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

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/*-------------------------------------------------------------------------
 *
 * pathnode.c
 *    Routines to manipulate pathlists and create path nodes
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/optimizer/util/pathnode.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include <math.h>

#include "foreign/fdwapi.h"
#include "miscadmin.h"
#include "nodes/extensible.h"
#include "optimizer/appendinfo.h"
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/optimizer.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/planmain.h"
#include "optimizer/tlist.h"
#include "parser/parsetree.h"
#include "utils/memutils.h"
#include "utils/selfuncs.h"

typedef enum
{
  COSTS_EQUAL,        /* path costs are fuzzily equal */
  COSTS_BETTER1,        /* first path is cheaper than second */
  COSTS_BETTER2,        /* second path is cheaper than first */
  COSTS_DIFFERENT,      /* neither path dominates the other on cost */
} PathCostComparison;

/*
 * STD_FUZZ_FACTOR is the normal fuzz factor for compare_path_costs_fuzzily.
 * XXX is it worth making this user-controllable?  It provides a tradeoff
 * between planner runtime and the accuracy of path cost comparisons.
 */
#define STD_FUZZ_FACTOR 1.01

static List *translate_sub_tlist(List *tlist, int relid);
static int  append_total_cost_compare(const ListCell *a, const ListCell *b);
static int  append_startup_cost_compare(const ListCell *a, const ListCell *b);
static List *reparameterize_pathlist_by_child(PlannerInfo *root,
                        List *pathlist,
                        RelOptInfo *child_rel);
static bool pathlist_is_reparameterizable_by_child(List *pathlist,
                           RelOptInfo *child_rel);


/*****************************************************************************
 *    MISC. PATH UTILITIES
 *****************************************************************************/

/*
 * compare_path_costs
 *    Return -1, 0, or +1 according as path1 is cheaper, the same cost,
 *    or more expensive than path2 for the specified criterion.
 */
int
compare_path_costs(Path *path1, Path *path2, CostSelector criterion)
{
  /* Number of disabled nodes, if different, trumps all else. */
  if (unlikely(path1->disabled_nodes != path2->disabled_nodes))
  {
    if (path1->disabled_nodes < path2->disabled_nodes)
      return -1;
    else
      return +1;
  }

  if (criterion == STARTUP_COST)
  {
    if (path1->startup_cost < path2->startup_cost)
      return -1;
    if (path1->startup_cost > path2->startup_cost)
      return +1;

    /*
     * If paths have the same startup cost (not at all unlikely), order
     * them by total cost.
     */
    if (path1->total_cost < path2->total_cost)
      return -1;
    if (path1->total_cost > path2->total_cost)
      return +1;
  }
  else
  {
    if (path1->total_cost < path2->total_cost)
      return -1;
    if (path1->total_cost > path2->total_cost)
      return +1;

    /*
     * If paths have the same total cost, order them by startup cost.
     */
    if (path1->startup_cost < path2->startup_cost)
      return -1;
    if (path1->startup_cost > path2->startup_cost)
      return +1;
  }
  return 0;
}

/*
 * compare_fractional_path_costs
 *    Return -1, 0, or +1 according as path1 is cheaper, the same cost,
 *    or more expensive than path2 for fetching the specified fraction
 *    of the total tuples.
 *
 * If fraction is <= 0 or > 1, we interpret it as 1, ie, we select the
 * path with the cheaper total_cost.
 */
int
compare_fractional_path_costs(Path *path1, Path *path2,
                double fraction)
{
  Cost    cost1,
        cost2;

  /* Number of disabled nodes, if different, trumps all else. */
  if (unlikely(path1->disabled_nodes != path2->disabled_nodes))
  {
    if (path1->disabled_nodes < path2->disabled_nodes)
      return -1;
    else
      return +1;
  }

  if (fraction <= 0.0 || fraction >= 1.0)
    return compare_path_costs(path1, path2, TOTAL_COST);
  cost1 = path1->startup_cost +
    fraction * (path1->total_cost - path1->startup_cost);
  cost2 = path2->startup_cost +
    fraction * (path2->total_cost - path2->startup_cost);
  if (cost1 < cost2)
    return -1;
  if (cost1 > cost2)
    return +1;
  return 0;
}

/*
 * compare_path_costs_fuzzily
 *    Compare the costs of two paths to see if either can be said to
 *    dominate the other.
 *
 * We use fuzzy comparisons so that add_path() can avoid keeping both of
 * a pair of paths that really have insignificantly different cost.
 *
 * The fuzz_factor argument must be 1.0 plus delta, where delta is the
 * fraction of the smaller cost that is considered to be a significant
 * difference.  For example, fuzz_factor = 1.01 makes the fuzziness limit
 * be 1% of the smaller cost.
 *
 * The two paths are said to have "equal" costs if both startup and total
 * costs are fuzzily the same.  Path1 is said to be better than path2 if
 * it has fuzzily better startup cost and fuzzily no worse total cost,
 * or if it has fuzzily better total cost and fuzzily no worse startup cost.
 * Path2 is better than path1 if the reverse holds.  Finally, if one path
 * is fuzzily better than the other on startup cost and fuzzily worse on
 * total cost, we just say that their costs are "different", since neither
 * dominates the other across the whole performance spectrum.
 *
 * This function also enforces a policy rule that paths for which the relevant
 * one of parent->consider_startup and parent->consider_param_startup is false
 * cannot survive comparisons solely on the grounds of good startup cost, so
 * we never return COSTS_DIFFERENT when that is true for the total-cost loser.
 * (But if total costs are fuzzily equal, we compare startup costs anyway,
 * in hopes of eliminating one path or the other.)
 */
static PathCostComparison
compare_path_costs_fuzzily(Path *path1, Path *path2, double fuzz_factor)
{
#define CONSIDER_PATH_STARTUP_COST(p)  \
  ((p)->param_info == NULL ? (p)->parent->consider_startup : (p)->parent->consider_param_startup)

  /* Number of disabled nodes, if different, trumps all else. */
  if (unlikely(path1->disabled_nodes != path2->disabled_nodes))
  {
    if (path1->disabled_nodes < path2->disabled_nodes)
      return COSTS_BETTER1;
    else
      return COSTS_BETTER2;
  }

  /*
   * Check total cost first since it's more likely to be different; many
   * paths have zero startup cost.
   */
  if (path1->total_cost > path2->total_cost * fuzz_factor)
  {
    /* path1 fuzzily worse on total cost */
    if (CONSIDER_PATH_STARTUP_COST(path1) &&
      path2->startup_cost > path1->startup_cost * fuzz_factor)
    {
      /* ... but path2 fuzzily worse on startup, so DIFFERENT */
      return COSTS_DIFFERENT;
    }
    /* else path2 dominates */
    return COSTS_BETTER2;
  }
  if (path2->total_cost > path1->total_cost * fuzz_factor)
  {
    /* path2 fuzzily worse on total cost */
    if (CONSIDER_PATH_STARTUP_COST(path2) &&
      path1->startup_cost > path2->startup_cost * fuzz_factor)
    {
      /* ... but path1 fuzzily worse on startup, so DIFFERENT */
      return COSTS_DIFFERENT;
    }
    /* else path1 dominates */
    return COSTS_BETTER1;
  }
  /* fuzzily the same on total cost ... */
  if (path1->startup_cost > path2->startup_cost * fuzz_factor)
  {
    /* ... but path1 fuzzily worse on startup, so path2 wins */
    return COSTS_BETTER2;
  }
  if (path2->startup_cost > path1->startup_cost * fuzz_factor)
  {
    /* ... but path2 fuzzily worse on startup, so path1 wins */
    return COSTS_BETTER1;
  }
  /* fuzzily the same on both costs */
  return COSTS_EQUAL;

#undef CONSIDER_PATH_STARTUP_COST
}

/*
 * set_cheapest
 *    Find the minimum-cost paths from among a relation's paths,
 *    and save them in the rel's cheapest-path fields.
 *
 * cheapest_total_path is normally the cheapest-total-cost unparameterized
 * path; but if there are no unparameterized paths, we assign it to be the
 * best (cheapest least-parameterized) parameterized path.  However, only
 * unparameterized paths are considered candidates for cheapest_startup_path,
 * so that will be NULL if there are no unparameterized paths.
 *
 * The cheapest_parameterized_paths list collects all parameterized paths
 * that have survived the add_path() tournament for this relation.  (Since
 * add_path ignores pathkeys for a parameterized path, these will be paths
 * that have best cost or best row count for their parameterization.  We
 * may also have both a parallel-safe and a non-parallel-safe path in some
 * cases for the same parameterization in some cases, but this should be
 * relatively rare since, most typically, all paths for the same relation
 * will be parallel-safe or none of them will.)
 *
 * cheapest_parameterized_paths always includes the cheapest-total
 * unparameterized path, too, if there is one; the users of that list find
 * it more convenient if that's included.
 *
 * This is normally called only after we've finished constructing the path
 * list for the rel node.
 */
void
set_cheapest(RelOptInfo *parent_rel)
{
  Path     *cheapest_startup_path;
  Path     *cheapest_total_path;
  Path     *best_param_path;
  List     *parameterized_paths;
  ListCell   *p;

  Assert(IsA(parent_rel, RelOptInfo));

  if (parent_rel->pathlist == NIL)
    elog(ERROR, "could not devise a query plan for the given query");

  cheapest_startup_path = cheapest_total_path = best_param_path = NULL;
  parameterized_paths = NIL;

  foreach(p, parent_rel->pathlist)
  {
    Path     *path = (Path *) lfirst(p);
    int     cmp;

    if (path->param_info)
    {
      /* Parameterized path, so add it to parameterized_paths */
      parameterized_paths = lappend(parameterized_paths, path);

      /*
       * If we have an unparameterized cheapest-total, we no longer care
       * about finding the best parameterized path, so move on.
       */
      if (cheapest_total_path)
        continue;

      /*
       * Otherwise, track the best parameterized path, which is the one
       * with least total cost among those of the minimum
       * parameterization.
       */
      if (best_param_path == NULL)
        best_param_path = path;
      else
      {
        switch (bms_subset_compare(PATH_REQ_OUTER(path),
                       PATH_REQ_OUTER(best_param_path)))
        {
          case BMS_EQUAL:
            /* keep the cheaper one */
            if (compare_path_costs(path, best_param_path,
                         TOTAL_COST) < 0)
              best_param_path = path;
            break;
          case BMS_SUBSET1:
            /* new path is less-parameterized */
            best_param_path = path;
            break;
          case BMS_SUBSET2:
            /* old path is less-parameterized, keep it */
            break;
          case BMS_DIFFERENT:

            /*
             * This means that neither path has the least possible
             * parameterization for the rel.  We'll sit on the old
             * path until something better comes along.
             */
            break;
        }
      }
    }
    else
    {
      /* Unparameterized path, so consider it for cheapest slots */
      if (cheapest_total_path == NULL)
      {
        cheapest_startup_path = cheapest_total_path = path;
        continue;
      }

      /*
       * If we find two paths of identical costs, try to keep the
       * better-sorted one.  The paths might have unrelated sort
       * orderings, in which case we can only guess which might be
       * better to keep, but if one is superior then we definitely
       * should keep that one.
       */
      cmp = compare_path_costs(cheapest_startup_path, path, STARTUP_COST);
      if (cmp > 0 ||
        (cmp == 0 &&
         compare_pathkeys(cheapest_startup_path->pathkeys,
                  path->pathkeys) == PATHKEYS_BETTER2))
        cheapest_startup_path = path;

      cmp = compare_path_costs(cheapest_total_path, path, TOTAL_COST);
      if (cmp > 0 ||
        (cmp == 0 &&
         compare_pathkeys(cheapest_total_path->pathkeys,
                  path->pathkeys) == PATHKEYS_BETTER2))
        cheapest_total_path = path;
    }
  }

  /* Add cheapest unparameterized path, if any, to parameterized_paths */
  if (cheapest_total_path)
    parameterized_paths = lcons(cheapest_total_path, parameterized_paths);

  /*
   * If there is no unparameterized path, use the best parameterized path as
   * cheapest_total_path (but not as cheapest_startup_path).
   */
  if (cheapest_total_path == NULL)
    cheapest_total_path = best_param_path;
  Assert(cheapest_total_path != NULL);

  parent_rel->cheapest_startup_path = cheapest_startup_path;
  parent_rel->cheapest_total_path = cheapest_total_path;
  parent_rel->cheapest_unique_path = NULL;  /* computed only if needed */
  parent_rel->cheapest_parameterized_paths = parameterized_paths;
}

/*
 * add_path
 *    Consider a potential implementation path for the specified parent rel,
 *    and add it to the rel's pathlist if it is worthy of consideration.
 *
 *    A path is worthy if it has a better sort order (better pathkeys) or
 *    cheaper cost (as defined below), or generates fewer rows, than any
 *    existing path that has the same or superset parameterization rels.  We
 *    also consider parallel-safe paths more worthy than others.
 *
 *    Cheaper cost can mean either a cheaper total cost or a cheaper startup
 *    cost; if one path is cheaper in one of these aspects and another is
 *    cheaper in the other, we keep both. However, when some path type is
 *    disabled (e.g. due to enable_seqscan=false), the number of times that
 *    a disabled path type is used is considered to be a higher-order
 *    component of the cost. Hence, if path A uses no disabled path type,
 *    and path B uses 1 or more disabled path types, A is cheaper, no matter
 *    what we estimate for the startup and total costs. The startup and total
 *    cost essentially act as a tiebreak when comparing paths that use equal
 *    numbers of disabled path nodes; but in practice this tiebreak is almost
 *    always used, since normally no path types are disabled.
 *
 *    In addition to possibly adding new_path, we also remove from the rel's
 *    pathlist any old paths that are dominated by new_path --- that is,
 *    new_path is cheaper, at least as well ordered, generates no more rows,
 *    requires no outer rels not required by the old path, and is no less
 *    parallel-safe.
 *
 *    In most cases, a path with a superset parameterization will generate
 *    fewer rows (since it has more join clauses to apply), so that those two
 *    figures of merit move in opposite directions; this means that a path of
 *    one parameterization can seldom dominate a path of another.  But such
 *    cases do arise, so we make the full set of checks anyway.
 *
 *    There are two policy decisions embedded in this function, along with
 *    its sibling add_path_precheck.  First, we treat all parameterized paths
 *    as having NIL pathkeys, so that they cannot win comparisons on the
 *    basis of sort order.  This is to reduce the number of parameterized
 *    paths that are kept; see discussion in src/backend/optimizer/README.
 *
 *    Second, we only consider cheap startup cost to be interesting if
 *    parent_rel->consider_startup is true for an unparameterized path, or
 *    parent_rel->consider_param_startup is true for a parameterized one.
 *    Again, this allows discarding useless paths sooner.
 *
 *    The pathlist is kept sorted by disabled_nodes and then by total_cost,
 *    with cheaper paths at the front.  Within this routine, that's simply a
 *    speed hack: doing it that way makes it more likely that we will reject
 *    an inferior path after a few comparisons, rather than many comparisons.
 *    However, add_path_precheck relies on this ordering to exit early
 *    when possible.
 *
 *    NOTE: discarded Path objects are immediately pfree'd to reduce planner
 *    memory consumption.  We dare not try to free the substructure of a Path,
 *    since much of it may be shared with other Paths or the query tree itself;
 *    but just recycling discarded Path nodes is a very useful savings in
 *    a large join tree.  We can recycle the List nodes of pathlist, too.
 *
 *    As noted in optimizer/README, deleting a previously-accepted Path is
 *    safe because we know that Paths of this rel cannot yet be referenced
 *    from any other rel, such as a higher-level join.  However, in some cases
 *    it is possible that a Path is referenced by another Path for its own
 *    rel; we must not delete such a Path, even if it is dominated by the new
 *    Path.  Currently this occurs only for IndexPath objects, which may be
 *    referenced as children of BitmapHeapPaths as well as being paths in
 *    their own right.  Hence, we don't pfree IndexPaths when rejecting them.
 *
 * 'parent_rel' is the relation entry to which the path corresponds.
 * 'new_path' is a potential path for parent_rel.
 *
 * Returns nothing, but modifies parent_rel->pathlist.
 */
void
add_path(RelOptInfo *parent_rel, Path *new_path)
{
  bool    accept_new = true;  /* unless we find a superior old path */
  int     insert_at = 0;  /* where to insert new item */
  List     *new_path_pathkeys;
  ListCell   *p1;

  /*
   * This is a convenient place to check for query cancel --- no part of the
   * planner goes very long without calling add_path().
   */
  CHECK_FOR_INTERRUPTS();

  /* Pretend parameterized paths have no pathkeys, per comment above */
  new_path_pathkeys = new_path->param_info ? NIL : new_path->pathkeys;

  /*
   * Loop to check proposed new path against old paths.  Note it is possible
   * for more than one old path to be tossed out because new_path dominates
   * it.
   */
  foreach(p1, parent_rel->pathlist)
  {
    Path     *old_path = (Path *) lfirst(p1);
    bool    remove_old = false; /* unless new proves superior */
    PathCostComparison costcmp;
    PathKeysComparison keyscmp;
    BMS_Comparison outercmp;

    /*
     * Do a fuzzy cost comparison with standard fuzziness limit.
     */
    costcmp = compare_path_costs_fuzzily(new_path, old_path,
                       STD_FUZZ_FACTOR);

    /*
     * If the two paths compare differently for startup and total cost,
     * then we want to keep both, and we can skip comparing pathkeys and
     * required_outer rels.  If they compare the same, proceed with the
     * other comparisons.  Row count is checked last.  (We make the tests
     * in this order because the cost comparison is most likely to turn
     * out "different", and the pathkeys comparison next most likely.  As
     * explained above, row count very seldom makes a difference, so even
     * though it's cheap to compare there's not much point in checking it
     * earlier.)
     */
    if (costcmp != COSTS_DIFFERENT)
    {
      /* Similarly check to see if either dominates on pathkeys */
      List     *old_path_pathkeys;

      old_path_pathkeys = old_path->param_info ? NIL : old_path->pathkeys;
      keyscmp = compare_pathkeys(new_path_pathkeys,
                     old_path_pathkeys);
      if (keyscmp != PATHKEYS_DIFFERENT)
      {
        switch (costcmp)
        {
          case COSTS_EQUAL:
            outercmp = bms_subset_compare(PATH_REQ_OUTER(new_path),
                            PATH_REQ_OUTER(old_path));
            if (keyscmp == PATHKEYS_BETTER1)
            {
              if ((outercmp == BMS_EQUAL ||
                 outercmp == BMS_SUBSET1) &&
                new_path->rows <= old_path->rows &&
                new_path->parallel_safe >= old_path->parallel_safe)
                remove_old = true; /* new dominates old */
            }
            else if (keyscmp == PATHKEYS_BETTER2)
            {
              if ((outercmp == BMS_EQUAL ||
                 outercmp == BMS_SUBSET2) &&
                new_path->rows >= old_path->rows &&
                new_path->parallel_safe <= old_path->parallel_safe)
                accept_new = false; /* old dominates new */
            }
            else  /* keyscmp == PATHKEYS_EQUAL */
            {
              if (outercmp == BMS_EQUAL)
              {
                /*
                 * Same pathkeys and outer rels, and fuzzily
                 * the same cost, so keep just one; to decide
                 * which, first check parallel-safety, then
                 * rows, then do a fuzzy cost comparison with
                 * very small fuzz limit.  (We used to do an
                 * exact cost comparison, but that results in
                 * annoying platform-specific plan variations
                 * due to roundoff in the cost estimates.)  If
                 * things are still tied, arbitrarily keep
                 * only the old path.  Notice that we will
                 * keep only the old path even if the
                 * less-fuzzy comparison decides the startup
                 * and total costs compare differently.
                 */
                if (new_path->parallel_safe >
                  old_path->parallel_safe)
                  remove_old = true; /* new dominates old */
                else if (new_path->parallel_safe <
                     old_path->parallel_safe)
                  accept_new = false; /* old dominates new */
                else if (new_path->rows < old_path->rows)
                  remove_old = true; /* new dominates old */
                else if (new_path->rows > old_path->rows)
                  accept_new = false; /* old dominates new */
                else if (compare_path_costs_fuzzily(new_path,
                                  old_path,
                                  1.0000000001) == COSTS_BETTER1)
                  remove_old = true; /* new dominates old */
                else
                  accept_new = false; /* old equals or
                             * dominates new */
              }
              else if (outercmp == BMS_SUBSET1 &&
                   new_path->rows <= old_path->rows &&
                   new_path->parallel_safe >= old_path->parallel_safe)
                remove_old = true; /* new dominates old */
              else if (outercmp == BMS_SUBSET2 &&
                   new_path->rows >= old_path->rows &&
                   new_path->parallel_safe <= old_path->parallel_safe)
                accept_new = false; /* old dominates new */
              /* else different parameterizations, keep both */
            }
            break;
          case COSTS_BETTER1:
            if (keyscmp != PATHKEYS_BETTER2)
            {
              outercmp = bms_subset_compare(PATH_REQ_OUTER(new_path),
                              PATH_REQ_OUTER(old_path));
              if ((outercmp == BMS_EQUAL ||
                 outercmp == BMS_SUBSET1) &&
                new_path->rows <= old_path->rows &&
                new_path->parallel_safe >= old_path->parallel_safe)
                remove_old = true; /* new dominates old */
            }
            break;
          case COSTS_BETTER2:
            if (keyscmp != PATHKEYS_BETTER1)
            {
              outercmp = bms_subset_compare(PATH_REQ_OUTER(new_path),
                              PATH_REQ_OUTER(old_path));
              if ((outercmp == BMS_EQUAL ||
                 outercmp == BMS_SUBSET2) &&
                new_path->rows >= old_path->rows &&
                new_path->parallel_safe <= old_path->parallel_safe)
                accept_new = false; /* old dominates new */
            }
            break;
          case COSTS_DIFFERENT:

            /*
             * can't get here, but keep this case to keep compiler
             * quiet
             */
            break;
        }
      }
    }

    /*
     * Remove current element from pathlist if dominated by new.
     */
    if (remove_old)
    {
      parent_rel->pathlist = foreach_delete_current(parent_rel->pathlist,
                              p1);

      /*
       * Delete the data pointed-to by the deleted cell, if possible
       */
      if (!IsA(old_path, IndexPath))
        pfree(old_path);
    }
    else
    {
      /*
       * new belongs after this old path if it has more disabled nodes
       * or if it has the same number of nodes but a greater total cost
       */
      if (new_path->disabled_nodes > old_path->disabled_nodes ||
        (new_path->disabled_nodes == old_path->disabled_nodes &&
         new_path->total_cost >= old_path->total_cost))
        insert_at = foreach_current_index(p1) + 1;
    }

    /*
     * If we found an old path that dominates new_path, we can quit
     * scanning the pathlist; we will not add new_path, and we assume
     * new_path cannot dominate any other elements of the pathlist.
     */
    if (!accept_new)
      break;
  }

  if (accept_new)
  {
    /* Accept the new path: insert it at proper place in pathlist */
    parent_rel->pathlist =
      list_insert_nth(parent_rel->pathlist, insert_at, new_path);
  }
  else
  {
    /* Reject and recycle the new path */
    if (!IsA(new_path, IndexPath))
      pfree(new_path);
  }
}

/*
 * add_path_precheck
 *    Check whether a proposed new path could possibly get accepted.
 *    We assume we know the path's pathkeys and parameterization accurately,
 *    and have lower bounds for its costs.
 *
 * Note that we do not know the path's rowcount, since getting an estimate for
 * that is too expensive to do before prechecking.  We assume here that paths
 * of a superset parameterization will generate fewer rows; if that holds,
 * then paths with different parameterizations cannot dominate each other
 * and so we can simply ignore existing paths of another parameterization.
 * (In the infrequent cases where that rule of thumb fails, add_path will
 * get rid of the inferior path.)
 *
 * At the time this is called, we haven't actually built a Path structure,
 * so the required information has to be passed piecemeal.
 */
bool
add_path_precheck(RelOptInfo *parent_rel, int disabled_nodes,
          Cost startup_cost, Cost total_cost,
          List *pathkeys, Relids required_outer)
{
  List     *new_path_pathkeys;
  bool    consider_startup;
  ListCell   *p1;

  /* Pretend parameterized paths have no pathkeys, per add_path policy */
  new_path_pathkeys = required_outer ? NIL : pathkeys;

  /* Decide whether new path's startup cost is interesting */
  consider_startup = required_outer ? parent_rel->consider_param_startup : parent_rel->consider_startup;

  foreach(p1, parent_rel->pathlist)
  {
    Path     *old_path = (Path *) lfirst(p1);
    PathKeysComparison keyscmp;

    /*
     * Since the pathlist is sorted by disabled_nodes and then by
     * total_cost, we can stop looking once we reach a path with more
     * disabled nodes, or the same number of disabled nodes plus a
     * total_cost larger than the new path's.
     */
    if (unlikely(old_path->disabled_nodes != disabled_nodes))
    {
      if (disabled_nodes < old_path->disabled_nodes)
        break;
    }
    else if (total_cost <= old_path->total_cost * STD_FUZZ_FACTOR)
      break;

    /*
     * We are looking for an old_path with the same parameterization (and
     * by assumption the same rowcount) that dominates the new path on
     * pathkeys as well as both cost metrics.  If we find one, we can
     * reject the new path.
     *
     * Cost comparisons here should match compare_path_costs_fuzzily.
     */
    /* new path can win on startup cost only if consider_startup */
    if (startup_cost > old_path->startup_cost * STD_FUZZ_FACTOR ||
      !consider_startup)
    {
      /* new path loses on cost, so check pathkeys... */
      List     *old_path_pathkeys;

      old_path_pathkeys = old_path->param_info ? NIL : old_path->pathkeys;
      keyscmp = compare_pathkeys(new_path_pathkeys,
                     old_path_pathkeys);
      if (keyscmp == PATHKEYS_EQUAL ||
        keyscmp == PATHKEYS_BETTER2)
      {
        /* new path does not win on pathkeys... */
        if (bms_equal(required_outer, PATH_REQ_OUTER(old_path)))
        {
          /* Found an old path that dominates the new one */
          return false;
        }
      }
    }
  }

  return true;
}

/*
 * add_partial_path
 *    Like add_path, our goal here is to consider whether a path is worthy
 *    of being kept around, but the considerations here are a bit different.
 *    A partial path is one which can be executed in any number of workers in
 *    parallel such that each worker will generate a subset of the path's
 *    overall result.
 *
 *    As in add_path, the partial_pathlist is kept sorted with the cheapest
 *    total path in front.  This is depended on by multiple places, which
 *    just take the front entry as the cheapest path without searching.
 *
 *    We don't generate parameterized partial paths for several reasons.  Most
 *    importantly, they're not safe to execute, because there's nothing to
 *    make sure that a parallel scan within the parameterized portion of the
 *    plan is running with the same value in every worker at the same time.
 *    Fortunately, it seems unlikely to be worthwhile anyway, because having
 *    each worker scan the entire outer relation and a subset of the inner
 *    relation will generally be a terrible plan.  The inner (parameterized)
 *    side of the plan will be small anyway.  There could be rare cases where
 *    this wins big - e.g. if join order constraints put a 1-row relation on
 *    the outer side of the topmost join with a parameterized plan on the inner
 *    side - but we'll have to be content not to handle such cases until
 *    somebody builds an executor infrastructure that can cope with them.
 *
 *    Because we don't consider parameterized paths here, we also don't
 *    need to consider the row counts as a measure of quality: every path will
 *    produce the same number of rows.  Neither do we need to consider startup
 *    costs: parallelism is only used for plans that will be run to completion.
 *    Therefore, this routine is much simpler than add_path: it needs to
 *    consider only disabled nodes, pathkeys and total cost.
 *
 *    As with add_path, we pfree paths that are found to be dominated by
 *    another partial path; this requires that there be no other references to
 *    such paths yet.  Hence, GatherPaths must not be created for a rel until
 *    we're done creating all partial paths for it.  Unlike add_path, we don't
 *    take an exception for IndexPaths as partial index paths won't be
 *    referenced by partial BitmapHeapPaths.
 */
void
add_partial_path(RelOptInfo *parent_rel, Path *new_path)
{
  bool    accept_new = true;  /* unless we find a superior old path */
  int     insert_at = 0;  /* where to insert new item */
  ListCell   *p1;

  /* Check for query cancel. */
  CHECK_FOR_INTERRUPTS();

  /* Path to be added must be parallel safe. */
  Assert(new_path->parallel_safe);

  /* Relation should be OK for parallelism, too. */
  Assert(parent_rel->consider_parallel);

  /*
   * As in add_path, throw out any paths which are dominated by the new
   * path, but throw out the new path if some existing path dominates it.
   */
  foreach(p1, parent_rel->partial_pathlist)
  {
    Path     *old_path = (Path *) lfirst(p1);
    bool    remove_old = false; /* unless new proves superior */
    PathKeysComparison keyscmp;

    /* Compare pathkeys. */
    keyscmp = compare_pathkeys(new_path->pathkeys, old_path->pathkeys);

    /* Unless pathkeys are incompatible, keep just one of the two paths. */
    if (keyscmp != PATHKEYS_DIFFERENT)
    {
      if (unlikely(new_path->disabled_nodes != old_path->disabled_nodes))
      {
        if (new_path->disabled_nodes > old_path->disabled_nodes)
          accept_new = false;
        else
          remove_old = true;
      }
      else if (new_path->total_cost > old_path->total_cost
           * STD_FUZZ_FACTOR)
      {
        /* New path costs more; keep it only if pathkeys are better. */
        if (keyscmp != PATHKEYS_BETTER1)
          accept_new = false;
      }
      else if (old_path->total_cost > new_path->total_cost
           * STD_FUZZ_FACTOR)
      {
        /* Old path costs more; keep it only if pathkeys are better. */
        if (keyscmp != PATHKEYS_BETTER2)
          remove_old = true;
      }
      else if (keyscmp == PATHKEYS_BETTER1)
      {
        /* Costs are about the same, new path has better pathkeys. */
        remove_old = true;
      }
      else if (keyscmp == PATHKEYS_BETTER2)
      {
        /* Costs are about the same, old path has better pathkeys. */
        accept_new = false;
      }
      else if (old_path->total_cost > new_path->total_cost * 1.0000000001)
      {
        /* Pathkeys are the same, and the old path costs more. */
        remove_old = true;
      }
      else
      {
        /*
         * Pathkeys are the same, and new path isn't materially
         * cheaper.
         */
        accept_new = false;
      }
    }

    /*
     * Remove current element from partial_pathlist if dominated by new.
     */
    if (remove_old)
    {
      parent_rel->partial_pathlist =
        foreach_delete_current(parent_rel->partial_pathlist, p1);
      pfree(old_path);
    }
    else
    {
      /* new belongs after this old path if it has cost >= old's */
      if (new_path->total_cost >= old_path->total_cost)
        insert_at = foreach_current_index(p1) + 1;
    }

    /*
     * If we found an old path that dominates new_path, we can quit
     * scanning the partial_pathlist; we will not add new_path, and we
     * assume new_path cannot dominate any later path.
     */
    if (!accept_new)
      break;
  }

  if (accept_new)
  {
    /* Accept the new path: insert it at proper place */
    parent_rel->partial_pathlist =
      list_insert_nth(parent_rel->partial_pathlist, insert_at, new_path);
  }
  else
  {
    /* Reject and recycle the new path */
    pfree(new_path);
  }
}

/*
 * add_partial_path_precheck
 *    Check whether a proposed new partial path could possibly get accepted.
 *
 * Unlike add_path_precheck, we can ignore startup cost and parameterization,
 * since they don't matter for partial paths (see add_partial_path).  But
 * we do want to make sure we don't add a partial path if there's already
 * a complete path that dominates it, since in that case the proposed path
 * is surely a loser.
 */
bool
add_partial_path_precheck(RelOptInfo *parent_rel, int disabled_nodes,
              Cost total_cost, List *pathkeys)
{
  ListCell   *p1;

  /*
   * Our goal here is twofold.  First, we want to find out whether this path
   * is clearly inferior to some existing partial path.  If so, we want to
   * reject it immediately.  Second, we want to find out whether this path
   * is clearly superior to some existing partial path -- at least, modulo
   * final cost computations.  If so, we definitely want to consider it.
   *
   * Unlike add_path(), we always compare pathkeys here.  This is because we
   * expect partial_pathlist to be very short, and getting a definitive
   * answer at this stage avoids the need to call add_path_precheck.
   */
  foreach(p1, parent_rel->partial_pathlist)
  {
    Path     *old_path = (Path *) lfirst(p1);
    PathKeysComparison keyscmp;

    keyscmp = compare_pathkeys(pathkeys, old_path->pathkeys);
    if (keyscmp != PATHKEYS_DIFFERENT)
    {
      if (total_cost > old_path->total_cost * STD_FUZZ_FACTOR &&
        keyscmp != PATHKEYS_BETTER1)
        return false;
      if (old_path->total_cost > total_cost * STD_FUZZ_FACTOR &&
        keyscmp != PATHKEYS_BETTER2)
        return true;
    }
  }

  /*
   * This path is neither clearly inferior to an existing partial path nor
   * clearly good enough that it might replace one.  Compare it to
   * non-parallel plans.  If it loses even before accounting for the cost of
   * the Gather node, we should definitely reject it.
   *
   * Note that we pass the total_cost to add_path_precheck twice.  This is
   * because it's never advantageous to consider the startup cost of a
   * partial path; the resulting plans, if run in parallel, will be run to
   * completion.
   */
  if (!add_path_precheck(parent_rel, disabled_nodes, total_cost, total_cost,
               pathkeys, NULL))
    return false;

  return true;
}


/*****************************************************************************
 *    PATH NODE CREATION ROUTINES
 *****************************************************************************/

/*
 * create_seqscan_path
 *    Creates a path corresponding to a sequential scan, returning the
 *    pathnode.
 */
Path *
create_seqscan_path(PlannerInfo *root, RelOptInfo *rel,
          Relids required_outer, int parallel_workers)
{
  Path     *pathnode = makeNode(Path);

  pathnode->pathtype = T_SeqScan;
  pathnode->parent = rel;
  pathnode->pathtarget = rel->reltarget;
  pathnode->param_info = get_baserel_parampathinfo(root, rel,
                           required_outer);
  pathnode->parallel_aware = (parallel_workers > 0);
  pathnode->parallel_safe = rel->consider_parallel;
  pathnode->parallel_workers = parallel_workers;
  pathnode->pathkeys = NIL; /* seqscan has unordered result */

  cost_seqscan(pathnode, root, rel, pathnode->param_info);

  return pathnode;
}

/*
 * create_samplescan_path
 *    Creates a path node for a sampled table scan.
 */
Path *
create_samplescan_path(PlannerInfo *root, RelOptInfo *rel, Relids required_outer)
{
  Path     *pathnode = makeNode(Path);

  pathnode->pathtype = T_SampleScan;
  pathnode->parent = rel;
  pathnode->pathtarget = rel->reltarget;
  pathnode->param_info = get_baserel_parampathinfo(root, rel,
                           required_outer);
  pathnode->parallel_aware = false;
  pathnode->parallel_safe = rel->consider_parallel;
  pathnode->parallel_workers = 0;
  pathnode->pathkeys = NIL; /* samplescan has unordered result */

  cost_samplescan(pathnode, root, rel, pathnode->param_info);

  return pathnode;
}

/*
 * create_index_path
 *    Creates a path node for an index scan.
 *
 * 'index' is a usable index.
 * 'indexclauses' is a list of IndexClause nodes representing clauses
 *      to be enforced as qual conditions in the scan.
 * 'indexorderbys' is a list of bare expressions (no RestrictInfos)
 *      to be used as index ordering operators in the scan.
 * 'indexorderbycols' is an integer list of index column numbers (zero based)
 *      the ordering operators can be used with.
 * 'pathkeys' describes the ordering of the path.
 * 'indexscandir' is either ForwardScanDirection or BackwardScanDirection.
 * 'indexonly' is true if an index-only scan is wanted.
 * 'required_outer' is the set of outer relids for a parameterized path.
 * 'loop_count' is the number of repetitions of the indexscan to factor into
 *    estimates of caching behavior.
 * 'partial_path' is true if constructing a parallel index scan path.
 *
 * Returns the new path node.
 */
IndexPath *
create_index_path(PlannerInfo *root,
          IndexOptInfo *index,
          List *indexclauses,
          List *indexorderbys,
          List *indexorderbycols,
          List *pathkeys,
          ScanDirection indexscandir,
          bool indexonly,
          Relids required_outer,
          double loop_count,
          bool partial_path)
{
  IndexPath  *pathnode = makeNode(IndexPath);
  RelOptInfo *rel = index->rel;

  pathnode->path.pathtype = indexonly ? T_IndexOnlyScan : T_IndexScan;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = rel->reltarget;
  pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
                              required_outer);
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel;
  pathnode->path.parallel_workers = 0;
  pathnode->path.pathkeys = pathkeys;

  pathnode->indexinfo = index;
  pathnode->indexclauses = indexclauses;
  pathnode->indexorderbys = indexorderbys;
  pathnode->indexorderbycols = indexorderbycols;
  pathnode->indexscandir = indexscandir;

  cost_index(pathnode, root, loop_count, partial_path);

  return pathnode;
}

/*
 * create_bitmap_heap_path
 *    Creates a path node for a bitmap scan.
 *
 * 'bitmapqual' is a tree of IndexPath, BitmapAndPath, and BitmapOrPath nodes.
 * 'required_outer' is the set of outer relids for a parameterized path.
 * 'loop_count' is the number of repetitions of the indexscan to factor into
 *    estimates of caching behavior.
 *
 * loop_count should match the value used when creating the component
 * IndexPaths.
 */
BitmapHeapPath *
create_bitmap_heap_path(PlannerInfo *root,
            RelOptInfo *rel,
            Path *bitmapqual,
            Relids required_outer,
            double loop_count,
            int parallel_degree)
{
  BitmapHeapPath *pathnode = makeNode(BitmapHeapPath);

  pathnode->path.pathtype = T_BitmapHeapScan;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = rel->reltarget;
  pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
                              required_outer);
  pathnode->path.parallel_aware = (parallel_degree > 0);
  pathnode->path.parallel_safe = rel->consider_parallel;
  pathnode->path.parallel_workers = parallel_degree;
  pathnode->path.pathkeys = NIL; /* always unordered */

  pathnode->bitmapqual = bitmapqual;

  cost_bitmap_heap_scan(&pathnode->path, root, rel,
              pathnode->path.param_info,
              bitmapqual, loop_count);

  return pathnode;
}

/*
 * create_bitmap_and_path
 *    Creates a path node representing a BitmapAnd.
 */
BitmapAndPath *
create_bitmap_and_path(PlannerInfo *root,
             RelOptInfo *rel,
             List *bitmapquals)
{
  BitmapAndPath *pathnode = makeNode(BitmapAndPath);
  Relids    required_outer = NULL;
  ListCell   *lc;

  pathnode->path.pathtype = T_BitmapAnd;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = rel->reltarget;

  /*
   * Identify the required outer rels as the union of what the child paths
   * depend on.  (Alternatively, we could insist that the caller pass this
   * in, but it's more convenient and reliable to compute it here.)
   */
  foreach(lc, bitmapquals)
  {
    Path     *bitmapqual = (Path *) lfirst(lc);

    required_outer = bms_add_members(required_outer,
                     PATH_REQ_OUTER(bitmapqual));
  }
  pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
                              required_outer);

  /*
   * Currently, a BitmapHeapPath, BitmapAndPath, or BitmapOrPath will be
   * parallel-safe if and only if rel->consider_parallel is set.  So, we can
   * set the flag for this path based only on the relation-level flag,
   * without actually iterating over the list of children.
   */
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel;
  pathnode->path.parallel_workers = 0;

  pathnode->path.pathkeys = NIL; /* always unordered */

  pathnode->bitmapquals = bitmapquals;

  /* this sets bitmapselectivity as well as the regular cost fields: */
  cost_bitmap_and_node(pathnode, root);

  return pathnode;
}

/*
 * create_bitmap_or_path
 *    Creates a path node representing a BitmapOr.
 */
BitmapOrPath *
create_bitmap_or_path(PlannerInfo *root,
            RelOptInfo *rel,
            List *bitmapquals)
{
  BitmapOrPath *pathnode = makeNode(BitmapOrPath);
  Relids    required_outer = NULL;
  ListCell   *lc;

  pathnode->path.pathtype = T_BitmapOr;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = rel->reltarget;

  /*
   * Identify the required outer rels as the union of what the child paths
   * depend on.  (Alternatively, we could insist that the caller pass this
   * in, but it's more convenient and reliable to compute it here.)
   */
  foreach(lc, bitmapquals)
  {
    Path     *bitmapqual = (Path *) lfirst(lc);

    required_outer = bms_add_members(required_outer,
                     PATH_REQ_OUTER(bitmapqual));
  }
  pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
                              required_outer);

  /*
   * Currently, a BitmapHeapPath, BitmapAndPath, or BitmapOrPath will be
   * parallel-safe if and only if rel->consider_parallel is set.  So, we can
   * set the flag for this path based only on the relation-level flag,
   * without actually iterating over the list of children.
   */
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel;
  pathnode->path.parallel_workers = 0;

  pathnode->path.pathkeys = NIL; /* always unordered */

  pathnode->bitmapquals = bitmapquals;

  /* this sets bitmapselectivity as well as the regular cost fields: */
  cost_bitmap_or_node(pathnode, root);

  return pathnode;
}

/*
 * create_tidscan_path
 *    Creates a path corresponding to a scan by TID, returning the pathnode.
 */
TidPath *
create_tidscan_path(PlannerInfo *root, RelOptInfo *rel, List *tidquals,
          Relids required_outer)
{
  TidPath    *pathnode = makeNode(TidPath);

  pathnode->path.pathtype = T_TidScan;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = rel->reltarget;
  pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
                              required_outer);
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel;
  pathnode->path.parallel_workers = 0;
  pathnode->path.pathkeys = NIL; /* always unordered */

  pathnode->tidquals = tidquals;

  cost_tidscan(&pathnode->path, root, rel, tidquals,
         pathnode->path.param_info);

  return pathnode;
}

/*
 * create_tidrangescan_path
 *    Creates a path corresponding to a scan by a range of TIDs, returning
 *    the pathnode.
 */
TidRangePath *
create_tidrangescan_path(PlannerInfo *root, RelOptInfo *rel,
             List *tidrangequals, Relids required_outer)
{
  TidRangePath *pathnode = makeNode(TidRangePath);

  pathnode->path.pathtype = T_TidRangeScan;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = rel->reltarget;
  pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
                              required_outer);
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel;
  pathnode->path.parallel_workers = 0;
  pathnode->path.pathkeys = NIL; /* always unordered */

  pathnode->tidrangequals = tidrangequals;

  cost_tidrangescan(&pathnode->path, root, rel, tidrangequals,
            pathnode->path.param_info);

  return pathnode;
}

/*
 * create_append_path
 *    Creates a path corresponding to an Append plan, returning the
 *    pathnode.
 *
 * Note that we must handle subpaths = NIL, representing a dummy access path.
 * Also, there are callers that pass root = NULL.
 *
 * 'rows', when passed as a non-negative number, will be used to overwrite the
 * returned path's row estimate.  Otherwise, the row estimate is calculated
 * by totalling the row estimates from the 'subpaths' list.
 */
AppendPath *
create_append_path(PlannerInfo *root,
           RelOptInfo *rel,
           List *subpaths, List *partial_subpaths,
           List *pathkeys, Relids required_outer,
           int parallel_workers, bool parallel_aware,
           double rows)
{
  AppendPath *pathnode = makeNode(AppendPath);
  ListCell   *l;

  Assert(!parallel_aware || parallel_workers > 0);

  pathnode->path.pathtype = T_Append;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = rel->reltarget;

  /*
   * If this is for a baserel (not a join or non-leaf partition), we prefer
   * to apply get_baserel_parampathinfo to construct a full ParamPathInfo
   * for the path.  This supports building a Memoize path atop this path,
   * and if this is a partitioned table the info may be useful for run-time
   * pruning (cf make_partition_pruneinfo()).
   *
   * However, if we don't have "root" then that won't work and we fall back
   * on the simpler get_appendrel_parampathinfo.  There's no point in doing
   * the more expensive thing for a dummy path, either.
   */
  if (rel->reloptkind == RELOPT_BASEREL && root && subpaths != NIL)
    pathnode->path.param_info = get_baserel_parampathinfo(root,
                                rel,
                                required_outer);
  else
    pathnode->path.param_info = get_appendrel_parampathinfo(rel,
                                required_outer);

  pathnode->path.parallel_aware = parallel_aware;
  pathnode->path.parallel_safe = rel->consider_parallel;
  pathnode->path.parallel_workers = parallel_workers;
  pathnode->path.pathkeys = pathkeys;

  /*
   * For parallel append, non-partial paths are sorted by descending total
   * costs. That way, the total time to finish all non-partial paths is
   * minimized.  Also, the partial paths are sorted by descending startup
   * costs.  There may be some paths that require to do startup work by a
   * single worker.  In such case, it's better for workers to choose the
   * expensive ones first, whereas the leader should choose the cheapest
   * startup plan.
   */
  if (pathnode->path.parallel_aware)
  {
    /*
     * We mustn't fiddle with the order of subpaths when the Append has
     * pathkeys.  The order they're listed in is critical to keeping the
     * pathkeys valid.
     */
    Assert(pathkeys == NIL);

    list_sort(subpaths, append_total_cost_compare);
    list_sort(partial_subpaths, append_startup_cost_compare);
  }
  pathnode->first_partial_path = list_length(subpaths);
  pathnode->subpaths = list_concat(subpaths, partial_subpaths);

  /*
   * Apply query-wide LIMIT if known and path is for sole base relation.
   * (Handling this at this low level is a bit klugy.)
   */
  if (root != NULL && bms_equal(rel->relids, root->all_query_rels))
    pathnode->limit_tuples = root->limit_tuples;
  else
    pathnode->limit_tuples = -1.0;

  foreach(l, pathnode->subpaths)
  {
    Path     *subpath = (Path *) lfirst(l);

    pathnode->path.parallel_safe = pathnode->path.parallel_safe &&
      subpath->parallel_safe;

    /* All child paths must have same parameterization */
    Assert(bms_equal(PATH_REQ_OUTER(subpath), required_outer));
  }

  Assert(!parallel_aware || pathnode->path.parallel_safe);

  /*
   * If there's exactly one child path then the output of the Append is
   * necessarily ordered the same as the child's, so we can inherit the
   * child's pathkeys if any, overriding whatever the caller might've said.
   * Furthermore, if the child's parallel awareness matches the Append's,
   * then the Append is a no-op and will be discarded later (in setrefs.c).
   * Then we can inherit the child's size and cost too, effectively charging
   * zero for the Append.  Otherwise, we must do the normal costsize
   * calculation.
   */
  if (list_length(pathnode->subpaths) == 1)
  {
    Path     *child = (Path *) linitial(pathnode->subpaths);

    if (child->parallel_aware == parallel_aware)
    {
      pathnode->path.rows = child->rows;
      pathnode->path.startup_cost = child->startup_cost;
      pathnode->path.total_cost = child->total_cost;
    }
    else
      cost_append(pathnode);
    /* Must do this last, else cost_append complains */
    pathnode->path.pathkeys = child->pathkeys;
  }
  else
    cost_append(pathnode);

  /* If the caller provided a row estimate, override the computed value. */
  if (rows >= 0)
    pathnode->path.rows = rows;

  return pathnode;
}

/*
 * append_total_cost_compare
 *    list_sort comparator for sorting append child paths
 *    by total_cost descending
 *
 * For equal total costs, we fall back to comparing startup costs; if those
 * are equal too, break ties using bms_compare on the paths' relids.
 * (This is to avoid getting unpredictable results from list_sort.)
 */
static int
append_total_cost_compare(const ListCell *a, const ListCell *b)
{
  Path     *path1 = (Path *) lfirst(a);
  Path     *path2 = (Path *) lfirst(b);
  int     cmp;

  cmp = compare_path_costs(path1, path2, TOTAL_COST);
  if (cmp != 0)
    return -cmp;
  return bms_compare(path1->parent->relids, path2->parent->relids);
}

/*
 * append_startup_cost_compare
 *    list_sort comparator for sorting append child paths
 *    by startup_cost descending
 *
 * For equal startup costs, we fall back to comparing total costs; if those
 * are equal too, break ties using bms_compare on the paths' relids.
 * (This is to avoid getting unpredictable results from list_sort.)
 */
static int
append_startup_cost_compare(const ListCell *a, const ListCell *b)
{
  Path     *path1 = (Path *) lfirst(a);
  Path     *path2 = (Path *) lfirst(b);
  int     cmp;

  cmp = compare_path_costs(path1, path2, STARTUP_COST);
  if (cmp != 0)
    return -cmp;
  return bms_compare(path1->parent->relids, path2->parent->relids);
}

/*
 * create_merge_append_path
 *    Creates a path corresponding to a MergeAppend plan, returning the
 *    pathnode.
 */
MergeAppendPath *
create_merge_append_path(PlannerInfo *root,
             RelOptInfo *rel,
             List *subpaths,
             List *pathkeys,
             Relids required_outer)
{
  MergeAppendPath *pathnode = makeNode(MergeAppendPath);
  int     input_disabled_nodes;
  Cost    input_startup_cost;
  Cost    input_total_cost;
  ListCell   *l;

  /*
   * We don't currently support parameterized MergeAppend paths, as
   * explained in the comments for generate_orderedappend_paths.
   */
  Assert(bms_is_empty(rel->lateral_relids) && bms_is_empty(required_outer));

  pathnode->path.pathtype = T_MergeAppend;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = rel->reltarget;
  pathnode->path.param_info = NULL;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel;
  pathnode->path.parallel_workers = 0;
  pathnode->path.pathkeys = pathkeys;
  pathnode->subpaths = subpaths;

  /*
   * Apply query-wide LIMIT if known and path is for sole base relation.
   * (Handling this at this low level is a bit klugy.)
   */
  if (bms_equal(rel->relids, root->all_query_rels))
    pathnode->limit_tuples = root->limit_tuples;
  else
    pathnode->limit_tuples = -1.0;

  /*
   * Add up the sizes and costs of the input paths.
   */
  pathnode->path.rows = 0;
  input_disabled_nodes = 0;
  input_startup_cost = 0;
  input_total_cost = 0;
  foreach(l, subpaths)
  {
    Path     *subpath = (Path *) lfirst(l);

    /* All child paths should be unparameterized */
    Assert(bms_is_empty(PATH_REQ_OUTER(subpath)));

    pathnode->path.rows += subpath->rows;
    pathnode->path.parallel_safe = pathnode->path.parallel_safe &&
      subpath->parallel_safe;

    if (pathkeys_contained_in(pathkeys, subpath->pathkeys))
    {
      /* Subpath is adequately ordered, we won't need to sort it */
      input_disabled_nodes += subpath->disabled_nodes;
      input_startup_cost += subpath->startup_cost;
      input_total_cost += subpath->total_cost;
    }
    else
    {
      /* We'll need to insert a Sort node, so include cost for that */
      Path    sort_path;  /* dummy for result of cost_sort */

      cost_sort(&sort_path,
            root,
            pathkeys,
            subpath->disabled_nodes,
            subpath->total_cost,
            subpath->rows,
            subpath->pathtarget->width,
            0.0,
            work_mem,
            pathnode->limit_tuples);
      input_disabled_nodes += sort_path.disabled_nodes;
      input_startup_cost += sort_path.startup_cost;
      input_total_cost += sort_path.total_cost;
    }
  }

  /*
   * Now we can compute total costs of the MergeAppend.  If there's exactly
   * one child path and its parallel awareness matches that of the
   * MergeAppend, then the MergeAppend is a no-op and will be discarded
   * later (in setrefs.c); otherwise we do the normal cost calculation.
   */
  if (list_length(subpaths) == 1 &&
    ((Path *) linitial(subpaths))->parallel_aware ==
    pathnode->path.parallel_aware)
  {
    pathnode->path.disabled_nodes = input_disabled_nodes;
    pathnode->path.startup_cost = input_startup_cost;
    pathnode->path.total_cost = input_total_cost;
  }
  else
    cost_merge_append(&pathnode->path, root,
              pathkeys, list_length(subpaths),
              input_disabled_nodes,
              input_startup_cost, input_total_cost,
              pathnode->path.rows);

  return pathnode;
}

/*
 * create_group_result_path
 *    Creates a path representing a Result-and-nothing-else plan.
 *
 * This is only used for degenerate grouping cases, in which we know we
 * need to produce one result row, possibly filtered by a HAVING qual.
 */
GroupResultPath *
create_group_result_path(PlannerInfo *root, RelOptInfo *rel,
             PathTarget *target, List *havingqual)
{
  GroupResultPath *pathnode = makeNode(GroupResultPath);

  pathnode->path.pathtype = T_Result;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = target;
  pathnode->path.param_info = NULL; /* there are no other rels... */
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel;
  pathnode->path.parallel_workers = 0;
  pathnode->path.pathkeys = NIL;
  pathnode->quals = havingqual;

  /*
   * We can't quite use cost_resultscan() because the quals we want to
   * account for are not baserestrict quals of the rel.  Might as well just
   * hack it here.
   */
  pathnode->path.rows = 1;
  pathnode->path.startup_cost = target->cost.startup;
  pathnode->path.total_cost = target->cost.startup +
    cpu_tuple_cost + target->cost.per_tuple;

  /*
   * Add cost of qual, if any --- but we ignore its selectivity, since our
   * rowcount estimate should be 1 no matter what the qual is.
   */
  if (havingqual)
  {
    QualCost  qual_cost;

    cost_qual_eval(&qual_cost, havingqual, root);
    /* havingqual is evaluated once at startup */
    pathnode->path.startup_cost += qual_cost.startup + qual_cost.per_tuple;
    pathnode->path.total_cost += qual_cost.startup + qual_cost.per_tuple;
  }

  return pathnode;
}

/*
 * create_material_path
 *    Creates a path corresponding to a Material plan, returning the
 *    pathnode.
 */
MaterialPath *
create_material_path(RelOptInfo *rel, Path *subpath)
{
  MaterialPath *pathnode = makeNode(MaterialPath);

  Assert(subpath->parent == rel);

  pathnode->path.pathtype = T_Material;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = rel->reltarget;
  pathnode->path.param_info = subpath->param_info;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel &&
    subpath->parallel_safe;
  pathnode->path.parallel_workers = subpath->parallel_workers;
  pathnode->path.pathkeys = subpath->pathkeys;

  pathnode->subpath = subpath;

  cost_material(&pathnode->path,
          subpath->disabled_nodes,
          subpath->startup_cost,
          subpath->total_cost,
          subpath->rows,
          subpath->pathtarget->width);

  return pathnode;
}

/*
 * create_memoize_path
 *    Creates a path corresponding to a Memoize plan, returning the pathnode.
 */
MemoizePath *
create_memoize_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
          List *param_exprs, List *hash_operators,
          bool singlerow, bool binary_mode, double calls)
{
  MemoizePath *pathnode = makeNode(MemoizePath);

  Assert(subpath->parent == rel);

  pathnode->path.pathtype = T_Memoize;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = rel->reltarget;
  pathnode->path.param_info = subpath->param_info;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel &&
    subpath->parallel_safe;
  pathnode->path.parallel_workers = subpath->parallel_workers;
  pathnode->path.pathkeys = subpath->pathkeys;

  pathnode->subpath = subpath;
  pathnode->hash_operators = hash_operators;
  pathnode->param_exprs = param_exprs;
  pathnode->singlerow = singlerow;
  pathnode->binary_mode = binary_mode;
  pathnode->calls = clamp_row_est(calls);

  /*
   * For now we set est_entries to 0.  cost_memoize_rescan() does all the
   * hard work to determine how many cache entries there are likely to be,
   * so it seems best to leave it up to that function to fill this field in.
   * If left at 0, the executor will make a guess at a good value.
   */
  pathnode->est_entries = 0;

  /* we should not generate this path type when enable_memoize=false */
  Assert(enable_memoize);
  pathnode->path.disabled_nodes = subpath->disabled_nodes;

  /*
   * Add a small additional charge for caching the first entry.  All the
   * harder calculations for rescans are performed in cost_memoize_rescan().
   */
  pathnode->path.startup_cost = subpath->startup_cost + cpu_tuple_cost;
  pathnode->path.total_cost = subpath->total_cost + cpu_tuple_cost;
  pathnode->path.rows = subpath->rows;

  return pathnode;
}

/*
 * create_unique_path
 *    Creates a path representing elimination of distinct rows from the
 *    input data.  Distinct-ness is defined according to the needs of the
 *    semijoin represented by sjinfo.  If it is not possible to identify
 *    how to make the data unique, NULL is returned.
 *
 * If used at all, this is likely to be called repeatedly on the same rel;
 * and the input subpath should always be the same (the cheapest_total path
 * for the rel).  So we cache the result.
 */
UniquePath *
create_unique_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
           SpecialJoinInfo *sjinfo)
{
  UniquePath *pathnode;
  Path    sort_path;    /* dummy for result of cost_sort */
  Path    agg_path;   /* dummy for result of cost_agg */
  MemoryContext oldcontext;
  int     numCols;

  /* Caller made a mistake if subpath isn't cheapest_total ... */
  Assert(subpath == rel->cheapest_total_path);
  Assert(subpath->parent == rel);
  /* ... or if SpecialJoinInfo is the wrong one */
  Assert(sjinfo->jointype == JOIN_SEMI);
  Assert(bms_equal(rel->relids, sjinfo->syn_righthand));

  /* If result already cached, return it */
  if (rel->cheapest_unique_path)
    return (UniquePath *) rel->cheapest_unique_path;

  /* If it's not possible to unique-ify, return NULL */
  if (!(sjinfo->semi_can_btree || sjinfo->semi_can_hash))
    return NULL;

  /*
   * When called during GEQO join planning, we are in a short-lived memory
   * context.  We must make sure that the path and any subsidiary data
   * structures created for a baserel survive the GEQO cycle, else the
   * baserel is trashed for future GEQO cycles.  On the other hand, when we
   * are creating those for a joinrel during GEQO, we don't want them to
   * clutter the main planning context.  Upshot is that the best solution is
   * to explicitly allocate memory in the same context the given RelOptInfo
   * is in.
   */
  oldcontext = MemoryContextSwitchTo(GetMemoryChunkContext(rel));

  pathnode = makeNode(UniquePath);

  pathnode->path.pathtype = T_Unique;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = rel->reltarget;
  pathnode->path.param_info = subpath->param_info;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel &&
    subpath->parallel_safe;
  pathnode->path.parallel_workers = subpath->parallel_workers;

  /*
   * Assume the output is unsorted, since we don't necessarily have pathkeys
   * to represent it.  (This might get overridden below.)
   */
  pathnode->path.pathkeys = NIL;

  pathnode->subpath = subpath;

  /*
   * Under GEQO and when planning child joins, the sjinfo might be
   * short-lived, so we'd better make copies of data structures we extract
   * from it.
   */
  pathnode->in_operators = copyObject(sjinfo->semi_operators);
  pathnode->uniq_exprs = copyObject(sjinfo->semi_rhs_exprs);

  /*
   * If the input is a relation and it has a unique index that proves the
   * semi_rhs_exprs are unique, then we don't need to do anything.  Note
   * that relation_has_unique_index_for automatically considers restriction
   * clauses for the rel, as well.
   */
  if (rel->rtekind == RTE_RELATION && sjinfo->semi_can_btree &&
    relation_has_unique_index_for(root, rel, NIL,
                    sjinfo->semi_rhs_exprs,
                    sjinfo->semi_operators))
  {
    pathnode->umethod = UNIQUE_PATH_NOOP;
    pathnode->path.rows = rel->rows;
    pathnode->path.disabled_nodes = subpath->disabled_nodes;
    pathnode->path.startup_cost = subpath->startup_cost;
    pathnode->path.total_cost = subpath->total_cost;
    pathnode->path.pathkeys = subpath->pathkeys;

    rel->cheapest_unique_path = (Path *) pathnode;

    MemoryContextSwitchTo(oldcontext);

    return pathnode;
  }

  /*
   * If the input is a subquery whose output must be unique already, then we
   * don't need to do anything.  The test for uniqueness has to consider
   * exactly which columns we are extracting; for example "SELECT DISTINCT
   * x,y" doesn't guarantee that x alone is distinct. So we cannot check for
   * this optimization unless semi_rhs_exprs consists only of simple Vars
   * referencing subquery outputs.  (Possibly we could do something with
   * expressions in the subquery outputs, too, but for now keep it simple.)
   */
  if (rel->rtekind == RTE_SUBQUERY)
  {
    RangeTblEntry *rte = planner_rt_fetch(rel->relid, root);

    if (query_supports_distinctness(rte->subquery))
    {
      List     *sub_tlist_colnos;

      sub_tlist_colnos = translate_sub_tlist(sjinfo->semi_rhs_exprs,
                           rel->relid);

      if (sub_tlist_colnos &&
        query_is_distinct_for(rte->subquery,
                    sub_tlist_colnos,
                    sjinfo->semi_operators))
      {
        pathnode->umethod = UNIQUE_PATH_NOOP;
        pathnode->path.rows = rel->rows;
        pathnode->path.disabled_nodes = subpath->disabled_nodes;
        pathnode->path.startup_cost = subpath->startup_cost;
        pathnode->path.total_cost = subpath->total_cost;
        pathnode->path.pathkeys = subpath->pathkeys;

        rel->cheapest_unique_path = (Path *) pathnode;

        MemoryContextSwitchTo(oldcontext);

        return pathnode;
      }
    }
  }

  /* Estimate number of output rows */
  pathnode->path.rows = estimate_num_groups(root,
                        sjinfo->semi_rhs_exprs,
                        rel->rows,
                        NULL,
                        NULL);
  numCols = list_length(sjinfo->semi_rhs_exprs);

  if (sjinfo->semi_can_btree)
  {
    /*
     * Estimate cost for sort+unique implementation
     */
    cost_sort(&sort_path, root, NIL,
          subpath->disabled_nodes,
          subpath->total_cost,
          rel->rows,
          subpath->pathtarget->width,
          0.0,
          work_mem,
          -1.0);

    /*
     * Charge one cpu_operator_cost per comparison per input tuple. We
     * assume all columns get compared at most of the tuples. (XXX
     * probably this is an overestimate.)  This should agree with
     * create_upper_unique_path.
     */
    sort_path.total_cost += cpu_operator_cost * rel->rows * numCols;
  }

  if (sjinfo->semi_can_hash)
  {
    /*
     * Estimate the overhead per hashtable entry at 64 bytes (same as in
     * planner.c).
     */
    int     hashentrysize = subpath->pathtarget->width + 64;

    if (hashentrysize * pathnode->path.rows > get_hash_memory_limit())
    {
      /*
       * We should not try to hash.  Hack the SpecialJoinInfo to
       * remember this, in case we come through here again.
       */
      sjinfo->semi_can_hash = false;
    }
    else
      cost_agg(&agg_path, root,
           AGG_HASHED, NULL,
           numCols, pathnode->path.rows,
           NIL,
           subpath->disabled_nodes,
           subpath->startup_cost,
           subpath->total_cost,
           rel->rows,
           subpath->pathtarget->width);
  }

  if (sjinfo->semi_can_btree && sjinfo->semi_can_hash)
  {
    if (agg_path.disabled_nodes < sort_path.disabled_nodes ||
      (agg_path.disabled_nodes == sort_path.disabled_nodes &&
       agg_path.total_cost < sort_path.total_cost))
      pathnode->umethod = UNIQUE_PATH_HASH;
    else
      pathnode->umethod = UNIQUE_PATH_SORT;
  }
  else if (sjinfo->semi_can_btree)
    pathnode->umethod = UNIQUE_PATH_SORT;
  else if (sjinfo->semi_can_hash)
    pathnode->umethod = UNIQUE_PATH_HASH;
  else
  {
    /* we can get here only if we abandoned hashing above */
    MemoryContextSwitchTo(oldcontext);
    return NULL;
  }

  if (pathnode->umethod == UNIQUE_PATH_HASH)
  {
    pathnode->path.disabled_nodes = agg_path.disabled_nodes;
    pathnode->path.startup_cost = agg_path.startup_cost;
    pathnode->path.total_cost = agg_path.total_cost;
  }
  else
  {
    pathnode->path.disabled_nodes = sort_path.disabled_nodes;
    pathnode->path.startup_cost = sort_path.startup_cost;
    pathnode->path.total_cost = sort_path.total_cost;
  }

  rel->cheapest_unique_path = (Path *) pathnode;

  MemoryContextSwitchTo(oldcontext);

  return pathnode;
}

/*
 * create_gather_merge_path
 *
 *    Creates a path corresponding to a gather merge scan, returning
 *    the pathnode.
 */
GatherMergePath *
create_gather_merge_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
             PathTarget *target, List *pathkeys,
             Relids required_outer, double *rows)
{
  GatherMergePath *pathnode = makeNode(GatherMergePath);
  int     input_disabled_nodes = 0;
  Cost    input_startup_cost = 0;
  Cost    input_total_cost = 0;

  Assert(subpath->parallel_safe);
  Assert(pathkeys);

  /*
   * The subpath should guarantee that it is adequately ordered either by
   * adding an explicit sort node or by using presorted input.  We cannot
   * add an explicit Sort node for the subpath in createplan.c on additional
   * pathkeys, because we can't guarantee the sort would be safe.  For
   * example, expressions may be volatile or otherwise parallel unsafe.
   */
  if (!pathkeys_contained_in(pathkeys, subpath->pathkeys))
    elog(ERROR, "gather merge input not sufficiently sorted");

  pathnode->path.pathtype = T_GatherMerge;
  pathnode->path.parent = rel;
  pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
                              required_outer);
  pathnode->path.parallel_aware = false;

  pathnode->subpath = subpath;
  pathnode->num_workers = subpath->parallel_workers;
  pathnode->path.pathkeys = pathkeys;
  pathnode->path.pathtarget = target ? target : rel->reltarget;

  input_disabled_nodes += subpath->disabled_nodes;
  input_startup_cost += subpath->startup_cost;
  input_total_cost += subpath->total_cost;

  cost_gather_merge(pathnode, root, rel, pathnode->path.param_info,
            input_disabled_nodes, input_startup_cost,
            input_total_cost, rows);

  return pathnode;
}

/*
 * translate_sub_tlist - get subquery column numbers represented by tlist
 *
 * The given targetlist usually contains only Vars referencing the given relid.
 * Extract their varattnos (ie, the column numbers of the subquery) and return
 * as an integer List.
 *
 * If any of the tlist items is not a simple Var, we cannot determine whether
 * the subquery's uniqueness condition (if any) matches ours, so punt and
 * return NIL.
 */
static List *
translate_sub_tlist(List *tlist, int relid)
{
  List     *result = NIL;
  ListCell   *l;

  foreach(l, tlist)
  {
    Var      *var = (Var *) lfirst(l);

    if (!var || !IsA(var, Var) ||
      var->varno != relid)
      return NIL;     /* punt */

    result = lappend_int(result, var->varattno);
  }
  return result;
}

/*
 * create_gather_path
 *    Creates a path corresponding to a gather scan, returning the
 *    pathnode.
 *
 * 'rows' may optionally be set to override row estimates from other sources.
 */
GatherPath *
create_gather_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
           PathTarget *target, Relids required_outer, double *rows)
{
  GatherPath *pathnode = makeNode(GatherPath);

  Assert(subpath->parallel_safe);

  pathnode->path.pathtype = T_Gather;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = target;
  pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
                              required_outer);
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = false;
  pathnode->path.parallel_workers = 0;
  pathnode->path.pathkeys = NIL; /* Gather has unordered result */

  pathnode->subpath = subpath;
  pathnode->num_workers = subpath->parallel_workers;
  pathnode->single_copy = false;

  if (pathnode->num_workers == 0)
  {
    pathnode->path.pathkeys = subpath->pathkeys;
    pathnode->num_workers = 1;
    pathnode->single_copy = true;
  }

  cost_gather(pathnode, root, rel, pathnode->path.param_info, rows);

  return pathnode;
}

/*
 * create_subqueryscan_path
 *    Creates a path corresponding to a scan of a subquery,
 *    returning the pathnode.
 *
 * Caller must pass trivial_pathtarget = true if it believes rel->reltarget to
 * be trivial, ie just a fetch of all the subquery output columns in order.
 * While we could determine that here, the caller can usually do it more
 * efficiently (or at least amortize it over multiple calls).
 */
SubqueryScanPath *
create_subqueryscan_path(PlannerInfo *root, RelOptInfo *rel, Path *subpath,
             bool trivial_pathtarget,
             List *pathkeys, Relids required_outer)
{
  SubqueryScanPath *pathnode = makeNode(SubqueryScanPath);

  pathnode->path.pathtype = T_SubqueryScan;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = rel->reltarget;
  pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
                              required_outer);
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel &&
    subpath->parallel_safe;
  pathnode->path.parallel_workers = subpath->parallel_workers;
  pathnode->path.pathkeys = pathkeys;
  pathnode->subpath = subpath;

  cost_subqueryscan(pathnode, root, rel, pathnode->path.param_info,
            trivial_pathtarget);

  return pathnode;
}

/*
 * create_functionscan_path
 *    Creates a path corresponding to a sequential scan of a function,
 *    returning the pathnode.
 */
Path *
create_functionscan_path(PlannerInfo *root, RelOptInfo *rel,
             List *pathkeys, Relids required_outer)
{
  Path     *pathnode = makeNode(Path);

  pathnode->pathtype = T_FunctionScan;
  pathnode->parent = rel;
  pathnode->pathtarget = rel->reltarget;
  pathnode->param_info = get_baserel_parampathinfo(root, rel,
                           required_outer);
  pathnode->parallel_aware = false;
  pathnode->parallel_safe = rel->consider_parallel;
  pathnode->parallel_workers = 0;
  pathnode->pathkeys = pathkeys;

  cost_functionscan(pathnode, root, rel, pathnode->param_info);

  return pathnode;
}

/*
 * create_tablefuncscan_path
 *    Creates a path corresponding to a sequential scan of a table function,
 *    returning the pathnode.
 */
Path *
create_tablefuncscan_path(PlannerInfo *root, RelOptInfo *rel,
              Relids required_outer)
{
  Path     *pathnode = makeNode(Path);

  pathnode->pathtype = T_TableFuncScan;
  pathnode->parent = rel;
  pathnode->pathtarget = rel->reltarget;
  pathnode->param_info = get_baserel_parampathinfo(root, rel,
                           required_outer);
  pathnode->parallel_aware = false;
  pathnode->parallel_safe = rel->consider_parallel;
  pathnode->parallel_workers = 0;
  pathnode->pathkeys = NIL; /* result is always unordered */

  cost_tablefuncscan(pathnode, root, rel, pathnode->param_info);

  return pathnode;
}

/*
 * create_valuesscan_path
 *    Creates a path corresponding to a scan of a VALUES list,
 *    returning the pathnode.
 */
Path *
create_valuesscan_path(PlannerInfo *root, RelOptInfo *rel,
             Relids required_outer)
{
  Path     *pathnode = makeNode(Path);

  pathnode->pathtype = T_ValuesScan;
  pathnode->parent = rel;
  pathnode->pathtarget = rel->reltarget;
  pathnode->param_info = get_baserel_parampathinfo(root, rel,
                           required_outer);
  pathnode->parallel_aware = false;
  pathnode->parallel_safe = rel->consider_parallel;
  pathnode->parallel_workers = 0;
  pathnode->pathkeys = NIL; /* result is always unordered */

  cost_valuesscan(pathnode, root, rel, pathnode->param_info);

  return pathnode;
}

/*
 * create_ctescan_path
 *    Creates a path corresponding to a scan of a non-self-reference CTE,
 *    returning the pathnode.
 */
Path *
create_ctescan_path(PlannerInfo *root, RelOptInfo *rel,
          List *pathkeys, Relids required_outer)
{
  Path     *pathnode = makeNode(Path);

  pathnode->pathtype = T_CteScan;
  pathnode->parent = rel;
  pathnode->pathtarget = rel->reltarget;
  pathnode->param_info = get_baserel_parampathinfo(root, rel,
                           required_outer);
  pathnode->parallel_aware = false;
  pathnode->parallel_safe = rel->consider_parallel;
  pathnode->parallel_workers = 0;
  pathnode->pathkeys = pathkeys;

  cost_ctescan(pathnode, root, rel, pathnode->param_info);

  return pathnode;
}

/*
 * create_namedtuplestorescan_path
 *    Creates a path corresponding to a scan of a named tuplestore, returning
 *    the pathnode.
 */
Path *
create_namedtuplestorescan_path(PlannerInfo *root, RelOptInfo *rel,
                Relids required_outer)
{
  Path     *pathnode = makeNode(Path);

  pathnode->pathtype = T_NamedTuplestoreScan;
  pathnode->parent = rel;
  pathnode->pathtarget = rel->reltarget;
  pathnode->param_info = get_baserel_parampathinfo(root, rel,
                           required_outer);
  pathnode->parallel_aware = false;
  pathnode->parallel_safe = rel->consider_parallel;
  pathnode->parallel_workers = 0;
  pathnode->pathkeys = NIL; /* result is always unordered */

  cost_namedtuplestorescan(pathnode, root, rel, pathnode->param_info);

  return pathnode;
}

/*
 * create_resultscan_path
 *    Creates a path corresponding to a scan of an RTE_RESULT relation,
 *    returning the pathnode.
 */
Path *
create_resultscan_path(PlannerInfo *root, RelOptInfo *rel,
             Relids required_outer)
{
  Path     *pathnode = makeNode(Path);

  pathnode->pathtype = T_Result;
  pathnode->parent = rel;
  pathnode->pathtarget = rel->reltarget;
  pathnode->param_info = get_baserel_parampathinfo(root, rel,
                           required_outer);
  pathnode->parallel_aware = false;
  pathnode->parallel_safe = rel->consider_parallel;
  pathnode->parallel_workers = 0;
  pathnode->pathkeys = NIL; /* result is always unordered */

  cost_resultscan(pathnode, root, rel, pathnode->param_info);

  return pathnode;
}

/*
 * create_worktablescan_path
 *    Creates a path corresponding to a scan of a self-reference CTE,
 *    returning the pathnode.
 */
Path *
create_worktablescan_path(PlannerInfo *root, RelOptInfo *rel,
              Relids required_outer)
{
  Path     *pathnode = makeNode(Path);

  pathnode->pathtype = T_WorkTableScan;
  pathnode->parent = rel;
  pathnode->pathtarget = rel->reltarget;
  pathnode->param_info = get_baserel_parampathinfo(root, rel,
                           required_outer);
  pathnode->parallel_aware = false;
  pathnode->parallel_safe = rel->consider_parallel;
  pathnode->parallel_workers = 0;
  pathnode->pathkeys = NIL; /* result is always unordered */

  /* Cost is the same as for a regular CTE scan */
  cost_ctescan(pathnode, root, rel, pathnode->param_info);

  return pathnode;
}

/*
 * create_foreignscan_path
 *    Creates a path corresponding to a scan of a foreign base table,
 *    returning the pathnode.
 *
 * This function is never called from core Postgres; rather, it's expected
 * to be called by the GetForeignPaths function of a foreign data wrapper.
 * We make the FDW supply all fields of the path, since we do not have any way
 * to calculate them in core.  However, there is a usually-sane default for
 * the pathtarget (rel->reltarget), so we let a NULL for "target" select that.
 */
ForeignPath *
create_foreignscan_path(PlannerInfo *root, RelOptInfo *rel,
            PathTarget *target,
            double rows, int disabled_nodes,
            Cost startup_cost, Cost total_cost,
            List *pathkeys,
            Relids required_outer,
            Path *fdw_outerpath,
            List *fdw_restrictinfo,
            List *fdw_private)
{
  ForeignPath *pathnode = makeNode(ForeignPath);

  /* Historically some FDWs were confused about when to use this */
  Assert(IS_SIMPLE_REL(rel));

  pathnode->path.pathtype = T_ForeignScan;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = target ? target : rel->reltarget;
  pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
                              required_outer);
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel;
  pathnode->path.parallel_workers = 0;
  pathnode->path.rows = rows;
  pathnode->path.disabled_nodes = disabled_nodes;
  pathnode->path.startup_cost = startup_cost;
  pathnode->path.total_cost = total_cost;
  pathnode->path.pathkeys = pathkeys;

  pathnode->fdw_outerpath = fdw_outerpath;
  pathnode->fdw_restrictinfo = fdw_restrictinfo;
  pathnode->fdw_private = fdw_private;

  return pathnode;
}

/*
 * create_foreign_join_path
 *    Creates a path corresponding to a scan of a foreign join,
 *    returning the pathnode.
 *
 * This function is never called from core Postgres; rather, it's expected
 * to be called by the GetForeignJoinPaths function of a foreign data wrapper.
 * We make the FDW supply all fields of the path, since we do not have any way
 * to calculate them in core.  However, there is a usually-sane default for
 * the pathtarget (rel->reltarget), so we let a NULL for "target" select that.
 */
ForeignPath *
create_foreign_join_path(PlannerInfo *root, RelOptInfo *rel,
             PathTarget *target,
             double rows, int disabled_nodes,
             Cost startup_cost, Cost total_cost,
             List *pathkeys,
             Relids required_outer,
             Path *fdw_outerpath,
             List *fdw_restrictinfo,
             List *fdw_private)
{
  ForeignPath *pathnode = makeNode(ForeignPath);

  /*
   * We should use get_joinrel_parampathinfo to handle parameterized paths,
   * but the API of this function doesn't support it, and existing
   * extensions aren't yet trying to build such paths anyway.  For the
   * moment just throw an error if someone tries it; eventually we should
   * revisit this.
   */
  if (!bms_is_empty(required_outer) || !bms_is_empty(rel->lateral_relids))
    elog(ERROR, "parameterized foreign joins are not supported yet");

  pathnode->path.pathtype = T_ForeignScan;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = target ? target : rel->reltarget;
  pathnode->path.param_info = NULL; /* XXX see above */
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel;
  pathnode->path.parallel_workers = 0;
  pathnode->path.rows = rows;
  pathnode->path.disabled_nodes = disabled_nodes;
  pathnode->path.startup_cost = startup_cost;
  pathnode->path.total_cost = total_cost;
  pathnode->path.pathkeys = pathkeys;

  pathnode->fdw_outerpath = fdw_outerpath;
  pathnode->fdw_restrictinfo = fdw_restrictinfo;
  pathnode->fdw_private = fdw_private;

  return pathnode;
}

/*
 * create_foreign_upper_path
 *    Creates a path corresponding to an upper relation that's computed
 *    directly by an FDW, returning the pathnode.
 *
 * This function is never called from core Postgres; rather, it's expected to
 * be called by the GetForeignUpperPaths function of a foreign data wrapper.
 * We make the FDW supply all fields of the path, since we do not have any way
 * to calculate them in core.  However, there is a usually-sane default for
 * the pathtarget (rel->reltarget), so we let a NULL for "target" select that.
 */
ForeignPath *
create_foreign_upper_path(PlannerInfo *root, RelOptInfo *rel,
              PathTarget *target,
              double rows, int disabled_nodes,
              Cost startup_cost, Cost total_cost,
              List *pathkeys,
              Path *fdw_outerpath,
              List *fdw_restrictinfo,
              List *fdw_private)
{
  ForeignPath *pathnode = makeNode(ForeignPath);

  /*
   * Upper relations should never have any lateral references, since joining
   * is complete.
   */
  Assert(bms_is_empty(rel->lateral_relids));

  pathnode->path.pathtype = T_ForeignScan;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = target ? target : rel->reltarget;
  pathnode->path.param_info = NULL;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel;
  pathnode->path.parallel_workers = 0;
  pathnode->path.rows = rows;
  pathnode->path.disabled_nodes = disabled_nodes;
  pathnode->path.startup_cost = startup_cost;
  pathnode->path.total_cost = total_cost;
  pathnode->path.pathkeys = pathkeys;

  pathnode->fdw_outerpath = fdw_outerpath;
  pathnode->fdw_restrictinfo = fdw_restrictinfo;
  pathnode->fdw_private = fdw_private;

  return pathnode;
}

/*
 * calc_nestloop_required_outer
 *    Compute the required_outer set for a nestloop join path
 *
 * Note: when considering a child join, the inputs nonetheless use top-level
 * parent relids
 *
 * Note: result must not share storage with either input
 */
Relids
calc_nestloop_required_outer(Relids outerrelids,
               Relids outer_paramrels,
               Relids innerrelids,
               Relids inner_paramrels)
{
  Relids    required_outer;

  /* inner_path can require rels from outer path, but not vice versa */
  Assert(!bms_overlap(outer_paramrels, innerrelids));
  /* easy case if inner path is not parameterized */
  if (!inner_paramrels)
    return bms_copy(outer_paramrels);
  /* else, form the union ... */
  required_outer = bms_union(outer_paramrels, inner_paramrels);
  /* ... and remove any mention of now-satisfied outer rels */
  required_outer = bms_del_members(required_outer,
                   outerrelids);
  return required_outer;
}

/*
 * calc_non_nestloop_required_outer
 *    Compute the required_outer set for a merge or hash join path
 *
 * Note: result must not share storage with either input
 */
Relids
calc_non_nestloop_required_outer(Path *outer_path, Path *inner_path)
{
  Relids    outer_paramrels = PATH_REQ_OUTER(outer_path);
  Relids    inner_paramrels = PATH_REQ_OUTER(inner_path);
  Relids    innerrelids PG_USED_FOR_ASSERTS_ONLY;
  Relids    outerrelids PG_USED_FOR_ASSERTS_ONLY;
  Relids    required_outer;

  /*
   * Any parameterization of the input paths refers to topmost parents of
   * the relevant relations, because reparameterize_path_by_child() hasn't
   * been called yet.  So we must consider topmost parents of the relations
   * being joined, too, while checking for disallowed parameterization
   * cases.
   */
  if (inner_path->parent->top_parent_relids)
    innerrelids = inner_path->parent->top_parent_relids;
  else
    innerrelids = inner_path->parent->relids;

  if (outer_path->parent->top_parent_relids)
    outerrelids = outer_path->parent->top_parent_relids;
  else
    outerrelids = outer_path->parent->relids;

  /* neither path can require rels from the other */
  Assert(!bms_overlap(outer_paramrels, innerrelids));
  Assert(!bms_overlap(inner_paramrels, outerrelids));
  /* form the union ... */
  required_outer = bms_union(outer_paramrels, inner_paramrels);
  /* we do not need an explicit test for empty; bms_union gets it right */
  return required_outer;
}

/*
 * create_nestloop_path
 *    Creates a pathnode corresponding to a nestloop join between two
 *    relations.
 *
 * 'joinrel' is the join relation.
 * 'jointype' is the type of join required
 * 'workspace' is the result from initial_cost_nestloop
 * 'extra' contains various information about the join
 * 'outer_path' is the outer path
 * 'inner_path' is the inner path
 * 'restrict_clauses' are the RestrictInfo nodes to apply at the join
 * 'pathkeys' are the path keys of the new join path
 * 'required_outer' is the set of required outer rels
 *
 * Returns the resulting path node.
 */
NestPath *
create_nestloop_path(PlannerInfo *root,
           RelOptInfo *joinrel,
           JoinType jointype,
           JoinCostWorkspace *workspace,
           JoinPathExtraData *extra,
           Path *outer_path,
           Path *inner_path,
           List *restrict_clauses,
           List *pathkeys,
           Relids required_outer)
{
  NestPath   *pathnode = makeNode(NestPath);
  Relids    inner_req_outer = PATH_REQ_OUTER(inner_path);
  Relids    outerrelids;

  /*
   * Paths are parameterized by top-level parents, so run parameterization
   * tests on the parent relids.
   */
  if (outer_path->parent->top_parent_relids)
    outerrelids = outer_path->parent->top_parent_relids;
  else
    outerrelids = outer_path->parent->relids;

  /*
   * If the inner path is parameterized by the outer, we must drop any
   * restrict_clauses that are due to be moved into the inner path.  We have
   * to do this now, rather than postpone the work till createplan time,
   * because the restrict_clauses list can affect the size and cost
   * estimates for this path.  We detect such clauses by checking for serial
   * number match to clauses already enforced in the inner path.
   */
  if (bms_overlap(inner_req_outer, outerrelids))
  {
    Bitmapset  *enforced_serials = get_param_path_clause_serials(inner_path);
    List     *jclauses = NIL;
    ListCell   *lc;

    foreach(lc, restrict_clauses)
    {
      RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);

      if (!bms_is_member(rinfo->rinfo_serial, enforced_serials))
        jclauses = lappend(jclauses, rinfo);
    }
    restrict_clauses = jclauses;
  }

  pathnode->jpath.path.pathtype = T_NestLoop;
  pathnode->jpath.path.parent = joinrel;
  pathnode->jpath.path.pathtarget = joinrel->reltarget;
  pathnode->jpath.path.param_info =
    get_joinrel_parampathinfo(root,
                  joinrel,
                  outer_path,
                  inner_path,
                  extra->sjinfo,
                  required_outer,
                  &restrict_clauses);
  pathnode->jpath.path.parallel_aware = false;
  pathnode->jpath.path.parallel_safe = joinrel->consider_parallel &&
    outer_path->parallel_safe && inner_path->parallel_safe;
  /* This is a foolish way to estimate parallel_workers, but for now... */
  pathnode->jpath.path.parallel_workers = outer_path->parallel_workers;
  pathnode->jpath.path.pathkeys = pathkeys;
  pathnode->jpath.jointype = jointype;
  pathnode->jpath.inner_unique = extra->inner_unique;
  pathnode->jpath.outerjoinpath = outer_path;
  pathnode->jpath.innerjoinpath = inner_path;
  pathnode->jpath.joinrestrictinfo = restrict_clauses;

  final_cost_nestloop(root, pathnode, workspace, extra);

  return pathnode;
}

/*
 * create_mergejoin_path
 *    Creates a pathnode corresponding to a mergejoin join between
 *    two relations
 *
 * 'joinrel' is the join relation
 * 'jointype' is the type of join required
 * 'workspace' is the result from initial_cost_mergejoin
 * 'extra' contains various information about the join
 * 'outer_path' is the outer path
 * 'inner_path' is the inner path
 * 'restrict_clauses' are the RestrictInfo nodes to apply at the join
 * 'pathkeys' are the path keys of the new join path
 * 'required_outer' is the set of required outer rels
 * 'mergeclauses' are the RestrictInfo nodes to use as merge clauses
 *    (this should be a subset of the restrict_clauses list)
 * 'outersortkeys' are the sort varkeys for the outer relation
 * 'innersortkeys' are the sort varkeys for the inner relation
 * 'outer_presorted_keys' is the number of presorted keys of the outer path
 */
MergePath *
create_mergejoin_path(PlannerInfo *root,
            RelOptInfo *joinrel,
            JoinType jointype,
            JoinCostWorkspace *workspace,
            JoinPathExtraData *extra,
            Path *outer_path,
            Path *inner_path,
            List *restrict_clauses,
            List *pathkeys,
            Relids required_outer,
            List *mergeclauses,
            List *outersortkeys,
            List *innersortkeys,
            int outer_presorted_keys)
{
  MergePath  *pathnode = makeNode(MergePath);

  pathnode->jpath.path.pathtype = T_MergeJoin;
  pathnode->jpath.path.parent = joinrel;
  pathnode->jpath.path.pathtarget = joinrel->reltarget;
  pathnode->jpath.path.param_info =
    get_joinrel_parampathinfo(root,
                  joinrel,
                  outer_path,
                  inner_path,
                  extra->sjinfo,
                  required_outer,
                  &restrict_clauses);
  pathnode->jpath.path.parallel_aware = false;
  pathnode->jpath.path.parallel_safe = joinrel->consider_parallel &&
    outer_path->parallel_safe && inner_path->parallel_safe;
  /* This is a foolish way to estimate parallel_workers, but for now... */
  pathnode->jpath.path.parallel_workers = outer_path->parallel_workers;
  pathnode->jpath.path.pathkeys = pathkeys;
  pathnode->jpath.jointype = jointype;
  pathnode->jpath.inner_unique = extra->inner_unique;
  pathnode->jpath.outerjoinpath = outer_path;
  pathnode->jpath.innerjoinpath = inner_path;
  pathnode->jpath.joinrestrictinfo = restrict_clauses;
  pathnode->path_mergeclauses = mergeclauses;
  pathnode->outersortkeys = outersortkeys;
  pathnode->innersortkeys = innersortkeys;
  pathnode->outer_presorted_keys = outer_presorted_keys;
  /* pathnode->skip_mark_restore will be set by final_cost_mergejoin */
  /* pathnode->materialize_inner will be set by final_cost_mergejoin */

  final_cost_mergejoin(root, pathnode, workspace, extra);

  return pathnode;
}

/*
 * create_hashjoin_path
 *    Creates a pathnode corresponding to a hash join between two relations.
 *
 * 'joinrel' is the join relation
 * 'jointype' is the type of join required
 * 'workspace' is the result from initial_cost_hashjoin
 * 'extra' contains various information about the join
 * 'outer_path' is the cheapest outer path
 * 'inner_path' is the cheapest inner path
 * 'parallel_hash' to select Parallel Hash of inner path (shared hash table)
 * 'restrict_clauses' are the RestrictInfo nodes to apply at the join
 * 'required_outer' is the set of required outer rels
 * 'hashclauses' are the RestrictInfo nodes to use as hash clauses
 *    (this should be a subset of the restrict_clauses list)
 */
HashPath *
create_hashjoin_path(PlannerInfo *root,
           RelOptInfo *joinrel,
           JoinType jointype,
           JoinCostWorkspace *workspace,
           JoinPathExtraData *extra,
           Path *outer_path,
           Path *inner_path,
           bool parallel_hash,
           List *restrict_clauses,
           Relids required_outer,
           List *hashclauses)
{
  HashPath   *pathnode = makeNode(HashPath);

  pathnode->jpath.path.pathtype = T_HashJoin;
  pathnode->jpath.path.parent = joinrel;
  pathnode->jpath.path.pathtarget = joinrel->reltarget;
  pathnode->jpath.path.param_info =
    get_joinrel_parampathinfo(root,
                  joinrel,
                  outer_path,
                  inner_path,
                  extra->sjinfo,
                  required_outer,
                  &restrict_clauses);
  pathnode->jpath.path.parallel_aware =
    joinrel->consider_parallel && parallel_hash;
  pathnode->jpath.path.parallel_safe = joinrel->consider_parallel &&
    outer_path->parallel_safe && inner_path->parallel_safe;
  /* This is a foolish way to estimate parallel_workers, but for now... */
  pathnode->jpath.path.parallel_workers = outer_path->parallel_workers;

  /*
   * A hashjoin never has pathkeys, since its output ordering is
   * unpredictable due to possible batching.  XXX If the inner relation is
   * small enough, we could instruct the executor that it must not batch,
   * and then we could assume that the output inherits the outer relation's
   * ordering, which might save a sort step.  However there is considerable
   * downside if our estimate of the inner relation size is badly off. For
   * the moment we don't risk it.  (Note also that if we wanted to take this
   * seriously, joinpath.c would have to consider many more paths for the
   * outer rel than it does now.)
   */
  pathnode->jpath.path.pathkeys = NIL;
  pathnode->jpath.jointype = jointype;
  pathnode->jpath.inner_unique = extra->inner_unique;
  pathnode->jpath.outerjoinpath = outer_path;
  pathnode->jpath.innerjoinpath = inner_path;
  pathnode->jpath.joinrestrictinfo = restrict_clauses;
  pathnode->path_hashclauses = hashclauses;
  /* final_cost_hashjoin will fill in pathnode->num_batches */

  final_cost_hashjoin(root, pathnode, workspace, extra);

  return pathnode;
}

/*
 * create_projection_path
 *    Creates a pathnode that represents performing a projection.
 *
 * 'rel' is the parent relation associated with the result
 * 'subpath' is the path representing the source of data
 * 'target' is the PathTarget to be computed
 */
ProjectionPath *
create_projection_path(PlannerInfo *root,
             RelOptInfo *rel,
             Path *subpath,
             PathTarget *target)
{
  ProjectionPath *pathnode = makeNode(ProjectionPath);
  PathTarget *oldtarget;

  /*
   * We mustn't put a ProjectionPath directly above another; it's useless
   * and will confuse create_projection_plan.  Rather than making sure all
   * callers handle that, let's implement it here, by stripping off any
   * ProjectionPath in what we're given.  Given this rule, there won't be
   * more than one.
   */
  if (IsA(subpath, ProjectionPath))
  {
    ProjectionPath *subpp = (ProjectionPath *) subpath;

    Assert(subpp->path.parent == rel);
    subpath = subpp->subpath;
    Assert(!IsA(subpath, ProjectionPath));
  }

  pathnode->path.pathtype = T_Result;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = target;
  /* For now, assume we are above any joins, so no parameterization */
  pathnode->path.param_info = NULL;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel &&
    subpath->parallel_safe &&
    is_parallel_safe(root, (Node *) target->exprs);
  pathnode->path.parallel_workers = subpath->parallel_workers;
  /* Projection does not change the sort order */
  pathnode->path.pathkeys = subpath->pathkeys;

  pathnode->subpath = subpath;

  /*
   * We might not need a separate Result node.  If the input plan node type
   * can project, we can just tell it to project something else.  Or, if it
   * can't project but the desired target has the same expression list as
   * what the input will produce anyway, we can still give it the desired
   * tlist (possibly changing its ressortgroupref labels, but nothing else).
   * Note: in the latter case, create_projection_plan has to recheck our
   * conclusion; see comments therein.
   */
  oldtarget = subpath->pathtarget;
  if (is_projection_capable_path(subpath) ||
    equal(oldtarget->exprs, target->exprs))
  {
    /* No separate Result node needed */
    pathnode->dummypp = true;

    /*
     * Set cost of plan as subpath's cost, adjusted for tlist replacement.
     */
    pathnode->path.rows = subpath->rows;
    pathnode->path.disabled_nodes = subpath->disabled_nodes;
    pathnode->path.startup_cost = subpath->startup_cost +
      (target->cost.startup - oldtarget->cost.startup);
    pathnode->path.total_cost = subpath->total_cost +
      (target->cost.startup - oldtarget->cost.startup) +
      (target->cost.per_tuple - oldtarget->cost.per_tuple) * subpath->rows;
  }
  else
  {
    /* We really do need the Result node */
    pathnode->dummypp = false;

    /*
     * The Result node's cost is cpu_tuple_cost per row, plus the cost of
     * evaluating the tlist.  There is no qual to worry about.
     */
    pathnode->path.rows = subpath->rows;
    pathnode->path.disabled_nodes = subpath->disabled_nodes;
    pathnode->path.startup_cost = subpath->startup_cost +
      target->cost.startup;
    pathnode->path.total_cost = subpath->total_cost +
      target->cost.startup +
      (cpu_tuple_cost + target->cost.per_tuple) * subpath->rows;
  }

  return pathnode;
}

/*
 * apply_projection_to_path
 *    Add a projection step, or just apply the target directly to given path.
 *
 * This has the same net effect as create_projection_path(), except that if
 * a separate Result plan node isn't needed, we just replace the given path's
 * pathtarget with the desired one.  This must be used only when the caller
 * knows that the given path isn't referenced elsewhere and so can be modified
 * in-place.
 *
 * If the input path is a GatherPath or GatherMergePath, we try to push the
 * new target down to its input as well; this is a yet more invasive
 * modification of the input path, which create_projection_path() can't do.
 *
 * Note that we mustn't change the source path's parent link; so when it is
 * add_path'd to "rel" things will be a bit inconsistent.  So far that has
 * not caused any trouble.
 *
 * 'rel' is the parent relation associated with the result
 * 'path' is the path representing the source of data
 * 'target' is the PathTarget to be computed
 */
Path *
apply_projection_to_path(PlannerInfo *root,
             RelOptInfo *rel,
             Path *path,
             PathTarget *target)
{
  QualCost  oldcost;

  /*
   * If given path can't project, we might need a Result node, so make a
   * separate ProjectionPath.
   */
  if (!is_projection_capable_path(path))
    return (Path *) create_projection_path(root, rel, path, target);

  /*
   * We can just jam the desired tlist into the existing path, being sure to
   * update its cost estimates appropriately.
   */
  oldcost = path->pathtarget->cost;
  path->pathtarget = target;

  path->startup_cost += target->cost.startup - oldcost.startup;
  path->total_cost += target->cost.startup - oldcost.startup +
    (target->cost.per_tuple - oldcost.per_tuple) * path->rows;

  /*
   * If the path happens to be a Gather or GatherMerge path, we'd like to
   * arrange for the subpath to return the required target list so that
   * workers can help project.  But if there is something that is not
   * parallel-safe in the target expressions, then we can't.
   */
  if ((IsA(path, GatherPath) || IsA(path, GatherMergePath)) &&
    is_parallel_safe(root, (Node *) target->exprs))
  {
    /*
     * We always use create_projection_path here, even if the subpath is
     * projection-capable, so as to avoid modifying the subpath in place.
     * It seems unlikely at present that there could be any other
     * references to the subpath, but better safe than sorry.
     *
     * Note that we don't change the parallel path's cost estimates; it
     * might be appropriate to do so, to reflect the fact that the bulk of
     * the target evaluation will happen in workers.
     */
    if (IsA(path, GatherPath))
    {
      GatherPath *gpath = (GatherPath *) path;

      gpath->subpath = (Path *)
        create_projection_path(root,
                     gpath->subpath->parent,
                     gpath->subpath,
                     target);
    }
    else
    {
      GatherMergePath *gmpath = (GatherMergePath *) path;

      gmpath->subpath = (Path *)
        create_projection_path(root,
                     gmpath->subpath->parent,
                     gmpath->subpath,
                     target);
    }
  }
  else if (path->parallel_safe &&
       !is_parallel_safe(root, (Node *) target->exprs))
  {
    /*
     * We're inserting a parallel-restricted target list into a path
     * currently marked parallel-safe, so we have to mark it as no longer
     * safe.
     */
    path->parallel_safe = false;
  }

  return path;
}

/*
 * create_set_projection_path
 *    Creates a pathnode that represents performing a projection that
 *    includes set-returning functions.
 *
 * 'rel' is the parent relation associated with the result
 * 'subpath' is the path representing the source of data
 * 'target' is the PathTarget to be computed
 */
ProjectSetPath *
create_set_projection_path(PlannerInfo *root,
               RelOptInfo *rel,
               Path *subpath,
               PathTarget *target)
{
  ProjectSetPath *pathnode = makeNode(ProjectSetPath);
  double    tlist_rows;
  ListCell   *lc;

  pathnode->path.pathtype = T_ProjectSet;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = target;
  /* For now, assume we are above any joins, so no parameterization */
  pathnode->path.param_info = NULL;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel &&
    subpath->parallel_safe &&
    is_parallel_safe(root, (Node *) target->exprs);
  pathnode->path.parallel_workers = subpath->parallel_workers;
  /* Projection does not change the sort order XXX? */
  pathnode->path.pathkeys = subpath->pathkeys;

  pathnode->subpath = subpath;

  /*
   * Estimate number of rows produced by SRFs for each row of input; if
   * there's more than one in this node, use the maximum.
   */
  tlist_rows = 1;
  foreach(lc, target->exprs)
  {
    Node     *node = (Node *) lfirst(lc);
    double    itemrows;

    itemrows = expression_returns_set_rows(root, node);
    if (tlist_rows < itemrows)
      tlist_rows = itemrows;
  }

  /*
   * In addition to the cost of evaluating the tlist, charge cpu_tuple_cost
   * per input row, and half of cpu_tuple_cost for each added output row.
   * This is slightly bizarre maybe, but it's what 9.6 did; we may revisit
   * this estimate later.
   */
  pathnode->path.disabled_nodes = subpath->disabled_nodes;
  pathnode->path.rows = subpath->rows * tlist_rows;
  pathnode->path.startup_cost = subpath->startup_cost +
    target->cost.startup;
  pathnode->path.total_cost = subpath->total_cost +
    target->cost.startup +
    (cpu_tuple_cost + target->cost.per_tuple) * subpath->rows +
    (pathnode->path.rows - subpath->rows) * cpu_tuple_cost / 2;

  return pathnode;
}

/*
 * create_incremental_sort_path
 *    Creates a pathnode that represents performing an incremental sort.
 *
 * 'rel' is the parent relation associated with the result
 * 'subpath' is the path representing the source of data
 * 'pathkeys' represents the desired sort order
 * 'presorted_keys' is the number of keys by which the input path is
 *    already sorted
 * 'limit_tuples' is the estimated bound on the number of output tuples,
 *    or -1 if no LIMIT or couldn't estimate
 */
IncrementalSortPath *
create_incremental_sort_path(PlannerInfo *root,
               RelOptInfo *rel,
               Path *subpath,
               List *pathkeys,
               int presorted_keys,
               double limit_tuples)
{
  IncrementalSortPath *sort = makeNode(IncrementalSortPath);
  SortPath   *pathnode = &sort->spath;

  pathnode->path.pathtype = T_IncrementalSort;
  pathnode->path.parent = rel;
  /* Sort doesn't project, so use source path's pathtarget */
  pathnode->path.pathtarget = subpath->pathtarget;
  /* For now, assume we are above any joins, so no parameterization */
  pathnode->path.param_info = NULL;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel &&
    subpath->parallel_safe;
  pathnode->path.parallel_workers = subpath->parallel_workers;
  pathnode->path.pathkeys = pathkeys;

  pathnode->subpath = subpath;

  cost_incremental_sort(&pathnode->path,
              root, pathkeys, presorted_keys,
              subpath->disabled_nodes,
              subpath->startup_cost,
              subpath->total_cost,
              subpath->rows,
              subpath->pathtarget->width,
              0.0,  /* XXX comparison_cost shouldn't be 0? */
              work_mem, limit_tuples);

  sort->nPresortedCols = presorted_keys;

  return sort;
}

/*
 * create_sort_path
 *    Creates a pathnode that represents performing an explicit sort.
 *
 * 'rel' is the parent relation associated with the result
 * 'subpath' is the path representing the source of data
 * 'pathkeys' represents the desired sort order
 * 'limit_tuples' is the estimated bound on the number of output tuples,
 *    or -1 if no LIMIT or couldn't estimate
 */
SortPath *
create_sort_path(PlannerInfo *root,
         RelOptInfo *rel,
         Path *subpath,
         List *pathkeys,
         double limit_tuples)
{
  SortPath   *pathnode = makeNode(SortPath);

  pathnode->path.pathtype = T_Sort;
  pathnode->path.parent = rel;
  /* Sort doesn't project, so use source path's pathtarget */
  pathnode->path.pathtarget = subpath->pathtarget;
  /* For now, assume we are above any joins, so no parameterization */
  pathnode->path.param_info = NULL;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel &&
    subpath->parallel_safe;
  pathnode->path.parallel_workers = subpath->parallel_workers;
  pathnode->path.pathkeys = pathkeys;

  pathnode->subpath = subpath;

  cost_sort(&pathnode->path, root, pathkeys,
        subpath->disabled_nodes,
        subpath->total_cost,
        subpath->rows,
        subpath->pathtarget->width,
        0.0,        /* XXX comparison_cost shouldn't be 0? */
        work_mem, limit_tuples);

  return pathnode;
}

/*
 * create_group_path
 *    Creates a pathnode that represents performing grouping of presorted input
 *
 * 'rel' is the parent relation associated with the result
 * 'subpath' is the path representing the source of data
 * 'target' is the PathTarget to be computed
 * 'groupClause' is a list of SortGroupClause's representing the grouping
 * 'qual' is the HAVING quals if any
 * 'numGroups' is the estimated number of groups
 */
GroupPath *
create_group_path(PlannerInfo *root,
          RelOptInfo *rel,
          Path *subpath,
          List *groupClause,
          List *qual,
          double numGroups)
{
  GroupPath  *pathnode = makeNode(GroupPath);
  PathTarget *target = rel->reltarget;

  pathnode->path.pathtype = T_Group;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = target;
  /* For now, assume we are above any joins, so no parameterization */
  pathnode->path.param_info = NULL;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel &&
    subpath->parallel_safe;
  pathnode->path.parallel_workers = subpath->parallel_workers;
  /* Group doesn't change sort ordering */
  pathnode->path.pathkeys = subpath->pathkeys;

  pathnode->subpath = subpath;

  pathnode->groupClause = groupClause;
  pathnode->qual = qual;

  cost_group(&pathnode->path, root,
         list_length(groupClause),
         numGroups,
         qual,
         subpath->disabled_nodes,
         subpath->startup_cost, subpath->total_cost,
         subpath->rows);

  /* add tlist eval cost for each output row */
  pathnode->path.startup_cost += target->cost.startup;
  pathnode->path.total_cost += target->cost.startup +
    target->cost.per_tuple * pathnode->path.rows;

  return pathnode;
}

/*
 * create_upper_unique_path
 *    Creates a pathnode that represents performing an explicit Unique step
 *    on presorted input.
 *
 * This produces a Unique plan node, but the use-case is so different from
 * create_unique_path that it doesn't seem worth trying to merge the two.
 *
 * 'rel' is the parent relation associated with the result
 * 'subpath' is the path representing the source of data
 * 'numCols' is the number of grouping columns
 * 'numGroups' is the estimated number of groups
 *
 * The input path must be sorted on the grouping columns, plus possibly
 * additional columns; so the first numCols pathkeys are the grouping columns
 */
UpperUniquePath *
create_upper_unique_path(PlannerInfo *root,
             RelOptInfo *rel,
             Path *subpath,
             int numCols,
             double numGroups)
{
  UpperUniquePath *pathnode = makeNode(UpperUniquePath);

  pathnode->path.pathtype = T_Unique;
  pathnode->path.parent = rel;
  /* Unique doesn't project, so use source path's pathtarget */
  pathnode->path.pathtarget = subpath->pathtarget;
  /* For now, assume we are above any joins, so no parameterization */
  pathnode->path.param_info = NULL;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel &&
    subpath->parallel_safe;
  pathnode->path.parallel_workers = subpath->parallel_workers;
  /* Unique doesn't change the input ordering */
  pathnode->path.pathkeys = subpath->pathkeys;

  pathnode->subpath = subpath;
  pathnode->numkeys = numCols;

  /*
   * Charge one cpu_operator_cost per comparison per input tuple. We assume
   * all columns get compared at most of the tuples.  (XXX probably this is
   * an overestimate.)
   */
  pathnode->path.disabled_nodes = subpath->disabled_nodes;
  pathnode->path.startup_cost = subpath->startup_cost;
  pathnode->path.total_cost = subpath->total_cost +
    cpu_operator_cost * subpath->rows * numCols;
  pathnode->path.rows = numGroups;

  return pathnode;
}

/*
 * create_agg_path
 *    Creates a pathnode that represents performing aggregation/grouping
 *
 * 'rel' is the parent relation associated with the result
 * 'subpath' is the path representing the source of data
 * 'target' is the PathTarget to be computed
 * 'aggstrategy' is the Agg node's basic implementation strategy
 * 'aggsplit' is the Agg node's aggregate-splitting mode
 * 'groupClause' is a list of SortGroupClause's representing the grouping
 * 'qual' is the HAVING quals if any
 * 'aggcosts' contains cost info about the aggregate functions to be computed
 * 'numGroups' is the estimated number of groups (1 if not grouping)
 */
AggPath *
create_agg_path(PlannerInfo *root,
        RelOptInfo *rel,
        Path *subpath,
        PathTarget *target,
        AggStrategy aggstrategy,
        AggSplit aggsplit,
        List *groupClause,
        List *qual,
        const AggClauseCosts *aggcosts,
        double numGroups)
{
  AggPath    *pathnode = makeNode(AggPath);

  pathnode->path.pathtype = T_Agg;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = target;
  /* For now, assume we are above any joins, so no parameterization */
  pathnode->path.param_info = NULL;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel &&
    subpath->parallel_safe;
  pathnode->path.parallel_workers = subpath->parallel_workers;

  if (aggstrategy == AGG_SORTED)
  {
    /*
     * Attempt to preserve the order of the subpath.  Additional pathkeys
     * may have been added in adjust_group_pathkeys_for_groupagg() to
     * support ORDER BY / DISTINCT aggregates.  Pathkeys added there
     * belong to columns within the aggregate function, so we must strip
     * these additional pathkeys off as those columns are unavailable
     * above the aggregate node.
     */
    if (list_length(subpath->pathkeys) > root->num_groupby_pathkeys)
      pathnode->path.pathkeys = list_copy_head(subpath->pathkeys,
                           root->num_groupby_pathkeys);
    else
      pathnode->path.pathkeys = subpath->pathkeys; /* preserves order */
  }
  else
    pathnode->path.pathkeys = NIL; /* output is unordered */

  pathnode->subpath = subpath;

  pathnode->aggstrategy = aggstrategy;
  pathnode->aggsplit = aggsplit;
  pathnode->numGroups = numGroups;
  pathnode->transitionSpace = aggcosts ? aggcosts->transitionSpace : 0;
  pathnode->groupClause = groupClause;
  pathnode->qual = qual;

  cost_agg(&pathnode->path, root,
       aggstrategy, aggcosts,
       list_length(groupClause), numGroups,
       qual,
       subpath->disabled_nodes,
       subpath->startup_cost, subpath->total_cost,
       subpath->rows, subpath->pathtarget->width);

  /* add tlist eval cost for each output row */
  pathnode->path.startup_cost += target->cost.startup;
  pathnode->path.total_cost += target->cost.startup +
    target->cost.per_tuple * pathnode->path.rows;

  return pathnode;
}

/*
 * create_groupingsets_path
 *    Creates a pathnode that represents performing GROUPING SETS aggregation
 *
 * GroupingSetsPath represents sorted grouping with one or more grouping sets.
 * The input path's result must be sorted to match the last entry in
 * rollup_groupclauses.
 *
 * 'rel' is the parent relation associated with the result
 * 'subpath' is the path representing the source of data
 * 'target' is the PathTarget to be computed
 * 'having_qual' is the HAVING quals if any
 * 'rollups' is a list of RollupData nodes
 * 'agg_costs' contains cost info about the aggregate functions to be computed
 */
GroupingSetsPath *
create_groupingsets_path(PlannerInfo *root,
             RelOptInfo *rel,
             Path *subpath,
             List *having_qual,
             AggStrategy aggstrategy,
             List *rollups,
             const AggClauseCosts *agg_costs)
{
  GroupingSetsPath *pathnode = makeNode(GroupingSetsPath);
  PathTarget *target = rel->reltarget;
  ListCell   *lc;
  bool    is_first = true;
  bool    is_first_sort = true;

  /* The topmost generated Plan node will be an Agg */
  pathnode->path.pathtype = T_Agg;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = target;
  pathnode->path.param_info = subpath->param_info;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel &&
    subpath->parallel_safe;
  pathnode->path.parallel_workers = subpath->parallel_workers;
  pathnode->subpath = subpath;

  /*
   * Simplify callers by downgrading AGG_SORTED to AGG_PLAIN, and AGG_MIXED
   * to AGG_HASHED, here if possible.
   */
  if (aggstrategy == AGG_SORTED &&
    list_length(rollups) == 1 &&
    ((RollupData *) linitial(rollups))->groupClause == NIL)
    aggstrategy = AGG_PLAIN;

  if (aggstrategy == AGG_MIXED &&
    list_length(rollups) == 1)
    aggstrategy = AGG_HASHED;

  /*
   * Output will be in sorted order by group_pathkeys if, and only if, there
   * is a single rollup operation on a non-empty list of grouping
   * expressions.
   */
  if (aggstrategy == AGG_SORTED && list_length(rollups) == 1)
    pathnode->path.pathkeys = root->group_pathkeys;
  else
    pathnode->path.pathkeys = NIL;

  pathnode->aggstrategy = aggstrategy;
  pathnode->rollups = rollups;
  pathnode->qual = having_qual;
  pathnode->transitionSpace = agg_costs ? agg_costs->transitionSpace : 0;

  Assert(rollups != NIL);
  Assert(aggstrategy != AGG_PLAIN || list_length(rollups) == 1);
  Assert(aggstrategy != AGG_MIXED || list_length(rollups) > 1);

  foreach(lc, rollups)
  {
    RollupData *rollup = lfirst(lc);
    List     *gsets = rollup->gsets;
    int     numGroupCols = list_length(linitial(gsets));

    /*
     * In AGG_SORTED or AGG_PLAIN mode, the first rollup takes the
     * (already-sorted) input, and following ones do their own sort.
     *
     * In AGG_HASHED mode, there is one rollup for each grouping set.
     *
     * In AGG_MIXED mode, the first rollups are hashed, the first
     * non-hashed one takes the (already-sorted) input, and following ones
     * do their own sort.
     */
    if (is_first)
    {
      cost_agg(&pathnode->path, root,
           aggstrategy,
           agg_costs,
           numGroupCols,
           rollup->numGroups,
           having_qual,
           subpath->disabled_nodes,
           subpath->startup_cost,
           subpath->total_cost,
           subpath->rows,
           subpath->pathtarget->width);
      is_first = false;
      if (!rollup->is_hashed)
        is_first_sort = false;
    }
    else
    {
      Path    sort_path;  /* dummy for result of cost_sort */
      Path    agg_path; /* dummy for result of cost_agg */

      if (rollup->is_hashed || is_first_sort)
      {
        /*
         * Account for cost of aggregation, but don't charge input
         * cost again
         */
        cost_agg(&agg_path, root,
             rollup->is_hashed ? AGG_HASHED : AGG_SORTED,
             agg_costs,
             numGroupCols,
             rollup->numGroups,
             having_qual,
             0, 0.0, 0.0,
             subpath->rows,
             subpath->pathtarget->width);
        if (!rollup->is_hashed)
          is_first_sort = false;
      }
      else
      {
        /* Account for cost of sort, but don't charge input cost again */
        cost_sort(&sort_path, root, NIL, 0,
              0.0,
              subpath->rows,
              subpath->pathtarget->width,
              0.0,
              work_mem,
              -1.0);

        /* Account for cost of aggregation */

        cost_agg(&agg_path, root,
             AGG_SORTED,
             agg_costs,
             numGroupCols,
             rollup->numGroups,
             having_qual,
             sort_path.disabled_nodes,
             sort_path.startup_cost,
             sort_path.total_cost,
             sort_path.rows,
             subpath->pathtarget->width);
      }

      pathnode->path.disabled_nodes += agg_path.disabled_nodes;
      pathnode->path.total_cost += agg_path.total_cost;
      pathnode->path.rows += agg_path.rows;
    }
  }

  /* add tlist eval cost for each output row */
  pathnode->path.startup_cost += target->cost.startup;
  pathnode->path.total_cost += target->cost.startup +
    target->cost.per_tuple * pathnode->path.rows;

  return pathnode;
}

/*
 * create_minmaxagg_path
 *    Creates a pathnode that represents computation of MIN/MAX aggregates
 *
 * 'rel' is the parent relation associated with the result
 * 'target' is the PathTarget to be computed
 * 'mmaggregates' is a list of MinMaxAggInfo structs
 * 'quals' is the HAVING quals if any
 */
MinMaxAggPath *
create_minmaxagg_path(PlannerInfo *root,
            RelOptInfo *rel,
            PathTarget *target,
            List *mmaggregates,
            List *quals)
{
  MinMaxAggPath *pathnode = makeNode(MinMaxAggPath);
  Cost    initplan_cost;
  int     initplan_disabled_nodes = 0;
  ListCell   *lc;

  /* The topmost generated Plan node will be a Result */
  pathnode->path.pathtype = T_Result;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = target;
  /* For now, assume we are above any joins, so no parameterization */
  pathnode->path.param_info = NULL;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = true;  /* might change below */
  pathnode->path.parallel_workers = 0;
  /* Result is one unordered row */
  pathnode->path.rows = 1;
  pathnode->path.pathkeys = NIL;

  pathnode->mmaggregates = mmaggregates;
  pathnode->quals = quals;

  /* Calculate cost of all the initplans, and check parallel safety */
  initplan_cost = 0;
  foreach(lc, mmaggregates)
  {
    MinMaxAggInfo *mminfo = (MinMaxAggInfo *) lfirst(lc);

    initplan_disabled_nodes += mminfo->path->disabled_nodes;
    initplan_cost += mminfo->pathcost;
    if (!mminfo->path->parallel_safe)
      pathnode->path.parallel_safe = false;
  }

  /* add tlist eval cost for each output row, plus cpu_tuple_cost */
  pathnode->path.disabled_nodes = initplan_disabled_nodes;
  pathnode->path.startup_cost = initplan_cost + target->cost.startup;
  pathnode->path.total_cost = initplan_cost + target->cost.startup +
    target->cost.per_tuple + cpu_tuple_cost;

  /*
   * Add cost of qual, if any --- but we ignore its selectivity, since our
   * rowcount estimate should be 1 no matter what the qual is.
   */
  if (quals)
  {
    QualCost  qual_cost;

    cost_qual_eval(&qual_cost, quals, root);
    pathnode->path.startup_cost += qual_cost.startup;
    pathnode->path.total_cost += qual_cost.startup + qual_cost.per_tuple;
  }

  /*
   * If the initplans were all parallel-safe, also check safety of the
   * target and quals.  (The Result node itself isn't parallelizable, but if
   * we are in a subquery then it can be useful for the outer query to know
   * that this one is parallel-safe.)
   */
  if (pathnode->path.parallel_safe)
    pathnode->path.parallel_safe =
      is_parallel_safe(root, (Node *) target->exprs) &&
      is_parallel_safe(root, (Node *) quals);

  return pathnode;
}

/*
 * create_windowagg_path
 *    Creates a pathnode that represents computation of window functions
 *
 * 'rel' is the parent relation associated with the result
 * 'subpath' is the path representing the source of data
 * 'target' is the PathTarget to be computed
 * 'windowFuncs' is a list of WindowFunc structs
 * 'runCondition' is a list of OpExprs to short-circuit WindowAgg execution
 * 'winclause' is a WindowClause that is common to all the WindowFuncs
 * 'qual' WindowClause.runconditions from lower-level WindowAggPaths.
 *    Must always be NIL when topwindow == false
 * 'topwindow' pass as true only for the top-level WindowAgg. False for all
 *    intermediate WindowAggs.
 *
 * The input must be sorted according to the WindowClause's PARTITION keys
 * plus ORDER BY keys.
 */
WindowAggPath *
create_windowagg_path(PlannerInfo *root,
            RelOptInfo *rel,
            Path *subpath,
            PathTarget *target,
            List *windowFuncs,
            List *runCondition,
            WindowClause *winclause,
            List *qual,
            bool topwindow)
{
  WindowAggPath *pathnode = makeNode(WindowAggPath);

  /* qual can only be set for the topwindow */
  Assert(qual == NIL || topwindow);

  pathnode->path.pathtype = T_WindowAgg;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = target;
  /* For now, assume we are above any joins, so no parameterization */
  pathnode->path.param_info = NULL;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel &&
    subpath->parallel_safe;
  pathnode->path.parallel_workers = subpath->parallel_workers;
  /* WindowAgg preserves the input sort order */
  pathnode->path.pathkeys = subpath->pathkeys;

  pathnode->subpath = subpath;
  pathnode->winclause = winclause;
  pathnode->qual = qual;
  pathnode->runCondition = runCondition;
  pathnode->topwindow = topwindow;

  /*
   * For costing purposes, assume that there are no redundant partitioning
   * or ordering columns; it's not worth the trouble to deal with that
   * corner case here.  So we just pass the unmodified list lengths to
   * cost_windowagg.
   */
  cost_windowagg(&pathnode->path, root,
           windowFuncs,
           winclause,
           subpath->disabled_nodes,
           subpath->startup_cost,
           subpath->total_cost,
           subpath->rows);

  /* add tlist eval cost for each output row */
  pathnode->path.startup_cost += target->cost.startup;
  pathnode->path.total_cost += target->cost.startup +
    target->cost.per_tuple * pathnode->path.rows;

  return pathnode;
}

/*
 * create_setop_path
 *    Creates a pathnode that represents computation of INTERSECT or EXCEPT
 *
 * 'rel' is the parent relation associated with the result
 * 'leftpath' is the path representing the left-hand source of data
 * 'rightpath' is the path representing the right-hand source of data
 * 'cmd' is the specific semantics (INTERSECT or EXCEPT, with/without ALL)
 * 'strategy' is the implementation strategy (sorted or hashed)
 * 'groupList' is a list of SortGroupClause's representing the grouping
 * 'numGroups' is the estimated number of distinct groups in left-hand input
 * 'outputRows' is the estimated number of output rows
 *
 * leftpath and rightpath must produce the same columns.  Moreover, if
 * strategy is SETOP_SORTED, leftpath and rightpath must both be sorted
 * by all the grouping columns.
 */
SetOpPath *
create_setop_path(PlannerInfo *root,
          RelOptInfo *rel,
          Path *leftpath,
          Path *rightpath,
          SetOpCmd cmd,
          SetOpStrategy strategy,
          List *groupList,
          double numGroups,
          double outputRows)
{
  SetOpPath  *pathnode = makeNode(SetOpPath);

  pathnode->path.pathtype = T_SetOp;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = rel->reltarget;
  /* For now, assume we are above any joins, so no parameterization */
  pathnode->path.param_info = NULL;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel &&
    leftpath->parallel_safe && rightpath->parallel_safe;
  pathnode->path.parallel_workers =
    leftpath->parallel_workers + rightpath->parallel_workers;
  /* SetOp preserves the input sort order if in sort mode */
  pathnode->path.pathkeys =
    (strategy == SETOP_SORTED) ? leftpath->pathkeys : NIL;

  pathnode->leftpath = leftpath;
  pathnode->rightpath = rightpath;
  pathnode->cmd = cmd;
  pathnode->strategy = strategy;
  pathnode->groupList = groupList;
  pathnode->numGroups = numGroups;

  /*
   * Compute cost estimates.  As things stand, we end up with the same total
   * cost in this node for sort and hash methods, but different startup
   * costs.  This could be refined perhaps, but it'll do for now.
   */
  pathnode->path.disabled_nodes =
    leftpath->disabled_nodes + rightpath->disabled_nodes;
  if (strategy == SETOP_SORTED)
  {
    /*
     * In sorted mode, we can emit output incrementally.  Charge one
     * cpu_operator_cost per comparison per input tuple.  Like cost_group,
     * we assume all columns get compared at most of the tuples.
     */
    pathnode->path.startup_cost =
      leftpath->startup_cost + rightpath->startup_cost;
    pathnode->path.total_cost =
      leftpath->total_cost + rightpath->total_cost +
      cpu_operator_cost * (leftpath->rows + rightpath->rows) * list_length(groupList);

    /*
     * Also charge a small amount per extracted tuple.  Like cost_sort,
     * charge only operator cost not cpu_tuple_cost, since SetOp does no
     * qual-checking or projection.
     */
    pathnode->path.total_cost += cpu_operator_cost * outputRows;
  }
  else
  {
    Size    hashentrysize;

    /*
     * In hashed mode, we must read all the input before we can emit
     * anything.  Also charge comparison costs to represent the cost of
     * hash table lookups.
     */
    pathnode->path.startup_cost =
      leftpath->total_cost + rightpath->total_cost +
      cpu_operator_cost * (leftpath->rows + rightpath->rows) * list_length(groupList);
    pathnode->path.total_cost = pathnode->path.startup_cost;

    /*
     * Also charge a small amount per extracted tuple.  Like cost_sort,
     * charge only operator cost not cpu_tuple_cost, since SetOp does no
     * qual-checking or projection.
     */
    pathnode->path.total_cost += cpu_operator_cost * outputRows;

    /*
     * Mark the path as disabled if enable_hashagg is off.  While this
     * isn't exactly a HashAgg node, it seems close enough to justify
     * letting that switch control it.
     */
    if (!enable_hashagg)
      pathnode->path.disabled_nodes++;

    /*
     * Also disable if it doesn't look like the hashtable will fit into
     * hash_mem.
     */
    hashentrysize = MAXALIGN(leftpath->pathtarget->width) +
      MAXALIGN(SizeofMinimalTupleHeader);
    if (hashentrysize * numGroups > get_hash_memory_limit())
      pathnode->path.disabled_nodes++;
  }
  pathnode->path.rows = outputRows;

  return pathnode;
}

/*
 * create_recursiveunion_path
 *    Creates a pathnode that represents a recursive UNION node
 *
 * 'rel' is the parent relation associated with the result
 * 'leftpath' is the source of data for the non-recursive term
 * 'rightpath' is the source of data for the recursive term
 * 'target' is the PathTarget to be computed
 * 'distinctList' is a list of SortGroupClause's representing the grouping
 * 'wtParam' is the ID of Param representing work table
 * 'numGroups' is the estimated number of groups
 *
 * For recursive UNION ALL, distinctList is empty and numGroups is zero
 */
RecursiveUnionPath *
create_recursiveunion_path(PlannerInfo *root,
               RelOptInfo *rel,
               Path *leftpath,
               Path *rightpath,
               PathTarget *target,
               List *distinctList,
               int wtParam,
               double numGroups)
{
  RecursiveUnionPath *pathnode = makeNode(RecursiveUnionPath);

  pathnode->path.pathtype = T_RecursiveUnion;
  pathnode->path.parent = rel;
  pathnode->path.pathtarget = target;
  /* For now, assume we are above any joins, so no parameterization */
  pathnode->path.param_info = NULL;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel &&
    leftpath->parallel_safe && rightpath->parallel_safe;
  /* Foolish, but we'll do it like joins for now: */
  pathnode->path.parallel_workers = leftpath->parallel_workers;
  /* RecursiveUnion result is always unsorted */
  pathnode->path.pathkeys = NIL;

  pathnode->leftpath = leftpath;
  pathnode->rightpath = rightpath;
  pathnode->distinctList = distinctList;
  pathnode->wtParam = wtParam;
  pathnode->numGroups = numGroups;

  cost_recursive_union(&pathnode->path, leftpath, rightpath);

  return pathnode;
}

/*
 * create_lockrows_path
 *    Creates a pathnode that represents acquiring row locks
 *
 * 'rel' is the parent relation associated with the result
 * 'subpath' is the path representing the source of data
 * 'rowMarks' is a list of PlanRowMark's
 * 'epqParam' is the ID of Param for EvalPlanQual re-eval
 */
LockRowsPath *
create_lockrows_path(PlannerInfo *root, RelOptInfo *rel,
           Path *subpath, List *rowMarks, int epqParam)
{
  LockRowsPath *pathnode = makeNode(LockRowsPath);

  pathnode->path.pathtype = T_LockRows;
  pathnode->path.parent = rel;
  /* LockRows doesn't project, so use source path's pathtarget */
  pathnode->path.pathtarget = subpath->pathtarget;
  /* For now, assume we are above any joins, so no parameterization */
  pathnode->path.param_info = NULL;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = false;
  pathnode->path.parallel_workers = 0;
  pathnode->path.rows = subpath->rows;

  /*
   * The result cannot be assumed sorted, since locking might cause the sort
   * key columns to be replaced with new values.
   */
  pathnode->path.pathkeys = NIL;

  pathnode->subpath = subpath;
  pathnode->rowMarks = rowMarks;
  pathnode->epqParam = epqParam;

  /*
   * We should charge something extra for the costs of row locking and
   * possible refetches, but it's hard to say how much.  For now, use
   * cpu_tuple_cost per row.
   */
  pathnode->path.disabled_nodes = subpath->disabled_nodes;
  pathnode->path.startup_cost = subpath->startup_cost;
  pathnode->path.total_cost = subpath->total_cost +
    cpu_tuple_cost * subpath->rows;

  return pathnode;
}

/*
 * create_modifytable_path
 *    Creates a pathnode that represents performing INSERT/UPDATE/DELETE/MERGE
 *    mods
 *
 * 'rel' is the parent relation associated with the result
 * 'subpath' is a Path producing source data
 * 'operation' is the operation type
 * 'canSetTag' is true if we set the command tag/es_processed
 * 'nominalRelation' is the parent RT index for use of EXPLAIN
 * 'rootRelation' is the partitioned/inherited table root RTI, or 0 if none
 * 'partColsUpdated' is true if any partitioning columns are being updated,
 *    either from the target relation or a descendent partitioned table.
 * 'resultRelations' is an integer list of actual RT indexes of target rel(s)
 * 'updateColnosLists' is a list of UPDATE target column number lists
 *    (one sublist per rel); or NIL if not an UPDATE
 * 'withCheckOptionLists' is a list of WCO lists (one per rel)
 * 'returningLists' is a list of RETURNING tlists (one per rel)
 * 'rowMarks' is a list of PlanRowMarks (non-locking only)
 * 'onconflict' is the ON CONFLICT clause, or NULL
 * 'epqParam' is the ID of Param for EvalPlanQual re-eval
 * 'mergeActionLists' is a list of lists of MERGE actions (one per rel)
 * 'mergeJoinConditions' is a list of join conditions for MERGE (one per rel)
 */
ModifyTablePath *
create_modifytable_path(PlannerInfo *root, RelOptInfo *rel,
            Path *subpath,
            CmdType operation, bool canSetTag,
            Index nominalRelation, Index rootRelation,
            bool partColsUpdated,
            List *resultRelations,
            List *updateColnosLists,
            List *withCheckOptionLists, List *returningLists,
            List *rowMarks, OnConflictExpr *onconflict,
            List *mergeActionLists, List *mergeJoinConditions,
            int epqParam)
{
  ModifyTablePath *pathnode = makeNode(ModifyTablePath);

  Assert(operation == CMD_MERGE ||
       (operation == CMD_UPDATE ?
      list_length(resultRelations) == list_length(updateColnosLists) :
      updateColnosLists == NIL));
  Assert(withCheckOptionLists == NIL ||
       list_length(resultRelations) == list_length(withCheckOptionLists));
  Assert(returningLists == NIL ||
       list_length(resultRelations) == list_length(returningLists));

  pathnode->path.pathtype = T_ModifyTable;
  pathnode->path.parent = rel;
  /* pathtarget is not interesting, just make it minimally valid */
  pathnode->path.pathtarget = rel->reltarget;
  /* For now, assume we are above any joins, so no parameterization */
  pathnode->path.param_info = NULL;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = false;
  pathnode->path.parallel_workers = 0;
  pathnode->path.pathkeys = NIL;

  /*
   * Compute cost & rowcount as subpath cost & rowcount (if RETURNING)
   *
   * Currently, we don't charge anything extra for the actual table
   * modification work, nor for the WITH CHECK OPTIONS or RETURNING
   * expressions if any.  It would only be window dressing, since
   * ModifyTable is always a top-level node and there is no way for the
   * costs to change any higher-level planning choices.  But we might want
   * to make it look better sometime.
   */
  pathnode->path.disabled_nodes = subpath->disabled_nodes;
  pathnode->path.startup_cost = subpath->startup_cost;
  pathnode->path.total_cost = subpath->total_cost;
  if (returningLists != NIL)
  {
    pathnode->path.rows = subpath->rows;

    /*
     * Set width to match the subpath output.  XXX this is totally wrong:
     * we should return an average of the RETURNING tlist widths.  But
     * it's what happened historically, and improving it is a task for
     * another day.  (Again, it's mostly window dressing.)
     */
    pathnode->path.pathtarget->width = subpath->pathtarget->width;
  }
  else
  {
    pathnode->path.rows = 0;
    pathnode->path.pathtarget->width = 0;
  }

  pathnode->subpath = subpath;
  pathnode->operation = operation;
  pathnode->canSetTag = canSetTag;
  pathnode->nominalRelation = nominalRelation;
  pathnode->rootRelation = rootRelation;
  pathnode->partColsUpdated = partColsUpdated;
  pathnode->resultRelations = resultRelations;
  pathnode->updateColnosLists = updateColnosLists;
  pathnode->withCheckOptionLists = withCheckOptionLists;
  pathnode->returningLists = returningLists;
  pathnode->rowMarks = rowMarks;
  pathnode->onconflict = onconflict;
  pathnode->epqParam = epqParam;
  pathnode->mergeActionLists = mergeActionLists;
  pathnode->mergeJoinConditions = mergeJoinConditions;

  return pathnode;
}

/*
 * create_limit_path
 *    Creates a pathnode that represents performing LIMIT/OFFSET
 *
 * In addition to providing the actual OFFSET and LIMIT expressions,
 * the caller must provide estimates of their values for costing purposes.
 * The estimates are as computed by preprocess_limit(), ie, 0 represents
 * the clause not being present, and -1 means it's present but we could
 * not estimate its value.
 *
 * 'rel' is the parent relation associated with the result
 * 'subpath' is the path representing the source of data
 * 'limitOffset' is the actual OFFSET expression, or NULL
 * 'limitCount' is the actual LIMIT expression, or NULL
 * 'offset_est' is the estimated value of the OFFSET expression
 * 'count_est' is the estimated value of the LIMIT expression
 */
LimitPath *
create_limit_path(PlannerInfo *root, RelOptInfo *rel,
          Path *subpath,
          Node *limitOffset, Node *limitCount,
          LimitOption limitOption,
          int64 offset_est, int64 count_est)
{
  LimitPath  *pathnode = makeNode(LimitPath);

  pathnode->path.pathtype = T_Limit;
  pathnode->path.parent = rel;
  /* Limit doesn't project, so use source path's pathtarget */
  pathnode->path.pathtarget = subpath->pathtarget;
  /* For now, assume we are above any joins, so no parameterization */
  pathnode->path.param_info = NULL;
  pathnode->path.parallel_aware = false;
  pathnode->path.parallel_safe = rel->consider_parallel &&
    subpath->parallel_safe;
  pathnode->path.parallel_workers = subpath->parallel_workers;
  pathnode->path.rows = subpath->rows;
  pathnode->path.disabled_nodes = subpath->disabled_nodes;
  pathnode->path.startup_cost = subpath->startup_cost;
  pathnode->path.total_cost = subpath->total_cost;
  pathnode->path.pathkeys = subpath->pathkeys;
  pathnode->subpath = subpath;
  pathnode->limitOffset = limitOffset;
  pathnode->limitCount = limitCount;
  pathnode->limitOption = limitOption;

  /*
   * Adjust the output rows count and costs according to the offset/limit.
   */
  adjust_limit_rows_costs(&pathnode->path.rows,
              &pathnode->path.startup_cost,
              &pathnode->path.total_cost,
              offset_est, count_est);

  return pathnode;
}

/*
 * adjust_limit_rows_costs
 *    Adjust the size and cost estimates for a LimitPath node according to the
 *    offset/limit.
 *
 * This is only a cosmetic issue if we are at top level, but if we are
 * building a subquery then it's important to report correct info to the outer
 * planner.
 *
 * When the offset or count couldn't be estimated, use 10% of the estimated
 * number of rows emitted from the subpath.
 *
 * XXX we don't bother to add eval costs of the offset/limit expressions
 * themselves to the path costs.  In theory we should, but in most cases those
 * expressions are trivial and it's just not worth the trouble.
 */
void
adjust_limit_rows_costs(double *rows, /* in/out parameter */
            Cost *startup_cost, /* in/out parameter */
            Cost *total_cost, /* in/out parameter */
            int64 offset_est,
            int64 count_est)
{
  double    input_rows = *rows;
  Cost    input_startup_cost = *startup_cost;
  Cost    input_total_cost = *total_cost;

  if (offset_est != 0)
  {
    double    offset_rows;

    if (offset_est > 0)
      offset_rows = (double) offset_est;
    else
      offset_rows = clamp_row_est(input_rows * 0.10);
    if (offset_rows > *rows)
      offset_rows = *rows;
    if (input_rows > 0)
      *startup_cost +=
        (input_total_cost - input_startup_cost)
        * offset_rows / input_rows;
    *rows -= offset_rows;
    if (*rows < 1)
      *rows = 1;
  }

  if (count_est != 0)
  {
    double    count_rows;

    if (count_est > 0)
      count_rows = (double) count_est;
    else
      count_rows = clamp_row_est(input_rows * 0.10);
    if (count_rows > *rows)
      count_rows = *rows;
    if (input_rows > 0)
      *total_cost = *startup_cost +
        (input_total_cost - input_startup_cost)
        * count_rows / input_rows;
    *rows = count_rows;
    if (*rows < 1)
      *rows = 1;
  }
}


/*
 * reparameterize_path
 *    Attempt to modify a Path to have greater parameterization
 *
 * We use this to attempt to bring all child paths of an appendrel to the
 * same parameterization level, ensuring that they all enforce the same set
 * of join quals (and thus that that parameterization can be attributed to
 * an append path built from such paths).  Currently, only a few path types
 * are supported here, though more could be added at need.  We return NULL
 * if we can't reparameterize the given path.
 *
 * Note: we intentionally do not pass created paths to add_path(); it would
 * possibly try to delete them on the grounds of being cost-inferior to the
 * paths they were made from, and we don't want that.  Paths made here are
 * not necessarily of general-purpose usefulness, but they can be useful
 * as members of an append path.
 */
Path *
reparameterize_path(PlannerInfo *root, Path *path,
          Relids required_outer,
          double loop_count)
{
  RelOptInfo *rel = path->parent;

  /* Can only increase, not decrease, path's parameterization */
  if (!bms_is_subset(PATH_REQ_OUTER(path), required_outer))
    return NULL;
  switch (path->pathtype)
  {
    case T_SeqScan:
      return create_seqscan_path(root, rel, required_outer, 0);
    case T_SampleScan:
      return (Path *) create_samplescan_path(root, rel, required_outer);
    case T_IndexScan:
    case T_IndexOnlyScan:
      {
        IndexPath  *ipath = (IndexPath *) path;
        IndexPath  *newpath = makeNode(IndexPath);

        /*
         * We can't use create_index_path directly, and would not want
         * to because it would re-compute the indexqual conditions
         * which is wasted effort.  Instead we hack things a bit:
         * flat-copy the path node, revise its param_info, and redo
         * the cost estimate.
         */
        memcpy(newpath, ipath, sizeof(IndexPath));
        newpath->path.param_info =
          get_baserel_parampathinfo(root, rel, required_outer);
        cost_index(newpath, root, loop_count, false);
        return (Path *) newpath;
      }
    case T_BitmapHeapScan:
      {
        BitmapHeapPath *bpath = (BitmapHeapPath *) path;

        return (Path *) create_bitmap_heap_path(root,
                            rel,
                            bpath->bitmapqual,
                            required_outer,
                            loop_count, 0);
      }
    case T_SubqueryScan:
      {
        SubqueryScanPath *spath = (SubqueryScanPath *) path;
        Path     *subpath = spath->subpath;
        bool    trivial_pathtarget;

        /*
         * If existing node has zero extra cost, we must have decided
         * its target is trivial.  (The converse is not true, because
         * it might have a trivial target but quals to enforce; but in
         * that case the new node will too, so it doesn't matter
         * whether we get the right answer here.)
         */
        trivial_pathtarget =
          (subpath->total_cost == spath->path.total_cost);

        return (Path *) create_subqueryscan_path(root,
                             rel,
                             subpath,
                             trivial_pathtarget,
                             spath->path.pathkeys,
                             required_outer);
      }
    case T_Result:
      /* Supported only for RTE_RESULT scan paths */
      if (IsA(path, Path))
        return create_resultscan_path(root, rel, required_outer);
      break;
    case T_Append:
      {
        AppendPath *apath = (AppendPath *) path;
        List     *childpaths = NIL;
        List     *partialpaths = NIL;
        int     i;
        ListCell   *lc;

        /* Reparameterize the children */
        i = 0;
        foreach(lc, apath->subpaths)
        {
          Path     *spath = (Path *) lfirst(lc);

          spath = reparameterize_path(root, spath,
                        required_outer,
                        loop_count);
          if (spath == NULL)
            return NULL;
          /* We have to re-split the regular and partial paths */
          if (i < apath->first_partial_path)
            childpaths = lappend(childpaths, spath);
          else
            partialpaths = lappend(partialpaths, spath);
          i++;
        }
        return (Path *)
          create_append_path(root, rel, childpaths, partialpaths,
                     apath->path.pathkeys, required_outer,
                     apath->path.parallel_workers,
                     apath->path.parallel_aware,
                     -1);
      }
    case T_Material:
      {
        MaterialPath *mpath = (MaterialPath *) path;
        Path     *spath = mpath->subpath;

        spath = reparameterize_path(root, spath,
                      required_outer,
                      loop_count);
        if (spath == NULL)
          return NULL;
        return (Path *) create_material_path(rel, spath);
      }
    case T_Memoize:
      {
        MemoizePath *mpath = (MemoizePath *) path;
        Path     *spath = mpath->subpath;

        spath = reparameterize_path(root, spath,
                      required_outer,
                      loop_count);
        if (spath == NULL)
          return NULL;
        return (Path *) create_memoize_path(root, rel,
                          spath,
                          mpath->param_exprs,
                          mpath->hash_operators,
                          mpath->singlerow,
                          mpath->binary_mode,
                          mpath->calls);
      }
    default:
      break;
  }
  return NULL;
}

/*
 * reparameterize_path_by_child
 *    Given a path parameterized by the parent of the given child relation,
 *    translate the path to be parameterized by the given child relation.
 *
 * Most fields in the path are not changed, but any expressions must be
 * adjusted to refer to the correct varnos, and any subpaths must be
 * recursively reparameterized.  Other fields that refer to specific relids
 * also need adjustment.
 *
 * The cost, number of rows, width and parallel path properties depend upon
 * path->parent, which does not change during the translation.  So we need
 * not change those.
 *
 * Currently, only a few path types are supported here, though more could be
 * added at need.  We return NULL if we can't reparameterize the given path.
 *
 * Note that this function can change referenced RangeTblEntries, RelOptInfos
 * and IndexOptInfos as well as the Path structures.  Therefore, it's only safe
 * to call during create_plan(), when we have made a final choice of which Path
 * to use for each RangeTblEntry/RelOptInfo/IndexOptInfo.
 *
 * Keep this code in sync with path_is_reparameterizable_by_child()!
 */
Path *
reparameterize_path_by_child(PlannerInfo *root, Path *path,
               RelOptInfo *child_rel)
{
  Path     *new_path;
  ParamPathInfo *new_ppi;
  ParamPathInfo *old_ppi;
  Relids    required_outer;

#define ADJUST_CHILD_ATTRS(node) \
  ((node) = (void *) adjust_appendrel_attrs_multilevel(root, \
                             (Node *) (node), \
                             child_rel, \
                             child_rel->top_parent))

#define REPARAMETERIZE_CHILD_PATH(path) \
do { \
  (path) = reparameterize_path_by_child(root, (path), child_rel); \
  if ((path) == NULL) \
    return NULL; \
} while(0)

#define REPARAMETERIZE_CHILD_PATH_LIST(pathlist) \
do { \
  if ((pathlist) != NIL) \
  { \
    (pathlist) = reparameterize_pathlist_by_child(root, (pathlist), \
                            child_rel); \
    if ((pathlist) == NIL) \
      return NULL; \
  } \
} while(0)

  /*
   * If the path is not parameterized by the parent of the given relation,
   * it doesn't need reparameterization.
   */
  if (!path->param_info ||
    !bms_overlap(PATH_REQ_OUTER(path), child_rel->top_parent_relids))
    return path;

  /*
   * If possible, reparameterize the given path.
   *
   * This function is currently only applied to the inner side of a nestloop
   * join that is being partitioned by the partitionwise-join code.  Hence,
   * we need only support path types that plausibly arise in that context.
   * (In particular, supporting sorted path types would be a waste of code
   * and cycles: even if we translated them here, they'd just lose in
   * subsequent cost comparisons.)  If we do see an unsupported path type,
   * that just means we won't be able to generate a partitionwise-join plan
   * using that path type.
   */
  switch (nodeTag(path))
  {
    case T_Path:
      new_path = path;
      ADJUST_CHILD_ATTRS(new_path->parent->baserestrictinfo);
      if (path->pathtype == T_SampleScan)
      {
        Index   scan_relid = path->parent->relid;
        RangeTblEntry *rte;

        /* it should be a base rel with a tablesample clause... */
        Assert(scan_relid > 0);
        rte = planner_rt_fetch(scan_relid, root);
        Assert(rte->rtekind == RTE_RELATION);
        Assert(rte->tablesample != NULL);

        ADJUST_CHILD_ATTRS(rte->tablesample);
      }
      break;

    case T_IndexPath:
      {
        IndexPath  *ipath = (IndexPath *) path;

        ADJUST_CHILD_ATTRS(ipath->indexinfo->indrestrictinfo);
        ADJUST_CHILD_ATTRS(ipath->indexclauses);
        new_path = (Path *) ipath;
      }
      break;

    case T_BitmapHeapPath:
      {
        BitmapHeapPath *bhpath = (BitmapHeapPath *) path;

        ADJUST_CHILD_ATTRS(bhpath->path.parent->baserestrictinfo);
        REPARAMETERIZE_CHILD_PATH(bhpath->bitmapqual);
        new_path = (Path *) bhpath;
      }
      break;

    case T_BitmapAndPath:
      {
        BitmapAndPath *bapath = (BitmapAndPath *) path;

        REPARAMETERIZE_CHILD_PATH_LIST(bapath->bitmapquals);
        new_path = (Path *) bapath;
      }
      break;

    case T_BitmapOrPath:
      {
        BitmapOrPath *bopath = (BitmapOrPath *) path;

        REPARAMETERIZE_CHILD_PATH_LIST(bopath->bitmapquals);
        new_path = (Path *) bopath;
      }
      break;

    case T_ForeignPath:
      {
        ForeignPath *fpath = (ForeignPath *) path;
        ReparameterizeForeignPathByChild_function rfpc_func;

        ADJUST_CHILD_ATTRS(fpath->path.parent->baserestrictinfo);
        if (fpath->fdw_outerpath)
          REPARAMETERIZE_CHILD_PATH(fpath->fdw_outerpath);
        if (fpath->fdw_restrictinfo)
          ADJUST_CHILD_ATTRS(fpath->fdw_restrictinfo);

        /* Hand over to FDW if needed. */
        rfpc_func =
          path->parent->fdwroutine->ReparameterizeForeignPathByChild;
        if (rfpc_func)
          fpath->fdw_private = rfpc_func(root, fpath->fdw_private,
                           child_rel);
        new_path = (Path *) fpath;
      }
      break;

    case T_CustomPath:
      {
        CustomPath *cpath = (CustomPath *) path;

        ADJUST_CHILD_ATTRS(cpath->path.parent->baserestrictinfo);
        REPARAMETERIZE_CHILD_PATH_LIST(cpath->custom_paths);
        if (cpath->custom_restrictinfo)
          ADJUST_CHILD_ATTRS(cpath->custom_restrictinfo);
        if (cpath->methods &&
          cpath->methods->ReparameterizeCustomPathByChild)
          cpath->custom_private =
            cpath->methods->ReparameterizeCustomPathByChild(root,
                                    cpath->custom_private,
                                    child_rel);
        new_path = (Path *) cpath;
      }
      break;

    case T_NestPath:
      {
        NestPath   *npath = (NestPath *) path;
        JoinPath   *jpath = (JoinPath *) npath;

        REPARAMETERIZE_CHILD_PATH(jpath->outerjoinpath);
        REPARAMETERIZE_CHILD_PATH(jpath->innerjoinpath);
        ADJUST_CHILD_ATTRS(jpath->joinrestrictinfo);
        new_path = (Path *) npath;
      }
      break;

    case T_MergePath:
      {
        MergePath  *mpath = (MergePath *) path;
        JoinPath   *jpath = (JoinPath *) mpath;

        REPARAMETERIZE_CHILD_PATH(jpath->outerjoinpath);
        REPARAMETERIZE_CHILD_PATH(jpath->innerjoinpath);
        ADJUST_CHILD_ATTRS(jpath->joinrestrictinfo);
        ADJUST_CHILD_ATTRS(mpath->path_mergeclauses);
        new_path = (Path *) mpath;
      }
      break;

    case T_HashPath:
      {
        HashPath   *hpath = (HashPath *) path;
        JoinPath   *jpath = (JoinPath *) hpath;

        REPARAMETERIZE_CHILD_PATH(jpath->outerjoinpath);
        REPARAMETERIZE_CHILD_PATH(jpath->innerjoinpath);
        ADJUST_CHILD_ATTRS(jpath->joinrestrictinfo);
        ADJUST_CHILD_ATTRS(hpath->path_hashclauses);
        new_path = (Path *) hpath;
      }
      break;

    case T_AppendPath:
      {
        AppendPath *apath = (AppendPath *) path;

        REPARAMETERIZE_CHILD_PATH_LIST(apath->subpaths);
        new_path = (Path *) apath;
      }
      break;

    case T_MaterialPath:
      {
        MaterialPath *mpath = (MaterialPath *) path;

        REPARAMETERIZE_CHILD_PATH(mpath->subpath);
        new_path = (Path *) mpath;
      }
      break;

    case T_MemoizePath:
      {
        MemoizePath *mpath = (MemoizePath *) path;

        REPARAMETERIZE_CHILD_PATH(mpath->subpath);
        ADJUST_CHILD_ATTRS(mpath->param_exprs);
        new_path = (Path *) mpath;
      }
      break;

    case T_GatherPath:
      {
        GatherPath *gpath = (GatherPath *) path;

        REPARAMETERIZE_CHILD_PATH(gpath->subpath);
        new_path = (Path *) gpath;
      }
      break;

    default:
      /* We don't know how to reparameterize this path. */
      return NULL;
  }

  /*
   * Adjust the parameterization information, which refers to the topmost
   * parent. The topmost parent can be multiple levels away from the given
   * child, hence use multi-level expression adjustment routines.
   */
  old_ppi = new_path->param_info;
  required_outer =
    adjust_child_relids_multilevel(root, old_ppi->ppi_req_outer,
                     child_rel,
                     child_rel->top_parent);

  /* If we already have a PPI for this parameterization, just return it */
  new_ppi = find_param_path_info(new_path->parent, required_outer);

  /*
   * If not, build a new one and link it to the list of PPIs. For the same
   * reason as explained in mark_dummy_rel(), allocate new PPI in the same
   * context the given RelOptInfo is in.
   */
  if (new_ppi == NULL)
  {
    MemoryContext oldcontext;
    RelOptInfo *rel = path->parent;

    oldcontext = MemoryContextSwitchTo(GetMemoryChunkContext(rel));

    new_ppi = makeNode(ParamPathInfo);
    new_ppi->ppi_req_outer = bms_copy(required_outer);
    new_ppi->ppi_rows = old_ppi->ppi_rows;
    new_ppi->ppi_clauses = old_ppi->ppi_clauses;
    ADJUST_CHILD_ATTRS(new_ppi->ppi_clauses);
    new_ppi->ppi_serials = bms_copy(old_ppi->ppi_serials);
    rel->ppilist = lappend(rel->ppilist, new_ppi);

    MemoryContextSwitchTo(oldcontext);
  }
  bms_free(required_outer);

  new_path->param_info = new_ppi;

  /*
   * Adjust the path target if the parent of the outer relation is
   * referenced in the targetlist. This can happen when only the parent of
   * outer relation is laterally referenced in this relation.
   */
  if (bms_overlap(path->parent->lateral_relids,
          child_rel->top_parent_relids))
  {
    new_path->pathtarget = copy_pathtarget(new_path->pathtarget);
    ADJUST_CHILD_ATTRS(new_path->pathtarget->exprs);
  }

  return new_path;
}

/*
 * path_is_reparameterizable_by_child
 *    Given a path parameterized by the parent of the given child relation,
 *    see if it can be translated to be parameterized by the child relation.
 *
 * This must return true if and only if reparameterize_path_by_child()
 * would succeed on this path.  Currently it's sufficient to verify that
 * the path and all of its subpaths (if any) are of the types handled by
 * that function.  However, subpaths that are not parameterized can be
 * disregarded since they won't require translation.
 */
bool
path_is_reparameterizable_by_child(Path *path, RelOptInfo *child_rel)
{
#define REJECT_IF_PATH_NOT_REPARAMETERIZABLE(path) \
do { \
  if (!path_is_reparameterizable_by_child(path, child_rel)) \
    return false; \
} while(0)

#define REJECT_IF_PATH_LIST_NOT_REPARAMETERIZABLE(pathlist) \
do { \
  if (!pathlist_is_reparameterizable_by_child(pathlist, child_rel)) \
    return false; \
} while(0)

  /*
   * If the path is not parameterized by the parent of the given relation,
   * it doesn't need reparameterization.
   */
  if (!path->param_info ||
    !bms_overlap(PATH_REQ_OUTER(path), child_rel->top_parent_relids))
    return true;

  /*
   * Check that the path type is one that reparameterize_path_by_child() can
   * handle, and recursively check subpaths.
   */
  switch (nodeTag(path))
  {
    case T_Path:
    case T_IndexPath:
      break;

    case T_BitmapHeapPath:
      {
        BitmapHeapPath *bhpath = (BitmapHeapPath *) path;

        REJECT_IF_PATH_NOT_REPARAMETERIZABLE(bhpath->bitmapqual);
      }
      break;

    case T_BitmapAndPath:
      {
        BitmapAndPath *bapath = (BitmapAndPath *) path;

        REJECT_IF_PATH_LIST_NOT_REPARAMETERIZABLE(bapath->bitmapquals);
      }
      break;

    case T_BitmapOrPath:
      {
        BitmapOrPath *bopath = (BitmapOrPath *) path;

        REJECT_IF_PATH_LIST_NOT_REPARAMETERIZABLE(bopath->bitmapquals);
      }
      break;

    case T_ForeignPath:
      {
        ForeignPath *fpath = (ForeignPath *) path;

        if (fpath->fdw_outerpath)
          REJECT_IF_PATH_NOT_REPARAMETERIZABLE(fpath->fdw_outerpath);
      }
      break;

    case T_CustomPath:
      {
        CustomPath *cpath = (CustomPath *) path;

        REJECT_IF_PATH_LIST_NOT_REPARAMETERIZABLE(cpath->custom_paths);
      }
      break;

    case T_NestPath:
    case T_MergePath:
    case T_HashPath:
      {
        JoinPath   *jpath = (JoinPath *) path;

        REJECT_IF_PATH_NOT_REPARAMETERIZABLE(jpath->outerjoinpath);
        REJECT_IF_PATH_NOT_REPARAMETERIZABLE(jpath->innerjoinpath);
      }
      break;

    case T_AppendPath:
      {
        AppendPath *apath = (AppendPath *) path;

        REJECT_IF_PATH_LIST_NOT_REPARAMETERIZABLE(apath->subpaths);
      }
      break;

    case T_MaterialPath:
      {
        MaterialPath *mpath = (MaterialPath *) path;

        REJECT_IF_PATH_NOT_REPARAMETERIZABLE(mpath->subpath);
      }
      break;

    case T_MemoizePath:
      {
        MemoizePath *mpath = (MemoizePath *) path;

        REJECT_IF_PATH_NOT_REPARAMETERIZABLE(mpath->subpath);
      }
      break;

    case T_GatherPath:
      {
        GatherPath *gpath = (GatherPath *) path;

        REJECT_IF_PATH_NOT_REPARAMETERIZABLE(gpath->subpath);
      }
      break;

    default:
      /* We don't know how to reparameterize this path. */
      return false;
  }

  return true;
}

/*
 * reparameterize_pathlist_by_child
 *    Helper function to reparameterize a list of paths by given child rel.
 *
 * Returns NIL to indicate failure, so pathlist had better not be NIL.
 */
static List *
reparameterize_pathlist_by_child(PlannerInfo *root,
                 List *pathlist,
                 RelOptInfo *child_rel)
{
  ListCell   *lc;
  List     *result = NIL;

  foreach(lc, pathlist)
  {
    Path     *path = reparameterize_path_by_child(root, lfirst(lc),
                            child_rel);

    if (path == NULL)
    {
      list_free(result);
      return NIL;
    }

    result = lappend(result, path);
  }

  return result;
}

/*
 * pathlist_is_reparameterizable_by_child
 *    Helper function to check if a list of paths can be reparameterized.
 */
static bool
pathlist_is_reparameterizable_by_child(List *pathlist, RelOptInfo *child_rel)
{
  ListCell   *lc;

  foreach(lc, pathlist)
  {
    Path     *path = (Path *) lfirst(lc);

    if (!path_is_reparameterizable_by_child(path, child_rel))
      return false;
  }

  return true;
}

Coverage Report

Created: 2025-06-13 06:06