Node     *parse;

    /*
     * Raw grammar re-uses CREATE INDEX infrastructure for unique index
     * inference clause, and so will accept opclasses by name and so on.
     *
     * Make no attempt to match ASC or DESC ordering, NULLS FIRST/NULLS
     * LAST ordering or opclass options, since those are not significant
     * for inference purposes (any unique index matching the inference
     * specification in other regards is accepted indifferently). Actively
     * reject this as wrong-headed.
     */
    if (ielem->ordering != SORTBY_DEFAULT)
      ereport(ERROR,
          (errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
           errmsg("%s is not allowed in ON CONFLICT clause",
              "ASC/DESC"),
           parser_errposition(pstate, ielem->location)));
    if (ielem->nulls_ordering != SORTBY_NULLS_DEFAULT)
      ereport(ERROR,
          (errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
           errmsg("%s is not allowed in ON CONFLICT clause",
              "NULLS FIRST/LAST"),
           parser_errposition(pstate, ielem->location)));
    if (ielem->opclassopts)
      ereport(ERROR,
          errcode(ERRCODE_INVALID_COLUMN_REFERENCE),
          errmsg("operator class options are not allowed in ON CONFLICT clause"),
          parser_errposition(pstate, ielem->location));

    if (!ielem->expr)
    {
      /* Simple index attribute */
      ColumnRef  *n;

      /*
       * Grammar won't have built raw expression for us in event of
       * plain column reference.  Create one directly, and perform
       * expression transformation.  Planner expects this, and performs
       * its own normalization for the purposes of matching against
       * pg_index.
       */
      n = makeNode(ColumnRef);
      n->fields = list_make1(makeString(ielem->name));
      /* Location is approximately that of inference specification */
      n->location = infer->location;
      parse = (Node *) n;
    }
    else
    {
      /* Do parse transformation of the raw expression */
      parse = (Node *) ielem->expr;
    }

    /*
     * transformExpr() will reject subqueries, aggregates, window
     * functions, and SRFs, based on being passed
     * EXPR_KIND_INDEX_EXPRESSION.  So we needn't worry about those
     * further ... not that they would match any available index
     * expression anyway.
     */
    pInfer->expr = transformExpr(pstate, parse, EXPR_KIND_INDEX_EXPRESSION);

    /* Perform lookup of collation and operator class as required */
    if (!ielem->collation)
      pInfer->infercollid = InvalidOid;
    else
      pInfer->infercollid = LookupCollation(pstate, ielem->collation,
                          ielem->location);

    if (!ielem->opclass)
      pInfer->inferopclass = InvalidOid;
    else
      pInfer->inferopclass = get_opclass_oid(BTREE_AM_OID,
                           ielem->opclass, false);

    result = lappend(result, pInfer);
  }

  return result;
}

/*
 * transformOnConflictArbiter -
 *    transform arbiter expressions in an ON CONFLICT clause.
 *
 * Transformed expressions used to infer one unique index relation to serve as
 * an ON CONFLICT arbiter.  Partial unique indexes may be inferred using WHERE
 * clause from inference specification clause.
 */
void
transformOnConflictArbiter(ParseState *pstate,
               OnConflictClause *onConflictClause,
               List **arbiterExpr, Node **arbiterWhere,
               Oid *constraint)
{
  InferClause *infer = onConflictClause->infer;

  *arbiterExpr = NIL;
  *arbiterWhere = NULL;
  *constraint = InvalidOid;

  if ((onConflictClause->action == ONCONFLICT_UPDATE ||
     onConflictClause->action == ONCONFLICT_SELECT) && !infer)
    ereport(ERROR,
        errcode(ERRCODE_SYNTAX_ERROR),
        errmsg("ON CONFLICT DO %s requires inference specification or constraint name",
             onConflictClause->action == ONCONFLICT_UPDATE ? "UPDATE" : "SELECT"),
        errhint("For example, ON CONFLICT (column_name)."),
        parser_errposition(pstate,
                   exprLocation((Node *) onConflictClause)));

  /*
   * To simplify certain aspects of its design, speculative insertion into
   * system catalogs is disallowed
   */
  if (IsCatalogRelation(pstate->p_target_relation))
    ereport(ERROR,
        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
         errmsg("ON CONFLICT is not supported with system catalog tables"),
         parser_errposition(pstate,
                  exprLocation((Node *) onConflictClause))));

  /* Same applies to table used by logical decoding as catalog table */
  if (RelationIsUsedAsCatalogTable(pstate->p_target_relation))
    ereport(ERROR,
        (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
         errmsg("ON CONFLICT is not supported on table \"%s\" used as a catalog table",
            RelationGetRelationName(pstate->p_target_relation)),
         parser_errposition(pstate,
                  exprLocation((Node *) onConflictClause))));

  /* ON CONFLICT DO NOTHING does not require an inference clause */
  if (infer)
  {
    if (infer->indexElems)
      *arbiterExpr = resolve_unique_index_expr(pstate, infer,
                           pstate->p_target_relation);

    /*
     * Handling inference WHERE clause (for partial unique index
     * inference)
     */
    if (infer->whereClause)
      *arbiterWhere = transformExpr(pstate, infer->whereClause,
                      EXPR_KIND_INDEX_PREDICATE);

    /*
     * If the arbiter is specified by constraint name, get the constraint
     * OID and mark the constrained columns as requiring SELECT privilege,
     * in the same way as would have happened if the arbiter had been
     * specified by explicit reference to the constraint's index columns.
     */
    if (infer->conname)
    {
      Oid     relid = RelationGetRelid(pstate->p_target_relation);
      RTEPermissionInfo *perminfo = pstate->p_target_nsitem->p_perminfo;
      Bitmapset  *conattnos;

      conattnos = get_relation_constraint_attnos(relid, infer->conname,
                             false, constraint);

      /* Make sure the rel as a whole is marked for SELECT access */
      perminfo->requiredPerms |= ACL_SELECT;
      /* Mark the constrained columns as requiring SELECT access */
      perminfo->selectedCols = bms_add_members(perminfo->selectedCols,
                           conattnos);
    }
  }

  /*
   * It's convenient to form a list of expressions based on the
   * representation used by CREATE INDEX, since the same restrictions are
   * appropriate (e.g. on subqueries).  However, from here on, a dedicated
   * primnode representation is used for inference elements, and so
   * assign_query_collations() can be trusted to do the right thing with the
   * post parse analysis query tree inference clause representation.
   */
}

/*
 * addTargetToSortList
 *    If the given targetlist entry isn't already in the SortGroupClause
 *    list, add it to the end of the list, using the given sort ordering
 *    info.
 *
 * Returns the updated SortGroupClause list.
 */
List *
addTargetToSortList(ParseState *pstate, TargetEntry *tle,
          List *sortlist, List *targetlist, SortBy *sortby)
{
  Oid     restype = exprType((Node *) tle->expr);
  Oid     sortop;
  Oid     eqop;
  bool    hashable;
  bool    reverse;
  int     location;
  ParseCallbackState pcbstate;

  /* if tlist item is an UNKNOWN literal, change it to TEXT */
  if (restype == UNKNOWNOID)
  {
    tle->expr = (Expr *) coerce_type(pstate, (Node *) tle->expr,
                     restype, TEXTOID, -1,
                     COERCION_IMPLICIT,
                     COERCE_IMPLICIT_CAST,
                     -1);
    restype = TEXTOID;
  }

  /*
   * Rather than clutter the API of get_sort_group_operators and the other
   * functions we're about to use, make use of error context callback to
   * mark any error reports with a parse position.  We point to the operator
   * location if present, else to the expression being sorted.  (NB: use the
   * original untransformed expression here; the TLE entry might well point
   * at a duplicate expression in the regular SELECT list.)
   */
  location = sortby->location;
  if (location < 0)
    location = exprLocation(sortby->node);
  setup_parser_errposition_callback(&pcbstate, pstate, location);

  /* determine the sortop, eqop, and directionality */
  switch (sortby->sortby_dir)
  {
    case SORTBY_DEFAULT:
    case SORTBY_ASC:
      get_sort_group_operators(restype,
                   true, true, false,
                   &sortop, &eqop, NULL,
                   &hashable);
      reverse = false;
      break;
    case SORTBY_DESC:
      get_sort_group_operators(restype,
                   false, true, true,
                   NULL, &eqop, &sortop,
                   &hashable);
      reverse = true;
      break;
    case SORTBY_USING:
      Assert(sortby->useOp != NIL);
      sortop = compatible_oper_opid(sortby->useOp,
                      restype,
                      restype,
                      false);

      /*
       * Verify it's a valid ordering operator, fetch the corresponding
       * equality operator, and determine whether to consider it like
       * ASC or DESC.
       */
      eqop = get_equality_op_for_ordering_op(sortop, &reverse);
      if (!OidIsValid(eqop))
        ereport(ERROR,
            (errcode(ERRCODE_WRONG_OBJECT_TYPE),
             errmsg("operator %s is not a valid ordering operator",
                strVal(llast(sortby->useOp))),
             errhint("Ordering operators must be \"<\" or \">\" members of btree operator families.")));

      /*
       * Also see if the equality operator is hashable.
       */
      hashable = op_hashjoinable(eqop, restype);
      break;
    default:
      elog(ERROR, "unrecognized sortby_dir: %d", sortby->sortby_dir);
      sortop = InvalidOid; /* keep compiler quiet */
      eqop = InvalidOid;
      hashable = false;
      reverse = false;
      break;
  }

  cancel_parser_errposition_callback(&pcbstate);

  /* avoid making duplicate sortlist entries */
  if (!targetIsInSortList(tle, sortop, sortlist))
  {
    SortGroupClause *sortcl = makeNode(SortGroupClause);

    sortcl->tleSortGroupRef = assignSortGroupRef(tle, targetlist);

    sortcl->eqop = eqop;
    sortcl->sortop = sortop;
    sortcl->hashable = hashable;
    sortcl->reverse_sort = reverse;

    switch (sortby->sortby_nulls)
    {
      case SORTBY_NULLS_DEFAULT:
        /* NULLS FIRST is default for DESC; other way for ASC */
        sortcl->nulls_first = reverse;
        break;
      case SORTBY_NULLS_FIRST:
        sortcl->nulls_first = true;
        break;
      case SORTBY_NULLS_LAST:
        sortcl->nulls_first = false;
        break;
      default:
        elog(ERROR, "unrecognized sortby_nulls: %d",
           sortby->sortby_nulls);
        break;
    }

    sortlist = lappend(sortlist, sortcl);
  }

  return sortlist;
}

/*
 * addTargetToGroupList
 *    If the given targetlist entry isn't already in the SortGroupClause
 *    list, add it to the end of the list, using default sort/group
 *    semantics.
 *
 * This is very similar to addTargetToSortList, except that we allow the
 * case where only a grouping (equality) operator can be found, and that
 * the TLE is considered "already in the list" if it appears there with any
 * sorting semantics.
 *
 * location is the parse location to be fingered in event of trouble.  Note
 * that we can't rely on exprLocation(tle->expr), because that might point
 * to a SELECT item that matches the GROUP BY item; it'd be pretty confusing
 * to report such a location.
 *
 * Returns the updated SortGroupClause list.
 */
static List *
addTargetToGroupList(ParseState *pstate, TargetEntry *tle,
           List *grouplist, List *targetlist, int location)
{
  Oid     restype = exprType((Node *) tle->expr);

  /* if tlist item is an UNKNOWN literal, change it to TEXT */
  if (restype == UNKNOWNOID)
  {
    tle->expr = (Expr *) coerce_type(pstate, (Node *) tle->expr,
                     restype, TEXTOID, -1,
                     COERCION_IMPLICIT,
                     COERCE_IMPLICIT_CAST,
                     -1);
    restype = TEXTOID;
  }

  /* avoid making duplicate grouplist entries */
  if (!targetIsInSortList(tle, InvalidOid, grouplist))
  {
    SortGroupClause *grpcl = makeNode(SortGroupClause);
    Oid     sortop;
    Oid     eqop;
    bool    hashable;
    ParseCallbackState pcbstate;

    setup_parser_errposition_callback(&pcbstate, pstate, location);

    /* determine the eqop and optional sortop */
    get_sort_group_operators(restype,
                 false, true, false,
                 &sortop, &eqop, NULL,
                 &hashable);

    cancel_parser_errposition_callback(&pcbstate);

    grpcl->tleSortGroupRef = assignSortGroupRef(tle, targetlist);
    grpcl->eqop = eqop;
    grpcl->sortop = sortop;
    grpcl->reverse_sort = false;  /* sortop is "less than", or
                     * InvalidOid */
    grpcl->nulls_first = false; /* OK with or without sortop */
    grpcl->hashable = hashable;

    grouplist = lappend(grouplist, grpcl);
  }

  return grouplist;
}

/*
 * assignSortGroupRef
 *    Assign the targetentry an unused ressortgroupref, if it doesn't
 *    already have one.  Return the assigned or pre-existing refnumber.
 *
 * 'tlist' is the targetlist containing (or to contain) the given targetentry.
 */
Index
assignSortGroupRef(TargetEntry *tle, List *tlist)
{
  Index   maxRef;
  ListCell   *l;

  if (tle->ressortgroupref) /* already has one? */
    return tle->ressortgroupref;

  /* easiest way to pick an unused refnumber: max used + 1 */
  maxRef = 0;
  foreach(l, tlist)
  {
    Index   ref = ((TargetEntry *) lfirst(l))->ressortgroupref;

    if (ref > maxRef)
      maxRef = ref;
  }
  tle->ressortgroupref = maxRef + 1;
  return tle->ressortgroupref;
}

/*
 * targetIsInSortList
 *    Is the given target item already in the sortlist?
 *    If sortop is not InvalidOid, also test for a match to the sortop.
 *
 * It is not an oversight that this function ignores the nulls_first flag.
 * We check sortop when determining if an ORDER BY item is redundant with
 * earlier ORDER BY items, because it's conceivable that "ORDER BY
 * foo USING <, foo USING <<<" is not redundant, if <<< distinguishes
 * values that < considers equal.  We need not check nulls_first
 * however, because a lower-order column with the same sortop but
 * opposite nulls direction is redundant.  Also, we can consider
 * ORDER BY foo ASC, foo DESC redundant, so check for a commutator match.
 *
 * Works for both ordering and grouping lists (sortop would normally be
 * InvalidOid when considering grouping).  Note that the main reason we need
 * this routine (and not just a quick test for nonzeroness of ressortgroupref)
 * is that a TLE might be in only one of the lists.
 */
bool
targetIsInSortList(TargetEntry *tle, Oid sortop, List *sortList)
{
  Index   ref = tle->ressortgroupref;
  ListCell   *l;

  /* no need to scan list if tle has no marker */
  if (ref == 0)
    return false;

  foreach(l, sortList)
  {
    SortGroupClause *scl = (SortGroupClause *) lfirst(l);

    if (scl->tleSortGroupRef == ref &&
      (sortop == InvalidOid ||
       sortop == scl->sortop ||
       sortop == get_commutator(scl->sortop)))
      return true;
  }
  return false;
}

/*
 * findWindowClause
 *    Find the named WindowClause in the list, or return NULL if not there
 */
static WindowClause *
findWindowClause(List *wclist, const char *name)
{
  ListCell   *l;

  foreach(l, wclist)
  {
    WindowClause *wc = (WindowClause *) lfirst(l);

    if (wc->name && strcmp(wc->name, name) == 0)
      return wc;
  }

  return NULL;
}

/*
 * transformFrameOffset
 *    Process a window frame offset expression
 *
 * In RANGE mode, rangeopfamily is the sort opfamily for the input ORDER BY
 * column, and rangeopcintype is the input data type the sort operator is
 * registered with.  We expect the in_range function to be registered with
 * that same type.  (In binary-compatible cases, it might be different from
 * the input column's actual type, so we can't use that for the lookups.)
 * We'll return the OID of the in_range function to *inRangeFunc.
 */
static Node *
transformFrameOffset(ParseState *pstate, int frameOptions,
           Oid rangeopfamily, Oid rangeopcintype, Oid *inRangeFunc,
           Node *clause)
{
  const char *constructName = NULL;
  Node     *node;

  *inRangeFunc = InvalidOid; /* default result */

  /* Quick exit if no offset expression */
  if (clause == NULL)
    return NULL;

  if (frameOptions & FRAMEOPTION_ROWS)
  {
    /* Transform the raw expression tree */
    node = transformExpr(pstate, clause, EXPR_KIND_WINDOW_FRAME_ROWS);

    /*
     * Like LIMIT clause, simply coerce to int8
     */
    constructName = "ROWS";
    node = coerce_to_specific_type(pstate, node, INT8OID, constructName);
  }
  else if (frameOptions & FRAMEOPTION_RANGE)
  {
    /*
     * We must look up the in_range support function that's to be used,
     * possibly choosing one of several, and coerce the "offset" value to
     * the appropriate input type.
     */
    Oid     nodeType;
    Oid     preferredType;
    int     nfuncs = 0;
    int     nmatches = 0;
    Oid     selectedType = InvalidOid;
    Oid     selectedFunc = InvalidOid;
    CatCList   *proclist;
    int     i;

    /* Transform the raw expression tree */
    node = transformExpr(pstate, clause, EXPR_KIND_WINDOW_FRAME_RANGE);
    nodeType = exprType(node);

    /*
     * If there are multiple candidates, we'll prefer the one that exactly
     * matches nodeType; or if nodeType is as yet unknown, prefer the one
     * that exactly matches the sort column type.  (The second rule is
     * like what we do for "known_type operator unknown".)
     */
    preferredType = (nodeType != UNKNOWNOID) ? nodeType : rangeopcintype;

    /* Find the in_range support functions applicable to this case */
    proclist = SearchSysCacheList2(AMPROCNUM,
                     ObjectIdGetDatum(rangeopfamily),
                     ObjectIdGetDatum(rangeopcintype));
    for (i = 0; i < proclist->n_members; i++)
    {
      HeapTuple proctup = &proclist->members[i]->tuple;
      Form_pg_amproc procform = (Form_pg_amproc) GETSTRUCT(proctup);

      /* The search will find all support proc types; ignore others */
      if (procform->amprocnum != BTINRANGE_PROC)
        continue;
      nfuncs++;

      /* Ignore function if given value can't be coerced to that type */
      if (!can_coerce_type(1, &nodeType, &procform->amprocrighttype,
                 COERCION_IMPLICIT))
        continue;
      nmatches++;

      /* Remember preferred match, or any match if didn't find that */
      if (selectedType != preferredType)
      {
        selectedType = procform->amprocrighttype;
        selectedFunc = procform->amproc;
      }
    }
    ReleaseCatCacheList(proclist);

    /*
     * Throw error if needed.  It seems worth taking the trouble to
     * distinguish "no support at all" from "you didn't match any
     * available offset type".
     */
    if (nfuncs == 0)
      ereport(ERROR,
          (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
           errmsg("RANGE with offset PRECEDING/FOLLOWING is not supported for column type %s",
              format_type_be(rangeopcintype)),
           parser_errposition(pstate, exprLocation(node))));
    if (nmatches == 0)
      ereport(ERROR,
          (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
           errmsg("RANGE with offset PRECEDING/FOLLOWING is not supported for column type %s and offset type %s",
              format_type_be(rangeopcintype),
              format_type_be(nodeType)),
           errhint("Cast the offset value to an appropriate type."),
           parser_errposition(pstate, exprLocation(node))));
    if (nmatches != 1 && selectedType != preferredType)
      ereport(ERROR,
          (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
           errmsg("RANGE with offset PRECEDING/FOLLOWING has multiple interpretations for column type %s and offset type %s",
              format_type_be(rangeopcintype),
              format_type_be(nodeType)),
           errhint("Cast the offset value to the exact intended type."),
           parser_errposition(pstate, exprLocation(node))));

    /* OK, coerce the offset to the right type */
    constructName = "RANGE";
    node = coerce_to_specific_type(pstate, node,
                     selectedType, constructName);
    *inRangeFunc = selectedFunc;
  }
  else if (frameOptions & FRAMEOPTION_GROUPS)
  {
    /* Transform the raw expression tree */
    node = transformExpr(pstate, clause, EXPR_KIND_WINDOW_FRAME_GROUPS);

    /*
     * Like LIMIT clause, simply coerce to int8
     */
    constructName = "GROUPS";
    node = coerce_to_specific_type(pstate, node, INT8OID, constructName);
  }
  else
  {
    Assert(false);
    node = NULL;
  }

  /* Disallow variables in frame offsets */
  checkExprIsVarFree(pstate, node, constructName);

  return node;
}

Coverage Report

Created: 2026-11-12 07:20