/src/postgres/src/backend/optimizer/path/joinrels.c

Source
/*-------------------------------------------------------------------------
 *
 * joinrels.c
 *    Routines to determine which relations should be joined
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/optimizer/path/joinrels.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "miscadmin.h"
#include "optimizer/appendinfo.h"
#include "optimizer/cost.h"
#include "optimizer/joininfo.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/planner.h"
#include "partitioning/partbounds.h"
#include "utils/memutils.h"


static void make_rels_by_clause_joins(PlannerInfo *root,
                    RelOptInfo *old_rel,
                    List *other_rels,
                    int first_rel_idx);
static void make_rels_by_clauseless_joins(PlannerInfo *root,
                      RelOptInfo *old_rel,
                      List *other_rels);
static bool has_join_restriction(PlannerInfo *root, RelOptInfo *rel);
static bool has_legal_joinclause(PlannerInfo *root, RelOptInfo *rel);
static bool restriction_is_constant_false(List *restrictlist,
                      RelOptInfo *joinrel,
                      bool only_pushed_down);
static void make_grouped_join_rel(PlannerInfo *root, RelOptInfo *rel1,
                  RelOptInfo *rel2, RelOptInfo *joinrel,
                  SpecialJoinInfo *sjinfo, List *restrictlist);
static void populate_joinrel_with_paths(PlannerInfo *root, RelOptInfo *rel1,
                    RelOptInfo *rel2, RelOptInfo *joinrel,
                    SpecialJoinInfo *sjinfo, List *restrictlist);
static void try_partitionwise_join(PlannerInfo *root, RelOptInfo *rel1,
                   RelOptInfo *rel2, RelOptInfo *joinrel,
                   SpecialJoinInfo *parent_sjinfo,
                   List *parent_restrictlist);
static SpecialJoinInfo *build_child_join_sjinfo(PlannerInfo *root,
                        SpecialJoinInfo *parent_sjinfo,
                        Relids left_relids, Relids right_relids);
static void free_child_join_sjinfo(SpecialJoinInfo *child_sjinfo,
                   SpecialJoinInfo *parent_sjinfo);
static void compute_partition_bounds(PlannerInfo *root, RelOptInfo *rel1,
                   RelOptInfo *rel2, RelOptInfo *joinrel,
                   SpecialJoinInfo *parent_sjinfo,
                   List **parts1, List **parts2);
static void get_matching_part_pairs(PlannerInfo *root, RelOptInfo *joinrel,
                  RelOptInfo *rel1, RelOptInfo *rel2,
                  List **parts1, List **parts2);


/*
 * join_search_one_level
 *    Consider ways to produce join relations containing exactly 'level'
 *    jointree items.  (This is one step of the dynamic-programming method
 *    embodied in standard_join_search.)  Join rel nodes for each feasible
 *    combination of lower-level rels are created and returned in a list.
 *    Implementation paths are created for each such joinrel, too.
 *
 * level: level of rels we want to make this time
 * root->join_rel_level[j], 1 <= j < level, is a list of rels containing j items
 *
 * The result is returned in root->join_rel_level[level].
 */
void
join_search_one_level(PlannerInfo *root, int level)
{
  List    **joinrels = root->join_rel_level;
  ListCell   *r;
  int     k;

  Assert(joinrels[level] == NIL);

  /* Set join_cur_level so that new joinrels are added to proper list */
  root->join_cur_level = level;

  /*
   * First, consider left-sided and right-sided plans, in which rels of
   * exactly level-1 member relations are joined against initial relations.
   * We prefer to join using join clauses, but if we find a rel of level-1
   * members that has no join clauses, we will generate Cartesian-product
   * joins against all initial rels not already contained in it.
   */
  foreach(r, joinrels[level - 1])
  {
    RelOptInfo *old_rel = (RelOptInfo *) lfirst(r);

    if (old_rel->joininfo != NIL || old_rel->has_eclass_joins ||
      has_join_restriction(root, old_rel))
    {
      int     first_rel;

      /*
       * There are join clauses or join order restrictions relevant to
       * this rel, so consider joins between this rel and (only) those
       * initial rels it is linked to by a clause or restriction.
       *
       * At level 2 this condition is symmetric, so there is no need to
       * look at initial rels before this one in the list; we already
       * considered such joins when we were at the earlier rel.  (The
       * mirror-image joins are handled automatically by make_join_rel.)
       * In later passes (level > 2), we join rels of the previous level
       * to each initial rel they don't already include but have a join
       * clause or restriction with.
       */
      if (level == 2)   /* consider remaining initial rels */
        first_rel = foreach_current_index(r) + 1;
      else
        first_rel = 0;

      make_rels_by_clause_joins(root, old_rel, joinrels[1], first_rel);
    }
    else
    {
      /*
       * Oops, we have a relation that is not joined to any other
       * relation, either directly or by join-order restrictions.
       * Cartesian product time.
       *
       * We consider a cartesian product with each not-already-included
       * initial rel, whether it has other join clauses or not.  At
       * level 2, if there are two or more clauseless initial rels, we
       * will redundantly consider joining them in both directions; but
       * such cases aren't common enough to justify adding complexity to
       * avoid the duplicated effort.
       */
      make_rels_by_clauseless_joins(root,
                      old_rel,
                      joinrels[1]);
    }
  }

  /*
   * Now, consider "bushy plans" in which relations of k initial rels are
   * joined to relations of level-k initial rels, for 2 <= k <= level-2.
   *
   * We only consider bushy-plan joins for pairs of rels where there is a
   * suitable join clause (or join order restriction), in order to avoid
   * unreasonable growth of planning time.
   */
  for (k = 2;; k++)
  {
    int     other_level = level - k;

    /*
     * Since make_join_rel(x, y) handles both x,y and y,x cases, we only
     * need to go as far as the halfway point.
     */
    if (k > other_level)
      break;

    foreach(r, joinrels[k])
    {
      RelOptInfo *old_rel = (RelOptInfo *) lfirst(r);
      int     first_rel;
      ListCell   *r2;

      /*
       * We can ignore relations without join clauses here, unless they
       * participate in join-order restrictions --- then we might have
       * to force a bushy join plan.
       */
      if (old_rel->joininfo == NIL && !old_rel->has_eclass_joins &&
        !has_join_restriction(root, old_rel))
        continue;

      if (k == other_level) /* only consider remaining rels */
        first_rel = foreach_current_index(r) + 1;
      else
        first_rel = 0;

      for_each_from(r2, joinrels[other_level], first_rel)
      {
        RelOptInfo *new_rel = (RelOptInfo *) lfirst(r2);

        if (!bms_overlap(old_rel->relids, new_rel->relids))
        {
          /*
           * OK, we can build a rel of the right level from this
           * pair of rels.  Do so if there is at least one relevant
           * join clause or join order restriction.
           */
          if (have_relevant_joinclause(root, old_rel, new_rel) ||
            have_join_order_restriction(root, old_rel, new_rel))
          {
            (void) make_join_rel(root, old_rel, new_rel);
          }
        }
      }
    }
  }

  /*----------
   * Last-ditch effort: if we failed to find any usable joins so far, force
   * a set of cartesian-product joins to be generated.  This handles the
   * special case where all the available rels have join clauses but we
   * cannot use any of those clauses yet.  This can only happen when we are
   * considering a join sub-problem (a sub-joinlist) and all the rels in the
   * sub-problem have only join clauses with rels outside the sub-problem.
   * An example is
   *
   *    SELECT ... FROM a INNER JOIN b ON TRUE, c, d, ...
   *    WHERE a.w = c.x and b.y = d.z;
   *
   * If the "a INNER JOIN b" sub-problem does not get flattened into the
   * upper level, we must be willing to make a cartesian join of a and b;
   * but the code above will not have done so, because it thought that both
   * a and b have joinclauses.  We consider only left-sided and right-sided
   * cartesian joins in this case (no bushy).
   *----------
   */
  if (joinrels[level] == NIL)
  {
    /*
     * This loop is just like the first one, except we always call
     * make_rels_by_clauseless_joins().
     */
    foreach(r, joinrels[level - 1])
    {
      RelOptInfo *old_rel = (RelOptInfo *) lfirst(r);

      make_rels_by_clauseless_joins(root,
                      old_rel,
                      joinrels[1]);
    }

    /*----------
     * When special joins are involved, there may be no legal way
     * to make an N-way join for some values of N.  For example consider
     *
     * SELECT ... FROM t1 WHERE
     *   x IN (SELECT ... FROM t2,t3 WHERE ...) AND
     *   y IN (SELECT ... FROM t4,t5 WHERE ...)
     *
     * We will flatten this query to a 5-way join problem, but there are
     * no 4-way joins that join_is_legal() will consider legal.  We have
     * to accept failure at level 4 and go on to discover a workable
     * bushy plan at level 5.
     *
     * However, if there are no special joins and no lateral references
     * then join_is_legal() should never fail, and so the following sanity
     * check is useful.
     *----------
     */
    if (joinrels[level] == NIL &&
      root->join_info_list == NIL &&
      !root->hasLateralRTEs)
      elog(ERROR, "failed to build any %d-way joins", level);
  }
}

/*
 * make_rels_by_clause_joins
 *    Build joins between the given relation 'old_rel' and other relations
 *    that participate in join clauses that 'old_rel' also participates in
 *    (or participate in join-order restrictions with it).
 *    The join rels are returned in root->join_rel_level[join_cur_level].
 *
 * Note: at levels above 2 we will generate the same joined relation in
 * multiple ways --- for example (a join b) join c is the same RelOptInfo as
 * (b join c) join a, though the second case will add a different set of Paths
 * to it.  This is the reason for using the join_rel_level mechanism, which
 * automatically ensures that each new joinrel is only added to the list once.
 *
 * 'old_rel' is the relation entry for the relation to be joined
 * 'other_rels': a list containing the other rels to be considered for joining
 * 'first_rel_idx': the first rel to be considered in 'other_rels'
 *
 * Currently, this is only used with initial rels in other_rels, but it
 * will work for joining to joinrels too.
 */
static void
make_rels_by_clause_joins(PlannerInfo *root,
              RelOptInfo *old_rel,
              List *other_rels,
              int first_rel_idx)
{
  ListCell   *l;

  for_each_from(l, other_rels, first_rel_idx)
  {
    RelOptInfo *other_rel = (RelOptInfo *) lfirst(l);

    if (!bms_overlap(old_rel->relids, other_rel->relids) &&
      (have_relevant_joinclause(root, old_rel, other_rel) ||
       have_join_order_restriction(root, old_rel, other_rel)))
    {
      (void) make_join_rel(root, old_rel, other_rel);
    }
  }
}

/*
 * make_rels_by_clauseless_joins
 *    Given a relation 'old_rel' and a list of other relations
 *    'other_rels', create a join relation between 'old_rel' and each
 *    member of 'other_rels' that isn't already included in 'old_rel'.
 *    The join rels are returned in root->join_rel_level[join_cur_level].
 *
 * 'old_rel' is the relation entry for the relation to be joined
 * 'other_rels': a list containing the other rels to be considered for joining
 *
 * Currently, this is only used with initial rels in other_rels, but it would
 * work for joining to joinrels too.
 */
static void
make_rels_by_clauseless_joins(PlannerInfo *root,
                RelOptInfo *old_rel,
                List *other_rels)
{
  ListCell   *l;

  foreach(l, other_rels)
  {
    RelOptInfo *other_rel = (RelOptInfo *) lfirst(l);

    if (!bms_overlap(other_rel->relids, old_rel->relids))
    {
      (void) make_join_rel(root, old_rel, other_rel);
    }
  }
}


/*
 * join_is_legal
 *     Determine whether a proposed join is legal given the query's
 *     join order constraints; and if it is, determine the join type.
 *
 * Caller must supply not only the two rels, but the union of their relids.
 * (We could simplify the API by computing joinrelids locally, but this
 * would be redundant work in the normal path through make_join_rel.
 * Note that this value does NOT include the RT index of any outer join that
 * might need to be performed here, so it's not the canonical identifier
 * of the join relation.)
 *
 * On success, *sjinfo_p is set to NULL if this is to be a plain inner join,
 * else it's set to point to the associated SpecialJoinInfo node.  Also,
 * *reversed_p is set true if the given relations need to be swapped to
 * match the SpecialJoinInfo node.
 */
static bool
join_is_legal(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,
        Relids joinrelids,
        SpecialJoinInfo **sjinfo_p, bool *reversed_p)
{
  SpecialJoinInfo *match_sjinfo;
  bool    reversed;
  bool    unique_ified;
  bool    must_be_leftjoin;
  ListCell   *l;

  /*
   * Ensure output params are set on failure return.  This is just to
   * suppress uninitialized-variable warnings from overly anal compilers.
   */
  *sjinfo_p = NULL;
  *reversed_p = false;

  /*
   * If we have any special joins, the proposed join might be illegal; and
   * in any case we have to determine its join type.  Scan the join info
   * list for matches and conflicts.
   */
  match_sjinfo = NULL;
  reversed = false;
  unique_ified = false;
  must_be_leftjoin = false;

  foreach(l, root->join_info_list)
  {
    SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l);

    /*
     * This special join is not relevant unless its RHS overlaps the
     * proposed join.  (Check this first as a fast path for dismissing
     * most irrelevant SJs quickly.)
     */
    if (!bms_overlap(sjinfo->min_righthand, joinrelids))
      continue;

    /*
     * Also, not relevant if proposed join is fully contained within RHS
     * (ie, we're still building up the RHS).
     */
    if (bms_is_subset(joinrelids, sjinfo->min_righthand))
      continue;

    /*
     * Also, not relevant if SJ is already done within either input.
     */
    if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
      bms_is_subset(sjinfo->min_righthand, rel1->relids))
      continue;
    if (bms_is_subset(sjinfo->min_lefthand, rel2->relids) &&
      bms_is_subset(sjinfo->min_righthand, rel2->relids))
      continue;

    /*
     * If it's a semijoin and we already joined the RHS to any other rels
     * within either input, then we must have unique-ified the RHS at that
     * point (see below).  Therefore the semijoin is no longer relevant in
     * this join path.
     */
    if (sjinfo->jointype == JOIN_SEMI)
    {
      if (bms_is_subset(sjinfo->syn_righthand, rel1->relids) &&
        !bms_equal(sjinfo->syn_righthand, rel1->relids))
        continue;
      if (bms_is_subset(sjinfo->syn_righthand, rel2->relids) &&
        !bms_equal(sjinfo->syn_righthand, rel2->relids))
        continue;
    }

    /*
     * If one input contains min_lefthand and the other contains
     * min_righthand, then we can perform the SJ at this join.
     *
     * Reject if we get matches to more than one SJ; that implies we're
     * considering something that's not really valid.
     */
    if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
      bms_is_subset(sjinfo->min_righthand, rel2->relids))
    {
      if (match_sjinfo)
        return false; /* invalid join path */
      match_sjinfo = sjinfo;
      reversed = false;
    }
    else if (bms_is_subset(sjinfo->min_lefthand, rel2->relids) &&
         bms_is_subset(sjinfo->min_righthand, rel1->relids))
    {
      if (match_sjinfo)
        return false; /* invalid join path */
      match_sjinfo = sjinfo;
      reversed = true;
    }
    else if (sjinfo->jointype == JOIN_SEMI &&
         bms_equal(sjinfo->syn_righthand, rel2->relids) &&
         create_unique_paths(root, rel2, sjinfo) != NULL)
    {
      /*----------
       * For a semijoin, we can join the RHS to anything else by
       * unique-ifying the RHS (if the RHS can be unique-ified).
       * We will only get here if we have the full RHS but less
       * than min_lefthand on the LHS.
       *
       * The reason to consider such a join path is exemplified by
       *  SELECT ... FROM a,b WHERE (a.x,b.y) IN (SELECT c1,c2 FROM c)
       * If we insist on doing this as a semijoin we will first have
       * to form the cartesian product of A*B.  But if we unique-ify
       * C then the semijoin becomes a plain innerjoin and we can join
       * in any order, eg C to A and then to B.  When C is much smaller
       * than A and B this can be a huge win.  So we allow C to be
       * joined to just A or just B here, and then make_join_rel has
       * to handle the case properly.
       *
       * Note that actually we'll allow unique-ified C to be joined to
       * some other relation D here, too.  That is legal, if usually not
       * very sane, and this routine is only concerned with legality not
       * with whether the join is good strategy.
       *----------
       */
      if (match_sjinfo)
        return false; /* invalid join path */
      match_sjinfo = sjinfo;
      reversed = false;
      unique_ified = true;
    }
    else if (sjinfo->jointype == JOIN_SEMI &&
         bms_equal(sjinfo->syn_righthand, rel1->relids) &&
         create_unique_paths(root, rel1, sjinfo) != NULL)
    {
      /* Reversed semijoin case */
      if (match_sjinfo)
        return false; /* invalid join path */
      match_sjinfo = sjinfo;
      reversed = true;
      unique_ified = true;
    }
    else
    {
      /*
       * Otherwise, the proposed join overlaps the RHS but isn't a valid
       * implementation of this SJ.  But don't panic quite yet: the RHS
       * violation might have occurred previously, in one or both input
       * relations, in which case we must have previously decided that
       * it was OK to commute some other SJ with this one.  If we need
       * to perform this join to finish building up the RHS, rejecting
       * it could lead to not finding any plan at all.  (This can occur
       * because of the heuristics elsewhere in this file that postpone
       * clauseless joins: we might not consider doing a clauseless join
       * within the RHS until after we've performed other, validly
       * commutable SJs with one or both sides of the clauseless join.)
       * This consideration boils down to the rule that if both inputs
       * overlap the RHS, we can allow the join --- they are either
       * fully within the RHS, or represent previously-allowed joins to
       * rels outside it.
       */
      if (bms_overlap(rel1->relids, sjinfo->min_righthand) &&
        bms_overlap(rel2->relids, sjinfo->min_righthand))
        continue;   /* assume valid previous violation of RHS */

      /*
       * The proposed join could still be legal, but only if we're
       * allowed to associate it into the RHS of this SJ.  That means
       * this SJ must be a LEFT join (not SEMI or ANTI, and certainly
       * not FULL) and the proposed join must not overlap the LHS.
       */
      if (sjinfo->jointype != JOIN_LEFT ||
        bms_overlap(joinrelids, sjinfo->min_lefthand))
        return false; /* invalid join path */

      /*
       * To be valid, the proposed join must be a LEFT join; otherwise
       * it can't associate into this SJ's RHS.  But we may not yet have
       * found the SpecialJoinInfo matching the proposed join, so we
       * can't test that yet.  Remember the requirement for later.
       */
      must_be_leftjoin = true;
    }
  }

  /*
   * Fail if violated any SJ's RHS and didn't match to a LEFT SJ: the
   * proposed join can't associate into an SJ's RHS.
   *
   * Also, fail if the proposed join's predicate isn't strict; we're
   * essentially checking to see if we can apply outer-join identity 3, and
   * that's a requirement.  (This check may be redundant with checks in
   * make_outerjoininfo, but I'm not quite sure, and it's cheap to test.)
   */
  if (must_be_leftjoin &&
    (match_sjinfo == NULL ||
     match_sjinfo->jointype != JOIN_LEFT ||
     !match_sjinfo->lhs_strict))
    return false;     /* invalid join path */

  /*
   * We also have to check for constraints imposed by LATERAL references.
   */
  if (root->hasLateralRTEs)
  {
    bool    lateral_fwd;
    bool    lateral_rev;
    Relids    join_lateral_rels;

    /*
     * The proposed rels could each contain lateral references to the
     * other, in which case the join is impossible.  If there are lateral
     * references in just one direction, then the join has to be done with
     * a nestloop with the lateral referencer on the inside.  If the join
     * matches an SJ that cannot be implemented by such a nestloop, the
     * join is impossible.
     *
     * Also, if the lateral reference is only indirect, we should reject
     * the join; whatever rel(s) the reference chain goes through must be
     * joined to first.
     */
    lateral_fwd = bms_overlap(rel1->relids, rel2->lateral_relids);
    lateral_rev = bms_overlap(rel2->relids, rel1->lateral_relids);
    if (lateral_fwd && lateral_rev)
      return false;   /* have lateral refs in both directions */
    if (lateral_fwd)
    {
      /* has to be implemented as nestloop with rel1 on left */
      if (match_sjinfo &&
        (reversed ||
         unique_ified ||
         match_sjinfo->jointype == JOIN_FULL))
        return false; /* not implementable as nestloop */
      /* check there is a direct reference from rel2 to rel1 */
      if (!bms_overlap(rel1->relids, rel2->direct_lateral_relids))
        return false; /* only indirect refs, so reject */
    }
    else if (lateral_rev)
    {
      /* has to be implemented as nestloop with rel2 on left */
      if (match_sjinfo &&
        (!reversed ||
         unique_ified ||
         match_sjinfo->jointype == JOIN_FULL))
        return false; /* not implementable as nestloop */
      /* check there is a direct reference from rel1 to rel2 */
      if (!bms_overlap(rel2->relids, rel1->direct_lateral_relids))
        return false; /* only indirect refs, so reject */
    }

    /*
     * LATERAL references could also cause problems later on if we accept
     * this join: if the join's minimum parameterization includes any rels
     * that would have to be on the inside of an outer join with this join
     * rel, then it's never going to be possible to build the complete
     * query using this join.  We should reject this join not only because
     * it'll save work, but because if we don't, the clauseless-join
     * heuristics might think that legality of this join means that some
     * other join rel need not be formed, and that could lead to failure
     * to find any plan at all.  We have to consider not only rels that
     * are directly on the inner side of an OJ with the joinrel, but also
     * ones that are indirectly so, so search to find all such rels.
     * Likewise, input rels of the current join search that laterally
     * reference the joinrel or any rel found so far cannot supply a
     * parameter to the joinrel, so include those too.
     */
    join_lateral_rels = min_join_parameterization(root, joinrelids,
                            rel1, rel2);
    if (join_lateral_rels)
    {
      Relids    join_plus_rhs = bms_copy(joinrelids);
      bool    more;

      do
      {
        more = false;
        foreach(l, root->join_info_list)
        {
          SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l);

          /* ignore full joins --- their ordering is predetermined */
          if (sjinfo->jointype == JOIN_FULL)
            continue;

          if (bms_overlap(sjinfo->min_lefthand, join_plus_rhs) &&
            !bms_is_subset(sjinfo->min_righthand, join_plus_rhs))
          {
            join_plus_rhs = bms_add_members(join_plus_rhs,
                            sjinfo->min_righthand);
            more = true;
          }
        }

        /*
         * Add input rels that laterally reference any rel found so
         * far.  An input rel can be a sub-joinlist's joinrel, which
         * must be taken as a whole.
         */
        foreach(l, root->initial_rels)
        {
          RelOptInfo *irel = (RelOptInfo *) lfirst(l);

          if (bms_overlap(irel->lateral_relids, join_plus_rhs) &&
            !bms_is_subset(irel->relids, join_plus_rhs))
          {
            join_plus_rhs = bms_add_members(join_plus_rhs,
                            irel->relids);
            more = true;
          }
        }
      } while (more);
      if (bms_overlap(join_plus_rhs, join_lateral_rels))
        return false; /* will not be able to join to some RHS rel */

      /*
       * Furthermore, the minimum parameterization can include
       * outer-join relids as well as baserel relids.  In such a case
       * the value laterally needed is an output of that outer join, so
       * the outer join must be formed strictly outside this join for
       * the value to be supplied to it.  That's not possible if any rel
       * needed to form the outer join is within join_plus_rhs, since
       * all such rels must join into this join's own join tree.  If we
       * accepted this join anyway, every path for it would require a
       * parameter that can never be supplied, so it could never appear
       * in a complete plan.
       */
      if (bms_overlap(join_lateral_rels, root->outer_join_rels))
      {
        foreach(l, root->join_info_list)
        {
          SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l);

          if (!bms_is_member(sjinfo->ojrelid, join_lateral_rels))
            continue;
          if (bms_overlap(join_plus_rhs, sjinfo->min_lefthand) ||
            bms_overlap(join_plus_rhs, sjinfo->min_righthand))
            return false; /* OJ can't be formed outside join */
        }
      }
    }
  }

  /* Otherwise, it's a valid join */
  *sjinfo_p = match_sjinfo;
  *reversed_p = reversed;
  return true;
}

/*
 * init_dummy_sjinfo
 *    Populate the given SpecialJoinInfo for a plain inner join between the
 *    left and right relations specified by left_relids and right_relids
 *    respectively.
 *
 * Normally, an inner join does not have a SpecialJoinInfo node associated with
 * it. But some functions involved in join planning require one containing at
 * least the information of which relations are being joined.  So we initialize
 * that information here.
 */
void
init_dummy_sjinfo(SpecialJoinInfo *sjinfo, Relids left_relids,
          Relids right_relids)
{
  sjinfo->type = T_SpecialJoinInfo;
  sjinfo->min_lefthand = left_relids;
  sjinfo->min_righthand = right_relids;
  sjinfo->syn_lefthand = left_relids;
  sjinfo->syn_righthand = right_relids;
  sjinfo->jointype = JOIN_INNER;
  sjinfo->ojrelid = 0;
  sjinfo->commute_above_l = NULL;
  sjinfo->commute_above_r = NULL;
  sjinfo->commute_below_l = NULL;
  sjinfo->commute_below_r = NULL;
  /* we don't bother trying to make the remaining fields valid */
  sjinfo->lhs_strict = false;
  sjinfo->semi_can_btree = false;
  sjinfo->semi_can_hash = false;
  sjinfo->semi_operators = NIL;
  sjinfo->semi_rhs_exprs = NIL;
}

/*
 * make_join_rel
 *     Find or create a join RelOptInfo that represents the join of
 *     the two given rels, and add to it path information for paths
 *     created with the two rels as outer and inner rel.
 *     (The join rel may already contain paths generated from other
 *     pairs of rels that add up to the same set of base rels.)
 *
 * NB: will return NULL if attempted join is not valid.  This can happen
 * when working with outer joins, or with IN or EXISTS clauses that have been
 * turned into joins.
 */
RelOptInfo *
make_join_rel(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2)
{
  Relids    joinrelids;
  SpecialJoinInfo *sjinfo;
  bool    reversed;
  List     *pushed_down_joins = NIL;
  SpecialJoinInfo sjinfo_data;
  RelOptInfo *joinrel;
  List     *restrictlist;

  /* We should never try to join two overlapping sets of rels. */
  Assert(!bms_overlap(rel1->relids, rel2->relids));

  /* Construct Relids set that identifies the joinrel (without OJ as yet). */
  joinrelids = bms_union(rel1->relids, rel2->relids);

  /* Check validity and determine join type. */
  if (!join_is_legal(root, rel1, rel2, joinrelids,
             &sjinfo, &reversed))
  {
    /* invalid join path */
    bms_free(joinrelids);
    return NULL;
  }

  /*
   * Add outer join relid(s) to form the canonical relids.  Any added outer
   * joins besides sjinfo itself are appended to pushed_down_joins.
   */
  joinrelids = add_outer_joins_to_relids(root, joinrelids, sjinfo,
                       &pushed_down_joins);

  /* Swap rels if needed to match the join info. */
  if (reversed)
  {
    RelOptInfo *trel = rel1;

    rel1 = rel2;
    rel2 = trel;
  }

  /*
   * If it's a plain inner join, then we won't have found anything in
   * join_info_list.  Make up a SpecialJoinInfo so that selectivity
   * estimation functions will know what's being joined.
   */
  if (sjinfo == NULL)
  {
    sjinfo = &sjinfo_data;
    init_dummy_sjinfo(sjinfo, rel1->relids, rel2->relids);
  }

  /*
   * Find or build the join RelOptInfo, and compute the restrictlist that
   * goes with this particular joining.
   */
  joinrel = build_join_rel(root, joinrelids, rel1, rel2,
               sjinfo, pushed_down_joins,
               &restrictlist);

  /*
   * If we've already proven this join is empty, we needn't consider any
   * more paths for it.
   */
  if (is_dummy_rel(joinrel))
  {
    bms_free(joinrelids);
    return joinrel;
  }

  /* Build a grouped join relation for 'joinrel' if possible. */
  make_grouped_join_rel(root, rel1, rel2, joinrel, sjinfo,
              restrictlist);

  /* Add paths to the join relation. */
  populate_joinrel_with_paths(root, rel1, rel2, joinrel, sjinfo,
                restrictlist);

  bms_free(joinrelids);

  return joinrel;
}

/*
 * add_outer_joins_to_relids
 *    Add relids to input_relids to represent any outer joins that will be
 *    calculated at this join.
 *
 * input_relids is the union of the relid sets of the two input relations.
 * Note that we modify this in-place and return it; caller must bms_copy()
 * it first, if a separate value is desired.
 *
 * sjinfo represents the join being performed.
 *
 * If the current join completes the calculation of any outer joins that
 * have been pushed down per outer-join identity 3, those relids will be
 * added to the result along with sjinfo's own relid.  If pushed_down_joins
 * is not NULL, then also the SpecialJoinInfos for such added outer joins will
 * be appended to *pushed_down_joins (so caller must initialize it to NIL).
 */
Relids
add_outer_joins_to_relids(PlannerInfo *root, Relids input_relids,
              SpecialJoinInfo *sjinfo,
              List **pushed_down_joins)
{
  /* Nothing to do if this isn't an outer join with an assigned relid. */
  if (sjinfo == NULL || sjinfo->ojrelid == 0)
    return input_relids;

  /*
   * If it's not a left join, we have no rules that would permit executing
   * it in non-syntactic order, so just form the syntactic relid set.  (This
   * is just a quick-exit test; we'd come to the same conclusion anyway,
   * since its commute_below_l and commute_above_l sets must be empty.)
   */
  if (sjinfo->jointype != JOIN_LEFT)
    return bms_add_member(input_relids, sjinfo->ojrelid);

  /*
   * We cannot add the OJ relid if this join has been pushed into the RHS of
   * a syntactically-lower left join per OJ identity 3.  (If it has, then we
   * cannot claim that its outputs represent the final state of its RHS.)
   * There will not be any other OJs that can be added either, so we're
   * done.
   */
  if (!bms_is_subset(sjinfo->commute_below_l, input_relids))
    return input_relids;

  /* OK to add OJ's own relid */
  input_relids = bms_add_member(input_relids, sjinfo->ojrelid);

  /*
   * Contrariwise, if we are now forming the final result of such a commuted
   * pair of OJs, it's time to add the relid(s) of the pushed-down join(s).
   * We can skip this if this join was never a candidate to be pushed up.
   */
  if (sjinfo->commute_above_l)
  {
    Relids    commute_above_rels = bms_copy(sjinfo->commute_above_l);
    ListCell   *lc;

    /*
     * The current join could complete the nulling of more than one
     * pushed-down join, so we have to examine all the SpecialJoinInfos.
     * Because join_info_list was built in bottom-up order, it's
     * sufficient to traverse it once: an ojrelid we add in one loop
     * iteration would not have affected decisions of earlier iterations.
     */
    foreach(lc, root->join_info_list)
    {
      SpecialJoinInfo *othersj = (SpecialJoinInfo *) lfirst(lc);

      if (othersj == sjinfo ||
        othersj->ojrelid == 0 || othersj->jointype != JOIN_LEFT)
        continue;   /* definitely not interesting */

      if (!bms_is_member(othersj->ojrelid, commute_above_rels))
        continue;

      /* Add it if not already present but conditions now satisfied */
      if (!bms_is_member(othersj->ojrelid, input_relids) &&
        bms_is_subset(othersj->min_lefthand, input_relids) &&
        bms_is_subset(othersj->min_righthand, input_relids) &&
        bms_is_subset(othersj->commute_below_l, input_relids))
      {
        input_relids = bms_add_member(input_relids, othersj->ojrelid);
        /* report such pushed down outer joins, if asked */
        if (pushed_down_joins != NULL)
          *pushed_down_joins = lappend(*pushed_down_joins, othersj);

        /*
         * We must also check any joins that othersj potentially
         * commutes with.  They likewise must appear later in
         * join_info_list than othersj itself, so we can visit them
         * later in this loop.
         */
        commute_above_rels = bms_add_members(commute_above_rels,
                           othersj->commute_above_l);
      }
    }
  }

  return input_relids;
}

/*
 * make_grouped_join_rel
 *    Build a grouped join relation for the given "joinrel" if eager
 *    aggregation is applicable and the resulting grouped paths are considered
 *    useful.
 *
 * There are two strategies for generating grouped paths for a join relation:
 *
 * 1. Join a grouped (partially aggregated) input relation with a non-grouped
 * input (e.g., AGG(B) JOIN A).
 *
 * 2. Apply partial aggregation (sorted or hashed) on top of existing
 * non-grouped join paths (e.g., AGG(A JOIN B)).
 *
 * To limit planning effort and avoid an explosion of alternatives, we adopt a
 * strategy where partial aggregation is only pushed to the lowest possible
 * level in the join tree that is deemed useful.  That is, if grouped paths can
 * be built using the first strategy, we skip consideration of the second
 * strategy for the same join level.
 *
 * Additionally, if there are multiple lowest useful levels where partial
 * aggregation could be applied, such as in a join tree with relations A, B,
 * and C where both "AGG(A JOIN B) JOIN C" and "A JOIN AGG(B JOIN C)" are valid
 * placements, we choose only the first one encountered during join search.
 * This avoids generating multiple versions of the same grouped relation based
 * on different aggregation placements.
 *
 * These heuristics also ensure that all grouped paths for the same grouped
 * relation produce the same set of rows, which is a basic assumption in the
 * planner.
 */
static void
make_grouped_join_rel(PlannerInfo *root, RelOptInfo *rel1,
            RelOptInfo *rel2, RelOptInfo *joinrel,
            SpecialJoinInfo *sjinfo, List *restrictlist)
{
  RelOptInfo *grouped_rel;
  RelOptInfo *grouped_rel1;
  RelOptInfo *grouped_rel2;
  bool    rel1_empty;
  bool    rel2_empty;
  Relids    apply_agg_at;

  /*
   * If there are no aggregate expressions or grouping expressions, eager
   * aggregation is not possible.
   */
  if (root->agg_clause_list == NIL ||
    root->group_expr_list == NIL)
    return;

  /* Retrieve the grouped relations for the two input rels */
  grouped_rel1 = rel1->grouped_rel;
  grouped_rel2 = rel2->grouped_rel;

  rel1_empty = (grouped_rel1 == NULL || IS_DUMMY_REL(grouped_rel1));
  rel2_empty = (grouped_rel2 == NULL || IS_DUMMY_REL(grouped_rel2));

  /* Find or construct a grouped joinrel for this joinrel */
  grouped_rel = joinrel->grouped_rel;
  if (grouped_rel == NULL)
  {
    RelAggInfo *agg_info = NULL;

    /*
     * Prepare the information needed to create grouped paths for this
     * join relation.
     */
    agg_info = create_rel_agg_info(root, joinrel, rel1_empty == rel2_empty);
    if (agg_info == NULL)
      return;

    /*
     * If grouped paths for the given join relation are not considered
     * useful, and no grouped paths can be built by joining grouped input
     * relations, skip building the grouped join relation.
     */
    if (!agg_info->agg_useful &&
      (rel1_empty == rel2_empty))
      return;

    /* build the grouped relation */
    grouped_rel = build_grouped_rel(root, joinrel);
    grouped_rel->reltarget = agg_info->target;

    if (rel1_empty != rel2_empty)
    {
      /*
       * If there is exactly one grouped input relation, then we can
       * build grouped paths by joining the input relations.  Set size
       * estimates for the grouped join relation based on the input
       * relations, and update the set of relids where partial
       * aggregation is applied to that of the grouped input relation.
       */
      set_joinrel_size_estimates(root, grouped_rel,
                     rel1_empty ? rel1 : grouped_rel1,
                     rel2_empty ? rel2 : grouped_rel2,
                     sjinfo, restrictlist);
      agg_info->apply_agg_at = rel1_empty ?
        grouped_rel2->agg_info->apply_agg_at :
        grouped_rel1->agg_info->apply_agg_at;
    }
    else
    {
      /*
       * Otherwise, grouped paths can be built by applying partial
       * aggregation on top of existing non-grouped join paths.  Set
       * size estimates for the grouped join relation based on the
       * estimated number of groups, and track the set of relids where
       * partial aggregation is applied.  Note that these values may be
       * updated later if it is determined that grouped paths can be
       * constructed by joining other input relations.
       */
      grouped_rel->rows = agg_info->grouped_rows;
      agg_info->apply_agg_at = bms_copy(joinrel->relids);
    }

    grouped_rel->agg_info = agg_info;
    joinrel->grouped_rel = grouped_rel;
  }

  Assert(IS_GROUPED_REL(grouped_rel));

  /* We may have already proven this grouped join relation to be dummy. */
  if (IS_DUMMY_REL(grouped_rel))
    return;

  /*
   * Nothing to do if there's no grouped input relation.  Also, joining two
   * grouped relations is not currently supported.
   */
  if (rel1_empty == rel2_empty)
    return;

  /*
   * Get the set of relids where partial aggregation is applied among the
   * given input relations.
   */
  apply_agg_at = rel1_empty ?
    grouped_rel2->agg_info->apply_agg_at :
    grouped_rel1->agg_info->apply_agg_at;

  /*
   * If it's not the designated level, skip building grouped paths.
   *
   * One exception is when it is a subset of the previously recorded level.
   * In that case, we need to update the designated level to this one, and
   * adjust the size estimates for the grouped join relation accordingly.
   * For example, suppose partial aggregation can be applied on top of (B
   * JOIN C).  If we first construct the join as ((A JOIN B) JOIN C), we'd
   * record the designated level as including all three relations (A B C).
   * Later, when we consider (A JOIN (B JOIN C)), we encounter the smaller
   * (B C) join level directly.  Since this is a subset of the previous
   * level and still valid for partial aggregation, we update the designated
   * level to (B C), and adjust the size estimates accordingly.
   */
  if (!bms_equal(apply_agg_at, grouped_rel->agg_info->apply_agg_at))
  {
    if (bms_is_subset(apply_agg_at, grouped_rel->agg_info->apply_agg_at))
    {
      /* Adjust the size estimates for the grouped join relation. */
      set_joinrel_size_estimates(root, grouped_rel,
                     rel1_empty ? rel1 : grouped_rel1,
                     rel2_empty ? rel2 : grouped_rel2,
                     sjinfo, restrictlist);
      grouped_rel->agg_info->apply_agg_at = apply_agg_at;
    }
    else
      return;
  }

  /* Make paths for the grouped join relation. */
  populate_joinrel_with_paths(root,
                rel1_empty ? rel1 : grouped_rel1,
                rel2_empty ? rel2 : grouped_rel2,
                grouped_rel,
                sjinfo,
                restrictlist);
}

/*
 * populate_joinrel_with_paths
 *    Add paths to the given joinrel for given pair of joining relations. The
 *    SpecialJoinInfo provides details about the join and the restrictlist
 *    contains the join clauses and the other clauses applicable for given pair
 *    of the joining relations.
 */
static void
populate_joinrel_with_paths(PlannerInfo *root, RelOptInfo *rel1,
              RelOptInfo *rel2, RelOptInfo *joinrel,
              SpecialJoinInfo *sjinfo, List *restrictlist)
{
  RelOptInfo *unique_rel2;

  /*
   * Consider paths using each rel as both outer and inner.  Depending on
   * the join type, a provably empty outer or inner rel might mean the join
   * is provably empty too; in which case throw away any previously computed
   * paths and mark the join as dummy.  (We do it this way since it's
   * conceivable that dummy-ness of a multi-element join might only be
   * noticeable for certain construction paths.)
   *
   * Also, a provably constant-false join restriction typically means that
   * we can skip evaluating one or both sides of the join.  We do this by
   * marking the appropriate rel as dummy.  For outer joins, a
   * constant-false restriction that is pushed down still means the whole
   * join is dummy, while a non-pushed-down one means that no inner rows
   * will join so we can treat the inner rel as dummy.
   *
   * We need only consider the jointypes that appear in join_info_list, plus
   * JOIN_INNER.
   */
  switch (sjinfo->jointype)
  {
    case JOIN_INNER:
      if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
        restriction_is_constant_false(restrictlist, joinrel, false))
      {
        mark_dummy_rel(joinrel);
        break;
      }
      add_paths_to_joinrel(root, joinrel, rel1, rel2,
                 JOIN_INNER, sjinfo,
                 restrictlist);
      add_paths_to_joinrel(root, joinrel, rel2, rel1,
                 JOIN_INNER, sjinfo,
                 restrictlist);
      break;
    case JOIN_LEFT:
      if (is_dummy_rel(rel1) ||
        restriction_is_constant_false(restrictlist, joinrel, true))
      {
        mark_dummy_rel(joinrel);
        break;
      }
      if (restriction_is_constant_false(restrictlist, joinrel, false) &&
        bms_is_subset(rel2->relids, sjinfo->syn_righthand))
        mark_dummy_rel(rel2);
      add_paths_to_joinrel(root, joinrel, rel1, rel2,
                 JOIN_LEFT, sjinfo,
                 restrictlist);
      add_paths_to_joinrel(root, joinrel, rel2, rel1,
                 JOIN_RIGHT, sjinfo,
                 restrictlist);
      break;
    case JOIN_FULL:
      if ((is_dummy_rel(rel1) && is_dummy_rel(rel2)) ||
        restriction_is_constant_false(restrictlist, joinrel, true))
      {
        mark_dummy_rel(joinrel);
        break;
      }
      add_paths_to_joinrel(root, joinrel, rel1, rel2,
                 JOIN_FULL, sjinfo,
                 restrictlist);
      add_paths_to_joinrel(root, joinrel, rel2, rel1,
                 JOIN_FULL, sjinfo,
                 restrictlist);

      /*
       * If there are join quals that aren't mergeable or hashable, we
       * may not be able to build any valid plan.  Complain here so that
       * we can give a somewhat-useful error message.  (Since we have no
       * flexibility of planning for a full join, there's no chance of
       * succeeding later with another pair of input rels.)
       */
      if (joinrel->pathlist == NIL)
        ereport(ERROR,
            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
             errmsg("FULL JOIN is only supported with merge-joinable or hash-joinable join conditions")));
      break;
    case JOIN_SEMI:

      /*
       * We might have a normal semijoin, or a case where we don't have
       * enough rels to do the semijoin but can unique-ify the RHS and
       * then do an innerjoin (see comments in join_is_legal).  In the
       * latter case we can't apply JOIN_SEMI joining.
       */
      if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
        bms_is_subset(sjinfo->min_righthand, rel2->relids))
      {
        if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
          restriction_is_constant_false(restrictlist, joinrel, false))
        {
          mark_dummy_rel(joinrel);
          break;
        }
        add_paths_to_joinrel(root, joinrel, rel1, rel2,
                   JOIN_SEMI, sjinfo,
                   restrictlist);
        add_paths_to_joinrel(root, joinrel, rel2, rel1,
                   JOIN_RIGHT_SEMI, sjinfo,
                   restrictlist);
      }

      /*
       * If we know how to unique-ify the RHS and one input rel is
       * exactly the RHS (not a superset) we can consider unique-ifying
       * it and then doing a regular join.  (The create_unique_paths
       * check here is probably redundant with what join_is_legal did,
       * but if so the check is cheap because it's cached.  So test
       * anyway to be sure.)
       */
      if (bms_equal(sjinfo->syn_righthand, rel2->relids) &&
        (unique_rel2 = create_unique_paths(root, rel2, sjinfo)) != NULL)
      {
        if (is_dummy_rel(rel1) || is_dummy_rel(rel2) ||
          restriction_is_constant_false(restrictlist, joinrel, false))
        {
          mark_dummy_rel(joinrel);
          break;
        }
        add_paths_to_joinrel(root, joinrel, rel1, unique_rel2,
                   JOIN_UNIQUE_INNER, sjinfo,
                   restrictlist);
        add_paths_to_joinrel(root, joinrel, unique_rel2, rel1,
                   JOIN_UNIQUE_OUTER, sjinfo,
                   restrictlist);
      }
      break;
    case JOIN_ANTI:
      if (is_dummy_rel(rel1) ||
        restriction_is_constant_false(restrictlist, joinrel, true))
      {
        mark_dummy_rel(joinrel);
        break;
      }
      if (restriction_is_constant_false(restrictlist, joinrel, false) &&
        bms_is_subset(rel2->relids, sjinfo->syn_righthand))
        mark_dummy_rel(rel2);
      add_paths_to_joinrel(root, joinrel, rel1, rel2,
                 JOIN_ANTI, sjinfo,
                 restrictlist);
      add_paths_to_joinrel(root, joinrel, rel2, rel1,
                 JOIN_RIGHT_ANTI, sjinfo,
                 restrictlist);
      break;
    default:
      /* other values not expected here */
      elog(ERROR, "unrecognized join type: %d", (int) sjinfo->jointype);
      break;
  }

  /* Apply partitionwise join technique, if possible. */
  try_partitionwise_join(root, rel1, rel2, joinrel, sjinfo, restrictlist);
}


/*
 * have_join_order_restriction
 *    Detect whether the two relations should be joined to satisfy
 *    a join-order restriction arising from special or lateral joins.
 *
 * In practice this is always used with have_relevant_joinclause(), and so
 * could be merged with that function, but it seems clearer to separate the
 * two concerns.  We need this test because there are degenerate cases where
 * a clauseless join must be performed to satisfy join-order restrictions.
 * Also, if one rel has a lateral reference to the other, or both are needed
 * to compute some PHV, we should consider joining them even if the join would
 * be clauseless.
 *
 * Note: this is only a problem if one side of a degenerate outer join
 * contains multiple rels, or a clauseless join is required within an
 * IN/EXISTS RHS; else we will find a join path via the "last ditch" case in
 * join_search_one_level().  We could dispense with this test if we were
 * willing to try bushy plans in the "last ditch" case, but that seems much
 * less efficient.
 */
bool
have_join_order_restriction(PlannerInfo *root,
              RelOptInfo *rel1, RelOptInfo *rel2)
{
  bool    result = false;
  ListCell   *l;

  /*
   * If either side has a direct lateral reference to the other, attempt the
   * join regardless of outer-join considerations.
   */
  if (bms_overlap(rel1->relids, rel2->direct_lateral_relids) ||
    bms_overlap(rel2->relids, rel1->direct_lateral_relids))
    return true;

  /*
   * Likewise, if both rels are needed to compute some PlaceHolderVar,
   * attempt the join regardless of outer-join considerations.  (This is not
   * very desirable, because a PHV with a large eval_at set will cause a lot
   * of probably-useless joins to be considered, but failing to do this can
   * cause us to fail to construct a plan at all.)
   */
  foreach(l, root->placeholder_list)
  {
    PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l);

    if (bms_is_subset(rel1->relids, phinfo->ph_eval_at) &&
      bms_is_subset(rel2->relids, phinfo->ph_eval_at))
      return true;
  }

  /*
   * It's possible that the rels correspond to the left and right sides of a
   * degenerate outer join, that is, one with no joinclause mentioning the
   * non-nullable side; in which case we should force the join to occur.
   *
   * Also, the two rels could represent a clauseless join that has to be
   * completed to build up the LHS or RHS of an outer join.
   */
  foreach(l, root->join_info_list)
  {
    SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l);

    /* ignore full joins --- other mechanisms handle them */
    if (sjinfo->jointype == JOIN_FULL)
      continue;

    /* Can we perform the SJ with these rels? */
    if (bms_is_subset(sjinfo->min_lefthand, rel1->relids) &&
      bms_is_subset(sjinfo->min_righthand, rel2->relids))
    {
      result = true;
      break;
    }
    if (bms_is_subset(sjinfo->min_lefthand, rel2->relids) &&
      bms_is_subset(sjinfo->min_righthand, rel1->relids))
    {
      result = true;
      break;
    }

    /*
     * Might we need to join these rels to complete the RHS?  We have to
     * use "overlap" tests since either rel might include a lower SJ that
     * has been proven to commute with this one.
     */
    if (bms_overlap(sjinfo->min_righthand, rel1->relids) &&
      bms_overlap(sjinfo->min_righthand, rel2->relids))
    {
      result = true;
      break;
    }

    /* Likewise for the LHS. */
    if (bms_overlap(sjinfo->min_lefthand, rel1->relids) &&
      bms_overlap(sjinfo->min_lefthand, rel2->relids))
    {
      result = true;
      break;
    }
  }

  /*
   * We do not force the join to occur if either input rel can legally be
   * joined to anything else using joinclauses.  This essentially means that
   * clauseless bushy joins are put off as long as possible. The reason is
   * that when there is a join order restriction high up in the join tree
   * (that is, with many rels inside the LHS or RHS), we would otherwise
   * expend lots of effort considering very stupid join combinations within
   * its LHS or RHS.
   */
  if (result)
  {
    if (has_legal_joinclause(root, rel1) ||
      has_legal_joinclause(root, rel2))
      result = false;
  }

  return result;
}


/*
 * has_join_restriction
 *    Detect whether the specified relation has join-order restrictions,
 *    due to being inside an outer join or an IN (sub-SELECT),
 *    or participating in any LATERAL references or multi-rel PHVs.
 *
 * Essentially, this tests whether have_join_order_restriction() could
 * succeed with this rel and some other one.  It's OK if we sometimes
 * say "true" incorrectly.  (Therefore, we don't bother with the relatively
 * expensive has_legal_joinclause test.)
 */
static bool
has_join_restriction(PlannerInfo *root, RelOptInfo *rel)
{
  ListCell   *l;

  if (rel->lateral_relids != NULL || rel->lateral_referencers != NULL)
    return true;

  foreach(l, root->placeholder_list)
  {
    PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l);

    if (bms_is_subset(rel->relids, phinfo->ph_eval_at) &&
      !bms_equal(rel->relids, phinfo->ph_eval_at))
      return true;
  }

  foreach(l, root->join_info_list)
  {
    SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(l);

    /* ignore full joins --- other mechanisms preserve their ordering */
    if (sjinfo->jointype == JOIN_FULL)
      continue;

    /* ignore if SJ is already contained in rel */
    if (bms_is_subset(sjinfo->min_lefthand, rel->relids) &&
      bms_is_subset(sjinfo->min_righthand, rel->relids))
      continue;

    /* restricted if it overlaps LHS or RHS, but doesn't contain SJ */
    if (bms_overlap(sjinfo->min_lefthand, rel->relids) ||
      bms_overlap(sjinfo->min_righthand, rel->relids))
      return true;
  }

  return false;
}


/*
 * has_legal_joinclause
 *    Detect whether the specified relation can legally be joined
 *    to any other rels using join clauses.
 *
 * We consider only joins to single other relations in the current
 * initial_rels list.  This is sufficient to get a "true" result in most real
 * queries, and an occasional erroneous "false" will only cost a bit more
 * planning time.  The reason for this limitation is that considering joins to
 * other joins would require proving that the other join rel can legally be
 * formed, which seems like too much trouble for something that's only a
 * heuristic to save planning time.  (Note: we must look at initial_rels
 * and not all of the query, since when we are planning a sub-joinlist we
 * may be forced to make clauseless joins within initial_rels even though
 * there are join clauses linking to other parts of the query.)
 */
static bool
has_legal_joinclause(PlannerInfo *root, RelOptInfo *rel)
{
  ListCell   *lc;

  foreach(lc, root->initial_rels)
  {
    RelOptInfo *rel2 = (RelOptInfo *) lfirst(lc);

    /* ignore rels that are already in "rel" */
    if (bms_overlap(rel->relids, rel2->relids))
      continue;

    if (have_relevant_joinclause(root, rel, rel2))
    {
      Relids    joinrelids;
      SpecialJoinInfo *sjinfo;
      bool    reversed;

      /* join_is_legal needs relids of the union */
      joinrelids = bms_union(rel->relids, rel2->relids);

      if (join_is_legal(root, rel, rel2, joinrelids,
                &sjinfo, &reversed))
      {
        /* Yes, this will work */
        bms_free(joinrelids);
        return true;
      }

      bms_free(joinrelids);
    }
  }

  return false;
}


/*
 * is_dummy_rel --- has relation been proven empty?
 */
bool
is_dummy_rel(RelOptInfo *rel)
{
  Path     *path;

  /*
   * A rel that is known dummy will have just one path that is a childless
   * Append.  (Even if somehow it has more paths, a childless Append will
   * have cost zero and hence should be at the front of the pathlist.)
   */
  if (rel->pathlist == NIL)
    return false;
  path = (Path *) linitial(rel->pathlist);

  /*
   * Initially, a dummy path will just be a childless Append.  But in later
   * planning stages we might stick a ProjectSetPath and/or ProjectionPath
   * on top, since Append can't project.  Rather than make assumptions about
   * which combinations can occur, just descend through whatever we find.
   */
  for (;;)
  {
    if (IsA(path, ProjectionPath))
      path = ((ProjectionPath *) path)->subpath;
    else if (IsA(path, ProjectSetPath))
      path = ((ProjectSetPath *) path)->subpath;
    else
      break;
  }
  if (IS_DUMMY_APPEND(path))
    return true;
  return false;
}

/*
 * Mark a relation as proven empty.
 *
 * During GEQO planning, this can get invoked more than once on the same
 * baserel struct, so it's worth checking to see if the rel is already marked
 * dummy.
 *
 * Also, when called during GEQO join planning, we are in a short-lived
 * memory context.  We must make sure that the dummy path attached to a
 * baserel survives the GEQO cycle, else the baserel is trashed for future
 * GEQO cycles.  On the other hand, when we are marking a joinrel during GEQO,
 * we don't want the dummy path to clutter the main planning context.  Upshot
 * is that the best solution is to explicitly make the dummy path in the same
 * context the given RelOptInfo is in.
 */
void
mark_dummy_rel(RelOptInfo *rel)
{
  MemoryContext oldcontext;
  AppendPathInput in = {0};

  /* Already marked? */
  if (is_dummy_rel(rel))
    return;

  /* No, so choose correct context to make the dummy path in */
  oldcontext = MemoryContextSwitchTo(GetMemoryChunkContext(rel));

  /* Set dummy size estimate */
  rel->rows = 0;

  /* Evict any previously chosen paths */
  rel->pathlist = NIL;
  rel->partial_pathlist = NIL;

  /* Set up the dummy path */
  add_path(rel, (Path *) create_append_path(NULL, rel, in,
                        NIL, rel->lateral_relids,
                        0, false, -1));

  /* Set or update cheapest_total_path and related fields */
  set_cheapest(rel);

  MemoryContextSwitchTo(oldcontext);
}


/*
 * restriction_is_constant_false --- is a restrictlist just FALSE?
 *
 * In cases where a qual is provably constant FALSE, eval_const_expressions
 * will generally have thrown away anything that's ANDed with it.  In outer
 * join situations this will leave us computing cartesian products only to
 * decide there's no match for an outer row, which is pretty stupid.  So,
 * we need to detect the case.
 *
 * If only_pushed_down is true, then consider only quals that are pushed-down
 * from the point of view of the joinrel.
 */
static bool
restriction_is_constant_false(List *restrictlist,
                RelOptInfo *joinrel,
                bool only_pushed_down)
{
  ListCell   *lc;

  /*
   * Despite the above comment, the restriction list we see here might
   * possibly have other members besides the FALSE constant, since other
   * quals could get "pushed down" to the outer join level.  So we check
   * each member of the list.
   */
  foreach(lc, restrictlist)
  {
    RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);

    if (only_pushed_down && !RINFO_IS_PUSHED_DOWN(rinfo, joinrel->relids))
      continue;

    if (rinfo->clause && IsA(rinfo->clause, Const))
    {
      Const    *con = (Const *) rinfo->clause;

      /* constant NULL is as good as constant FALSE for our purposes */
      if (con->constisnull)
        return true;
      if (!DatumGetBool(con->constvalue))
        return true;
    }
  }
  return false;
}

/*
 * Assess whether join between given two partitioned relations can be broken
 * down into joins between matching partitions; a technique called
 * "partitionwise join"
 *
 * Partitionwise join is possible when a. Joining relations have same
 * partitioning scheme b. There exists an equi-join between the partition keys
 * of the two relations.
 *
 * Partitionwise join is planned as follows (details: optimizer/README.)
 *
 * 1. Create the RelOptInfos for joins between matching partitions i.e
 * child-joins and add paths to them.
 *
 * 2. Construct Append or MergeAppend paths across the set of child joins.
 * This second phase is implemented by generate_partitionwise_join_paths().
 *
 * The RelOptInfo, SpecialJoinInfo and restrictlist for each child join are
 * obtained by translating the respective parent join structures.
 */
static void
try_partitionwise_join(PlannerInfo *root, RelOptInfo *rel1, RelOptInfo *rel2,
             RelOptInfo *joinrel, SpecialJoinInfo *parent_sjinfo,
             List *parent_restrictlist)
{
  bool    rel1_is_simple = IS_SIMPLE_REL(rel1);
  bool    rel2_is_simple = IS_SIMPLE_REL(rel2);
  List     *parts1 = NIL;
  List     *parts2 = NIL;
  ListCell   *lcr1 = NULL;
  ListCell   *lcr2 = NULL;
  int     cnt_parts;

  /* Guard against stack overflow due to overly deep partition hierarchy. */
  check_stack_depth();

  /* Nothing to do, if the join relation is not partitioned. */
  if (joinrel->part_scheme == NULL || joinrel->nparts == 0)
    return;

  /* The join relation should have consider_partitionwise_join set. */
  Assert(joinrel->consider_partitionwise_join);

  /*
   * We can not perform partitionwise join if either of the joining
   * relations is not partitioned.
   */
  if (!IS_PARTITIONED_REL(rel1) || !IS_PARTITIONED_REL(rel2))
    return;

  Assert(REL_HAS_ALL_PART_PROPS(rel1) && REL_HAS_ALL_PART_PROPS(rel2));

  /* The joining relations should have consider_partitionwise_join set. */
  Assert(rel1->consider_partitionwise_join &&
       rel2->consider_partitionwise_join);

  /*
   * The partition scheme of the join relation should match that of the
   * joining relations.
   */
  Assert(joinrel->part_scheme == rel1->part_scheme &&
       joinrel->part_scheme == rel2->part_scheme);

  Assert(!(joinrel->partbounds_merged && (joinrel->nparts <= 0)));

  compute_partition_bounds(root, rel1, rel2, joinrel, parent_sjinfo,
               &parts1, &parts2);

  if (joinrel->partbounds_merged)
  {
    lcr1 = list_head(parts1);
    lcr2 = list_head(parts2);
  }

  /*
   * Create child-join relations for this partitioned join, if those don't
   * exist. Add paths to child-joins for a pair of child relations
   * corresponding to the given pair of parent relations.
   */
  for (cnt_parts = 0; cnt_parts < joinrel->nparts; cnt_parts++)
  {
    RelOptInfo *child_rel1;
    RelOptInfo *child_rel2;
    bool    rel1_empty;
    bool    rel2_empty;
    SpecialJoinInfo *child_sjinfo;
    List     *child_restrictlist;
    RelOptInfo *child_joinrel;
    AppendRelInfo **appinfos;
    int     nappinfos;
    Relids    child_relids;

    if (joinrel->partbounds_merged)
    {
      child_rel1 = lfirst_node(RelOptInfo, lcr1);
      child_rel2 = lfirst_node(RelOptInfo, lcr2);
      lcr1 = lnext(parts1, lcr1);
      lcr2 = lnext(parts2, lcr2);
    }
    else
    {
      child_rel1 = rel1->part_rels[cnt_parts];
      child_rel2 = rel2->part_rels[cnt_parts];
    }

    rel1_empty = (child_rel1 == NULL || IS_DUMMY_REL(child_rel1));
    rel2_empty = (child_rel2 == NULL || IS_DUMMY_REL(child_rel2));

    /*
     * Check for cases where we can prove that this segment of the join
     * returns no rows, due to one or both inputs being empty (including
     * inputs that have been pruned away entirely).  If so just ignore it.
     * These rules are equivalent to populate_joinrel_with_paths's rules
     * for dummy input relations.
     */
    switch (parent_sjinfo->jointype)
    {
      case JOIN_INNER:
      case JOIN_SEMI:
        if (rel1_empty || rel2_empty)
          continue; /* ignore this join segment */
        break;
      case JOIN_LEFT:
      case JOIN_ANTI:
        if (rel1_empty)
          continue; /* ignore this join segment */
        break;
      case JOIN_FULL:
        if (rel1_empty && rel2_empty)
          continue; /* ignore this join segment */
        break;
      default:
        /* other values not expected here */
        elog(ERROR, "unrecognized join type: %d",
           (int) parent_sjinfo->jointype);
        break;
    }

    /*
     * If a child has been pruned entirely then we can't generate paths
     * for it, so we have to reject partitionwise joining unless we were
     * able to eliminate this partition above.
     */
    if (child_rel1 == NULL || child_rel2 == NULL)
    {
      /*
       * Mark the joinrel as unpartitioned so that later functions treat
       * it correctly.
       */
      joinrel->nparts = 0;
      return;
    }

    /*
     * If a leaf relation has consider_partitionwise_join=false, it means
     * that it's a dummy relation for which we skipped setting up tlist
     * expressions and adding EC members in set_append_rel_size(), so
     * again we have to fail here.
     */
    if (rel1_is_simple && !child_rel1->consider_partitionwise_join)
    {
      Assert(child_rel1->reloptkind == RELOPT_OTHER_MEMBER_REL);
      Assert(IS_DUMMY_REL(child_rel1));
      joinrel->nparts = 0;
      return;
    }
    if (rel2_is_simple && !child_rel2->consider_partitionwise_join)
    {
      Assert(child_rel2->reloptkind == RELOPT_OTHER_MEMBER_REL);
      Assert(IS_DUMMY_REL(child_rel2));
      joinrel->nparts = 0;
      return;
    }

    /* We should never try to join two overlapping sets of rels. */
    Assert(!bms_overlap(child_rel1->relids, child_rel2->relids));

    /*
     * Construct SpecialJoinInfo from parent join relations's
     * SpecialJoinInfo.
     */
    child_sjinfo = build_child_join_sjinfo(root, parent_sjinfo,
                         child_rel1->relids,
                         child_rel2->relids);

    /* Find the AppendRelInfo structures */
    child_relids = bms_union(child_rel1->relids, child_rel2->relids);
    appinfos = find_appinfos_by_relids(root, child_relids,
                       &nappinfos);

    /*
     * Construct restrictions applicable to the child join from those
     * applicable to the parent join.
     */
    child_restrictlist =
      (List *) adjust_appendrel_attrs(root,
                      (Node *) parent_restrictlist,
                      nappinfos, appinfos);

    /* Find or construct the child join's RelOptInfo */
    child_joinrel = joinrel->part_rels[cnt_parts];
    if (!child_joinrel)
    {
      child_joinrel = build_child_join_rel(root, child_rel1, child_rel2,
                         joinrel, child_restrictlist,
                         child_sjinfo, nappinfos, appinfos);
      joinrel->part_rels[cnt_parts] = child_joinrel;
      joinrel->live_parts = bms_add_member(joinrel->live_parts, cnt_parts);
      joinrel->all_partrels = bms_add_members(joinrel->all_partrels,
                          child_joinrel->relids);
    }

    /* Assert we got the right one */
    Assert(bms_equal(child_joinrel->relids,
             adjust_child_relids(joinrel->relids,
                       nappinfos, appinfos)));

    /* Build a grouped join relation for 'child_joinrel' if possible */
    make_grouped_join_rel(root, child_rel1, child_rel2,
                child_joinrel, child_sjinfo,
                child_restrictlist);

    /* And make paths for the child join */
    populate_joinrel_with_paths(root, child_rel1, child_rel2,
                  child_joinrel, child_sjinfo,
                  child_restrictlist);

    /*
     * When there are thousands of partitions involved, this loop will
     * accumulate a significant amount of memory usage from objects that
     * are only needed within the loop.  Free these local objects eagerly
     * at the end of each iteration.
     */
    pfree(appinfos);
    bms_free(child_relids);
    free_child_join_sjinfo(child_sjinfo, parent_sjinfo);
  }
}

/*
 * Construct the SpecialJoinInfo for a child-join by translating
 * SpecialJoinInfo for the join between parents. left_relids and right_relids
 * are the relids of left and right side of the join respectively.
 *
 * If translations are added to or removed from this function, consider
 * updating free_child_join_sjinfo() accordingly.
 */
static SpecialJoinInfo *
build_child_join_sjinfo(PlannerInfo *root, SpecialJoinInfo *parent_sjinfo,
            Relids left_relids, Relids right_relids)
{
  SpecialJoinInfo *sjinfo = makeNode(SpecialJoinInfo);
  AppendRelInfo **left_appinfos;
  int     left_nappinfos;
  AppendRelInfo **right_appinfos;
  int     right_nappinfos;

  /* Dummy SpecialJoinInfos can be created without any translation. */
  if (parent_sjinfo->jointype == JOIN_INNER)
  {
    Assert(parent_sjinfo->ojrelid == 0);
    init_dummy_sjinfo(sjinfo, left_relids, right_relids);
    return sjinfo;
  }

  memcpy(sjinfo, parent_sjinfo, sizeof(SpecialJoinInfo));
  left_appinfos = find_appinfos_by_relids(root, left_relids,
                      &left_nappinfos);
  right_appinfos = find_appinfos_by_relids(root, right_relids,
                       &right_nappinfos);

  sjinfo->min_lefthand = adjust_child_relids(sjinfo->min_lefthand,
                         left_nappinfos, left_appinfos);
  sjinfo->min_righthand = adjust_child_relids(sjinfo->min_righthand,
                        right_nappinfos,
                        right_appinfos);
  sjinfo->syn_lefthand = adjust_child_relids(sjinfo->syn_lefthand,
                         left_nappinfos, left_appinfos);
  sjinfo->syn_righthand = adjust_child_relids(sjinfo->syn_righthand,
                        right_nappinfos,
                        right_appinfos);
  /* outer-join relids need no adjustment */
  sjinfo->semi_rhs_exprs = (List *) adjust_appendrel_attrs(root,
                               (Node *) sjinfo->semi_rhs_exprs,
                               right_nappinfos,
                               right_appinfos);

  pfree(left_appinfos);
  pfree(right_appinfos);

  return sjinfo;
}

/*
 * free_child_join_sjinfo
 *    Free memory consumed by a SpecialJoinInfo created by
 *    build_child_join_sjinfo()
 *
 * Only members that are translated copies of their counterpart in the parent
 * SpecialJoinInfo are freed here.
 */
static void
free_child_join_sjinfo(SpecialJoinInfo *child_sjinfo,
             SpecialJoinInfo *parent_sjinfo)
{
  /*
   * Dummy SpecialJoinInfos of inner joins do not have any translated fields
   * and hence no fields that to be freed.
   */
  if (child_sjinfo->jointype != JOIN_INNER)
  {
    if (child_sjinfo->min_lefthand != parent_sjinfo->min_lefthand)
      bms_free(child_sjinfo->min_lefthand);

    if (child_sjinfo->min_righthand != parent_sjinfo->min_righthand)
      bms_free(child_sjinfo->min_righthand);

    if (child_sjinfo->syn_lefthand != parent_sjinfo->syn_lefthand)
      bms_free(child_sjinfo->syn_lefthand);

    if (child_sjinfo->syn_righthand != parent_sjinfo->syn_righthand)
      bms_free(child_sjinfo->syn_righthand);

    Assert(child_sjinfo->commute_above_l == parent_sjinfo->commute_above_l);
    Assert(child_sjinfo->commute_above_r == parent_sjinfo->commute_above_r);
    Assert(child_sjinfo->commute_below_l == parent_sjinfo->commute_below_l);
    Assert(child_sjinfo->commute_below_r == parent_sjinfo->commute_below_r);

    Assert(child_sjinfo->semi_operators == parent_sjinfo->semi_operators);

    /*
     * semi_rhs_exprs may in principle be freed, but a simple pfree() does
     * not suffice, so we leave it alone.
     */
  }

  pfree(child_sjinfo);
}

/*
 * compute_partition_bounds
 *    Compute the partition bounds for a join rel from those for inputs
 */
static void
compute_partition_bounds(PlannerInfo *root, RelOptInfo *rel1,
             RelOptInfo *rel2, RelOptInfo *joinrel,
             SpecialJoinInfo *parent_sjinfo,
             List **parts1, List **parts2)
{
  /*
   * If we don't have the partition bounds for the join rel yet, try to
   * compute those along with pairs of partitions to be joined.
   */
  if (joinrel->nparts == -1)
  {
    PartitionScheme part_scheme = joinrel->part_scheme;
    PartitionBoundInfo boundinfo = NULL;
    int     nparts = 0;

    Assert(joinrel->boundinfo == NULL);
    Assert(joinrel->part_rels == NULL);

    /*
     * See if the partition bounds for inputs are exactly the same, in
     * which case we don't need to work hard: the join rel will have the
     * same partition bounds as inputs, and the partitions with the same
     * cardinal positions will form the pairs.
     *
     * Note: even in cases where one or both inputs have merged bounds, it
     * would be possible for both the bounds to be exactly the same, but
     * it seems unlikely to be worth the cycles to check.
     */
    if (!rel1->partbounds_merged &&
      !rel2->partbounds_merged &&
      rel1->nparts == rel2->nparts &&
      partition_bounds_equal(part_scheme->partnatts,
                   part_scheme->parttyplen,
                   part_scheme->parttypbyval,
                   rel1->boundinfo, rel2->boundinfo))
    {
      boundinfo = rel1->boundinfo;
      nparts = rel1->nparts;
    }
    else
    {
      /* Try merging the partition bounds for inputs. */
      boundinfo = partition_bounds_merge(part_scheme->partnatts,
                         part_scheme->partsupfunc,
                         part_scheme->partcollation,
                         rel1, rel2,
                         parent_sjinfo->jointype,
                         parts1, parts2);
      if (boundinfo == NULL)
      {
        joinrel->nparts = 0;
        return;
      }
      nparts = list_length(*parts1);
      joinrel->partbounds_merged = true;
    }

    Assert(nparts > 0);
    joinrel->boundinfo = boundinfo;
    joinrel->nparts = nparts;
    joinrel->part_rels = palloc0_array(RelOptInfo *, nparts);
  }
  else
  {
    Assert(joinrel->nparts > 0);
    Assert(joinrel->boundinfo);
    Assert(joinrel->part_rels);

    /*
     * If the join rel's partbounds_merged flag is true, it means inputs
     * are not guaranteed to have the same partition bounds, therefore we
     * can't assume that the partitions at the same cardinal positions
     * form the pairs; let get_matching_part_pairs() generate the pairs.
     * Otherwise, nothing to do since we can assume that.
     */
    if (joinrel->partbounds_merged)
    {
      get_matching_part_pairs(root, joinrel, rel1, rel2,
                  parts1, parts2);
      Assert(list_length(*parts1) == joinrel->nparts);
      Assert(list_length(*parts2) == joinrel->nparts);
    }
  }
}

/*
 * get_matching_part_pairs
 *    Generate pairs of partitions to be joined from inputs
 */
static void
get_matching_part_pairs(PlannerInfo *root, RelOptInfo *joinrel,
            RelOptInfo *rel1, RelOptInfo *rel2,
            List **parts1, List **parts2)
{
  bool    rel1_is_simple = IS_SIMPLE_REL(rel1);
  bool    rel2_is_simple = IS_SIMPLE_REL(rel2);
  int     cnt_parts;

  *parts1 = NIL;
  *parts2 = NIL;

  for (cnt_parts = 0; cnt_parts < joinrel->nparts; cnt_parts++)
  {
    RelOptInfo *child_joinrel = joinrel->part_rels[cnt_parts];
    RelOptInfo *child_rel1;
    RelOptInfo *child_rel2;
    Relids    child_relids1;
    Relids    child_relids2;

    /*
     * If this segment of the join is empty, it means that this segment
     * was ignored when previously creating child-join paths for it in
     * try_partitionwise_join() as it would not contribute to the join
     * result, due to one or both inputs being empty; add NULL to each of
     * the given lists so that this segment will be ignored again in that
     * function.
     */
    if (!child_joinrel)
    {
      *parts1 = lappend(*parts1, NULL);
      *parts2 = lappend(*parts2, NULL);
      continue;
    }

    /*
     * Get a relids set of partition(s) involved in this join segment that
     * are from the rel1 side.
     */
    child_relids1 = bms_intersect(child_joinrel->relids,
                    rel1->all_partrels);
    Assert(bms_num_members(child_relids1) == bms_num_members(rel1->relids));

    /*
     * Get a child rel for rel1 with the relids.  Note that we should have
     * the child rel even if rel1 is a join rel, because in that case the
     * partitions specified in the relids would have matching/overlapping
     * boundaries, so the specified partitions should be considered as
     * ones to be joined when planning partitionwise joins of rel1,
     * meaning that the child rel would have been built by the time we get
     * here.
     */
    if (rel1_is_simple)
    {
      int     varno = bms_singleton_member(child_relids1);

      child_rel1 = find_base_rel(root, varno);
    }
    else
      child_rel1 = find_join_rel(root, child_relids1);
    Assert(child_rel1);

    /*
     * Get a relids set of partition(s) involved in this join segment that
     * are from the rel2 side.
     */
    child_relids2 = bms_intersect(child_joinrel->relids,
                    rel2->all_partrels);
    Assert(bms_num_members(child_relids2) == bms_num_members(rel2->relids));

    /*
     * Get a child rel for rel2 with the relids.  See above comments.
     */
    if (rel2_is_simple)
    {
      int     varno = bms_singleton_member(child_relids2);

      child_rel2 = find_base_rel(root, varno);
    }
    else
      child_rel2 = find_join_rel(root, child_relids2);
    Assert(child_rel2);

    /*
     * The join of rel1 and rel2 is legal, so is the join of the child
     * rels obtained above; add them to the given lists as a join pair
     * producing this join segment.
     */
    *parts1 = lappend(*parts1, child_rel1);
    *parts2 = lappend(*parts2, child_rel2);
  }
}

Coverage Report

Created: 2026-10-16 06:48