/Users/deen/code/yugabyte-db/src/postgres/src/backend/optimizer/path/allpaths.c

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/*-------------------------------------------------------------------------
 *
 * allpaths.c
 *    Routines to find possible search paths for processing a query
 *
 * Portions Copyright (c) 1996-2018, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/optimizer/path/allpaths.c
 *
 * The following only applies to changes made to this file as part of
 * YugaByte development.
 *
 * Portions Copyright (c) YugaByte, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you
 * may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied.  See the License for the specific language governing
 * permissions and limitations under the License.
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include <limits.h>
#include <math.h>
#include <utils/rel.h>

#include "miscadmin.h"
#include "access/sysattr.h"
#include "access/tsmapi.h"
#include "catalog/pg_class.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_database.h"
#include "foreign/fdwapi.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#ifdef OPTIMIZER_DEBUG
#include "nodes/print.h"
#endif
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/geqo.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/plancat.h"
#include "optimizer/planner.h"
#include "optimizer/prep.h"
#include "optimizer/restrictinfo.h"
#include "optimizer/tlist.h"
#include "optimizer/var.h"
#include "parser/parse_clause.h"
#include "parser/parsetree.h"
#include "partitioning/partprune.h"
#include "rewrite/rewriteManip.h"
#include "utils/lsyscache.h"

/*  YB includes. */
#include "executor/ybc_fdw.h"
#include "pg_yb_utils.h"

/* results of subquery_is_pushdown_safe */
typedef struct pushdown_safety_info
{
  bool     *unsafeColumns;  /* which output columns are unsafe to use */
  bool    unsafeVolatile; /* don't push down volatile quals */
  bool    unsafeLeaky;  /* don't push down leaky quals */
} pushdown_safety_info;

/* These parameters are set by GUC */
bool    enable_geqo = false;  /* just in case GUC doesn't set it */
int     geqo_threshold;
int     min_parallel_table_scan_size;
int     min_parallel_index_scan_size;

/* Hook for plugins to get control in set_rel_pathlist() */
set_rel_pathlist_hook_type set_rel_pathlist_hook = NULL;

/* Hook for plugins to replace standard_join_search() */
join_search_hook_type join_search_hook = NULL;


static void set_base_rel_consider_startup(PlannerInfo *root);
static void set_base_rel_sizes(PlannerInfo *root);
static void set_base_rel_pathlists(PlannerInfo *root);
static void set_rel_size(PlannerInfo *root, RelOptInfo *rel,
       Index rti, RangeTblEntry *rte);
static void set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
         Index rti, RangeTblEntry *rte);
static void set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel,
           RangeTblEntry *rte);
static void create_plain_partial_paths(PlannerInfo *root, RelOptInfo *rel);
static void set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
              RangeTblEntry *rte);
static void set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
             RangeTblEntry *rte);
static void set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel,
             RangeTblEntry *rte);
static void set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
               RangeTblEntry *rte);
static void set_foreign_size(PlannerInfo *root, RelOptInfo *rel,
         RangeTblEntry *rte);
static void set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel,
           RangeTblEntry *rte);
static void set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
          Index rti, RangeTblEntry *rte);
static void set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
            Index rti, RangeTblEntry *rte);
static void generate_mergeappend_paths(PlannerInfo *root, RelOptInfo *rel,
               List *live_childrels,
               List *all_child_pathkeys,
               List *partitioned_rels);
static Path *get_cheapest_parameterized_child_path(PlannerInfo *root,
                    RelOptInfo *rel,
                    Relids required_outer);
static void accumulate_append_subpath(Path *path,
              List **subpaths, List **special_subpaths);
static void set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
            Index rti, RangeTblEntry *rte);
static void set_function_pathlist(PlannerInfo *root, RelOptInfo *rel,
            RangeTblEntry *rte);
static void set_values_pathlist(PlannerInfo *root, RelOptInfo *rel,
          RangeTblEntry *rte);
static void set_tablefunc_pathlist(PlannerInfo *root, RelOptInfo *rel,
             RangeTblEntry *rte);
static void set_cte_pathlist(PlannerInfo *root, RelOptInfo *rel,
         RangeTblEntry *rte);
static void set_namedtuplestore_pathlist(PlannerInfo *root, RelOptInfo *rel,
               RangeTblEntry *rte);
static void set_worktable_pathlist(PlannerInfo *root, RelOptInfo *rel,
             RangeTblEntry *rte);
static RelOptInfo *make_rel_from_joinlist(PlannerInfo *root, List *joinlist);
static bool subquery_is_pushdown_safe(Query *subquery, Query *topquery,
              pushdown_safety_info *safetyInfo);
static bool recurse_pushdown_safe(Node *setOp, Query *topquery,
            pushdown_safety_info *safetyInfo);
static void check_output_expressions(Query *subquery,
             pushdown_safety_info *safetyInfo);
static void compare_tlist_datatypes(List *tlist, List *colTypes,
            pushdown_safety_info *safetyInfo);
static bool targetIsInAllPartitionLists(TargetEntry *tle, Query *query);
static bool qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,
            pushdown_safety_info *safetyInfo);
static void subquery_push_qual(Query *subquery,
           RangeTblEntry *rte, Index rti, Node *qual);
static void recurse_push_qual(Node *setOp, Query *topquery,
          RangeTblEntry *rte, Index rti, Node *qual);
static void remove_unused_subquery_outputs(Query *subquery, RelOptInfo *rel);


/*
 * make_one_rel
 *    Finds all possible access paths for executing a query, returning a
 *    single rel that represents the join of all base rels in the query.
 */
RelOptInfo *
make_one_rel(PlannerInfo *root, List *joinlist)
{
  RelOptInfo *rel;
  Index   rti;

  /*
   * Construct the all_baserels Relids set.
   */
  root->all_baserels = NULL;
  for (rti = 1; rti < root->simple_rel_array_size; rti++)
  {
    RelOptInfo *brel = root->simple_rel_array[rti];

    /* there may be empty slots corresponding to non-baserel RTEs */
    if (brel == NULL)
      continue;

    Assert(brel->relid == rti); /* sanity check on array */

    /* ignore RTEs that are "other rels" */
    if (brel->reloptkind != RELOPT_BASEREL)
      continue;

    root->all_baserels = bms_add_member(root->all_baserels, brel->relid);
  }

  if (IsYugaByteEnabled())
  {
    for (rti = 1; rti < root->simple_rel_array_size; rti++)
    {
      RelOptInfo *relation = root->simple_rel_array[rti];

      if (relation != NULL && relation->rtekind == RTE_RELATION)
      {
        RangeTblEntry *rte = root->simple_rte_array[rti];
        if (IsYBRelationById(rte->relid)) {
          /*
           * Set the YugaByte FDW routine because we will use the foreign
           * scan API below.
           */
          relation->fdwroutine = (FdwRoutine *) ybc_fdw_handler();
        }
      }
    }
  }

  /* Mark base rels as to whether we care about fast-start plans */
  set_base_rel_consider_startup(root);

  /*
   * Compute size estimates and consider_parallel flags for each base rel,
   * then generate access paths.
   */
  set_base_rel_sizes(root);
  set_base_rel_pathlists(root);

  /*
   * Generate access paths for the entire join tree.
   */
  rel = make_rel_from_joinlist(root, joinlist);

  /*
   * The result should join all and only the query's base rels.
   */
  Assert(bms_equal(rel->relids, root->all_baserels));

  return rel;
}

/*
 * set_base_rel_consider_startup
 *    Set the consider_[param_]startup flags for each base-relation entry.
 *
 * For the moment, we only deal with consider_param_startup here; because the
 * logic for consider_startup is pretty trivial and is the same for every base
 * relation, we just let build_simple_rel() initialize that flag correctly to
 * start with.  If that logic ever gets more complicated it would probably
 * be better to move it here.
 */
static void
set_base_rel_consider_startup(PlannerInfo *root)
{
  /*
   * Since parameterized paths can only be used on the inside of a nestloop
   * join plan, there is usually little value in considering fast-start
   * plans for them.  However, for relations that are on the RHS of a SEMI
   * or ANTI join, a fast-start plan can be useful because we're only going
   * to care about fetching one tuple anyway.
   *
   * To minimize growth of planning time, we currently restrict this to
   * cases where the RHS is a single base relation, not a join; there is no
   * provision for consider_param_startup to get set at all on joinrels.
   * Also we don't worry about appendrels.  costsize.c's costing rules for
   * nestloop semi/antijoins don't consider such cases either.
   */
  ListCell   *lc;

  foreach(lc, root->join_info_list)
  {
    SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(lc);
    int     varno;

    if ((sjinfo->jointype == JOIN_SEMI || sjinfo->jointype == JOIN_ANTI) &&
      bms_get_singleton_member(sjinfo->syn_righthand, &varno))
    {
      RelOptInfo *rel = find_base_rel(root, varno);

      rel->consider_param_startup = true;
    }
  }
}

/*
 * set_base_rel_sizes
 *    Set the size estimates (rows and widths) for each base-relation entry.
 *    Also determine whether to consider parallel paths for base relations.
 *
 * We do this in a separate pass over the base rels so that rowcount
 * estimates are available for parameterized path generation, and also so
 * that each rel's consider_parallel flag is set correctly before we begin to
 * generate paths.
 */
static void
set_base_rel_sizes(PlannerInfo *root)
{
  Index   rti;

  for (rti = 1; rti < root->simple_rel_array_size; rti++)
  {
    RelOptInfo *rel = root->simple_rel_array[rti];
    RangeTblEntry *rte;

    /* there may be empty slots corresponding to non-baserel RTEs */
    if (rel == NULL)
      continue;

    Assert(rel->relid == rti);  /* sanity check on array */

    /* ignore RTEs that are "other rels" */
    if (rel->reloptkind != RELOPT_BASEREL)
      continue;

    rte = root->simple_rte_array[rti];

    /*
     * If parallelism is allowable for this query in general, see whether
     * it's allowable for this rel in particular.  We have to do this
     * before set_rel_size(), because (a) if this rel is an inheritance
     * parent, set_append_rel_size() will use and perhaps change the rel's
     * consider_parallel flag, and (b) for some RTE types, set_rel_size()
     * goes ahead and makes paths immediately.
     */
    if (root->glob->parallelModeOK)
      set_rel_consider_parallel(root, rel, rte);

    set_rel_size(root, rel, rti, rte);
  }
}

/*
 * set_base_rel_pathlists
 *    Finds all paths available for scanning each base-relation entry.
 *    Sequential scan and any available indices are considered.
 *    Each useful path is attached to its relation's 'pathlist' field.
 */
static void
set_base_rel_pathlists(PlannerInfo *root)
{
  Index   rti;

  for (rti = 1; rti < root->simple_rel_array_size; rti++)
  {
    RelOptInfo *rel = root->simple_rel_array[rti];

    /* there may be empty slots corresponding to non-baserel RTEs */
    if (rel == NULL)
      continue;

    Assert(rel->relid == rti);  /* sanity check on array */

    /* ignore RTEs that are "other rels" */
    if (rel->reloptkind != RELOPT_BASEREL)
      continue;

    set_rel_pathlist(root, rel, rti, root->simple_rte_array[rti]);
  }
}

/*
 * set_rel_size
 *    Set size estimates for a base relation
 */
static void
set_rel_size(PlannerInfo *root, RelOptInfo *rel,
       Index rti, RangeTblEntry *rte)
{
  if (rel->reloptkind == RELOPT_BASEREL &&
    relation_excluded_by_constraints(root, rel, rte))
  {
    /*
     * We proved we don't need to scan the rel via constraint exclusion,
     * so set up a single dummy path for it.  Here we only check this for
     * regular baserels; if it's an otherrel, CE was already checked in
     * set_append_rel_size().
     *
     * In this case, we go ahead and set up the relation's path right away
     * instead of leaving it for set_rel_pathlist to do.  This is because
     * we don't have a convention for marking a rel as dummy except by
     * assigning a dummy path to it.
     */
    set_dummy_rel_pathlist(rel);
  }
  else if (rte->inh)
  {
    /* It's an "append relation", process accordingly */
    set_append_rel_size(root, rel, rti, rte);
  }
  else
  {
    switch (rel->rtekind)
    {
      case RTE_RELATION:
        if (rte->relkind == RELKIND_FOREIGN_TABLE)
        {
          /* Foreign table */
          set_foreign_size(root, rel, rte);
        }
        else if (rte->relkind == RELKIND_PARTITIONED_TABLE)
        {
          /*
           * A partitioned table without any partitions is marked as
           * a dummy rel.
           */
          set_dummy_rel_pathlist(rel);
        }
        else if (rte->tablesample != NULL)
        {
          if (IsYBRelationById(rte->relid))
          {
            /* TODO we don't support tablesample queries yet. */
            ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("'TABLESAMPLE' clause is not yet "
                    "supported by YugaByte")));
          }

          /* Sampled relation */
          set_tablesample_rel_size(root, rel, rte);
        }
        else
        {
          /* Plain relation */
          if (IsYBRelationById(rte->relid))
          {
            set_foreign_size(root, rel, rte);
          }
          else
          {
            /* Use regular scan for initdb tables. */
            set_plain_rel_size(root, rel, rte);
          }
        }
        break;
      case RTE_SUBQUERY:

        /*
         * Subqueries don't support making a choice between
         * parameterized and unparameterized paths, so just go ahead
         * and build their paths immediately.
         */
        set_subquery_pathlist(root, rel, rti, rte);
        break;
      case RTE_FUNCTION:
        set_function_size_estimates(root, rel);
        break;
      case RTE_TABLEFUNC:
        set_tablefunc_size_estimates(root, rel);
        break;
      case RTE_VALUES:
        set_values_size_estimates(root, rel);
        break;
      case RTE_CTE:

        /*
         * CTEs don't support making a choice between parameterized
         * and unparameterized paths, so just go ahead and build their
         * paths immediately.
         */
        if (rte->self_reference)
          set_worktable_pathlist(root, rel, rte);
        else
          set_cte_pathlist(root, rel, rte);
        break;
      case RTE_NAMEDTUPLESTORE:
        set_namedtuplestore_pathlist(root, rel, rte);
        break;
      default:
        elog(ERROR, "unexpected rtekind: %d", (int) rel->rtekind);
        break;
    }
  }

  /*
   * We insist that all non-dummy rels have a nonzero rowcount estimate.
   */
  Assert(rel->rows > 0 || IS_DUMMY_REL(rel));
}

/*
 * set_rel_pathlist
 *    Build access paths for a base relation
 */
static void
set_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
         Index rti, RangeTblEntry *rte)
{
  if (IS_DUMMY_REL(rel))
  {
    /* We already proved the relation empty, so nothing more to do */
  }
  else if (rte->inh)
  {
    /* It's an "append relation", process accordingly */
    set_append_rel_pathlist(root, rel, rti, rte);
  }
  else
  {
    switch (rel->rtekind)
    {
      case RTE_RELATION:
        if (rte->relkind == RELKIND_FOREIGN_TABLE)
        {
          /* Foreign table */
          set_foreign_pathlist(root, rel, rte);
        }
        else if (rte->tablesample != NULL)
        {
          if (IsYBRelationById(rte->relid))
          {
            /* TODO we don't support tablesample queries yet. */
            ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                errmsg("'TABLESAMPLE' clause is not yet "
                     "supported by YugaByte")));
          }

          /* Sampled relation */
          set_tablesample_rel_pathlist(root, rel, rte);
        }
        else
        {
          /* Plain relation */
          if (IsYBRelationById(rte->relid))
          {
            /*
             * Using a foreign scan which will use the YB FDW by
             * default.
             */
            set_foreign_pathlist(root, rel, rte);
          }
          else
          {
            /* Use regular scan for initdb tables. */
            set_plain_rel_pathlist(root, rel, rte);
          }
        }
        break;
      case RTE_SUBQUERY:
        /* Subquery --- fully handled during set_rel_size */
        break;
      case RTE_FUNCTION:
        /* RangeFunction */
        set_function_pathlist(root, rel, rte);
        break;
      case RTE_TABLEFUNC:
        /* Table Function */
        set_tablefunc_pathlist(root, rel, rte);
        break;
      case RTE_VALUES:
        /* Values list */
        set_values_pathlist(root, rel, rte);
        break;
      case RTE_CTE:
        /* CTE reference --- fully handled during set_rel_size */
        break;
      case RTE_NAMEDTUPLESTORE:
        /* tuplestore reference --- fully handled during set_rel_size */
        break;
      default:
        elog(ERROR, "unexpected rtekind: %d", (int) rel->rtekind);
        break;
    }
  }

  /*
   * Allow a plugin to editorialize on the set of Paths for this base
   * relation.  It could add new paths (such as CustomPaths) by calling
   * add_path(), or add_partial_path() if parallel aware.  It could also
   * delete or modify paths added by the core code.
   */
  if (set_rel_pathlist_hook)
    (*set_rel_pathlist_hook) (root, rel, rti, rte);

  /*
   * If this is a baserel, we should normally consider gathering any partial
   * paths we may have created for it.  We have to do this after calling the
   * set_rel_pathlist_hook, else it cannot add partial paths to be included
   * here.
   *
   * However, if this is an inheritance child, skip it.  Otherwise, we could
   * end up with a very large number of gather nodes, each trying to grab
   * its own pool of workers.  Instead, we'll consider gathering partial
   * paths for the parent appendrel.
   *
   * Also, if this is the topmost scan/join rel (that is, the only baserel),
   * we postpone gathering until the final scan/join targetlist is available
   * (see grouping_planner).
   */
  if (rel->reloptkind == RELOPT_BASEREL &&
    bms_membership(root->all_baserels) != BMS_SINGLETON)
    generate_gather_paths(root, rel, false);

  /* Now find the cheapest of the paths for this rel */
  set_cheapest(rel);

#ifdef OPTIMIZER_DEBUG
  debug_print_rel(root, rel);
#endif
}

/*
 * set_plain_rel_size
 *    Set size estimates for a plain relation (no subquery, no inheritance)
 */
static void
set_plain_rel_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
  /*
   * Test any partial indexes of rel for applicability.  We must do this
   * first since partial unique indexes can affect size estimates.
   */
  check_index_predicates(root, rel);

  /* Mark rel with estimated output rows, width, etc */
  set_baserel_size_estimates(root, rel);
}

/*
 * If this relation could possibly be scanned from within a worker, then set
 * its consider_parallel flag.
 */
static void
set_rel_consider_parallel(PlannerInfo *root, RelOptInfo *rel,
              RangeTblEntry *rte)
{
  /*
   * The flag has previously been initialized to false, so we can just
   * return if it becomes clear that we can't safely set it.
   */
  Assert(!rel->consider_parallel);

  /* Don't call this if parallelism is disallowed for the entire query. */
  Assert(root->glob->parallelModeOK);

  /* This should only be called for baserels and appendrel children. */
  Assert(IS_SIMPLE_REL(rel));

  /* Assorted checks based on rtekind. */
  switch (rte->rtekind)
  {
    case RTE_RELATION:

      /*
       * Currently, parallel workers can't access the leader's temporary
       * tables.  We could possibly relax this if the wrote all of its
       * local buffers at the start of the query and made no changes
       * thereafter (maybe we could allow hint bit changes), and if we
       * taught the workers to read them.  Writing a large number of
       * temporary buffers could be expensive, though, and we don't have
       * the rest of the necessary infrastructure right now anyway.  So
       * for now, bail out if we see a temporary table.
       */
      if (get_rel_persistence(rte->relid) == RELPERSISTENCE_TEMP)
        return;

      /*
       * Table sampling can be pushed down to workers if the sample
       * function and its arguments are safe.
       */
      if (rte->tablesample != NULL)
      {
        char    proparallel = func_parallel(rte->tablesample->tsmhandler);

        if (proparallel != PROPARALLEL_SAFE)
          return;
        if (!is_parallel_safe(root, (Node *) rte->tablesample->args))
          return;
      }

      /*
       * Ask FDWs whether they can support performing a ForeignScan
       * within a worker.  Most often, the answer will be no.  For
       * example, if the nature of the FDW is such that it opens a TCP
       * connection with a remote server, each parallel worker would end
       * up with a separate connection, and these connections might not
       * be appropriately coordinated between workers and the leader.
       */
      if (rte->relkind == RELKIND_FOREIGN_TABLE)
      {
        Assert(rel->fdwroutine);
        if (!rel->fdwroutine->IsForeignScanParallelSafe)
          return;
        if (!rel->fdwroutine->IsForeignScanParallelSafe(root, rel, rte))
          return;
      }

      if (IsYugaByteEnabled())
      {
        /* If YB scan, disable parallelization for now. */
        return;
      }

      /*
       * There are additional considerations for appendrels, which we'll
       * deal with in set_append_rel_size and set_append_rel_pathlist.
       * For now, just set consider_parallel based on the rel's own
       * quals and targetlist.
       */
      break;

    case RTE_SUBQUERY:

      /*
       * There's no intrinsic problem with scanning a subquery-in-FROM
       * (as distinct from a SubPlan or InitPlan) in a parallel worker.
       * If the subquery doesn't happen to have any parallel-safe paths,
       * then flagging it as consider_parallel won't change anything,
       * but that's true for plain tables, too.  We must set
       * consider_parallel based on the rel's own quals and targetlist,
       * so that if a subquery path is parallel-safe but the quals and
       * projection we're sticking onto it are not, we correctly mark
       * the SubqueryScanPath as not parallel-safe.  (Note that
       * set_subquery_pathlist() might push some of these quals down
       * into the subquery itself, but that doesn't change anything.)
       *
       * We can't push sub-select containing LIMIT/OFFSET to workers as
       * there is no guarantee that the row order will be fully
       * deterministic, and applying LIMIT/OFFSET will lead to
       * inconsistent results at the top-level.  (In some cases, where
       * the result is ordered, we could relax this restriction.  But it
       * doesn't currently seem worth expending extra effort to do so.)
       */
      {
        Query    *subquery = castNode(Query, rte->subquery);

        if (limit_needed(subquery))
          return;
      }
      break;

    case RTE_JOIN:
      /* Shouldn't happen; we're only considering baserels here. */
      Assert(false);
      return;

    case RTE_FUNCTION:
      /* Check for parallel-restricted functions. */
      if (!is_parallel_safe(root, (Node *) rte->functions))
        return;
      break;

    case RTE_TABLEFUNC:
      /* not parallel safe */
      return;

    case RTE_VALUES:
      /* Check for parallel-restricted functions. */
      if (!is_parallel_safe(root, (Node *) rte->values_lists))
        return;
      break;

    case RTE_CTE:

      /*
       * CTE tuplestores aren't shared among parallel workers, so we
       * force all CTE scans to happen in the leader.  Also, populating
       * the CTE would require executing a subplan that's not available
       * in the worker, might be parallel-restricted, and must get
       * executed only once.
       */
      return;

    case RTE_NAMEDTUPLESTORE:

      /*
       * tuplestore cannot be shared, at least without more
       * infrastructure to support that.
       */
      return;
  }

  /*
   * If there's anything in baserestrictinfo that's parallel-restricted, we
   * give up on parallelizing access to this relation.  We could consider
   * instead postponing application of the restricted quals until we're
   * above all the parallelism in the plan tree, but it's not clear that
   * that would be a win in very many cases, and it might be tricky to make
   * outer join clauses work correctly.  It would likely break equivalence
   * classes, too.
   */
  if (!is_parallel_safe(root, (Node *) rel->baserestrictinfo))
    return;

  /*
   * Likewise, if the relation's outputs are not parallel-safe, give up.
   * (Usually, they're just Vars, but sometimes they're not.)
   */
  if (!is_parallel_safe(root, (Node *) rel->reltarget->exprs))
    return;

  /* We have a winner. */
  rel->consider_parallel = true;
}

/*
 * set_plain_rel_pathlist
 *    Build access paths for a plain relation (no subquery, no inheritance)
 */
static void
set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
  Relids    required_outer;

  /*
   * We don't support pushing join clauses into the quals of a seqscan, but
   * it could still have required parameterization due to LATERAL refs in
   * its tlist.
   */
  required_outer = rel->lateral_relids;

  /* Consider sequential scan */
  add_path(rel, create_seqscan_path(root, rel, required_outer, 0));

  /* If appropriate, consider parallel sequential scan */
  if (rel->consider_parallel && required_outer == NULL)
    create_plain_partial_paths(root, rel);

  /* Consider index scans */
  create_index_paths(root, rel);

  /* Consider TID scans */
  create_tidscan_paths(root, rel);
}

/*
 * create_plain_partial_paths
 *    Build partial access paths for parallel scan of a plain relation
 */
static void
create_plain_partial_paths(PlannerInfo *root, RelOptInfo *rel)
{
  int     parallel_workers;

  parallel_workers = compute_parallel_worker(rel, rel->pages, -1,
                         max_parallel_workers_per_gather);

  /* If any limit was set to zero, the user doesn't want a parallel scan. */
  if (parallel_workers <= 0)
    return;

  /* Add an unordered partial path based on a parallel sequential scan. */
  add_partial_path(rel, create_seqscan_path(root, rel, NULL, parallel_workers));
}

/*
 * set_tablesample_rel_size
 *    Set size estimates for a sampled relation
 */
static void
set_tablesample_rel_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
  TableSampleClause *tsc = rte->tablesample;
  TsmRoutine *tsm;
  BlockNumber pages;
  double    tuples;

  /*
   * Test any partial indexes of rel for applicability.  We must do this
   * first since partial unique indexes can affect size estimates.
   */
  check_index_predicates(root, rel);

  /*
   * Call the sampling method's estimation function to estimate the number
   * of pages it will read and the number of tuples it will return.  (Note:
   * we assume the function returns sane values.)
   */
  tsm = GetTsmRoutine(tsc->tsmhandler);
  tsm->SampleScanGetSampleSize(root, rel, tsc->args,
                 &pages, &tuples);

  /*
   * For the moment, because we will only consider a SampleScan path for the
   * rel, it's okay to just overwrite the pages and tuples estimates for the
   * whole relation.  If we ever consider multiple path types for sampled
   * rels, we'll need more complication.
   */
  rel->pages = pages;
  rel->tuples = tuples;

  /* Mark rel with estimated output rows, width, etc */
  set_baserel_size_estimates(root, rel);
}

/*
 * set_tablesample_rel_pathlist
 *    Build access paths for a sampled relation
 */
static void
set_tablesample_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
  Relids    required_outer;
  Path     *path;

  /*
   * We don't support pushing join clauses into the quals of a samplescan,
   * but it could still have required parameterization due to LATERAL refs
   * in its tlist or TABLESAMPLE arguments.
   */
  required_outer = rel->lateral_relids;

  /* Consider sampled scan */
  path = create_samplescan_path(root, rel, required_outer);

  /*
   * If the sampling method does not support repeatable scans, we must avoid
   * plans that would scan the rel multiple times.  Ideally, we'd simply
   * avoid putting the rel on the inside of a nestloop join; but adding such
   * a consideration to the planner seems like a great deal of complication
   * to support an uncommon usage of second-rate sampling methods.  Instead,
   * if there is a risk that the query might perform an unsafe join, just
   * wrap the SampleScan in a Materialize node.  We can check for joins by
   * counting the membership of all_baserels (note that this correctly
   * counts inheritance trees as single rels).  If we're inside a subquery,
   * we can't easily check whether a join might occur in the outer query, so
   * just assume one is possible.
   *
   * GetTsmRoutine is relatively expensive compared to the other tests here,
   * so check repeatable_across_scans last, even though that's a bit odd.
   */
  if ((root->query_level > 1 ||
     bms_membership(root->all_baserels) != BMS_SINGLETON) &&
    !(GetTsmRoutine(rte->tablesample->tsmhandler)->repeatable_across_scans))
  {
    path = (Path *) create_material_path(rel, path);
  }

  add_path(rel, path);

  /* For the moment, at least, there are no other paths to consider */
}

/*
 * set_foreign_size
 *    Set size estimates for a foreign table RTE
 */
static void
set_foreign_size(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
  /* Mark rel with estimated output rows, width, etc */
  set_foreign_size_estimates(root, rel);

  /* Let FDW adjust the size estimates, if it can */
  rel->fdwroutine->GetForeignRelSize(root, rel, rte->relid);

  /* ... but do not let it set the rows estimate to zero */
  rel->rows = clamp_row_est(rel->rows);
}

/*
 * set_foreign_pathlist
 *    Build access paths for a foreign table RTE
 */
static void
set_foreign_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
  /* Call the FDW's GetForeignPaths function to generate path(s) */
  rel->fdwroutine->GetForeignPaths(root, rel, rte->relid);
}

/*
 * set_append_rel_size
 *    Set size estimates for a simple "append relation"
 *
 * The passed-in rel and RTE represent the entire append relation.  The
 * relation's contents are computed by appending together the output of the
 * individual member relations.  Note that in the non-partitioned inheritance
 * case, the first member relation is actually the same table as is mentioned
 * in the parent RTE ... but it has a different RTE and RelOptInfo.  This is
 * a good thing because their outputs are not the same size.
 */
static void
set_append_rel_size(PlannerInfo *root, RelOptInfo *rel,
          Index rti, RangeTblEntry *rte)
{
  int     parentRTindex = rti;
  bool    has_live_children;
  double    parent_rows;
  double    parent_size;
  double     *parent_attrsizes;
  int     nattrs;
  ListCell   *l;
  Relids    live_children = NULL;
  bool    did_pruning = false;

  /* Guard against stack overflow due to overly deep inheritance tree. */
  check_stack_depth();

  Assert(IS_SIMPLE_REL(rel));

  /*
   * Initialize partitioned_child_rels to contain this RT index.
   *
   * Note that during the set_append_rel_pathlist() phase, we will bubble up
   * the indexes of partitioned relations that appear down in the tree, so
   * that when we've created Paths for all the children, the root
   * partitioned table's list will contain all such indexes.
   */
  if (rte->relkind == RELKIND_PARTITIONED_TABLE)
    rel->partitioned_child_rels = list_make1_int(rti);

  /*
   * If the partitioned relation has any baserestrictinfo quals then we
   * attempt to use these quals to prune away partitions that cannot
   * possibly contain any tuples matching these quals.  In this case we'll
   * store the relids of all partitions which could possibly contain a
   * matching tuple, and skip anything else in the loop below.
   */
  if (enable_partition_pruning &&
    rte->relkind == RELKIND_PARTITIONED_TABLE &&
    rel->baserestrictinfo != NIL)
  {
    live_children = prune_append_rel_partitions(root, rel);
    did_pruning = true;
  }

  /*
   * If this is a partitioned baserel, set the consider_partitionwise_join
   * flag; currently, we only consider partitionwise joins with the baserel
   * if its targetlist doesn't contain a whole-row Var.
   */
  if (enable_partitionwise_join &&
    rel->reloptkind == RELOPT_BASEREL &&
    rte->relkind == RELKIND_PARTITIONED_TABLE &&
    rel->attr_needed[InvalidAttrNumber - rel->min_attr] == NULL)
    rel->consider_partitionwise_join = true;

  /*
   * Initialize to compute size estimates for whole append relation.
   *
   * We handle width estimates by weighting the widths of different child
   * rels proportionally to their number of rows.  This is sensible because
   * the use of width estimates is mainly to compute the total relation
   * "footprint" if we have to sort or hash it.  To do this, we sum the
   * total equivalent size (in "double" arithmetic) and then divide by the
   * total rowcount estimate.  This is done separately for the total rel
   * width and each attribute.
   *
   * Note: if you consider changing this logic, beware that child rels could
   * have zero rows and/or width, if they were excluded by constraints.
   */
  has_live_children = false;
  parent_rows = 0;
  parent_size = 0;
  nattrs = rel->max_attr - rel->min_attr + 1;
  parent_attrsizes = (double *) palloc0(nattrs * sizeof(double));

  foreach(l, root->append_rel_list)
  {
    AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
    int     childRTindex;
    RangeTblEntry *childRTE;
    RelOptInfo *childrel;
    List     *childquals;
    Index   cq_min_security;
    bool    have_const_false_cq;
    ListCell   *parentvars;
    ListCell   *childvars;
    ListCell   *lc;

    /* append_rel_list contains all append rels; ignore others */
    if (appinfo->parent_relid != parentRTindex)
      continue;

    childRTindex = appinfo->child_relid;
    childRTE = root->simple_rte_array[childRTindex];

    /*
     * The child rel's RelOptInfo was already created during
     * add_base_rels_to_query.
     */
    childrel = find_base_rel(root, childRTindex);
    Assert(childrel->reloptkind == RELOPT_OTHER_MEMBER_REL);

    /*
     * We have to copy the parent's targetlist and quals to the child,
     * with appropriate substitution of variables.  However, only the
     * baserestrictinfo quals are needed before we can check for
     * constraint exclusion; so do that first and then check to see if we
     * can disregard this child.
     *
     * The child rel's targetlist might contain non-Var expressions, which
     * means that substitution into the quals could produce opportunities
     * for const-simplification, and perhaps even pseudoconstant quals.
     * Therefore, transform each RestrictInfo separately to see if it
     * reduces to a constant or pseudoconstant.  (We must process them
     * separately to keep track of the security level of each qual.)
     */
    childquals = NIL;
    cq_min_security = UINT_MAX;
    have_const_false_cq = false;
    foreach(lc, rel->baserestrictinfo)
    {
      RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
      Node     *childqual;
      ListCell   *lc2;

      Assert(IsA(rinfo, RestrictInfo));
      childqual = adjust_appendrel_attrs(root,
                         (Node *) rinfo->clause,
                         1, &appinfo);
      childqual = eval_const_expressions(root, childqual);
      /* check for flat-out constant */
      if (childqual && IsA(childqual, Const))
      {
        if (((Const *) childqual)->constisnull ||
          !DatumGetBool(((Const *) childqual)->constvalue))
        {
          /* Restriction reduces to constant FALSE or NULL */
          have_const_false_cq = true;
          break;
        }
        /* Restriction reduces to constant TRUE, so drop it */
        continue;
      }
      /* might have gotten an AND clause, if so flatten it */
      foreach(lc2, make_ands_implicit((Expr *) childqual))
      {
        Node     *onecq = (Node *) lfirst(lc2);
        bool    pseudoconstant;

        /* check for pseudoconstant (no Vars or volatile functions) */
        pseudoconstant =
          !contain_vars_of_level(onecq, 0) &&
          !contain_volatile_functions(onecq);
        if (pseudoconstant)
        {
          /* tell createplan.c to check for gating quals */
          root->hasPseudoConstantQuals = true;
        }
        /* reconstitute RestrictInfo with appropriate properties */
        childquals = lappend(childquals,
                   make_restrictinfo((Expr *) onecq,
                             rinfo->is_pushed_down,
                             rinfo->outerjoin_delayed,
                             pseudoconstant,
                             rinfo->security_level,
                             NULL, NULL, NULL));
        /* track minimum security level among child quals */
        cq_min_security = Min(cq_min_security, rinfo->security_level);
      }
    }

    /*
     * In addition to the quals inherited from the parent, we might have
     * securityQuals associated with this particular child node.
     * (Currently this can only happen in appendrels originating from
     * UNION ALL; inheritance child tables don't have their own
     * securityQuals, see expand_inherited_rtentry().)  Pull any such
     * securityQuals up into the baserestrictinfo for the child.  This is
     * similar to process_security_barrier_quals() for the parent rel,
     * except that we can't make any general deductions from such quals,
     * since they don't hold for the whole appendrel.
     */
    if (childRTE->securityQuals)
    {
      Index   security_level = 0;

      foreach(lc, childRTE->securityQuals)
      {
        List     *qualset = (List *) lfirst(lc);
        ListCell   *lc2;

        foreach(lc2, qualset)
        {
          Expr     *qual = (Expr *) lfirst(lc2);

          /* not likely that we'd see constants here, so no check */
          childquals = lappend(childquals,
                     make_restrictinfo(qual,
                               true, false, false,
                               security_level,
                               NULL, NULL, NULL));
          cq_min_security = Min(cq_min_security, security_level);
        }
        security_level++;
      }
      Assert(security_level <= root->qual_security_level);
    }

    /*
     * OK, we've got all the baserestrictinfo quals for this child.
     */
    childrel->baserestrictinfo = childquals;
    childrel->baserestrict_min_security = cq_min_security;

    if (have_const_false_cq)
    {
      /*
       * Some restriction clause reduced to constant FALSE or NULL after
       * substitution, so this child need not be scanned.
       */
      set_dummy_rel_pathlist(childrel);
      continue;
    }

    if (did_pruning && !bms_is_member(appinfo->child_relid, live_children))
    {
      /* This partition was pruned; skip it. */
      set_dummy_rel_pathlist(childrel);
      continue;
    }

    if (relation_excluded_by_constraints(root, childrel, childRTE))
    {
      /*
       * This child need not be scanned, so we can omit it from the
       * appendrel.
       */
      set_dummy_rel_pathlist(childrel);
      continue;
    }

    /*
     * CE failed, so finish copying/modifying targetlist and join quals.
     *
     * NB: the resulting childrel->reltarget->exprs may contain arbitrary
     * expressions, which otherwise would not occur in a rel's targetlist.
     * Code that might be looking at an appendrel child must cope with
     * such.  (Normally, a rel's targetlist would only include Vars and
     * PlaceHolderVars.)  XXX we do not bother to update the cost or width
     * fields of childrel->reltarget; not clear if that would be useful.
     */
    childrel->joininfo = (List *)
      adjust_appendrel_attrs(root,
                   (Node *) rel->joininfo,
                   1, &appinfo);
    childrel->reltarget->exprs = (List *)
      adjust_appendrel_attrs(root,
                   (Node *) rel->reltarget->exprs,
                   1, &appinfo);

    /*
     * We have to make child entries in the EquivalenceClass data
     * structures as well.  This is needed either if the parent
     * participates in some eclass joins (because we will want to consider
     * inner-indexscan joins on the individual children) or if the parent
     * has useful pathkeys (because we should try to build MergeAppend
     * paths that produce those sort orderings).
     */
    if (rel->has_eclass_joins || has_useful_pathkeys(root, rel))
      add_child_rel_equivalences(root, appinfo, rel, childrel);
    childrel->has_eclass_joins = rel->has_eclass_joins;

    /*
     * Note: we could compute appropriate attr_needed data for the child's
     * variables, by transforming the parent's attr_needed through the
     * translated_vars mapping.  However, currently there's no need
     * because attr_needed is only examined for base relations not
     * otherrels.  So we just leave the child's attr_needed empty.
     */

    /*
     * If we consider partitionwise joins with the parent rel, do the same
     * for partitioned child rels.
     *
     * Note: here we abuse the consider_partitionwise_join flag by setting
     * it *even* for child rels that are not partitioned.  In that case,
     * we set it to tell try_partitionwise_join() that it doesn't need to
     * generate their targetlists and EC entries as they have already been
     * generated here, as opposed to the dummy child rels for which the
     * flag is left set to false so that it will generate them.
     */
    if (rel->consider_partitionwise_join)
      childrel->consider_partitionwise_join = true;

    /*
     * If parallelism is allowable for this query in general, see whether
     * it's allowable for this childrel in particular.  But if we've
     * already decided the appendrel is not parallel-safe as a whole,
     * there's no point in considering parallelism for this child.  For
     * consistency, do this before calling set_rel_size() for the child.
     */
    if (root->glob->parallelModeOK && rel->consider_parallel)
      set_rel_consider_parallel(root, childrel, childRTE);

    /*
     * Compute the child's size.
     */
    set_rel_size(root, childrel, childRTindex, childRTE);

    /*
     * It is possible that constraint exclusion detected a contradiction
     * within a child subquery, even though we didn't prove one above. If
     * so, we can skip this child.
     */
    if (IS_DUMMY_REL(childrel))
      continue;

    /* We have at least one live child. */
    has_live_children = true;

    /*
     * If any live child is not parallel-safe, treat the whole appendrel
     * as not parallel-safe.  In future we might be able to generate plans
     * in which some children are farmed out to workers while others are
     * not; but we don't have that today, so it's a waste to consider
     * partial paths anywhere in the appendrel unless it's all safe.
     * (Child rels visited before this one will be unmarked in
     * set_append_rel_pathlist().)
     */
    if (!childrel->consider_parallel)
      rel->consider_parallel = false;

    /*
     * Accumulate size information from each live child.
     */
    Assert(childrel->rows > 0);

    parent_rows += childrel->rows;
    parent_size += childrel->reltarget->width * childrel->rows;

    /*
     * Accumulate per-column estimates too.  We need not do anything for
     * PlaceHolderVars in the parent list.  If child expression isn't a
     * Var, or we didn't record a width estimate for it, we have to fall
     * back on a datatype-based estimate.
     *
     * By construction, child's targetlist is 1-to-1 with parent's.
     */
    forboth(parentvars, rel->reltarget->exprs,
        childvars, childrel->reltarget->exprs)
    {
      Var      *parentvar = (Var *) lfirst(parentvars);
      Node     *childvar = (Node *) lfirst(childvars);

      if (IsA(parentvar, Var))
      {
        int     pndx = parentvar->varattno - rel->min_attr;
        int32   child_width = 0;

        if (IsA(childvar, Var) &&
          ((Var *) childvar)->varno == childrel->relid)
        {
          int     cndx = ((Var *) childvar)->varattno - childrel->min_attr;

          child_width = childrel->attr_widths[cndx];
        }
        if (child_width <= 0)
          child_width = get_typavgwidth(exprType(childvar),
                          exprTypmod(childvar));
        Assert(child_width > 0);
        parent_attrsizes[pndx] += child_width * childrel->rows;
      }
    }
  }

  if (has_live_children)
  {
    /*
     * Save the finished size estimates.
     */
    int     i;

    Assert(parent_rows > 0);
    rel->rows = parent_rows;
    rel->reltarget->width = rint(parent_size / parent_rows);
    for (i = 0; i < nattrs; i++)
      rel->attr_widths[i] = rint(parent_attrsizes[i] / parent_rows);

    /*
     * Set "raw tuples" count equal to "rows" for the appendrel; needed
     * because some places assume rel->tuples is valid for any baserel.
     */
    rel->tuples = parent_rows;
  }
  else
  {
    /*
     * All children were excluded by constraints, so mark the whole
     * appendrel dummy.  We must do this in this phase so that the rel's
     * dummy-ness is visible when we generate paths for other rels.
     */
    set_dummy_rel_pathlist(rel);
  }

  pfree(parent_attrsizes);
}

/*
 * set_append_rel_pathlist
 *    Build access paths for an "append relation"
 */
static void
set_append_rel_pathlist(PlannerInfo *root, RelOptInfo *rel,
            Index rti, RangeTblEntry *rte)
{
  int     parentRTindex = rti;
  List     *live_childrels = NIL;
  ListCell   *l;

  /*
   * Generate access paths for each member relation, and remember the
   * non-dummy children.
   */
  foreach(l, root->append_rel_list)
  {
    AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
    int     childRTindex;
    RangeTblEntry *childRTE;
    RelOptInfo *childrel;

    /* append_rel_list contains all append rels; ignore others */
    if (appinfo->parent_relid != parentRTindex)
      continue;

    /* Re-locate the child RTE and RelOptInfo */
    childRTindex = appinfo->child_relid;
    childRTE = root->simple_rte_array[childRTindex];
    childrel = root->simple_rel_array[childRTindex];

    /*
     * If set_append_rel_size() decided the parent appendrel was
     * parallel-unsafe at some point after visiting this child rel, we
     * need to propagate the unsafety marking down to the child, so that
     * we don't generate useless partial paths for it.
     */
    if (!rel->consider_parallel)
      childrel->consider_parallel = false;

    /*
     * Compute the child's access paths.
     */
    set_rel_pathlist(root, childrel, childRTindex, childRTE);

    /*
     * If child is dummy, ignore it.
     */
    if (IS_DUMMY_REL(childrel))
      continue;

    /* Bubble up childrel's partitioned children. */
    if (rel->part_scheme)
      rel->partitioned_child_rels =
        list_concat(rel->partitioned_child_rels,
              list_copy(childrel->partitioned_child_rels));

    /*
     * Child is live, so add it to the live_childrels list for use below.
     */
    live_childrels = lappend(live_childrels, childrel);
  }

  /* Add paths to the append relation. */
  add_paths_to_append_rel(root, rel, live_childrels);
}


/*
 * add_paths_to_append_rel
 *    Generate paths for the given append relation given the set of non-dummy
 *    child rels.
 *
 * The function collects all parameterizations and orderings supported by the
 * non-dummy children. For every such parameterization or ordering, it creates
 * an append path collecting one path from each non-dummy child with given
 * parameterization or ordering. Similarly it collects partial paths from
 * non-dummy children to create partial append paths.
 */
void
add_paths_to_append_rel(PlannerInfo *root, RelOptInfo *rel,
            List *live_childrels)
{
  List     *subpaths = NIL;
  bool    subpaths_valid = true;
  List     *partial_subpaths = NIL;
  List     *pa_partial_subpaths = NIL;
  List     *pa_nonpartial_subpaths = NIL;
  bool    partial_subpaths_valid = true;
  bool    pa_subpaths_valid;
  List     *all_child_pathkeys = NIL;
  List     *all_child_outers = NIL;
  ListCell   *l;
  List     *partitioned_rels = NIL;
  double    partial_rows = -1;

  /* If appropriate, consider parallel append */
  pa_subpaths_valid = enable_parallel_append && rel->consider_parallel;

  /*
   * AppendPath generated for partitioned tables must record the RT indexes
   * of partitioned tables that are direct or indirect children of this
   * Append rel.
   *
   * AppendPath may be for a sub-query RTE (UNION ALL), in which case, 'rel'
   * itself does not represent a partitioned relation, but the child sub-
   * queries may contain references to partitioned relations.  The loop
   * below will look for such children and collect them in a list to be
   * passed to the path creation function.  (This assumes that we don't need
   * to look through multiple levels of subquery RTEs; if we ever do, we
   * could consider stuffing the list we generate here into sub-query RTE's
   * RelOptInfo, just like we do for partitioned rels, which would be used
   * when populating our parent rel with paths.  For the present, that
   * appears to be unnecessary.)
   */
  if (rel->part_scheme != NULL)
  {
    if (IS_SIMPLE_REL(rel))
      partitioned_rels = list_make1(rel->partitioned_child_rels);
    else if (IS_JOIN_REL(rel))
    {
      int     relid = -1;
      List     *partrels = NIL;

      /*
       * For a partitioned joinrel, concatenate the component rels'
       * partitioned_child_rels lists.
       */
      while ((relid = bms_next_member(rel->relids, relid)) >= 0)
      {
        RelOptInfo *component;

        Assert(relid >= 1 && relid < root->simple_rel_array_size);
        component = root->simple_rel_array[relid];
        Assert(component->part_scheme != NULL);
        Assert(list_length(component->partitioned_child_rels) >= 1);
        partrels =
          list_concat(partrels,
                list_copy(component->partitioned_child_rels));
      }

      partitioned_rels = list_make1(partrels);
    }

    Assert(list_length(partitioned_rels) >= 1);
  }

  /*
   * For every non-dummy child, remember the cheapest path.  Also, identify
   * all pathkeys (orderings) and parameterizations (required_outer sets)
   * available for the non-dummy member relations.
   */
  foreach(l, live_childrels)
  {
    RelOptInfo *childrel = lfirst(l);
    ListCell   *lcp;
    Path     *cheapest_partial_path = NULL;

    /*
     * For UNION ALLs with non-empty partitioned_child_rels, accumulate
     * the Lists of child relations.
     */
    if (rel->rtekind == RTE_SUBQUERY && childrel->partitioned_child_rels != NIL)
      partitioned_rels = lappend(partitioned_rels,
                     childrel->partitioned_child_rels);

    /*
     * If child has an unparameterized cheapest-total path, add that to
     * the unparameterized Append path we are constructing for the parent.
     * If not, there's no workable unparameterized path.
     *
     * With partitionwise aggregates, the child rel's pathlist may be
     * empty, so don't assume that a path exists here.
     */
    if (childrel->pathlist != NIL &&
      childrel->cheapest_total_path->param_info == NULL)
      accumulate_append_subpath(childrel->cheapest_total_path,
                    &subpaths, NULL);
    else
      subpaths_valid = false;

    /* Same idea, but for a partial plan. */
    if (childrel->partial_pathlist != NIL)
    {
      cheapest_partial_path = linitial(childrel->partial_pathlist);
      accumulate_append_subpath(cheapest_partial_path,
                    &partial_subpaths, NULL);
    }
    else
      partial_subpaths_valid = false;

    /*
     * Same idea, but for a parallel append mixing partial and non-partial
     * paths.
     */
    if (pa_subpaths_valid)
    {
      Path     *nppath = NULL;

      nppath =
        get_cheapest_parallel_safe_total_inner(childrel->pathlist);

      if (cheapest_partial_path == NULL && nppath == NULL)
      {
        /* Neither a partial nor a parallel-safe path?  Forget it. */
        pa_subpaths_valid = false;
      }
      else if (nppath == NULL ||
           (cheapest_partial_path != NULL &&
            cheapest_partial_path->total_cost < nppath->total_cost))
      {
        /* Partial path is cheaper or the only option. */
        Assert(cheapest_partial_path != NULL);
        accumulate_append_subpath(cheapest_partial_path,
                      &pa_partial_subpaths,
                      &pa_nonpartial_subpaths);

      }
      else
      {
        /*
         * Either we've got only a non-partial path, or we think that
         * a single backend can execute the best non-partial path
         * faster than all the parallel backends working together can
         * execute the best partial path.
         *
         * It might make sense to be more aggressive here.  Even if
         * the best non-partial path is more expensive than the best
         * partial path, it could still be better to choose the
         * non-partial path if there are several such paths that can
         * be given to different workers.  For now, we don't try to
         * figure that out.
         */
        accumulate_append_subpath(nppath,
                      &pa_nonpartial_subpaths,
                      NULL);
      }
    }

    /*
     * Collect lists of all the available path orderings and
     * parameterizations for all the children.  We use these as a
     * heuristic to indicate which sort orderings and parameterizations we
     * should build Append and MergeAppend paths for.
     */
    foreach(lcp, childrel->pathlist)
    {
      Path     *childpath = (Path *) lfirst(lcp);
      List     *childkeys = childpath->pathkeys;
      Relids    childouter = PATH_REQ_OUTER(childpath);

      /* Unsorted paths don't contribute to pathkey list */
      if (childkeys != NIL)
      {
        ListCell   *lpk;
        bool    found = false;

        /* Have we already seen this ordering? */
        foreach(lpk, all_child_pathkeys)
        {
          List     *existing_pathkeys = (List *) lfirst(lpk);

          if (compare_pathkeys(existing_pathkeys,
                     childkeys) == PATHKEYS_EQUAL)
          {
            found = true;
            break;
          }
        }
        if (!found)
        {
          /* No, so add it to all_child_pathkeys */
          all_child_pathkeys = lappend(all_child_pathkeys,
                         childkeys);
        }
      }

      /* Unparameterized paths don't contribute to param-set list */
      if (childouter)
      {
        ListCell   *lco;
        bool    found = false;

        /* Have we already seen this param set? */
        foreach(lco, all_child_outers)
        {
          Relids    existing_outers = (Relids) lfirst(lco);

          if (bms_equal(existing_outers, childouter))
          {
            found = true;
            break;
          }
        }
        if (!found)
        {
          /* No, so add it to all_child_outers */
          all_child_outers = lappend(all_child_outers,
                         childouter);
        }
      }
    }
  }

  /*
   * If we found unparameterized paths for all children, build an unordered,
   * unparameterized Append path for the rel.  (Note: this is correct even
   * if we have zero or one live subpath due to constraint exclusion.)
   */
  if (subpaths_valid)
    add_path(rel, (Path *) create_append_path(root, rel, subpaths, NIL,
                          NULL, 0, false,
                          partitioned_rels, -1));

  /*
   * Consider an append of unordered, unparameterized partial paths.  Make
   * it parallel-aware if possible.
   */
  if (partial_subpaths_valid)
  {
    AppendPath *appendpath;
    ListCell   *lc;
    int     parallel_workers = 0;

    /* Find the highest number of workers requested for any subpath. */
    foreach(lc, partial_subpaths)
    {
      Path     *path = lfirst(lc);

      parallel_workers = Max(parallel_workers, path->parallel_workers);
    }
    Assert(parallel_workers > 0);

    /*
     * If the use of parallel append is permitted, always request at least
     * log2(# of children) workers.  We assume it can be useful to have
     * extra workers in this case because they will be spread out across
     * the children.  The precise formula is just a guess, but we don't
     * want to end up with a radically different answer for a table with N
     * partitions vs. an unpartitioned table with the same data, so the
     * use of some kind of log-scaling here seems to make some sense.
     */
    if (enable_parallel_append)
    {
      parallel_workers = Max(parallel_workers,
                   fls(list_length(live_childrels)));
      parallel_workers = Min(parallel_workers,
                   max_parallel_workers_per_gather);
    }
    Assert(parallel_workers > 0);

    /* Generate a partial append path. */
    appendpath = create_append_path(root, rel, NIL, partial_subpaths,
                    NULL, parallel_workers,
                    enable_parallel_append,
                    partitioned_rels, -1);

    /*
     * Make sure any subsequent partial paths use the same row count
     * estimate.
     */
    partial_rows = appendpath->path.rows;

    /* Add the path. */
    add_partial_path(rel, (Path *) appendpath);
  }

  /*
   * Consider a parallel-aware append using a mix of partial and non-partial
   * paths.  (This only makes sense if there's at least one child which has
   * a non-partial path that is substantially cheaper than any partial path;
   * otherwise, we should use the append path added in the previous step.)
   */
  if (pa_subpaths_valid && pa_nonpartial_subpaths != NIL)
  {
    AppendPath *appendpath;
    ListCell   *lc;
    int     parallel_workers = 0;

    /*
     * Find the highest number of workers requested for any partial
     * subpath.
     */
    foreach(lc, pa_partial_subpaths)
    {
      Path     *path = lfirst(lc);

      parallel_workers = Max(parallel_workers, path->parallel_workers);
    }

    /*
     * Same formula here as above.  It's even more important in this
     * instance because the non-partial paths won't contribute anything to
     * the planned number of parallel workers.
     */
    parallel_workers = Max(parallel_workers,
                 fls(list_length(live_childrels)));
    parallel_workers = Min(parallel_workers,
                 max_parallel_workers_per_gather);
    Assert(parallel_workers > 0);

    appendpath = create_append_path(root, rel, pa_nonpartial_subpaths,
                    pa_partial_subpaths,
                    NULL, parallel_workers, true,
                    partitioned_rels, partial_rows);
    add_partial_path(rel, (Path *) appendpath);
  }

  /*
   * Also build unparameterized MergeAppend paths based on the collected
   * list of child pathkeys.
   */
  if (subpaths_valid)
    generate_mergeappend_paths(root, rel, live_childrels,
                   all_child_pathkeys,
                   partitioned_rels);

  /*
   * Build Append paths for each parameterization seen among the child rels.
   * (This may look pretty expensive, but in most cases of practical
   * interest, the child rels will expose mostly the same parameterizations,
   * so that not that many cases actually get considered here.)
   *
   * The Append node itself cannot enforce quals, so all qual checking must
   * be done in the child paths.  This means that to have a parameterized
   * Append path, we must have the exact same parameterization for each
   * child path; otherwise some children might be failing to check the
   * moved-down quals.  To make them match up, we can try to increase the
   * parameterization of lesser-parameterized paths.
   */
  foreach(l, all_child_outers)
  {
    Relids    required_outer = (Relids) lfirst(l);
    ListCell   *lcr;

    /* Select the child paths for an Append with this parameterization */
    subpaths = NIL;
    subpaths_valid = true;
    foreach(lcr, live_childrels)
    {
      RelOptInfo *childrel = (RelOptInfo *) lfirst(lcr);
      Path     *subpath;

      if (childrel->pathlist == NIL)
      {
        /* failed to make a suitable path for this child */
        subpaths_valid = false;
        break;
      }

      subpath = get_cheapest_parameterized_child_path(root,
                              childrel,
                              required_outer);
      if (subpath == NULL)
      {
        /* failed to make a suitable path for this child */
        subpaths_valid = false;
        break;
      }
      accumulate_append_subpath(subpath, &subpaths, NULL);
    }

    if (subpaths_valid)
      add_path(rel, (Path *)
           create_append_path(root, rel, subpaths, NIL,
                    required_outer, 0, false,
                    partitioned_rels, -1));
  }
}

/*
 * generate_mergeappend_paths
 *    Generate MergeAppend paths for an append relation
 *
 * Generate a path for each ordering (pathkey list) appearing in
 * all_child_pathkeys.
 *
 * We consider both cheapest-startup and cheapest-total cases, ie, for each
 * interesting ordering, collect all the cheapest startup subpaths and all the
 * cheapest total paths, and build a MergeAppend path for each case.
 *
 * We don't currently generate any parameterized MergeAppend paths.  While
 * it would not take much more code here to do so, it's very unclear that it
 * is worth the planning cycles to investigate such paths: there's little
 * use for an ordered path on the inside of a nestloop.  In fact, it's likely
 * that the current coding of add_path would reject such paths out of hand,
 * because add_path gives no credit for sort ordering of parameterized paths,
 * and a parameterized MergeAppend is going to be more expensive than the
 * corresponding parameterized Append path.  If we ever try harder to support
 * parameterized mergejoin plans, it might be worth adding support for
 * parameterized MergeAppends to feed such joins.  (See notes in
 * optimizer/README for why that might not ever happen, though.)
 */
static void
generate_mergeappend_paths(PlannerInfo *root, RelOptInfo *rel,
               List *live_childrels,
               List *all_child_pathkeys,
               List *partitioned_rels)
{
  ListCell   *lcp;

  foreach(lcp, all_child_pathkeys)
  {
    List     *pathkeys = (List *) lfirst(lcp);
    List     *startup_subpaths = NIL;
    List     *total_subpaths = NIL;
    bool    startup_neq_total = false;
    ListCell   *lcr;

    /* Select the child paths for this ordering... */
    foreach(lcr, live_childrels)
    {
      RelOptInfo *childrel = (RelOptInfo *) lfirst(lcr);
      Path     *cheapest_startup,
             *cheapest_total;

      /* Locate the right paths, if they are available. */
      cheapest_startup =
        get_cheapest_path_for_pathkeys(childrel->pathlist,
                         pathkeys,
                         NULL,
                         STARTUP_COST,
                         false);
      cheapest_total =
        get_cheapest_path_for_pathkeys(childrel->pathlist,
                         pathkeys,
                         NULL,
                         TOTAL_COST,
                         false);

      /*
       * If we can't find any paths with the right order just use the
       * cheapest-total path; we'll have to sort it later.
       */
      if (cheapest_startup == NULL || cheapest_total == NULL)
      {
        cheapest_startup = cheapest_total =
          childrel->cheapest_total_path;
        /* Assert we do have an unparameterized path for this child */
        Assert(cheapest_total->param_info == NULL);
      }

      /*
       * Notice whether we actually have different paths for the
       * "cheapest" and "total" cases; frequently there will be no point
       * in two create_merge_append_path() calls.
       */
      if (cheapest_startup != cheapest_total)
        startup_neq_total = true;

      accumulate_append_subpath(cheapest_startup,
                    &startup_subpaths, NULL);
      accumulate_append_subpath(cheapest_total,
                    &total_subpaths, NULL);
    }

    /* ... and build the MergeAppend paths */
    add_path(rel, (Path *) create_merge_append_path(root,
                            rel,
                            startup_subpaths,
                            pathkeys,
                            NULL,
                            partitioned_rels));
    if (startup_neq_total)
      add_path(rel, (Path *) create_merge_append_path(root,
                              rel,
                              total_subpaths,
                              pathkeys,
                              NULL,
                              partitioned_rels));
  }
}

/*
 * get_cheapest_parameterized_child_path
 *    Get cheapest path for this relation that has exactly the requested
 *    parameterization.
 *
 * Returns NULL if unable to create such a path.
 */
static Path *
get_cheapest_parameterized_child_path(PlannerInfo *root, RelOptInfo *rel,
                    Relids required_outer)
{
  Path     *cheapest;
  ListCell   *lc;

  /*
   * Look up the cheapest existing path with no more than the needed
   * parameterization.  If it has exactly the needed parameterization, we're
   * done.
   */
  cheapest = get_cheapest_path_for_pathkeys(rel->pathlist,
                        NIL,
                        required_outer,
                        TOTAL_COST,
                        false);
  Assert(cheapest != NULL);
  if (bms_equal(PATH_REQ_OUTER(cheapest), required_outer))
    return cheapest;

  /*
   * Otherwise, we can "reparameterize" an existing path to match the given
   * parameterization, which effectively means pushing down additional
   * joinquals to be checked within the path's scan.  However, some existing
   * paths might check the available joinquals already while others don't;
   * therefore, it's not clear which existing path will be cheapest after
   * reparameterization.  We have to go through them all and find out.
   */
  cheapest = NULL;
  foreach(lc, rel->pathlist)
  {
    Path     *path = (Path *) lfirst(lc);

    /* Can't use it if it needs more than requested parameterization */
    if (!bms_is_subset(PATH_REQ_OUTER(path), required_outer))
      continue;

    /*
     * Reparameterization can only increase the path's cost, so if it's
     * already more expensive than the current cheapest, forget it.
     */
    if (cheapest != NULL &&
      compare_path_costs(cheapest, path, TOTAL_COST) <= 0)
      continue;

    /* Reparameterize if needed, then recheck cost */
    if (!bms_equal(PATH_REQ_OUTER(path), required_outer))
    {
      path = reparameterize_path(root, path, required_outer, 1.0);
      if (path == NULL)
        continue;   /* failed to reparameterize this one */
      Assert(bms_equal(PATH_REQ_OUTER(path), required_outer));

      if (cheapest != NULL &&
        compare_path_costs(cheapest, path, TOTAL_COST) <= 0)
        continue;
    }

    /* We have a new best path */
    cheapest = path;
  }

  /* Return the best path, or NULL if we found no suitable candidate */
  return cheapest;
}

/*
 * accumulate_append_subpath
 *    Add a subpath to the list being built for an Append or MergeAppend.
 *
 * It's possible that the child is itself an Append or MergeAppend path, in
 * which case we can "cut out the middleman" and just add its child paths to
 * our own list.  (We don't try to do this earlier because we need to apply
 * both levels of transformation to the quals.)
 *
 * Note that if we omit a child MergeAppend in this way, we are effectively
 * omitting a sort step, which seems fine: if the parent is to be an Append,
 * its result would be unsorted anyway, while if the parent is to be a
 * MergeAppend, there's no point in a separate sort on a child.
 * its result would be unsorted anyway.
 *
 * Normally, either path is a partial path and subpaths is a list of partial
 * paths, or else path is a non-partial plan and subpaths is a list of those.
 * However, if path is a parallel-aware Append, then we add its partial path
 * children to subpaths and the rest to special_subpaths.  If the latter is
 * NULL, we don't flatten the path at all (unless it contains only partial
 * paths).
 */
static void
accumulate_append_subpath(Path *path, List **subpaths, List **special_subpaths)
{
  if (IsA(path, AppendPath))
  {
    AppendPath *apath = (AppendPath *) path;

    if (!apath->path.parallel_aware || apath->first_partial_path == 0)
    {
      /* list_copy is important here to avoid sharing list substructure */
      *subpaths = list_concat(*subpaths, list_copy(apath->subpaths));
      return;
    }
    else if (special_subpaths != NULL)
    {
      List     *new_special_subpaths;

      /* Split Parallel Append into partial and non-partial subpaths */
      *subpaths = list_concat(*subpaths,
                  list_copy_tail(apath->subpaths,
                           apath->first_partial_path));
      new_special_subpaths =
        list_truncate(list_copy(apath->subpaths),
                apath->first_partial_path);
      *special_subpaths = list_concat(*special_subpaths,
                      new_special_subpaths);
      return;
    }
  }
  else if (IsA(path, MergeAppendPath))
  {
    MergeAppendPath *mpath = (MergeAppendPath *) path;

    /* list_copy is important here to avoid sharing list substructure */
    *subpaths = list_concat(*subpaths, list_copy(mpath->subpaths));
    return;
  }

  *subpaths = lappend(*subpaths, path);
}

/*
 * set_dummy_rel_pathlist
 *    Build a dummy path for a relation that's been excluded by constraints
 *
 * Rather than inventing a special "dummy" path type, we represent this as an
 * AppendPath with no members (see also IS_DUMMY_PATH/IS_DUMMY_REL macros).
 *
 * This is exported because inheritance_planner() has need for it.
 */
void
set_dummy_rel_pathlist(RelOptInfo *rel)
{
  /* Set dummy size estimates --- we leave attr_widths[] as zeroes */
  rel->rows = 0;
  rel->reltarget->width = 0;

  /* Discard any pre-existing paths; no further need for them */
  rel->pathlist = NIL;
  rel->partial_pathlist = NIL;

  add_path(rel, (Path *) create_append_path(NULL, rel, NIL, NIL, NULL,
                        0, false, NIL, -1));

  /*
   * We set the cheapest path immediately, to ensure that IS_DUMMY_REL()
   * will recognize the relation as dummy if anyone asks.  This is redundant
   * when we're called from set_rel_size(), but not when called from
   * elsewhere, and doing it twice is harmless anyway.
   */
  set_cheapest(rel);
}

/* quick-and-dirty test to see if any joining is needed */
static bool
has_multiple_baserels(PlannerInfo *root)
{
  int     num_base_rels = 0;
  Index   rti;

  for (rti = 1; rti < root->simple_rel_array_size; rti++)
  {
    RelOptInfo *brel = root->simple_rel_array[rti];

    if (brel == NULL)
      continue;

    /* ignore RTEs that are "other rels" */
    if (brel->reloptkind == RELOPT_BASEREL)
      if (++num_base_rels > 1)
        return true;
  }
  return false;
}

/*
 * set_subquery_pathlist
 *    Generate SubqueryScan access paths for a subquery RTE
 *
 * We don't currently support generating parameterized paths for subqueries
 * by pushing join clauses down into them; it seems too expensive to re-plan
 * the subquery multiple times to consider different alternatives.
 * (XXX that could stand to be reconsidered, now that we use Paths.)
 * So the paths made here will be parameterized if the subquery contains
 * LATERAL references, otherwise not.  As long as that's true, there's no need
 * for a separate set_subquery_size phase: just make the paths right away.
 */
static void
set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
            Index rti, RangeTblEntry *rte)
{
  Query    *parse = root->parse;
  Query    *subquery = rte->subquery;
  Relids    required_outer;
  pushdown_safety_info safetyInfo;
  double    tuple_fraction;
  RelOptInfo *sub_final_rel;
  ListCell   *lc;

  /*
   * Must copy the Query so that planning doesn't mess up the RTE contents
   * (really really need to fix the planner to not scribble on its input,
   * someday ... but see remove_unused_subquery_outputs to start with).
   */
  subquery = copyObject(subquery);

  /*
   * If it's a LATERAL subquery, it might contain some Vars of the current
   * query level, requiring it to be treated as parameterized, even though
   * we don't support pushing down join quals into subqueries.
   */
  required_outer = rel->lateral_relids;

  /*
   * Zero out result area for subquery_is_pushdown_safe, so that it can set
   * flags as needed while recursing.  In particular, we need a workspace
   * for keeping track of unsafe-to-reference columns.  unsafeColumns[i]
   * will be set true if we find that output column i of the subquery is
   * unsafe to use in a pushed-down qual.
   */
  memset(&safetyInfo, 0, sizeof(safetyInfo));
  safetyInfo.unsafeColumns = (bool *)
    palloc0((list_length(subquery->targetList) + 1) * sizeof(bool));

  /*
   * If the subquery has the "security_barrier" flag, it means the subquery
   * originated from a view that must enforce row level security.  Then we
   * must not push down quals that contain leaky functions.  (Ideally this
   * would be checked inside subquery_is_pushdown_safe, but since we don't
   * currently pass the RTE to that function, we must do it here.)
   */
  safetyInfo.unsafeLeaky = rte->security_barrier;

  /*
   * If there are any restriction clauses that have been attached to the
   * subquery relation, consider pushing them down to become WHERE or HAVING
   * quals of the subquery itself.  This transformation is useful because it
   * may allow us to generate a better plan for the subquery than evaluating
   * all the subquery output rows and then filtering them.
   *
   * There are several cases where we cannot push down clauses. Restrictions
   * involving the subquery are checked by subquery_is_pushdown_safe().
   * Restrictions on individual clauses are checked by
   * qual_is_pushdown_safe().  Also, we don't want to push down
   * pseudoconstant clauses; better to have the gating node above the
   * subquery.
   *
   * Non-pushed-down clauses will get evaluated as qpquals of the
   * SubqueryScan node.
   *
   * XXX Are there any cases where we want to make a policy decision not to
   * push down a pushable qual, because it'd result in a worse plan?
   */
  if (rel->baserestrictinfo != NIL &&
    subquery_is_pushdown_safe(subquery, subquery, &safetyInfo))
  {
    /* OK to consider pushing down individual quals */
    List     *upperrestrictlist = NIL;
    ListCell   *l;

    foreach(l, rel->baserestrictinfo)
    {
      RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
      Node     *clause = (Node *) rinfo->clause;

      if (!rinfo->pseudoconstant &&
        qual_is_pushdown_safe(subquery, rti, clause, &safetyInfo))
      {
        /* Push it down */
        subquery_push_qual(subquery, rte, rti, clause);
      }
      else
      {
        /* Keep it in the upper query */
        upperrestrictlist = lappend(upperrestrictlist, rinfo);
      }
    }
    rel->baserestrictinfo = upperrestrictlist;
    /* We don't bother recomputing baserestrict_min_security */
  }

  pfree(safetyInfo.unsafeColumns);

  /*
   * The upper query might not use all the subquery's output columns; if
   * not, we can simplify.
   */
  remove_unused_subquery_outputs(subquery, rel);

  /*
   * We can safely pass the outer tuple_fraction down to the subquery if the
   * outer level has no joining, aggregation, or sorting to do. Otherwise
   * we'd better tell the subquery to plan for full retrieval. (XXX This
   * could probably be made more intelligent ...)
   */
  if (parse->hasAggs ||
    parse->groupClause ||
    parse->groupingSets ||
    parse->havingQual ||
    parse->distinctClause ||
    parse->sortClause ||
    has_multiple_baserels(root))
    tuple_fraction = 0.0;  /* default case */
  else
    tuple_fraction = root->tuple_fraction;

  /* plan_params should not be in use in current query level */
  Assert(root->plan_params == NIL);

  /* Generate a subroot and Paths for the subquery */
  rel->subroot = subquery_planner(root->glob, subquery,
                  root,
                  false, tuple_fraction);

  /* Isolate the params needed by this specific subplan */
  rel->subplan_params = root->plan_params;
  root->plan_params = NIL;

  /*
   * It's possible that constraint exclusion proved the subquery empty. If
   * so, it's desirable to produce an unadorned dummy path so that we will
   * recognize appropriate optimizations at this query level.
   */
  sub_final_rel = fetch_upper_rel(rel->subroot, UPPERREL_FINAL, NULL);

  if (IS_DUMMY_REL(sub_final_rel))
  {
    set_dummy_rel_pathlist(rel);
    return;
  }

  /*
   * Mark rel with estimated output rows, width, etc.  Note that we have to
   * do this before generating outer-query paths, else cost_subqueryscan is
   * not happy.
   */
  set_subquery_size_estimates(root, rel);

  /*
   * For each Path that subquery_planner produced, make a SubqueryScanPath
   * in the outer query.
   */
  foreach(lc, sub_final_rel->pathlist)
  {
    Path     *subpath = (Path *) lfirst(lc);
    List     *pathkeys;

    /* Convert subpath's pathkeys to outer representation */
    pathkeys = convert_subquery_pathkeys(root,
                       rel,
                       subpath->pathkeys,
                       make_tlist_from_pathtarget(subpath->pathtarget));

    /* Generate outer path using this subpath */
    add_path(rel, (Path *)
         create_subqueryscan_path(root, rel, subpath,
                      pathkeys, required_outer));
  }

  /* If outer rel allows parallelism, do same for partial paths. */
  if (rel->consider_parallel && bms_is_empty(required_outer))
  {
    /* If consider_parallel is false, there should be no partial paths. */
    Assert(sub_final_rel->consider_parallel ||
         sub_final_rel->partial_pathlist == NIL);

    /* Same for partial paths. */
    foreach(lc, sub_final_rel->partial_pathlist)
    {
      Path     *subpath = (Path *) lfirst(lc);
      List     *pathkeys;

      /* Convert subpath's pathkeys to outer representation */
      pathkeys = convert_subquery_pathkeys(root,
                         rel,
                         subpath->pathkeys,
                         make_tlist_from_pathtarget(subpath->pathtarget));

      /* Generate outer path using this subpath */
      add_partial_path(rel, (Path *)
               create_subqueryscan_path(root, rel, subpath,
                            pathkeys,
                            required_outer));
    }
  }
}

/*
 * set_function_pathlist
 *    Build the (single) access path for a function RTE
 */
static void
set_function_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
  Relids    required_outer;
  List     *pathkeys = NIL;

  /*
   * We don't support pushing join clauses into the quals of a function
   * scan, but it could still have required parameterization due to LATERAL
   * refs in the function expression.
   */
  required_outer = rel->lateral_relids;

  /*
   * The result is considered unordered unless ORDINALITY was used, in which
   * case it is ordered by the ordinal column (the last one).  See if we
   * care, by checking for uses of that Var in equivalence classes.
   */
  if (rte->funcordinality)
  {
    AttrNumber  ordattno = rel->max_attr;
    Var      *var = NULL;
    ListCell   *lc;

    /*
     * Is there a Var for it in rel's targetlist?  If not, the query did
     * not reference the ordinality column, or at least not in any way
     * that would be interesting for sorting.
     */
    foreach(lc, rel->reltarget->exprs)
    {
      Var      *node = (Var *) lfirst(lc);

      /* checking varno/varlevelsup is just paranoia */
      if (IsA(node, Var) &&
        node->varattno == ordattno &&
        node->varno == rel->relid &&
        node->varlevelsup == 0)
      {
        var = node;
        break;
      }
    }

    /*
     * Try to build pathkeys for this Var with int8 sorting.  We tell
     * build_expression_pathkey not to build any new equivalence class; if
     * the Var isn't already mentioned in some EC, it means that nothing
     * cares about the ordering.
     */
    if (var)
      pathkeys = build_expression_pathkey(root,
                        (Expr *) var,
                        NULL, /* below outer joins */
                        Int8LessOperator,
                        rel->relids,
                        false);
  }

  /* Generate appropriate path */
  add_path(rel, create_functionscan_path(root, rel,
                       pathkeys, required_outer));
}

/*
 * set_values_pathlist
 *    Build the (single) access path for a VALUES RTE
 */
static void
set_values_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
  Relids    required_outer;

  /*
   * We don't support pushing join clauses into the quals of a values scan,
   * but it could still have required parameterization due to LATERAL refs
   * in the values expressions.
   */
  required_outer = rel->lateral_relids;

  /* Generate appropriate path */
  add_path(rel, create_valuesscan_path(root, rel, required_outer));
}

/*
 * set_tablefunc_pathlist
 *    Build the (single) access path for a table func RTE
 */
static void
set_tablefunc_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
  Relids    required_outer;

  /*
   * We don't support pushing join clauses into the quals of a tablefunc
   * scan, but it could still have required parameterization due to LATERAL
   * refs in the function expression.
   */
  required_outer = rel->lateral_relids;

  /* Generate appropriate path */
  add_path(rel, create_tablefuncscan_path(root, rel,
                      required_outer));
}

/*
 * set_cte_pathlist
 *    Build the (single) access path for a non-self-reference CTE RTE
 *
 * There's no need for a separate set_cte_size phase, since we don't
 * support join-qual-parameterized paths for CTEs.
 */
static void
set_cte_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
  Plan     *cteplan;
  PlannerInfo *cteroot;
  Index   levelsup;
  int     ndx;
  ListCell   *lc;
  int     plan_id;
  Relids    required_outer;

  /*
   * Find the referenced CTE, and locate the plan previously made for it.
   */
  levelsup = rte->ctelevelsup;
  cteroot = root;
  while (levelsup-- > 0)
  {
    cteroot = cteroot->parent_root;
    if (!cteroot)     /* shouldn't happen */
      elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
  }

  /*
   * Note: cte_plan_ids can be shorter than cteList, if we are still working
   * on planning the CTEs (ie, this is a side-reference from another CTE).
   * So we mustn't use forboth here.
   */
  ndx = 0;
  foreach(lc, cteroot->parse->cteList)
  {
    CommonTableExpr *cte = (CommonTableExpr *) lfirst(lc);

    if (strcmp(cte->ctename, rte->ctename) == 0)
      break;
    ndx++;
  }
  if (lc == NULL)       /* shouldn't happen */
    elog(ERROR, "could not find CTE \"%s\"", rte->ctename);
  if (ndx >= list_length(cteroot->cte_plan_ids))
    elog(ERROR, "could not find plan for CTE \"%s\"", rte->ctename);
  plan_id = list_nth_int(cteroot->cte_plan_ids, ndx);
  Assert(plan_id > 0);
  cteplan = (Plan *) list_nth(root->glob->subplans, plan_id - 1);

  /* Mark rel with estimated output rows, width, etc */
  set_cte_size_estimates(root, rel, cteplan->plan_rows);

  /*
   * We don't support pushing join clauses into the quals of a CTE scan, but
   * it could still have required parameterization due to LATERAL refs in
   * its tlist.
   */
  required_outer = rel->lateral_relids;

  /* Generate appropriate path */
  add_path(rel, create_ctescan_path(root, rel, required_outer));
}

/*
 * set_namedtuplestore_pathlist
 *    Build the (single) access path for a named tuplestore RTE
 *
 * There's no need for a separate set_namedtuplestore_size phase, since we
 * don't support join-qual-parameterized paths for tuplestores.
 */
static void
set_namedtuplestore_pathlist(PlannerInfo *root, RelOptInfo *rel,
               RangeTblEntry *rte)
{
  Relids    required_outer;

  /* Mark rel with estimated output rows, width, etc */
  set_namedtuplestore_size_estimates(root, rel);

  /*
   * We don't support pushing join clauses into the quals of a tuplestore
   * scan, but it could still have required parameterization due to LATERAL
   * refs in its tlist.
   */
  required_outer = rel->lateral_relids;

  /* Generate appropriate path */
  add_path(rel, create_namedtuplestorescan_path(root, rel, required_outer));

  /* Select cheapest path (pretty easy in this case...) */
  set_cheapest(rel);
}

/*
 * set_worktable_pathlist
 *    Build the (single) access path for a self-reference CTE RTE
 *
 * There's no need for a separate set_worktable_size phase, since we don't
 * support join-qual-parameterized paths for CTEs.
 */
static void
set_worktable_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
{
  Path     *ctepath;
  PlannerInfo *cteroot;
  Index   levelsup;
  Relids    required_outer;

  /*
   * We need to find the non-recursive term's path, which is in the plan
   * level that's processing the recursive UNION, which is one level *below*
   * where the CTE comes from.
   */
  levelsup = rte->ctelevelsup;
  if (levelsup == 0)     /* shouldn't happen */
    elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
  levelsup--;
  cteroot = root;
  while (levelsup-- > 0)
  {
    cteroot = cteroot->parent_root;
    if (!cteroot)     /* shouldn't happen */
      elog(ERROR, "bad levelsup for CTE \"%s\"", rte->ctename);
  }
  ctepath = cteroot->non_recursive_path;
  if (!ctepath)       /* shouldn't happen */
    elog(ERROR, "could not find path for CTE \"%s\"", rte->ctename);

  /* Mark rel with estimated output rows, width, etc */
  set_cte_size_estimates(root, rel, ctepath->rows);

  /*
   * We don't support pushing join clauses into the quals of a worktable
   * scan, but it could still have required parameterization due to LATERAL
   * refs in its tlist.  (I'm not sure this is actually possible given the
   * restrictions on recursive references, but it's easy enough to support.)
   */
  required_outer = rel->lateral_relids;

  /* Generate appropriate path */
  add_path(rel, create_worktablescan_path(root, rel, required_outer));
}

/*
 * generate_gather_paths
 *    Generate parallel access paths for a relation by pushing a Gather or
 *    Gather Merge on top of a partial path.
 *
 * This must not be called until after we're done creating all partial paths
 * for the specified relation.  (Otherwise, add_partial_path might delete a
 * path that some GatherPath or GatherMergePath has a reference to.)
 *
 * If we're generating paths for a scan or join relation, override_rows will
 * be false, and we'll just use the relation's size estimate.  When we're
 * being called for a partially-grouped path, though, we need to override
 * the rowcount estimate.  (It's not clear that the particular value we're
 * using here is actually best, but the underlying rel has no estimate so
 * we must do something.)
 */
void
generate_gather_paths(PlannerInfo *root, RelOptInfo *rel, bool override_rows)
{
  Path     *cheapest_partial_path;
  Path     *simple_gather_path;
  ListCell   *lc;
  double    rows;
  double     *rowsp = NULL;

  /* If there are no partial paths, there's nothing to do here. */
  if (rel->partial_pathlist == NIL)
    return;

  /* Should we override the rel's rowcount estimate? */
  if (override_rows)
    rowsp = &rows;

  /*
   * The output of Gather is always unsorted, so there's only one partial
   * path of interest: the cheapest one.  That will be the one at the front
   * of partial_pathlist because of the way add_partial_path works.
   */
  cheapest_partial_path = linitial(rel->partial_pathlist);
  rows =
    cheapest_partial_path->rows * cheapest_partial_path->parallel_workers;
  simple_gather_path = (Path *)
    create_gather_path(root, rel, cheapest_partial_path, rel->reltarget,
               NULL, rowsp);
  add_path(rel, simple_gather_path);

  /*
   * For each useful ordering, we can consider an order-preserving Gather
   * Merge.
   */
  foreach(lc, rel->partial_pathlist)
  {
    Path     *subpath = (Path *) lfirst(lc);
    GatherMergePath *path;

    if (subpath->pathkeys == NIL)
      continue;

    rows = subpath->rows * subpath->parallel_workers;
    path = create_gather_merge_path(root, rel, subpath, rel->reltarget,
                    subpath->pathkeys, NULL, rowsp);
    add_path(rel, &path->path);
  }
}

/*
 * make_rel_from_joinlist
 *    Build access paths using a "joinlist" to guide the join path search.
 *
 * See comments for deconstruct_jointree() for definition of the joinlist
 * data structure.
 */
static RelOptInfo *
make_rel_from_joinlist(PlannerInfo *root, List *joinlist)
{
  int     levels_needed;
  List     *initial_rels;
  ListCell   *jl;

  /*
   * Count the number of child joinlist nodes.  This is the depth of the
   * dynamic-programming algorithm we must employ to consider all ways of
   * joining the child nodes.
   */
  levels_needed = list_length(joinlist);

  if (levels_needed <= 0)
    return NULL;     /* nothing to do? */

  /*
   * Construct a list of rels corresponding to the child joinlist nodes.
   * This may contain both base rels and rels constructed according to
   * sub-joinlists.
   */
  initial_rels = NIL;
  foreach(jl, joinlist)
  {
    Node     *jlnode = (Node *) lfirst(jl);
    RelOptInfo *thisrel;

    if (IsA(jlnode, RangeTblRef))
    {
      int     varno = ((RangeTblRef *) jlnode)->rtindex;

      thisrel = find_base_rel(root, varno);
    }
    else if (IsA(jlnode, List))
    {
      /* Recurse to handle subproblem */
      thisrel = make_rel_from_joinlist(root, (List *) jlnode);
    }
    else
    {
      elog(ERROR, "unrecognized joinlist node type: %d",
         (int) nodeTag(jlnode));
      thisrel = NULL;   /* keep compiler quiet */
    }

    initial_rels = lappend(initial_rels, thisrel);
  }

  if (levels_needed == 1)
  {
    /*
     * Single joinlist node, so we're done.
     */
    return (RelOptInfo *) linitial(initial_rels);
  }
  else
  {
    /*
     * Consider the different orders in which we could join the rels,
     * using a plugin, GEQO, or the regular join search code.
     *
     * We put the initial_rels list into a PlannerInfo field because
     * has_legal_joinclause() needs to look at it (ugly :-().
     */
    root->initial_rels = initial_rels;

    if (join_search_hook)
      return (*join_search_hook) (root, levels_needed, initial_rels);
    else if (enable_geqo && levels_needed >= geqo_threshold)
      return geqo(root, levels_needed, initial_rels);
    else
      return standard_join_search(root, levels_needed, initial_rels);
  }
}

/*
 * standard_join_search
 *    Find possible joinpaths for a query by successively finding ways
 *    to join component relations into join relations.
 *
 * 'levels_needed' is the number of iterations needed, ie, the number of
 *    independent jointree items in the query.  This is > 1.
 *
 * 'initial_rels' is a list of RelOptInfo nodes for each independent
 *    jointree item.  These are the components to be joined together.
 *    Note that levels_needed == list_length(initial_rels).
 *
 * Returns the final level of join relations, i.e., the relation that is
 * the result of joining all the original relations together.
 * At least one implementation path must be provided for this relation and
 * all required sub-relations.
 *
 * To support loadable plugins that modify planner behavior by changing the
 * join searching algorithm, we provide a hook variable that lets a plugin
 * replace or supplement this function.  Any such hook must return the same
 * final join relation as the standard code would, but it might have a
 * different set of implementation paths attached, and only the sub-joinrels
 * needed for these paths need have been instantiated.
 *
 * Note to plugin authors: the functions invoked during standard_join_search()
 * modify root->join_rel_list and root->join_rel_hash.  If you want to do more
 * than one join-order search, you'll probably need to save and restore the
 * original states of those data structures.  See geqo_eval() for an example.
 */
RelOptInfo *
standard_join_search(PlannerInfo *root, int levels_needed, List *initial_rels)
{
  int     lev;
  RelOptInfo *rel;

  /*
   * This function cannot be invoked recursively within any one planning
   * problem, so join_rel_level[] can't be in use already.
   */
  Assert(root->join_rel_level == NULL);

  /*
   * We employ a simple "dynamic programming" algorithm: we first find all
   * ways to build joins of two jointree items, then all ways to build joins
   * of three items (from two-item joins and single items), then four-item
   * joins, and so on until we have considered all ways to join all the
   * items into one rel.
   *
   * root->join_rel_level[j] is a list of all the j-item rels.  Initially we
   * set root->join_rel_level[1] to represent all the single-jointree-item
   * relations.
   */
  root->join_rel_level = (List **) palloc0((levels_needed + 1) * sizeof(List *));

  root->join_rel_level[1] = initial_rels;

  for (lev = 2; lev <= levels_needed; lev++)
  {
    ListCell   *lc;

    /*
     * Determine all possible pairs of relations to be joined at this
     * level, and build paths for making each one from every available
     * pair of lower-level relations.
     */
    join_search_one_level(root, lev);

    /*
     * Run generate_partitionwise_join_paths() and generate_gather_paths()
     * for each just-processed joinrel.  We could not do this earlier
     * because both regular and partial paths can get added to a
     * particular joinrel at multiple times within join_search_one_level.
     *
     * After that, we're done creating paths for the joinrel, so run
     * set_cheapest().
     */
    foreach(lc, root->join_rel_level[lev])
    {
      rel = (RelOptInfo *) lfirst(lc);

      /* Create paths for partitionwise joins. */
      generate_partitionwise_join_paths(root, rel);

      /*
       * Except for the topmost scan/join rel, consider gathering
       * partial paths.  We'll do the same for the topmost scan/join rel
       * once we know the final targetlist (see grouping_planner).
       */
      if (lev < levels_needed)
        generate_gather_paths(root, rel, false);

      /* Find and save the cheapest paths for this rel */
      set_cheapest(rel);

#ifdef OPTIMIZER_DEBUG
      debug_print_rel(root, rel);
#endif
    }
  }

  /*
   * We should have a single rel at the final level.
   */
  if (root->join_rel_level[levels_needed] == NIL)
    elog(ERROR, "failed to build any %d-way joins", levels_needed);
  Assert(list_length(root->join_rel_level[levels_needed]) == 1);

  rel = (RelOptInfo *) linitial(root->join_rel_level[levels_needed]);

  root->join_rel_level = NULL;

  return rel;
}

/*****************************************************************************
 *      PUSHING QUALS DOWN INTO SUBQUERIES
 *****************************************************************************/

/*
 * subquery_is_pushdown_safe - is a subquery safe for pushing down quals?
 *
 * subquery is the particular component query being checked.  topquery
 * is the top component of a set-operations tree (the same Query if no
 * set-op is involved).
 *
 * Conditions checked here:
 *
 * 1. If the subquery has a LIMIT clause, we must not push down any quals,
 * since that could change the set of rows returned.
 *
 * 2. If the subquery contains EXCEPT or EXCEPT ALL set ops we cannot push
 * quals into it, because that could change the results.
 *
 * 3. If the subquery uses DISTINCT, we cannot push volatile quals into it.
 * This is because upper-level quals should semantically be evaluated only
 * once per distinct row, not once per original row, and if the qual is
 * volatile then extra evaluations could change the results.  (This issue
 * does not apply to other forms of aggregation such as GROUP BY, because
 * when those are present we push into HAVING not WHERE, so that the quals
 * are still applied after aggregation.)
 *
 * 4. If the subquery contains window functions, we cannot push volatile quals
 * into it.  The issue here is a bit different from DISTINCT: a volatile qual
 * might succeed for some rows of a window partition and fail for others,
 * thereby changing the partition contents and thus the window functions'
 * results for rows that remain.
 *
 * 5. If the subquery contains any set-returning functions in its targetlist,
 * we cannot push volatile quals into it.  That would push them below the SRFs
 * and thereby change the number of times they are evaluated.  Also, a
 * volatile qual could succeed for some SRF output rows and fail for others,
 * a behavior that cannot occur if it's evaluated before SRF expansion.
 *
 * In addition, we make several checks on the subquery's output columns to see
 * if it is safe to reference them in pushed-down quals.  If output column k
 * is found to be unsafe to reference, we set safetyInfo->unsafeColumns[k]
 * to true, but we don't reject the subquery overall since column k might not
 * be referenced by some/all quals.  The unsafeColumns[] array will be
 * consulted later by qual_is_pushdown_safe().  It's better to do it this way
 * than to make the checks directly in qual_is_pushdown_safe(), because when
 * the subquery involves set operations we have to check the output
 * expressions in each arm of the set op.
 *
 * Note: pushing quals into a DISTINCT subquery is theoretically dubious:
 * we're effectively assuming that the quals cannot distinguish values that
 * the DISTINCT's equality operator sees as equal, yet there are many
 * counterexamples to that assumption.  However use of such a qual with a
 * DISTINCT subquery would be unsafe anyway, since there's no guarantee which
 * "equal" value will be chosen as the output value by the DISTINCT operation.
 * So we don't worry too much about that.  Another objection is that if the
 * qual is expensive to evaluate, running it for each original row might cost
 * more than we save by eliminating rows before the DISTINCT step.  But it
 * would be very hard to estimate that at this stage, and in practice pushdown
 * seldom seems to make things worse, so we ignore that problem too.
 *
 * Note: likewise, pushing quals into a subquery with window functions is a
 * bit dubious: the quals might remove some rows of a window partition while
 * leaving others, causing changes in the window functions' results for the
 * surviving rows.  We insist that such a qual reference only partitioning
 * columns, but again that only protects us if the qual does not distinguish
 * values that the partitioning equality operator sees as equal.  The risks
 * here are perhaps larger than for DISTINCT, since no de-duplication of rows
 * occurs and thus there is no theoretical problem with such a qual.  But
 * we'll do this anyway because the potential performance benefits are very
 * large, and we've seen no field complaints about the longstanding comparable
 * behavior with DISTINCT.
 */
static bool
subquery_is_pushdown_safe(Query *subquery, Query *topquery,
              pushdown_safety_info *safetyInfo)
{
  SetOperationStmt *topop;

  /* Check point 1 */
  if (subquery->limitOffset != NULL || subquery->limitCount != NULL)
    return false;

  /* Check points 3, 4, and 5 */
  if (subquery->distinctClause ||
    subquery->hasWindowFuncs ||
    subquery->hasTargetSRFs)
    safetyInfo->unsafeVolatile = true;

  /*
   * If we're at a leaf query, check for unsafe expressions in its target
   * list, and mark any unsafe ones in unsafeColumns[].  (Non-leaf nodes in
   * setop trees have only simple Vars in their tlists, so no need to check
   * them.)
   */
  if (subquery->setOperations == NULL)
    check_output_expressions(subquery, safetyInfo);

  /* Are we at top level, or looking at a setop component? */
  if (subquery == topquery)
  {
    /* Top level, so check any component queries */
    if (subquery->setOperations != NULL)
      if (!recurse_pushdown_safe(subquery->setOperations, topquery,
                     safetyInfo))
        return false;
  }
  else
  {
    /* Setop component must not have more components (too weird) */
    if (subquery->setOperations != NULL)
      return false;
    /* Check whether setop component output types match top level */
    topop = castNode(SetOperationStmt, topquery->setOperations);
    Assert(topop);
    compare_tlist_datatypes(subquery->targetList,
                topop->colTypes,
                safetyInfo);
  }
  return true;
}

/*
 * Helper routine to recurse through setOperations tree
 */
static bool
recurse_pushdown_safe(Node *setOp, Query *topquery,
            pushdown_safety_info *safetyInfo)
{
  if (IsA(setOp, RangeTblRef))
  {
    RangeTblRef *rtr = (RangeTblRef *) setOp;
    RangeTblEntry *rte = rt_fetch(rtr->rtindex, topquery->rtable);
    Query    *subquery = rte->subquery;

    Assert(subquery != NULL);
    return subquery_is_pushdown_safe(subquery, topquery, safetyInfo);
  }
  else if (IsA(setOp, SetOperationStmt))
  {
    SetOperationStmt *op = (SetOperationStmt *) setOp;

    /* EXCEPT is no good (point 2 for subquery_is_pushdown_safe) */
    if (op->op == SETOP_EXCEPT)
      return false;
    /* Else recurse */
    if (!recurse_pushdown_safe(op->larg, topquery, safetyInfo))
      return false;
    if (!recurse_pushdown_safe(op->rarg, topquery, safetyInfo))
      return false;
  }
  else
  {
    elog(ERROR, "unrecognized node type: %d",
       (int) nodeTag(setOp));
  }
  return true;
}

/*
 * check_output_expressions - check subquery's output expressions for safety
 *
 * There are several cases in which it's unsafe to push down an upper-level
 * qual if it references a particular output column of a subquery.  We check
 * each output column of the subquery and set unsafeColumns[k] to true if
 * that column is unsafe for a pushed-down qual to reference.  The conditions
 * checked here are:
 *
 * 1. We must not push down any quals that refer to subselect outputs that
 * return sets, else we'd introduce functions-returning-sets into the
 * subquery's WHERE/HAVING quals.
 *
 * 2. We must not push down any quals that refer to subselect outputs that
 * contain volatile functions, for fear of introducing strange results due
 * to multiple evaluation of a volatile function.
 *
 * 3. If the subquery uses DISTINCT ON, we must not push down any quals that
 * refer to non-DISTINCT output columns, because that could change the set
 * of rows returned.  (This condition is vacuous for DISTINCT, because then
 * there are no non-DISTINCT output columns, so we needn't check.  Note that
 * subquery_is_pushdown_safe already reported that we can't use volatile
 * quals if there's DISTINCT or DISTINCT ON.)
 *
 * 4. If the subquery has any window functions, we must not push down quals
 * that reference any output columns that are not listed in all the subquery's
 * window PARTITION BY clauses.  We can push down quals that use only
 * partitioning columns because they should succeed or fail identically for
 * every row of any one window partition, and totally excluding some
 * partitions will not change a window function's results for remaining
 * partitions.  (Again, this also requires nonvolatile quals, but
 * subquery_is_pushdown_safe handles that.)
 */
static void
check_output_expressions(Query *subquery, pushdown_safety_info *safetyInfo)
{
  ListCell   *lc;

  foreach(lc, subquery->targetList)
  {
    TargetEntry *tle = (TargetEntry *) lfirst(lc);

    if (tle->resjunk)
      continue;     /* ignore resjunk columns */

    /* We need not check further if output col is already known unsafe */
    if (safetyInfo->unsafeColumns[tle->resno])
      continue;

    /* Functions returning sets are unsafe (point 1) */
    if (subquery->hasTargetSRFs &&
      expression_returns_set((Node *) tle->expr))
    {
      safetyInfo->unsafeColumns[tle->resno] = true;
      continue;
    }

    /* Volatile functions are unsafe (point 2) */
    if (contain_volatile_functions((Node *) tle->expr))
    {
      safetyInfo->unsafeColumns[tle->resno] = true;
      continue;
    }

    /* If subquery uses DISTINCT ON, check point 3 */
    if (subquery->hasDistinctOn &&
      !targetIsInSortList(tle, InvalidOid, subquery->distinctClause))
    {
      /* non-DISTINCT column, so mark it unsafe */
      safetyInfo->unsafeColumns[tle->resno] = true;
      continue;
    }

    /* If subquery uses window functions, check point 4 */
    if (subquery->hasWindowFuncs &&
      !targetIsInAllPartitionLists(tle, subquery))
    {
      /* not present in all PARTITION BY clauses, so mark it unsafe */
      safetyInfo->unsafeColumns[tle->resno] = true;
      continue;
    }
  }
}

/*
 * For subqueries using UNION/UNION ALL/INTERSECT/INTERSECT ALL, we can
 * push quals into each component query, but the quals can only reference
 * subquery columns that suffer no type coercions in the set operation.
 * Otherwise there are possible semantic gotchas.  So, we check the
 * component queries to see if any of them have output types different from
 * the top-level setop outputs.  unsafeColumns[k] is set true if column k
 * has different type in any component.
 *
 * We don't have to care about typmods here: the only allowed difference
 * between set-op input and output typmods is input is a specific typmod
 * and output is -1, and that does not require a coercion.
 *
 * tlist is a subquery tlist.
 * colTypes is an OID list of the top-level setop's output column types.
 * safetyInfo->unsafeColumns[] is the result array.
 */
static void
compare_tlist_datatypes(List *tlist, List *colTypes,
            pushdown_safety_info *safetyInfo)
{
  ListCell   *l;
  ListCell   *colType = list_head(colTypes);

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

    if (tle->resjunk)
      continue;     /* ignore resjunk columns */
    if (colType == NULL)
      elog(ERROR, "wrong number of tlist entries");
    if (exprType((Node *) tle->expr) != lfirst_oid(colType))
      safetyInfo->unsafeColumns[tle->resno] = true;
    colType = lnext(colType);
  }
  if (colType != NULL)
    elog(ERROR, "wrong number of tlist entries");
}

/*
 * targetIsInAllPartitionLists
 *    True if the TargetEntry is listed in the PARTITION BY clause
 *    of every window defined in the query.
 *
 * It would be safe to ignore windows not actually used by any window
 * function, but it's not easy to get that info at this stage; and it's
 * unlikely to be useful to spend any extra cycles getting it, since
 * unreferenced window definitions are probably infrequent in practice.
 */
static bool
targetIsInAllPartitionLists(TargetEntry *tle, Query *query)
{
  ListCell   *lc;

  foreach(lc, query->windowClause)
  {
    WindowClause *wc = (WindowClause *) lfirst(lc);

    if (!targetIsInSortList(tle, InvalidOid, wc->partitionClause))
      return false;
  }
  return true;
}

/*
 * qual_is_pushdown_safe - is a particular qual safe to push down?
 *
 * qual is a restriction clause applying to the given subquery (whose RTE
 * has index rti in the parent query).
 *
 * Conditions checked here:
 *
 * 1. The qual must not contain any SubPlans (mainly because I'm not sure
 * it will work correctly: SubLinks will already have been transformed into
 * SubPlans in the qual, but not in the subquery).  Note that SubLinks that
 * transform to initplans are safe, and will be accepted here because what
 * we'll see in the qual is just a Param referencing the initplan output.
 *
 * 2. If unsafeVolatile is set, the qual must not contain any volatile
 * functions.
 *
 * 3. If unsafeLeaky is set, the qual must not contain any leaky functions
 * that are passed Var nodes, and therefore might reveal values from the
 * subquery as side effects.
 *
 * 4. The qual must not refer to the whole-row output of the subquery
 * (since there is no easy way to name that within the subquery itself).
 *
 * 5. The qual must not refer to any subquery output columns that were
 * found to be unsafe to reference by subquery_is_pushdown_safe().
 */
static bool
qual_is_pushdown_safe(Query *subquery, Index rti, Node *qual,
            pushdown_safety_info *safetyInfo)
{
  bool    safe = true;
  List     *vars;
  ListCell   *vl;

  /* Refuse subselects (point 1) */
  if (contain_subplans(qual))
    return false;

  /* Refuse volatile quals if we found they'd be unsafe (point 2) */
  if (safetyInfo->unsafeVolatile &&
    contain_volatile_functions(qual))
    return false;

  /* Refuse leaky quals if told to (point 3) */
  if (safetyInfo->unsafeLeaky &&
    contain_leaked_vars(qual))
    return false;

  /*
   * It would be unsafe to push down window function calls, but at least for
   * the moment we could never see any in a qual anyhow.  (The same applies
   * to aggregates, which we check for in pull_var_clause below.)
   */
  Assert(!contain_window_function(qual));

  /*
   * Examine all Vars used in clause; since it's a restriction clause, all
   * such Vars must refer to subselect output columns.
   */
  vars = pull_var_clause(qual, PVC_INCLUDE_PLACEHOLDERS);
  foreach(vl, vars)
  {
    Var      *var = (Var *) lfirst(vl);

    /*
     * XXX Punt if we find any PlaceHolderVars in the restriction clause.
     * It's not clear whether a PHV could safely be pushed down, and even
     * less clear whether such a situation could arise in any cases of
     * practical interest anyway.  So for the moment, just refuse to push
     * down.
     */
    if (!IsA(var, Var))
    {
      safe = false;
      break;
    }

    Assert(var->varno == rti);
    Assert(var->varattno >= 0);

    /* Check point 4 */
    if (var->varattno == 0)
    {
      safe = false;
      break;
    }

    /* Check point 5 */
    if (safetyInfo->unsafeColumns[var->varattno])
    {
      safe = false;
      break;
    }
  }

  list_free(vars);

  return safe;
}

/*
 * subquery_push_qual - push down a qual that we have determined is safe
 */
static void
subquery_push_qual(Query *subquery, RangeTblEntry *rte, Index rti, Node *qual)
{
  if (subquery->setOperations != NULL)
  {
    /* Recurse to push it separately to each component query */
    recurse_push_qual(subquery->setOperations, subquery,
              rte, rti, qual);
  }
  else
  {
    /*
     * We need to replace Vars in the qual (which must refer to outputs of
     * the subquery) with copies of the subquery's targetlist expressions.
     * Note that at this point, any uplevel Vars in the qual should have
     * been replaced with Params, so they need no work.
     *
     * This step also ensures that when we are pushing into a setop tree,
     * each component query gets its own copy of the qual.
     */
    qual = ReplaceVarsFromTargetList(qual, rti, 0, rte,
                     subquery->targetList,
                     REPLACEVARS_REPORT_ERROR, 0,
                     &subquery->hasSubLinks);

    /*
     * Now attach the qual to the proper place: normally WHERE, but if the
     * subquery uses grouping or aggregation, put it in HAVING (since the
     * qual really refers to the group-result rows).
     */
    if (subquery->hasAggs || subquery->groupClause || subquery->groupingSets || subquery->havingQual)
      subquery->havingQual = make_and_qual(subquery->havingQual, qual);
    else
      subquery->jointree->quals =
        make_and_qual(subquery->jointree->quals, qual);

    /*
     * We need not change the subquery's hasAggs or hasSubLinks flags,
     * since we can't be pushing down any aggregates that weren't there
     * before, and we don't push down subselects at all.
     */
  }
}

/*
 * Helper routine to recurse through setOperations tree
 */
static void
recurse_push_qual(Node *setOp, Query *topquery,
          RangeTblEntry *rte, Index rti, Node *qual)
{
  if (IsA(setOp, RangeTblRef))
  {
    RangeTblRef *rtr = (RangeTblRef *) setOp;
    RangeTblEntry *subrte = rt_fetch(rtr->rtindex, topquery->rtable);
    Query    *subquery = subrte->subquery;

    Assert(subquery != NULL);
    subquery_push_qual(subquery, rte, rti, qual);
  }
  else if (IsA(setOp, SetOperationStmt))
  {
    SetOperationStmt *op = (SetOperationStmt *) setOp;

    recurse_push_qual(op->larg, topquery, rte, rti, qual);
    recurse_push_qual(op->rarg, topquery, rte, rti, qual);
  }
  else
  {
    elog(ERROR, "unrecognized node type: %d",
       (int) nodeTag(setOp));
  }
}

/*****************************************************************************
 *      SIMPLIFYING SUBQUERY TARGETLISTS
 *****************************************************************************/

/*
 * remove_unused_subquery_outputs
 *    Remove subquery targetlist items we don't need
 *
 * It's possible, even likely, that the upper query does not read all the
 * output columns of the subquery.  We can remove any such outputs that are
 * not needed by the subquery itself (e.g., as sort/group columns) and do not
 * affect semantics otherwise (e.g., volatile functions can't be removed).
 * This is useful not only because we might be able to remove expensive-to-
 * compute expressions, but because deletion of output columns might allow
 * optimizations such as join removal to occur within the subquery.
 *
 * To avoid affecting column numbering in the targetlist, we don't physically
 * remove unused tlist entries, but rather replace their expressions with NULL
 * constants.  This is implemented by modifying subquery->targetList.
 */
static void
remove_unused_subquery_outputs(Query *subquery, RelOptInfo *rel)
{
  Bitmapset  *attrs_used = NULL;
  ListCell   *lc;

  /*
   * Do nothing if subquery has UNION/INTERSECT/EXCEPT: in principle we
   * could update all the child SELECTs' tlists, but it seems not worth the
   * trouble presently.
   */
  if (subquery->setOperations)
    return;

  /*
   * If subquery has regular DISTINCT (not DISTINCT ON), we're wasting our
   * time: all its output columns must be used in the distinctClause.
   */
  if (subquery->distinctClause && !subquery->hasDistinctOn)
    return;

  /*
   * Collect a bitmap of all the output column numbers used by the upper
   * query.
   *
   * Add all the attributes needed for joins or final output.  Note: we must
   * look at rel's targetlist, not the attr_needed data, because attr_needed
   * isn't computed for inheritance child rels, cf set_append_rel_size().
   * (XXX might be worth changing that sometime.)
   */
  pull_varattnos((Node *) rel->reltarget->exprs, rel->relid, &attrs_used);

  /* Add all the attributes used by un-pushed-down restriction clauses. */
  foreach(lc, rel->baserestrictinfo)
  {
    RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);

    pull_varattnos((Node *) rinfo->clause, rel->relid, &attrs_used);
  }

  /*
   * If there's a whole-row reference to the subquery, we can't remove
   * anything.
   */
  if (bms_is_member(0 - FirstLowInvalidHeapAttributeNumber, attrs_used))
    return;

  /*
   * Run through the tlist and zap entries we don't need.  It's okay to
   * modify the tlist items in-place because set_subquery_pathlist made a
   * copy of the subquery.
   */
  foreach(lc, subquery->targetList)
  {
    TargetEntry *tle = (TargetEntry *) lfirst(lc);
    Node     *texpr = (Node *) tle->expr;

    /*
     * If it has a sortgroupref number, it's used in some sort/group
     * clause so we'd better not remove it.  Also, don't remove any
     * resjunk columns, since their reason for being has nothing to do
     * with anybody reading the subquery's output.  (It's likely that
     * resjunk columns in a sub-SELECT would always have ressortgroupref
     * set, but even if they don't, it seems imprudent to remove them.)
     */
    if (tle->ressortgroupref || tle->resjunk)
      continue;

    /*
     * If it's used by the upper query, we can't remove it.
     */
    if (bms_is_member(tle->resno - FirstLowInvalidHeapAttributeNumber,
              attrs_used))
      continue;

    /*
     * If it contains a set-returning function, we can't remove it since
     * that could change the number of rows returned by the subquery.
     */
    if (subquery->hasTargetSRFs &&
      expression_returns_set(texpr))
      continue;

    /*
     * If it contains volatile functions, we daren't remove it for fear
     * that the user is expecting their side-effects to happen.
     */
    if (contain_volatile_functions(texpr))
      continue;

    /*
     * OK, we don't need it.  Replace the expression with a NULL constant.
     * Preserve the exposed type of the expression, in case something
     * looks at the rowtype of the subquery's result.
     */
    tle->expr = (Expr *) makeNullConst(exprType(texpr),
                       exprTypmod(texpr),
                       exprCollation(texpr));
  }
}

/*
 * create_partial_bitmap_paths
 *    Build partial bitmap heap path for the relation
 */
void
create_partial_bitmap_paths(PlannerInfo *root, RelOptInfo *rel,
              Path *bitmapqual)
{
  int     parallel_workers;
  double    pages_fetched;

  /* Compute heap pages for bitmap heap scan */
  pages_fetched = compute_bitmap_pages(root, rel, bitmapqual, 1.0,
                     NULL, NULL);

  parallel_workers = compute_parallel_worker(rel, pages_fetched, -1,
                         max_parallel_workers_per_gather);

  if (parallel_workers <= 0)
    return;

  add_partial_path(rel, (Path *) create_bitmap_heap_path(root, rel,
                               bitmapqual, rel->lateral_relids, 1.0, parallel_workers));
}

/*
 * Compute the number of parallel workers that should be used to scan a
 * relation.  We compute the parallel workers based on the size of the heap to
 * be scanned and the size of the index to be scanned, then choose a minimum
 * of those.
 *
 * "heap_pages" is the number of pages from the table that we expect to scan, or
 * -1 if we don't expect to scan any.
 *
 * "index_pages" is the number of pages from the index that we expect to scan, or
 * -1 if we don't expect to scan any.
 *
 * "max_workers" is caller's limit on the number of workers.  This typically
 * comes from a GUC.
 */
int
compute_parallel_worker(RelOptInfo *rel, double heap_pages, double index_pages,
            int max_workers)
{
  int     parallel_workers = 0;

  /*
   * If the user has set the parallel_workers reloption, use that; otherwise
   * select a default number of workers.
   */
  if (rel->rel_parallel_workers != -1)
    parallel_workers = rel->rel_parallel_workers;
  else
  {
    /*
     * If the number of pages being scanned is insufficient to justify a
     * parallel scan, just return zero ... unless it's an inheritance
     * child. In that case, we want to generate a parallel path here
     * anyway.  It might not be worthwhile just for this relation, but
     * when combined with all of its inheritance siblings it may well pay
     * off.
     */
    if (rel->reloptkind == RELOPT_BASEREL &&
      ((heap_pages >= 0 && heap_pages < min_parallel_table_scan_size) ||
       (index_pages >= 0 && index_pages < min_parallel_index_scan_size)))
      return 0;

    if (heap_pages >= 0)
    {
      int     heap_parallel_threshold;
      int     heap_parallel_workers = 1;

      /*
       * Select the number of workers based on the log of the size of
       * the relation.  This probably needs to be a good deal more
       * sophisticated, but we need something here for now.  Note that
       * the upper limit of the min_parallel_table_scan_size GUC is
       * chosen to prevent overflow here.
       */
      heap_parallel_threshold = Max(min_parallel_table_scan_size, 1);
      while (heap_pages >= (BlockNumber) (heap_parallel_threshold * 3))
      {
        heap_parallel_workers++;
        heap_parallel_threshold *= 3;
        if (heap_parallel_threshold > INT_MAX / 3)
          break;   /* avoid overflow */
      }

      parallel_workers = heap_parallel_workers;
    }

    if (index_pages >= 0)
    {
      int     index_parallel_workers = 1;
      int     index_parallel_threshold;

      /* same calculation as for heap_pages above */
      index_parallel_threshold = Max(min_parallel_index_scan_size, 1);
      while (index_pages >= (BlockNumber) (index_parallel_threshold * 3))
      {
        index_parallel_workers++;
        index_parallel_threshold *= 3;
        if (index_parallel_threshold > INT_MAX / 3)
          break;   /* avoid overflow */
      }

      if (parallel_workers > 0)
        parallel_workers = Min(parallel_workers, index_parallel_workers);
      else
        parallel_workers = index_parallel_workers;
    }
  }

  /* In no case use more than caller supplied maximum number of workers */
  parallel_workers = Min(parallel_workers, max_workers);

  return parallel_workers;
}

/*
 * generate_partitionwise_join_paths
 *    Create paths representing partitionwise join for given partitioned
 *    join relation.
 *
 * This must not be called until after we are done adding paths for all
 * child-joins. Otherwise, add_path might delete a path to which some path
 * generated here has a reference.
 */
void
generate_partitionwise_join_paths(PlannerInfo *root, RelOptInfo *rel)
{
  List     *live_children = NIL;
  int     cnt_parts;
  int     num_parts;
  RelOptInfo **part_rels;

  /* Handle only join relations here. */
  if (!IS_JOIN_REL(rel))
    return;

  /* We've nothing to do if the relation is not partitioned. */
  if (!IS_PARTITIONED_REL(rel))
    return;

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

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

  num_parts = rel->nparts;
  part_rels = rel->part_rels;

  /* Collect non-dummy child-joins. */
  for (cnt_parts = 0; cnt_parts < num_parts; cnt_parts++)
  {
    RelOptInfo *child_rel = part_rels[cnt_parts];

    Assert(child_rel != NULL);

    /* Add partitionwise join paths for partitioned child-joins. */
    generate_partitionwise_join_paths(root, child_rel);

    /* Dummy children will not be scanned, so ignore those. */
    if (IS_DUMMY_REL(child_rel))
      continue;

    set_cheapest(child_rel);

#ifdef OPTIMIZER_DEBUG
    debug_print_rel(root, child_rel);
#endif

    live_children = lappend(live_children, child_rel);
  }

  /* If all child-joins are dummy, parent join is also dummy. */
  if (!live_children)
  {
    mark_dummy_rel(rel);
    return;
  }

  /* Build additional paths for this rel from child-join paths. */
  add_paths_to_append_rel(root, rel, live_children);
  list_free(live_children);
}


/*****************************************************************************
 *      DEBUG SUPPORT
 *****************************************************************************/

#ifdef OPTIMIZER_DEBUG

static void
print_relids(PlannerInfo *root, Relids relids)
{
  int     x;
  bool    first = true;

  x = -1;
  while ((x = bms_next_member(relids, x)) >= 0)
  {
    if (!first)
      printf(" ");
    if (x < root->simple_rel_array_size &&
      root->simple_rte_array[x])
      printf("%s", root->simple_rte_array[x]->eref->aliasname);
    else
      printf("%d", x);
    first = false;
  }
}

static void
print_restrictclauses(PlannerInfo *root, List *clauses)
{
  ListCell   *l;

  foreach(l, clauses)
  {
    RestrictInfo *c = lfirst(l);

    print_expr((Node *) c->clause, root->parse->rtable);
    if (lnext(l))
      printf(", ");
  }
}

static void
print_path(PlannerInfo *root, Path *path, int indent)
{
  const char *ptype;
  bool    join = false;
  Path     *subpath = NULL;
  int     i;

  switch (nodeTag(path))
  {
    case T_Path:
      switch (path->pathtype)
      {
        case T_SeqScan:
          ptype = "SeqScan";
          break;
        case T_SampleScan:
          ptype = "SampleScan";
          break;
        case T_SubqueryScan:
          ptype = "SubqueryScan";
          break;
        case T_FunctionScan:
          ptype = "FunctionScan";
          break;
        case T_TableFuncScan:
          ptype = "TableFuncScan";
          break;
        case T_ValuesScan:
          ptype = "ValuesScan";
          break;
        case T_CteScan:
          ptype = "CteScan";
          break;
        case T_WorkTableScan:
          ptype = "WorkTableScan";
          break;
        default:
          ptype = "???Path";
          break;
      }
      break;
    case T_IndexPath:
      ptype = "IdxScan";
      break;
    case T_BitmapHeapPath:
      ptype = "BitmapHeapScan";
      break;
    case T_BitmapAndPath:
      ptype = "BitmapAndPath";
      break;
    case T_BitmapOrPath:
      ptype = "BitmapOrPath";
      break;
    case T_TidPath:
      ptype = "TidScan";
      break;
    case T_SubqueryScanPath:
      ptype = "SubqueryScanScan";
      break;
    case T_ForeignPath:
      ptype = "ForeignScan";
      break;
    case T_CustomPath:
      ptype = "CustomScan";
      break;
    case T_NestPath:
      ptype = "NestLoop";
      join = true;
      break;
    case T_MergePath:
      ptype = "MergeJoin";
      join = true;
      break;
    case T_HashPath:
      ptype = "HashJoin";
      join = true;
      break;
    case T_AppendPath:
      ptype = "Append";
      break;
    case T_MergeAppendPath:
      ptype = "MergeAppend";
      break;
    case T_ResultPath:
      ptype = "Result";
      break;
    case T_MaterialPath:
      ptype = "Material";
      subpath = ((MaterialPath *) path)->subpath;
      break;
    case T_UniquePath:
      ptype = "Unique";
      subpath = ((UniquePath *) path)->subpath;
      break;
    case T_GatherPath:
      ptype = "Gather";
      subpath = ((GatherPath *) path)->subpath;
      break;
    case T_GatherMergePath:
      ptype = "GatherMerge";
      subpath = ((GatherMergePath *) path)->subpath;
      break;
    case T_ProjectionPath:
      ptype = "Projection";
      subpath = ((ProjectionPath *) path)->subpath;
      break;
    case T_ProjectSetPath:
      ptype = "ProjectSet";
      subpath = ((ProjectSetPath *) path)->subpath;
      break;
    case T_SortPath:
      ptype = "Sort";
      subpath = ((SortPath *) path)->subpath;
      break;
    case T_GroupPath:
      ptype = "Group";
      subpath = ((GroupPath *) path)->subpath;
      break;
    case T_UpperUniquePath:
      ptype = "UpperUnique";
      subpath = ((UpperUniquePath *) path)->subpath;
      break;
    case T_AggPath:
      ptype = "Agg";
      subpath = ((AggPath *) path)->subpath;
      break;
    case T_GroupingSetsPath:
      ptype = "GroupingSets";
      subpath = ((GroupingSetsPath *) path)->subpath;
      break;
    case T_MinMaxAggPath:
      ptype = "MinMaxAgg";
      break;
    case T_WindowAggPath:
      ptype = "WindowAgg";
      subpath = ((WindowAggPath *) path)->subpath;
      break;
    case T_SetOpPath:
      ptype = "SetOp";
      subpath = ((SetOpPath *) path)->subpath;
      break;
    case T_RecursiveUnionPath:
      ptype = "RecursiveUnion";
      break;
    case T_LockRowsPath:
      ptype = "LockRows";
      subpath = ((LockRowsPath *) path)->subpath;
      break;
    case T_ModifyTablePath:
      ptype = "ModifyTable";
      break;
    case T_LimitPath:
      ptype = "Limit";
      subpath = ((LimitPath *) path)->subpath;
      break;
    default:
      ptype = "???Path";
      break;
  }

  for (i = 0; i < indent; i++)
    printf("\t");
  printf("%s", ptype);

  if (path->parent)
  {
    printf("(");
    print_relids(root, path->parent->relids);
    printf(")");
  }
  if (path->param_info)
  {
    printf(" required_outer (");
    print_relids(root, path->param_info->ppi_req_outer);
    printf(")");
  }
  printf(" rows=%.0f cost=%.2f..%.2f\n",
       path->rows, path->startup_cost, path->total_cost);

  if (path->pathkeys)
  {
    for (i = 0; i < indent; i++)
      printf("\t");
    printf("  pathkeys: ");
    print_pathkeys(path->pathkeys, root->parse->rtable);
  }

  if (join)
  {
    JoinPath   *jp = (JoinPath *) path;

    for (i = 0; i < indent; i++)
      printf("\t");
    printf("  clauses: ");
    print_restrictclauses(root, jp->joinrestrictinfo);
    printf("\n");

    if (IsA(path, MergePath))
    {
      MergePath  *mp = (MergePath *) path;

      for (i = 0; i < indent; i++)
        printf("\t");
      printf("  sortouter=%d sortinner=%d materializeinner=%d\n",
           ((mp->outersortkeys) ? 1 : 0),
           ((mp->innersortkeys) ? 1 : 0),
           ((mp->materialize_inner) ? 1 : 0));
    }

    print_path(root, jp->outerjoinpath, indent + 1);
    print_path(root, jp->innerjoinpath, indent + 1);
  }

  if (subpath)
    print_path(root, subpath, indent + 1);
}

void
debug_print_rel(PlannerInfo *root, RelOptInfo *rel)
{
  ListCell   *l;

  printf("RELOPTINFO (");
  print_relids(root, rel->relids);
  printf("): rows=%.0f width=%d\n", rel->rows, rel->reltarget->width);

  if (rel->baserestrictinfo)
  {
    printf("\tbaserestrictinfo: ");
    print_restrictclauses(root, rel->baserestrictinfo);
    printf("\n");
  }

  if (rel->joininfo)
  {
    printf("\tjoininfo: ");
    print_restrictclauses(root, rel->joininfo);
    printf("\n");
  }

  printf("\tpath list:\n");
  foreach(l, rel->pathlist)
    print_path(root, lfirst(l), 1);
  if (rel->cheapest_parameterized_paths)
  {
    printf("\n\tcheapest parameterized paths:\n");
    foreach(l, rel->cheapest_parameterized_paths)
      print_path(root, lfirst(l), 1);
  }
  if (rel->cheapest_startup_path)
  {
    printf("\n\tcheapest startup path:\n");
    print_path(root, rel->cheapest_startup_path, 1);
  }
  if (rel->cheapest_total_path)
  {
    printf("\n\tcheapest total path:\n");
    print_path(root, rel->cheapest_total_path, 1);
  }
  printf("\n");
  fflush(stdout);
}

#endif              /* OPTIMIZER_DEBUG */

YugabyteDB (2.13.0.0-b42, bfc6a6643e7399ac8a0e81d06a3ee6d6571b33ab)

Coverage Report

Created: 2022-03-09 17:30