relnode.c

Go to the documentation of this file.

/*-------------------------------------------------------------------------
 *
 * relnode.c
 *    Relation-node lookup/construction routines
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/optimizer/util/relnode.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include <limits.h>
 
#include "access/nbtree.h"
#include "catalog/pg_constraint.h"
#include "miscadmin.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/appendinfo.h"
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/inherit.h"
#include "optimizer/optimizer.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/placeholder.h"
#include "optimizer/plancat.h"
#include "optimizer/planner.h"
#include "optimizer/restrictinfo.h"
#include "optimizer/tlist.h"
#include "parser/parse_oper.h"
#include "parser/parse_relation.h"
#include "rewrite/rewriteManip.h"
#include "utils/hsearch.h"
#include "utils/lsyscache.h"
#include "utils/selfuncs.h"
#include "utils/typcache.h"
 
 
typedef struct JoinHashEntry
{
    Relids      join_relids;    /* hash key --- MUST BE FIRST */
    RelOptInfo *join_rel;
} JoinHashEntry;
 
/* Hook for plugins to get control during joinrel setup */
joinrel_setup_hook_type joinrel_setup_hook = NULL;
 
static void build_joinrel_tlist(PlannerInfo *root, RelOptInfo *joinrel,
                                RelOptInfo *input_rel,
                                SpecialJoinInfo *sjinfo,
                                List *pushed_down_joins,
                                bool can_null);
static List *build_joinrel_restrictlist(PlannerInfo *root,
                                        RelOptInfo *joinrel,
                                        RelOptInfo *outer_rel,
                                        RelOptInfo *inner_rel,
                                        SpecialJoinInfo *sjinfo);
static void build_joinrel_joinlist(RelOptInfo *joinrel,
                                   RelOptInfo *outer_rel,
                                   RelOptInfo *inner_rel);
static List *subbuild_joinrel_restrictlist(PlannerInfo *root,
                                           RelOptInfo *joinrel,
                                           RelOptInfo *input_rel,
                                           Relids both_input_relids,
                                           List *new_restrictlist);
static List *subbuild_joinrel_joinlist(RelOptInfo *joinrel,
                                       List *joininfo_list,
                                       List *new_joininfo);
static void set_foreign_rel_properties(RelOptInfo *joinrel,
                                       RelOptInfo *outer_rel, RelOptInfo *inner_rel);
static void add_join_rel(PlannerInfo *root, RelOptInfo *joinrel);
static void build_joinrel_partition_info(PlannerInfo *root,
                                         RelOptInfo *joinrel,
                                         RelOptInfo *outer_rel, RelOptInfo *inner_rel,
                                         SpecialJoinInfo *sjinfo,
                                         List *restrictlist);
static bool have_partkey_equi_join(PlannerInfo *root, RelOptInfo *joinrel,
                                   RelOptInfo *rel1, RelOptInfo *rel2,
                                   JoinType jointype, List *restrictlist);
static int  match_expr_to_partition_keys(Expr *expr, RelOptInfo *rel,
                                         bool strict_op);
static void set_joinrel_partition_key_exprs(RelOptInfo *joinrel,
                                            RelOptInfo *outer_rel, RelOptInfo *inner_rel,
                                            JoinType jointype);
static void build_child_join_reltarget(PlannerInfo *root,
                                       RelOptInfo *parentrel,
                                       RelOptInfo *childrel,
                                       int nappinfos,
                                       AppendRelInfo **appinfos);
static bool eager_aggregation_possible_for_relation(PlannerInfo *root,
                                                    RelOptInfo *rel);
static bool init_grouping_targets(PlannerInfo *root, RelOptInfo *rel,
                                  PathTarget *target, PathTarget *agg_input,
                                  List **group_clauses, List **group_exprs);
static bool is_var_in_aggref_only(PlannerInfo *root, Var *var);
static bool is_var_needed_by_join(PlannerInfo *root, Var *var, RelOptInfo *rel);
static Index get_expression_sortgroupref(PlannerInfo *root, Expr *expr);
 
 
/*
 * setup_simple_rel_arrays
 *    Prepare the arrays we use for quickly accessing base relations
 *    and AppendRelInfos.
 */
void
setup_simple_rel_arrays(PlannerInfo *root)
{
    int         size;
    Index       rti;
    ListCell   *lc;
 
    /* Arrays are accessed using RT indexes (1..N) */
    size = list_length(root->parse->rtable) + 1;
    root->simple_rel_array_size = size;
 
    /*
     * simple_rel_array is initialized to all NULLs, since no RelOptInfos
     * exist yet.  It'll be filled by later calls to build_simple_rel().
     */
    root->simple_rel_array = (RelOptInfo **)
        palloc0_array(RelOptInfo *, size);
 
    /* simple_rte_array is an array equivalent of the rtable list */
    root->simple_rte_array = (RangeTblEntry **)
        palloc0_array(RangeTblEntry *, size);
    rti = 1;
    foreach(lc, root->parse->rtable)
    {
        RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc);
 
        root->simple_rte_array[rti++] = rte;
    }
 
    /* append_rel_array is not needed if there are no AppendRelInfos */
    if (root->append_rel_list == NIL)
    {
        root->append_rel_array = NULL;
        return;
    }
 
    root->append_rel_array = (AppendRelInfo **)
        palloc0_array(AppendRelInfo *, size);
 
    /*
     * append_rel_array is filled with any already-existing AppendRelInfos,
     * which currently could only come from UNION ALL flattening.  We might
     * add more later during inheritance expansion, but it's the
     * responsibility of the expansion code to update the array properly.
     */
    foreach(lc, root->append_rel_list)
    {
        AppendRelInfo *appinfo = lfirst_node(AppendRelInfo, lc);
        int         child_relid = appinfo->child_relid;
 
        /* Sanity check */
        Assert(child_relid < size);
 
        if (root->append_rel_array[child_relid])
            elog(ERROR, "child relation already exists");
 
        root->append_rel_array[child_relid] = appinfo;
    }
}
 
/*
 * expand_planner_arrays
 *      Expand the PlannerInfo's per-RTE arrays by add_size members
 *      and initialize the newly added entries to NULLs
 *
 * Note: this causes the append_rel_array to become allocated even if
 * it was not before.  This is okay for current uses, because we only call
 * this when adding child relations, which always have AppendRelInfos.
 */
void
expand_planner_arrays(PlannerInfo *root, int add_size)
{
    int         new_size;
 
    Assert(add_size > 0);
 
    new_size = root->simple_rel_array_size + add_size;
 
    root->simple_rel_array =
        repalloc0_array(root->simple_rel_array, RelOptInfo *, root->simple_rel_array_size, new_size);
 
    root->simple_rte_array =
        repalloc0_array(root->simple_rte_array, RangeTblEntry *, root->simple_rel_array_size, new_size);
 
    if (root->append_rel_array)
        root->append_rel_array =
            repalloc0_array(root->append_rel_array, AppendRelInfo *, root->simple_rel_array_size, new_size);
    else
        root->append_rel_array =
            palloc0_array(AppendRelInfo *, new_size);
 
    root->simple_rel_array_size = new_size;
}
 
/*
 * build_simple_rel
 *    Construct a new RelOptInfo for a base relation or 'other' relation.
 */
RelOptInfo *
build_simple_rel(PlannerInfo *root, int relid, RelOptInfo *parent)
{
    RelOptInfo *rel;
    RangeTblEntry *rte;
 
    /* Rel should not exist already */
    Assert(relid > 0 && relid < root->simple_rel_array_size);
    if (root->simple_rel_array[relid] != NULL)
        elog(ERROR, "rel %d already exists", relid);
 
    /* Fetch RTE for relation */
    rte = root->simple_rte_array[relid];
    Assert(rte != NULL);
 
    rel = makeNode(RelOptInfo);
    rel->reloptkind = parent ? RELOPT_OTHER_MEMBER_REL : RELOPT_BASEREL;
    rel->relids = bms_make_singleton(relid);
    rel->rows = 0;
    /* cheap startup cost is interesting iff not all tuples to be retrieved */
    rel->consider_startup = (root->tuple_fraction > 0);
    rel->consider_param_startup = false;    /* might get changed later */
    rel->consider_parallel = false; /* might get changed later */
    rel->pgs_mask = root->glob->default_pgs_mask;
    rel->reltarget = create_empty_pathtarget();
    rel->pathlist = NIL;
    rel->ppilist = NIL;
    rel->partial_pathlist = NIL;
    rel->cheapest_startup_path = NULL;
    rel->cheapest_total_path = NULL;
    rel->cheapest_parameterized_paths = NIL;
    rel->relid = relid;
    rel->rtekind = rte->rtekind;
    /* min_attr, max_attr, attr_needed, attr_widths are set below */
    rel->notnullattnums = NULL;
    rel->lateral_vars = NIL;
    rel->indexlist = NIL;
    rel->statlist = NIL;
    rel->pages = 0;
    rel->tuples = 0;
    rel->allvisfrac = 0;
    rel->eclass_indexes = NULL;
    rel->subroot = NULL;
    rel->subplan_params = NIL;
    rel->rel_parallel_workers = -1; /* set up in get_relation_info */
    rel->amflags = 0;
    rel->serverid = InvalidOid;
    if (rte->rtekind == RTE_RELATION)
    {
        Assert(parent == NULL ||
               parent->rtekind == RTE_RELATION ||
               parent->rtekind == RTE_SUBQUERY);
 
        /*
         * For any RELATION rte, we need a userid with which to check
         * permission access. Baserels simply use their own
         * RTEPermissionInfo's checkAsUser.
         *
         * For otherrels normally there's no RTEPermissionInfo, so we use the
         * parent's, which normally has one. The exceptional case is that the
         * parent is a subquery, in which case the otherrel will have its own.
         */
        if (rel->reloptkind == RELOPT_BASEREL ||
            (rel->reloptkind == RELOPT_OTHER_MEMBER_REL &&
             parent->rtekind == RTE_SUBQUERY))
        {
            RTEPermissionInfo *perminfo;
 
            perminfo = getRTEPermissionInfo(root->parse->rteperminfos, rte);
            rel->userid = perminfo->checkAsUser;
        }
        else
            rel->userid = parent->userid;
    }
    else
        rel->userid = InvalidOid;
    rel->useridiscurrent = false;
    rel->fdwroutine = NULL;
    rel->fdw_private = NULL;
    rel->unique_for_rels = NIL;
    rel->non_unique_for_rels = NIL;
    rel->unique_rel = NULL;
    rel->unique_pathkeys = NIL;
    rel->unique_groupclause = NIL;
    rel->baserestrictinfo = NIL;
    rel->baserestrictcost.startup = 0;
    rel->baserestrictcost.per_tuple = 0;
    rel->baserestrict_min_security = UINT_MAX;
    rel->joininfo = NIL;
    rel->has_eclass_joins = false;
    rel->consider_partitionwise_join = false;   /* might get changed later */
    rel->agg_info = NULL;
    rel->grouped_rel = NULL;
    rel->part_scheme = NULL;
    rel->nparts = -1;
    rel->boundinfo = NULL;
    rel->partbounds_merged = false;
    rel->partition_qual = NIL;
    rel->part_rels = NULL;
    rel->live_parts = NULL;
    rel->all_partrels = NULL;
    rel->partexprs = NULL;
    rel->nullable_partexprs = NULL;
 
    /*
     * Pass assorted information down the inheritance hierarchy.
     */
    if (parent)
    {
        /* We keep back-links to immediate parent and topmost parent. */
        rel->parent = parent;
        rel->top_parent = parent->top_parent ? parent->top_parent : parent;
        rel->top_parent_relids = rel->top_parent->relids;
 
        /*
         * A child rel is below the same outer joins as its parent.  (We
         * presume this info was already calculated for the parent.)
         */
        rel->nulling_relids = parent->nulling_relids;
 
        /*
         * Also propagate lateral-reference information from appendrel parent
         * rels to their child rels.  We intentionally give each child rel the
         * same minimum parameterization, even though it's quite possible that
         * some don't reference all the lateral rels.  This is because any
         * append path for the parent will have to have the same
         * parameterization for every child anyway, and there's no value in
         * forcing extra reparameterize_path() calls.  Similarly, a lateral
         * reference to the parent prevents use of otherwise-movable join rels
         * for each child.
         *
         * It's possible for child rels to have their own children, in which
         * case the topmost parent's lateral info propagates all the way down.
         */
        rel->direct_lateral_relids = parent->direct_lateral_relids;
        rel->lateral_relids = parent->lateral_relids;
        rel->lateral_referencers = parent->lateral_referencers;
    }
    else
    {
        rel->parent = NULL;
        rel->top_parent = NULL;
        rel->top_parent_relids = NULL;
        rel->nulling_relids = NULL;
        rel->direct_lateral_relids = NULL;
        rel->lateral_relids = NULL;
        rel->lateral_referencers = NULL;
    }
 
    /* Check type of rtable entry */
    switch (rte->rtekind)
    {
        case RTE_RELATION:
            /* Table --- retrieve statistics from the system catalogs */
            get_relation_info(root, rte->relid, rte->inh, rel);
            break;
        case RTE_SUBQUERY:
        case RTE_FUNCTION:
        case RTE_TABLEFUNC:
        case RTE_VALUES:
        case RTE_CTE:
        case RTE_NAMEDTUPLESTORE:
 
            /*
             * Subquery, function, tablefunc, values list, CTE, or ENR --- set
             * up attr range and arrays
             *
             * Note: 0 is included in range to support whole-row Vars
             */
            rel->min_attr = 0;
            rel->max_attr = list_length(rte->eref->colnames);
            rel->attr_needed = (Relids *)
                palloc0_array(Relids, rel->max_attr - rel->min_attr + 1);
            rel->attr_widths = (int32 *)
                palloc0_array(int32, rel->max_attr - rel->min_attr + 1);
            break;
        case RTE_RESULT:
            /* RTE_RESULT has no columns, nor could it have whole-row Var */
            rel->min_attr = 0;
            rel->max_attr = -1;
            rel->attr_needed = NULL;
            rel->attr_widths = NULL;
            break;
        default:
            elog(ERROR, "unrecognized RTE kind: %d",
                 (int) rte->rtekind);
            break;
    }
 
    /*
     * We must apply the partially filled in RelOptInfo before calling
     * apply_child_basequals due to some transformations within that function
     * which require the RelOptInfo to be available in the simple_rel_array.
     */
    root->simple_rel_array[relid] = rel;
 
    /*
     * Apply the parent's quals to the child, with appropriate substitution of
     * variables.  If the resulting clause is constant-FALSE or NULL after
     * applying transformations, apply_child_basequals returns false to
     * indicate that scanning this relation won't yield any rows.  In this
     * case, we mark the child as dummy right away.  (We must do this
     * immediately so that pruning works correctly when recursing in
     * expand_partitioned_rtentry.)
     */
    if (parent)
    {
        AppendRelInfo *appinfo = root->append_rel_array[relid];
 
        Assert(appinfo != NULL);
        if (!apply_child_basequals(root, parent, rel, rte, appinfo))
        {
            /*
             * Restriction clause reduced to constant FALSE or NULL.  Mark as
             * dummy so we won't scan this relation.
             */
            mark_dummy_rel(rel);
        }
    }
 
    return rel;
}
 
/*
 * build_simple_grouped_rel
 *    Construct a new RelOptInfo representing a grouped version of the input
 *    simple relation.
 */
RelOptInfo *
build_simple_grouped_rel(PlannerInfo *root, RelOptInfo *rel)
{
    RelOptInfo *grouped_rel;
    RelAggInfo *agg_info;
 
    /*
     * We should have available aggregate expressions and grouping
     * expressions, otherwise we cannot reach here.
     */
    Assert(root->agg_clause_list != NIL);
    Assert(root->group_expr_list != NIL);
 
    /* nothing to do for dummy rel */
    if (IS_DUMMY_REL(rel))
        return NULL;
 
    /*
     * Prepare the information needed to create grouped paths for this simple
     * relation.
     */
    agg_info = create_rel_agg_info(root, rel, true);
    if (agg_info == NULL)
        return NULL;
 
    /*
     * If grouped paths for the given simple relation are not considered
     * useful, skip building the grouped relation.
     */
    if (!agg_info->agg_useful)
        return NULL;
 
    /* Track the set of relids at which partial aggregation is applied */
    agg_info->apply_agg_at = bms_copy(rel->relids);
 
    /* build the grouped relation */
    grouped_rel = build_grouped_rel(root, rel);
    grouped_rel->reltarget = agg_info->target;
    grouped_rel->rows = agg_info->grouped_rows;
    grouped_rel->agg_info = agg_info;
 
    rel->grouped_rel = grouped_rel;
 
    return grouped_rel;
}
 
/*
 * build_grouped_rel
 *    Build a grouped relation by flat copying the input relation and resetting
 *    the necessary fields.
 */
RelOptInfo *
build_grouped_rel(PlannerInfo *root, RelOptInfo *rel)
{
    RelOptInfo *grouped_rel;
 
    grouped_rel = makeNode(RelOptInfo);
    memcpy(grouped_rel, rel, sizeof(RelOptInfo));
 
    /*
     * clear path info
     */
    grouped_rel->pathlist = NIL;
    grouped_rel->ppilist = NIL;
    grouped_rel->partial_pathlist = NIL;
    grouped_rel->cheapest_startup_path = NULL;
    grouped_rel->cheapest_total_path = NULL;
    grouped_rel->cheapest_parameterized_paths = NIL;
 
    /*
     * clear partition info
     */
    grouped_rel->part_scheme = NULL;
    grouped_rel->nparts = -1;
    grouped_rel->boundinfo = NULL;
    grouped_rel->partbounds_merged = false;
    grouped_rel->partition_qual = NIL;
    grouped_rel->part_rels = NULL;
    grouped_rel->live_parts = NULL;
    grouped_rel->all_partrels = NULL;
    grouped_rel->partexprs = NULL;
    grouped_rel->nullable_partexprs = NULL;
    grouped_rel->consider_partitionwise_join = false;
 
    /*
     * clear size estimates
     */
    grouped_rel->rows = 0;
 
    return grouped_rel;
}
 
/*
 * find_base_rel
 *    Find a base or otherrel relation entry, which must already exist.
 */
RelOptInfo *
find_base_rel(PlannerInfo *root, int relid)
{
    RelOptInfo *rel;
 
    /* use an unsigned comparison to prevent negative array element access */
    if ((uint32) relid < (uint32) root->simple_rel_array_size)
    {
        rel = root->simple_rel_array[relid];
        if (rel)
            return rel;
    }
 
    elog(ERROR, "no relation entry for relid %d", relid);
 
    return NULL;                /* keep compiler quiet */
}
 
/*
 * find_base_rel_noerr
 *    Find a base or otherrel relation entry, returning NULL if there's none
 */
RelOptInfo *
find_base_rel_noerr(PlannerInfo *root, int relid)
{
    /* use an unsigned comparison to prevent negative array element access */
    if ((uint32) relid < (uint32) root->simple_rel_array_size)
        return root->simple_rel_array[relid];
    return NULL;
}
 
/*
 * find_base_rel_ignore_join
 *    Find a base or otherrel relation entry, which must already exist.
 *
 * Unlike find_base_rel, if relid references an outer join then this
 * will return NULL rather than raising an error.  This is convenient
 * for callers that must deal with relid sets including both base and
 * outer joins.
 */
RelOptInfo *
find_base_rel_ignore_join(PlannerInfo *root, int relid)
{
    /* use an unsigned comparison to prevent negative array element access */
    if ((uint32) relid < (uint32) root->simple_rel_array_size)
    {
        RelOptInfo *rel;
        RangeTblEntry *rte;
 
        rel = root->simple_rel_array[relid];
        if (rel)
            return rel;
 
        /*
         * We could just return NULL here, but for debugging purposes it seems
         * best to actually verify that the relid is an outer join and not
         * something weird.
         */
        rte = root->simple_rte_array[relid];
        if (rte && rte->rtekind == RTE_JOIN && rte->jointype != JOIN_INNER)
            return NULL;
    }
 
    elog(ERROR, "no relation entry for relid %d", relid);
 
    return NULL;                /* keep compiler quiet */
}
 
/*
 * build_join_rel_hash
 *    Construct the auxiliary hash table for join relations.
 */
static void
build_join_rel_hash(PlannerInfo *root)
{
    HTAB       *hashtab;
    HASHCTL     hash_ctl;
    ListCell   *l;
 
    /* Create the hash table */
    hash_ctl.keysize = sizeof(Relids);
    hash_ctl.entrysize = sizeof(JoinHashEntry);
    hash_ctl.hash = bitmap_hash;
    hash_ctl.match = bitmap_match;
    hash_ctl.hcxt = CurrentMemoryContext;
    hashtab = hash_create("JoinRelHashTable",
                          256L,
                          &hash_ctl,
                          HASH_ELEM | HASH_FUNCTION | HASH_COMPARE | HASH_CONTEXT);
 
    /* Insert all the already-existing joinrels */
    foreach(l, root->join_rel_list)
    {
        RelOptInfo *rel = (RelOptInfo *) lfirst(l);
        JoinHashEntry *hentry;
        bool        found;
 
        hentry = (JoinHashEntry *) hash_search(hashtab,
                                               &(rel->relids),
                                               HASH_ENTER,
                                               &found);
        Assert(!found);
        hentry->join_rel = rel;
    }
 
    root->join_rel_hash = hashtab;
}
 
/*
 * find_join_rel
 *    Returns relation entry corresponding to 'relids' (a set of RT indexes),
 *    or NULL if none exists.  This is for join relations.
 */
RelOptInfo *
find_join_rel(PlannerInfo *root, Relids relids)
{
    /*
     * Switch to using hash lookup when list grows "too long".  The threshold
     * is arbitrary and is known only here.
     */
    if (!root->join_rel_hash && list_length(root->join_rel_list) > 32)
        build_join_rel_hash(root);
 
    /*
     * Use either hashtable lookup or linear search, as appropriate.
     *
     * Note: the seemingly redundant hashkey variable is used to avoid taking
     * the address of relids; unless the compiler is exceedingly smart, doing
     * so would force relids out of a register and thus probably slow down the
     * list-search case.
     */
    if (root->join_rel_hash)
    {
        Relids      hashkey = relids;
        JoinHashEntry *hentry;
 
        hentry = (JoinHashEntry *) hash_search(root->join_rel_hash,
                                               &hashkey,
                                               HASH_FIND,
                                               NULL);
        if (hentry)
            return hentry->join_rel;
    }
    else
    {
        ListCell   *l;
 
        foreach(l, root->join_rel_list)
        {
            RelOptInfo *rel = (RelOptInfo *) lfirst(l);
 
            if (bms_equal(rel->relids, relids))
                return rel;
        }
    }
 
    return NULL;
}
 
/*
 * set_foreign_rel_properties
 *      Set up foreign-join fields if outer and inner relation are foreign
 *      tables (or joins) belonging to the same server and assigned to the same
 *      user to check access permissions as.
 *
 * In addition to an exact match of userid, we allow the case where one side
 * has zero userid (implying current user) and the other side has explicit
 * userid that happens to equal the current user; but in that case, pushdown of
 * the join is only valid for the current user.  The useridiscurrent field
 * records whether we had to make such an assumption for this join or any
 * sub-join.
 *
 * Otherwise these fields are left invalid, so GetForeignJoinPaths will not be
 * called for the join relation.
 */
static void
set_foreign_rel_properties(RelOptInfo *joinrel, RelOptInfo *outer_rel,
                           RelOptInfo *inner_rel)
{
    if (OidIsValid(outer_rel->serverid) &&
        inner_rel->serverid == outer_rel->serverid)
    {
        if (inner_rel->userid == outer_rel->userid)
        {
            joinrel->serverid = outer_rel->serverid;
            joinrel->userid = outer_rel->userid;
            joinrel->useridiscurrent = outer_rel->useridiscurrent || inner_rel->useridiscurrent;
            joinrel->fdwroutine = outer_rel->fdwroutine;
        }
        else if (!OidIsValid(inner_rel->userid) &&
                 outer_rel->userid == GetUserId())
        {
            joinrel->serverid = outer_rel->serverid;
            joinrel->userid = outer_rel->userid;
            joinrel->useridiscurrent = true;
            joinrel->fdwroutine = outer_rel->fdwroutine;
        }
        else if (!OidIsValid(outer_rel->userid) &&
                 inner_rel->userid == GetUserId())
        {
            joinrel->serverid = outer_rel->serverid;
            joinrel->userid = inner_rel->userid;
            joinrel->useridiscurrent = true;
            joinrel->fdwroutine = outer_rel->fdwroutine;
        }
    }
}
 
/*
 * add_join_rel
 *      Add given join relation to the list of join relations in the given
 *      PlannerInfo. Also add it to the auxiliary hashtable if there is one.
 */
static void
add_join_rel(PlannerInfo *root, RelOptInfo *joinrel)
{
    /* GEQO requires us to append the new joinrel to the end of the list! */
    root->join_rel_list = lappend(root->join_rel_list, joinrel);
 
    /* store it into the auxiliary hashtable if there is one. */
    if (root->join_rel_hash)
    {
        JoinHashEntry *hentry;
        bool        found;
 
        hentry = (JoinHashEntry *) hash_search(root->join_rel_hash,
                                               &(joinrel->relids),
                                               HASH_ENTER,
                                               &found);
        Assert(!found);
        hentry->join_rel = joinrel;
    }
}
 
/*
 * build_join_rel
 *    Returns relation entry corresponding to the union of two given rels,
 *    creating a new relation entry if none already exists.
 *
 * 'joinrelids' is the Relids set that uniquely identifies the join
 * 'outer_rel' and 'inner_rel' are relation nodes for the relations to be
 *      joined
 * 'sjinfo': join context info
 * 'pushed_down_joins': any pushed-down outer joins that are now completed
 * 'restrictlist_ptr': result variable.  If not NULL, *restrictlist_ptr
 *      receives the list of RestrictInfo nodes that apply to this
 *      particular pair of joinable relations.
 *
 * restrictlist_ptr makes the routine's API a little grotty, but it saves
 * duplicated calculation of the restrictlist...
 */
RelOptInfo *
build_join_rel(PlannerInfo *root,
               Relids joinrelids,
               RelOptInfo *outer_rel,
               RelOptInfo *inner_rel,
               SpecialJoinInfo *sjinfo,
               List *pushed_down_joins,
               List **restrictlist_ptr)
{
    RelOptInfo *joinrel;
    List       *restrictlist;
 
    /* This function should be used only for join between parents. */
    Assert(!IS_OTHER_REL(outer_rel) && !IS_OTHER_REL(inner_rel));
 
    /*
     * See if we already have a joinrel for this set of base rels.
     */
    joinrel = find_join_rel(root, joinrelids);
 
    if (joinrel)
    {
        /*
         * Yes, so we only need to figure the restrictlist for this particular
         * pair of component relations.
         */
        if (restrictlist_ptr)
            *restrictlist_ptr = build_joinrel_restrictlist(root,
                                                           joinrel,
                                                           outer_rel,
                                                           inner_rel,
                                                           sjinfo);
        return joinrel;
    }
 
    /*
     * Nope, so make one.
     */
    joinrel = makeNode(RelOptInfo);
    joinrel->reloptkind = RELOPT_JOINREL;
    joinrel->relids = bms_copy(joinrelids);
    joinrel->rows = 0;
    /* cheap startup cost is interesting iff not all tuples to be retrieved */
    joinrel->consider_startup = (root->tuple_fraction > 0);
    joinrel->consider_param_startup = false;
    joinrel->consider_parallel = false;
    joinrel->pgs_mask = root->glob->default_pgs_mask;
    joinrel->reltarget = create_empty_pathtarget();
    joinrel->pathlist = NIL;
    joinrel->ppilist = NIL;
    joinrel->partial_pathlist = NIL;
    joinrel->cheapest_startup_path = NULL;
    joinrel->cheapest_total_path = NULL;
    joinrel->cheapest_parameterized_paths = NIL;
    /* init direct_lateral_relids from children; we'll finish it up below */
    joinrel->direct_lateral_relids =
        bms_union(outer_rel->direct_lateral_relids,
                  inner_rel->direct_lateral_relids);
    joinrel->lateral_relids = min_join_parameterization(root, joinrel->relids,
                                                        outer_rel, inner_rel);
    joinrel->relid = 0;         /* indicates not a baserel */
    joinrel->rtekind = RTE_JOIN;
    joinrel->min_attr = 0;
    joinrel->max_attr = 0;
    joinrel->attr_needed = NULL;
    joinrel->attr_widths = NULL;
    joinrel->notnullattnums = NULL;
    joinrel->nulling_relids = NULL;
    joinrel->lateral_vars = NIL;
    joinrel->lateral_referencers = NULL;
    joinrel->indexlist = NIL;
    joinrel->statlist = NIL;
    joinrel->pages = 0;
    joinrel->tuples = 0;
    joinrel->allvisfrac = 0;
    joinrel->eclass_indexes = NULL;
    joinrel->subroot = NULL;
    joinrel->subplan_params = NIL;
    joinrel->rel_parallel_workers = -1;
    joinrel->amflags = 0;
    joinrel->serverid = InvalidOid;
    joinrel->userid = InvalidOid;
    joinrel->useridiscurrent = false;
    joinrel->fdwroutine = NULL;
    joinrel->fdw_private = NULL;
    joinrel->unique_for_rels = NIL;
    joinrel->non_unique_for_rels = NIL;
    joinrel->unique_rel = NULL;
    joinrel->unique_pathkeys = NIL;
    joinrel->unique_groupclause = NIL;
    joinrel->baserestrictinfo = NIL;
    joinrel->baserestrictcost.startup = 0;
    joinrel->baserestrictcost.per_tuple = 0;
    joinrel->baserestrict_min_security = UINT_MAX;
    joinrel->joininfo = NIL;
    joinrel->has_eclass_joins = false;
    joinrel->consider_partitionwise_join = false;   /* might get changed later */
    joinrel->agg_info = NULL;
    joinrel->grouped_rel = NULL;
    joinrel->parent = NULL;
    joinrel->top_parent = NULL;
    joinrel->top_parent_relids = NULL;
    joinrel->part_scheme = NULL;
    joinrel->nparts = -1;
    joinrel->boundinfo = NULL;
    joinrel->partbounds_merged = false;
    joinrel->partition_qual = NIL;
    joinrel->part_rels = NULL;
    joinrel->live_parts = NULL;
    joinrel->all_partrels = NULL;
    joinrel->partexprs = NULL;
    joinrel->nullable_partexprs = NULL;
 
    /* Compute information relevant to the foreign relations. */
    set_foreign_rel_properties(joinrel, outer_rel, inner_rel);
 
    /*
     * Fill the joinrel's tlist with just the Vars and PHVs that need to be
     * output from this join (ie, are needed for higher joinclauses or final
     * output).
     *
     * NOTE: the tlist order for a join rel will depend on which pair of outer
     * and inner rels we first try to build it from.  But the contents should
     * be the same regardless.
     */
    build_joinrel_tlist(root, joinrel, outer_rel, sjinfo, pushed_down_joins,
                        (sjinfo->jointype == JOIN_FULL));
    build_joinrel_tlist(root, joinrel, inner_rel, sjinfo, pushed_down_joins,
                        (sjinfo->jointype != JOIN_INNER));
    add_placeholders_to_joinrel(root, joinrel, outer_rel, inner_rel, sjinfo);
 
    /*
     * add_placeholders_to_joinrel also took care of adding the ph_lateral
     * sets of any PlaceHolderVars computed here to direct_lateral_relids, so
     * now we can finish computing that.  This is much like the computation of
     * the transitively-closed lateral_relids in min_join_parameterization,
     * except that here we *do* have to consider the added PHVs.
     */
    joinrel->direct_lateral_relids =
        bms_del_members(joinrel->direct_lateral_relids, joinrel->relids);
 
    /*
     * Construct restrict and join clause lists for the new joinrel. (The
     * caller might or might not need the restrictlist, but I need it anyway
     * for set_joinrel_size_estimates().)
     */
    restrictlist = build_joinrel_restrictlist(root, joinrel,
                                              outer_rel, inner_rel,
                                              sjinfo);
    if (restrictlist_ptr)
        *restrictlist_ptr = restrictlist;
    build_joinrel_joinlist(joinrel, outer_rel, inner_rel);
 
    /*
     * This is also the right place to check whether the joinrel has any
     * pending EquivalenceClass joins.
     */
    joinrel->has_eclass_joins = has_relevant_eclass_joinclause(root, joinrel);
 
    /*
     * Set estimates of the joinrel's size.
     */
    set_joinrel_size_estimates(root, joinrel, outer_rel, inner_rel,
                               sjinfo, restrictlist);
 
    /*
     * Set the consider_parallel flag if this joinrel could potentially be
     * scanned within a parallel worker.  If this flag is false for either
     * inner_rel or outer_rel, then it must be false for the joinrel also.
     * Even if both are true, there might be parallel-restricted expressions
     * in the targetlist or quals.
     *
     * Note that if there are more than two rels in this relation, they could
     * be divided between inner_rel and outer_rel in any arbitrary way.  We
     * assume this doesn't matter, because we should hit all the same baserels
     * and joinclauses while building up to this joinrel no matter which we
     * take; therefore, we should make the same decision here however we get
     * here.
     */
    if (inner_rel->consider_parallel && outer_rel->consider_parallel &&
        is_parallel_safe(root, (Node *) restrictlist) &&
        is_parallel_safe(root, (Node *) joinrel->reltarget->exprs))
        joinrel->consider_parallel = true;
 
    /*
     * Allow a plugin to editorialize on the new joinrel's properties. Actions
     * might include altering the size estimate, clearing consider_parallel,
     * or adjusting pgs_mask.
     */
    if (joinrel_setup_hook)
        (*joinrel_setup_hook) (root, joinrel, outer_rel, inner_rel, sjinfo,
                               restrictlist);
 
    /* Store the partition information. */
    build_joinrel_partition_info(root, joinrel, outer_rel, inner_rel, sjinfo,
                                 restrictlist);
 
    /* Add the joinrel to the PlannerInfo. */
    add_join_rel(root, joinrel);
 
    /*
     * Also, if dynamic-programming join search is active, add the new joinrel
     * to the appropriate sublist.  Note: you might think the Assert on number
     * of members should be for equality, but some of the level 1 rels might
     * have been joinrels already, so we can only assert <=.
     */
    if (root->join_rel_level)
    {
        Assert(root->join_cur_level > 0);
        Assert(root->join_cur_level <= bms_num_members(joinrel->relids));
        root->join_rel_level[root->join_cur_level] =
            lappend(root->join_rel_level[root->join_cur_level], joinrel);
    }
 
    return joinrel;
}
 
/*
 * build_child_join_rel
 *    Builds RelOptInfo representing join between given two child relations.
 *
 * 'outer_rel' and 'inner_rel' are the RelOptInfos of child relations being
 *      joined
 * 'parent_joinrel' is the RelOptInfo representing the join between parent
 *      relations. Some of the members of new RelOptInfo are produced by
 *      translating corresponding members of this RelOptInfo
 * 'restrictlist': list of RestrictInfo nodes that apply to this particular
 *      pair of joinable relations
 * 'sjinfo': child join's join-type details
 * 'nappinfos' and 'appinfos': AppendRelInfo array for child relids
 */
RelOptInfo *
build_child_join_rel(PlannerInfo *root, RelOptInfo *outer_rel,
                     RelOptInfo *inner_rel, RelOptInfo *parent_joinrel,
                     List *restrictlist, SpecialJoinInfo *sjinfo,
                     int nappinfos, AppendRelInfo **appinfos)
{
    RelOptInfo *joinrel = makeNode(RelOptInfo);
 
    /* Only joins between "other" relations land here. */
    Assert(IS_OTHER_REL(outer_rel) && IS_OTHER_REL(inner_rel));
 
    /* The parent joinrel should have consider_partitionwise_join set. */
    Assert(parent_joinrel->consider_partitionwise_join);
 
    joinrel->reloptkind = RELOPT_OTHER_JOINREL;
    joinrel->relids = adjust_child_relids(parent_joinrel->relids,
                                          nappinfos, appinfos);
    joinrel->rows = 0;
    /* cheap startup cost is interesting iff not all tuples to be retrieved */
    joinrel->consider_startup = (root->tuple_fraction > 0);
    joinrel->consider_param_startup = false;
    joinrel->consider_parallel = false;
    joinrel->pgs_mask = root->glob->default_pgs_mask;
    joinrel->reltarget = create_empty_pathtarget();
    joinrel->pathlist = NIL;
    joinrel->ppilist = NIL;
    joinrel->partial_pathlist = NIL;
    joinrel->cheapest_startup_path = NULL;
    joinrel->cheapest_total_path = NULL;
    joinrel->cheapest_parameterized_paths = NIL;
    joinrel->direct_lateral_relids = NULL;
    joinrel->lateral_relids = NULL;
    joinrel->relid = 0;         /* indicates not a baserel */
    joinrel->rtekind = RTE_JOIN;
    joinrel->min_attr = 0;
    joinrel->max_attr = 0;
    joinrel->attr_needed = NULL;
    joinrel->attr_widths = NULL;
    joinrel->notnullattnums = NULL;
    joinrel->nulling_relids = NULL;
    joinrel->lateral_vars = NIL;
    joinrel->lateral_referencers = NULL;
    joinrel->indexlist = NIL;
    joinrel->pages = 0;
    joinrel->tuples = 0;
    joinrel->allvisfrac = 0;
    joinrel->eclass_indexes = NULL;
    joinrel->subroot = NULL;
    joinrel->subplan_params = NIL;
    joinrel->amflags = 0;
    joinrel->serverid = InvalidOid;
    joinrel->userid = InvalidOid;
    joinrel->useridiscurrent = false;
    joinrel->fdwroutine = NULL;
    joinrel->fdw_private = NULL;
    joinrel->unique_rel = NULL;
    joinrel->unique_pathkeys = NIL;
    joinrel->unique_groupclause = NIL;
    joinrel->baserestrictinfo = NIL;
    joinrel->baserestrictcost.startup = 0;
    joinrel->baserestrictcost.per_tuple = 0;
    joinrel->joininfo = NIL;
    joinrel->has_eclass_joins = false;
    joinrel->consider_partitionwise_join = false;   /* might get changed later */
    joinrel->agg_info = NULL;
    joinrel->grouped_rel = NULL;
    joinrel->parent = parent_joinrel;
    joinrel->top_parent = parent_joinrel->top_parent ? parent_joinrel->top_parent : parent_joinrel;
    joinrel->top_parent_relids = joinrel->top_parent->relids;
    joinrel->part_scheme = NULL;
    joinrel->nparts = -1;
    joinrel->boundinfo = NULL;
    joinrel->partbounds_merged = false;
    joinrel->partition_qual = NIL;
    joinrel->part_rels = NULL;
    joinrel->live_parts = NULL;
    joinrel->all_partrels = NULL;
    joinrel->partexprs = NULL;
    joinrel->nullable_partexprs = NULL;
 
    /* Compute information relevant to foreign relations. */
    set_foreign_rel_properties(joinrel, outer_rel, inner_rel);
 
    /* Set up reltarget struct */
    build_child_join_reltarget(root, parent_joinrel, joinrel,
                               nappinfos, appinfos);
 
    /* Construct joininfo list. */
    joinrel->joininfo = (List *) adjust_appendrel_attrs(root,
                                                        (Node *) parent_joinrel->joininfo,
                                                        nappinfos,
                                                        appinfos);
 
    /*
     * Lateral relids referred in child join will be same as that referred in
     * the parent relation.
     */
    joinrel->direct_lateral_relids = (Relids) bms_copy(parent_joinrel->direct_lateral_relids);
    joinrel->lateral_relids = (Relids) bms_copy(parent_joinrel->lateral_relids);
 
    /*
     * If the parent joinrel has pending equivalence classes, so does the
     * child.
     */
    joinrel->has_eclass_joins = parent_joinrel->has_eclass_joins;
 
    /* Child joinrel is parallel safe if parent is parallel safe. */
    joinrel->consider_parallel = parent_joinrel->consider_parallel;
 
    /* Set estimates of the child-joinrel's size. */
    set_joinrel_size_estimates(root, joinrel, outer_rel, inner_rel,
                               sjinfo, restrictlist);
 
    /*
     * Allow a plugin to editorialize on the new joinrel's properties. Actions
     * might include altering the size estimate, clearing consider_parallel,
     * or adjusting pgs_mask. (However, note that clearing consider_parallel
     * would be better done in the parent joinrel rather than here.)
     */
    if (joinrel_setup_hook)
        (*joinrel_setup_hook) (root, joinrel, outer_rel, inner_rel, sjinfo,
                               restrictlist);
 
    /* Is the join between partitions itself partitioned? */
    build_joinrel_partition_info(root, joinrel, outer_rel, inner_rel, sjinfo,
                                 restrictlist);
 
    /* We build the join only once. */
    Assert(!find_join_rel(root, joinrel->relids));
 
    /* Add the relation to the PlannerInfo. */
    add_join_rel(root, joinrel);
 
    /*
     * We might need EquivalenceClass members corresponding to the child join,
     * so that we can represent sort pathkeys for it.  As with children of
     * baserels, we shouldn't need this unless there are relevant eclass joins
     * (implying that a merge join might be possible) or pathkeys to sort by.
     */
    if (joinrel->has_eclass_joins || has_useful_pathkeys(root, parent_joinrel))
        add_child_join_rel_equivalences(root,
                                        nappinfos, appinfos,
                                        parent_joinrel, joinrel);
 
    return joinrel;
}
 
/*
 * min_join_parameterization
 *
 * Determine the minimum possible parameterization of a joinrel, that is, the
 * set of other rels it contains LATERAL references to.  We save this value in
 * the join's RelOptInfo.  This function is split out of build_join_rel()
 * because join_is_legal() needs the value to check a prospective join.
 */
Relids
min_join_parameterization(PlannerInfo *root,
                          Relids joinrelids,
                          RelOptInfo *outer_rel,
                          RelOptInfo *inner_rel)
{
    Relids      result;
 
    /*
     * Basically we just need the union of the inputs' lateral_relids, less
     * whatever is already in the join.
     *
     * It's not immediately obvious that this is a valid way to compute the
     * result, because it might seem that we're ignoring possible lateral refs
     * of PlaceHolderVars that are due to be computed at the join but not in
     * either input.  However, because create_lateral_join_info() already
     * charged all such PHV refs to each member baserel of the join, they'll
     * be accounted for already in the inputs' lateral_relids.  Likewise, we
     * do not need to worry about doing transitive closure here, because that
     * was already accounted for in the original baserel lateral_relids.
     */
    result = bms_union(outer_rel->lateral_relids, inner_rel->lateral_relids);
    result = bms_del_members(result, joinrelids);
    return result;
}
 
/*
 * build_joinrel_tlist
 *    Builds a join relation's target list from an input relation.
 *    (This is invoked twice to handle the two input relations.)
 *
 * The join's targetlist includes all Vars of its member relations that
 * will still be needed above the join.  This subroutine adds all such
 * Vars from the specified input rel's tlist to the join rel's tlist.
 * Likewise for any PlaceHolderVars emitted by the input rel.
 *
 * We also compute the expected width of the join's output, making use
 * of data that was cached at the baserel level by set_rel_width().
 *
 * Pass can_null as true if the join is an outer join that can null Vars
 * from this input relation.  If so, we will (normally) add the join's relid
 * to the nulling bitmaps of Vars and PHVs bubbled up from the input.
 *
 * When forming an outer join's target list, special handling is needed in
 * case the outer join was commuted with another one per outer join identity 3
 * (see optimizer/README).  We must take steps to ensure that the output Vars
 * have the same nulling bitmaps that they would if the two joins had been
 * done in syntactic order; else they won't match Vars appearing higher in
 * the query tree.  An exception to the match-the-syntactic-order rule is
 * that when an outer join is pushed down into another one's RHS per identity
 * 3, we can't mark its Vars as nulled until the now-upper outer join is also
 * completed.  So we need to do three things:
 *
 * First, we add the outer join's relid to the nulling bitmap only if the
 * outer join has been completely performed and the Var or PHV actually
 * comes from within the syntactically nullable side(s) of the outer join.
 * This takes care of the possibility that we have transformed
 *      (A leftjoin B on (Pab)) leftjoin C on (Pbc)
 * to
 *      A leftjoin (B leftjoin C on (Pbc)) on (Pab)
 * Here the pushed-down B/C join cannot mark C columns as nulled yet,
 * while the now-upper A/B join must not mark C columns as nulled by itself.
 *
 * Second, perform the same operation for each SpecialJoinInfo listed in
 * pushed_down_joins (which, in this example, would be the B/C join when
 * we are at the now-upper A/B join).  This allows the now-upper join to
 * complete the marking of "C" Vars that now have fully valid values.
 *
 * Third, any relid in sjinfo->commute_above_r that is already part of
 * the joinrel is added to the nulling bitmaps of nullable Vars and PHVs.
 * This takes care of the reverse case where we implement
 *      A leftjoin (B leftjoin C on (Pbc)) on (Pab)
 * as
 *      (A leftjoin B on (Pab)) leftjoin C on (Pbc)
 * The C columns emitted by the B/C join need to be shown as nulled by both
 * the B/C and A/B joins, even though they've not physically traversed the
 * A/B join.
 */
static void
build_joinrel_tlist(PlannerInfo *root, RelOptInfo *joinrel,
                    RelOptInfo *input_rel,
                    SpecialJoinInfo *sjinfo,
                    List *pushed_down_joins,
                    bool can_null)
{
    Relids      relids = joinrel->relids;
    int64       tuple_width = joinrel->reltarget->width;
    ListCell   *vars;
    ListCell   *lc;
 
    foreach(vars, input_rel->reltarget->exprs)
    {
        Var        *var = (Var *) lfirst(vars);
 
        /*
         * For a PlaceHolderVar, we have to look up the PlaceHolderInfo.
         */
        if (IsA(var, PlaceHolderVar))
        {
            PlaceHolderVar *phv = (PlaceHolderVar *) var;
            PlaceHolderInfo *phinfo = find_placeholder_info(root, phv);
 
            /* Is it still needed above this joinrel? */
            if (bms_nonempty_difference(phinfo->ph_needed, relids))
            {
                /*
                 * Yup, add it to the output.  If this join potentially nulls
                 * this input, we have to update the PHV's phnullingrels,
                 * which means making a copy.
                 */
                if (can_null)
                {
                    phv = copyObject(phv);
                    /* See comments above to understand this logic */
                    if (sjinfo->ojrelid != 0 &&
                        bms_is_member(sjinfo->ojrelid, relids) &&
                        (bms_is_subset(phv->phrels, sjinfo->syn_righthand) ||
                         (sjinfo->jointype == JOIN_FULL &&
                          bms_is_subset(phv->phrels, sjinfo->syn_lefthand))))
                        phv->phnullingrels = bms_add_member(phv->phnullingrels,
                                                            sjinfo->ojrelid);
                    foreach(lc, pushed_down_joins)
                    {
                        SpecialJoinInfo *othersj = (SpecialJoinInfo *) lfirst(lc);
 
                        Assert(bms_is_member(othersj->ojrelid, relids));
                        if (bms_is_subset(phv->phrels, othersj->syn_righthand))
                            phv->phnullingrels = bms_add_member(phv->phnullingrels,
                                                                othersj->ojrelid);
                    }
                    phv->phnullingrels =
                        bms_join(phv->phnullingrels,
                                 bms_intersect(sjinfo->commute_above_r,
                                               relids));
                }
 
                joinrel->reltarget->exprs = lappend(joinrel->reltarget->exprs,
                                                    phv);
                /* Bubbling up the precomputed result has cost zero */
                tuple_width += phinfo->ph_width;
            }
            continue;
        }
 
        /*
         * Otherwise, anything in a baserel or joinrel targetlist ought to be
         * a Var.  (More general cases can only appear in appendrel child
         * rels, which will never be seen here.)
         */
        if (!IsA(var, Var))
            elog(ERROR, "unexpected node type in rel targetlist: %d",
                 (int) nodeTag(var));
 
        if (var->varno == ROWID_VAR)
        {
            /* UPDATE/DELETE/MERGE row identity vars are always needed */
            RowIdentityVarInfo *ridinfo = (RowIdentityVarInfo *)
                list_nth(root->row_identity_vars, var->varattno - 1);
 
            /* Update reltarget width estimate from RowIdentityVarInfo */
            tuple_width += ridinfo->rowidwidth;
        }
        else
        {
            RelOptInfo *baserel;
            int         ndx;
 
            /* Get the Var's original base rel */
            baserel = find_base_rel(root, var->varno);
 
            /* Is it still needed above this joinrel? */
            ndx = var->varattno - baserel->min_attr;
            if (!bms_nonempty_difference(baserel->attr_needed[ndx], relids))
                continue;       /* nope, skip it */
 
            /* Update reltarget width estimate from baserel's attr_widths */
            tuple_width += baserel->attr_widths[ndx];
        }
 
        /*
         * Add the Var to the output.  If this join potentially nulls this
         * input, we have to update the Var's varnullingrels, which means
         * making a copy.  But note that we don't ever add nullingrel bits to
         * row identity Vars (cf. comments in setrefs.c).
         */
        if (can_null && var->varno != ROWID_VAR)
        {
            var = copyObject(var);
            /* See comments above to understand this logic */
            if (sjinfo->ojrelid != 0 &&
                bms_is_member(sjinfo->ojrelid, relids) &&
                (bms_is_member(var->varno, sjinfo->syn_righthand) ||
                 (sjinfo->jointype == JOIN_FULL &&
                  bms_is_member(var->varno, sjinfo->syn_lefthand))))
                var->varnullingrels = bms_add_member(var->varnullingrels,
                                                     sjinfo->ojrelid);
            foreach(lc, pushed_down_joins)
            {
                SpecialJoinInfo *othersj = (SpecialJoinInfo *) lfirst(lc);
 
                Assert(bms_is_member(othersj->ojrelid, relids));
                if (bms_is_member(var->varno, othersj->syn_righthand))
                    var->varnullingrels = bms_add_member(var->varnullingrels,
                                                         othersj->ojrelid);
            }
            var->varnullingrels =
                bms_join(var->varnullingrels,
                         bms_intersect(sjinfo->commute_above_r,
                                       relids));
        }
 
        joinrel->reltarget->exprs = lappend(joinrel->reltarget->exprs,
                                            var);
 
        /* Vars have cost zero, so no need to adjust reltarget->cost */
    }
 
    joinrel->reltarget->width = clamp_width_est(tuple_width);
}
 
/*
 * build_joinrel_restrictlist
 * build_joinrel_joinlist
 *    These routines build lists of restriction and join clauses for a
 *    join relation from the joininfo lists of the relations it joins.
 *
 *    These routines are separate because the restriction list must be
 *    built afresh for each pair of input sub-relations we consider, whereas
 *    the join list need only be computed once for any join RelOptInfo.
 *    The join list is fully determined by the set of rels making up the
 *    joinrel, so we should get the same results (up to ordering) from any
 *    candidate pair of sub-relations.  But the restriction list is whatever
 *    is not handled in the sub-relations, so it depends on which
 *    sub-relations are considered.
 *
 *    If a join clause from an input relation refers to base+OJ rels still not
 *    present in the joinrel, then it is still a join clause for the joinrel;
 *    we put it into the joininfo list for the joinrel.  Otherwise,
 *    the clause is now a restrict clause for the joined relation, and we
 *    return it to the caller of build_joinrel_restrictlist() to be stored in
 *    join paths made from this pair of sub-relations.  (It will not need to
 *    be considered further up the join tree.)
 *
 *    In many cases we will find the same RestrictInfos in both input
 *    relations' joinlists, so be careful to eliminate duplicates.
 *    Pointer equality should be a sufficient test for dups, since all
 *    the various joinlist entries ultimately refer to RestrictInfos
 *    pushed into them by distribute_restrictinfo_to_rels().
 *
 * 'joinrel' is a join relation node
 * 'outer_rel' and 'inner_rel' are a pair of relations that can be joined
 *      to form joinrel.
 * 'sjinfo': join context info
 *
 * build_joinrel_restrictlist() returns a list of relevant restrictinfos,
 * whereas build_joinrel_joinlist() stores its results in the joinrel's
 * joininfo list.  One or the other must accept each given clause!
 *
 * NB: Formerly, we made deep(!) copies of each input RestrictInfo to pass
 * up to the join relation.  I believe this is no longer necessary, because
 * RestrictInfo nodes are no longer context-dependent.  Instead, just include
 * the original nodes in the lists made for the join relation.
 */
static List *
build_joinrel_restrictlist(PlannerInfo *root,
                           RelOptInfo *joinrel,
                           RelOptInfo *outer_rel,
                           RelOptInfo *inner_rel,
                           SpecialJoinInfo *sjinfo)
{
    List       *result;
    Relids      both_input_relids;
 
    both_input_relids = bms_union(outer_rel->relids, inner_rel->relids);
 
    /*
     * Collect all the clauses that syntactically belong at this level,
     * eliminating any duplicates (important since we will see many of the
     * same clauses arriving from both input relations).
     */
    result = subbuild_joinrel_restrictlist(root, joinrel, outer_rel,
                                           both_input_relids, NIL);
    result = subbuild_joinrel_restrictlist(root, joinrel, inner_rel,
                                           both_input_relids, result);
 
    /*
     * Add on any clauses derived from EquivalenceClasses.  These cannot be
     * redundant with the clauses in the joininfo lists, so don't bother
     * checking.
     */
    result = list_concat(result,
                         generate_join_implied_equalities(root,
                                                          joinrel->relids,
                                                          outer_rel->relids,
                                                          inner_rel,
                                                          sjinfo));
 
    return result;
}
 
static void
build_joinrel_joinlist(RelOptInfo *joinrel,
                       RelOptInfo *outer_rel,
                       RelOptInfo *inner_rel)
{
    List       *result;
 
    /*
     * Collect all the clauses that syntactically belong above this level,
     * eliminating any duplicates (important since we will see many of the
     * same clauses arriving from both input relations).
     */
    result = subbuild_joinrel_joinlist(joinrel, outer_rel->joininfo, NIL);
    result = subbuild_joinrel_joinlist(joinrel, inner_rel->joininfo, result);
 
    joinrel->joininfo = result;
}
 
static List *
subbuild_joinrel_restrictlist(PlannerInfo *root,
                              RelOptInfo *joinrel,
                              RelOptInfo *input_rel,
                              Relids both_input_relids,
                              List *new_restrictlist)
{
    ListCell   *l;
 
    foreach(l, input_rel->joininfo)
    {
        RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
 
        if (bms_is_subset(rinfo->required_relids, joinrel->relids))
        {
            /*
             * This clause should become a restriction clause for the joinrel,
             * since it refers to no outside rels.  However, if it's a clone
             * clause then it might be too late to evaluate it, so we have to
             * check.  (If it is too late, just ignore the clause, taking it
             * on faith that another clone was or will be selected.)  Clone
             * clauses should always be outer-join clauses, so we compare
             * against both_input_relids.
             */
            if (rinfo->has_clone || rinfo->is_clone)
            {
                Assert(!RINFO_IS_PUSHED_DOWN(rinfo, joinrel->relids));
                if (!bms_is_subset(rinfo->required_relids, both_input_relids))
                    continue;
                if (bms_overlap(rinfo->incompatible_relids, both_input_relids))
                    continue;
            }
            else
            {
                /*
                 * For non-clone clauses, we just Assert it's OK.  These might
                 * be either join or filter clauses; if it's a join clause
                 * then it should not refer to the current join's output.
                 * (There is little point in checking incompatible_relids,
                 * because it'll be NULL.)
                 */
                Assert(RINFO_IS_PUSHED_DOWN(rinfo, joinrel->relids) ||
                       bms_is_subset(rinfo->required_relids,
                                     both_input_relids));
            }
 
            /*
             * OK, so add it to the list, being careful to eliminate
             * duplicates.  (Since RestrictInfo nodes in different joinlists
             * will have been multiply-linked rather than copied, pointer
             * equality should be a sufficient test.)
             */
            new_restrictlist = list_append_unique_ptr(new_restrictlist, rinfo);
        }
        else
        {
            /*
             * This clause is still a join clause at this level, so we ignore
             * it in this routine.
             */
        }
    }
 
    return new_restrictlist;
}
 
static List *
subbuild_joinrel_joinlist(RelOptInfo *joinrel,
                          List *joininfo_list,
                          List *new_joininfo)
{
    ListCell   *l;
 
    /* Expected to be called only for join between parent relations. */
    Assert(joinrel->reloptkind == RELOPT_JOINREL);
 
    foreach(l, joininfo_list)
    {
        RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
 
        if (bms_is_subset(rinfo->required_relids, joinrel->relids))
        {
            /*
             * This clause becomes a restriction clause for the joinrel, since
             * it refers to no outside rels.  So we can ignore it in this
             * routine.
             */
        }
        else
        {
            /*
             * This clause is still a join clause at this level, so add it to
             * the new joininfo list, being careful to eliminate duplicates.
             * (Since RestrictInfo nodes in different joinlists will have been
             * multiply-linked rather than copied, pointer equality should be
             * a sufficient test.)
             */
            new_joininfo = list_append_unique_ptr(new_joininfo, rinfo);
        }
    }
 
    return new_joininfo;
}
 
 
/*
 * fetch_upper_rel
 *      Build a RelOptInfo describing some post-scan/join query processing,
 *      or return a pre-existing one if somebody already built it.
 *
 * An "upper" relation is identified by an UpperRelationKind and a Relids set.
 * The meaning of the Relids set is not specified here, and very likely will
 * vary for different relation kinds.
 *
 * Most of the fields in an upper-level RelOptInfo are not used and are not
 * set here (though makeNode should ensure they're zeroes).  We basically only
 * care about fields that are of interest to add_path() and set_cheapest().
 */
RelOptInfo *
fetch_upper_rel(PlannerInfo *root, UpperRelationKind kind, Relids relids)
{
    RelOptInfo *upperrel;
    ListCell   *lc;
 
    /*
     * For the moment, our indexing data structure is just a List for each
     * relation kind.  If we ever get so many of one kind that this stops
     * working well, we can improve it.  No code outside this function should
     * assume anything about how to find a particular upperrel.
     */
 
    /* If we already made this upperrel for the query, return it */
    foreach(lc, root->upper_rels[kind])
    {
        upperrel = (RelOptInfo *) lfirst(lc);
 
        if (bms_equal(upperrel->relids, relids))
            return upperrel;
    }
 
    upperrel = makeNode(RelOptInfo);
    upperrel->reloptkind = RELOPT_UPPER_REL;
    upperrel->relids = bms_copy(relids);
    upperrel->pgs_mask = root->glob->default_pgs_mask;
 
    /* cheap startup cost is interesting iff not all tuples to be retrieved */
    upperrel->consider_startup = (root->tuple_fraction > 0);
    upperrel->consider_param_startup = false;
    upperrel->consider_parallel = false;    /* might get changed later */
    upperrel->reltarget = create_empty_pathtarget();
    upperrel->pathlist = NIL;
    upperrel->cheapest_startup_path = NULL;
    upperrel->cheapest_total_path = NULL;
    upperrel->cheapest_parameterized_paths = NIL;
 
    root->upper_rels[kind] = lappend(root->upper_rels[kind], upperrel);
 
    return upperrel;
}
 
 
/*
 * find_childrel_parents
 *      Compute the set of parent relids of an appendrel child rel.
 *
 * Since appendrels can be nested, a child could have multiple levels of
 * appendrel ancestors.  This function computes a Relids set of all the
 * parent relation IDs.
 */
Relids
find_childrel_parents(PlannerInfo *root, RelOptInfo *rel)
{
    Relids      result = NULL;
 
    Assert(rel->reloptkind == RELOPT_OTHER_MEMBER_REL);
    Assert(rel->relid > 0 && rel->relid < root->simple_rel_array_size);
 
    do
    {
        AppendRelInfo *appinfo = root->append_rel_array[rel->relid];
        Index       prelid = appinfo->parent_relid;
 
        result = bms_add_member(result, prelid);
 
        /* traverse up to the parent rel, loop if it's also a child rel */
        rel = find_base_rel(root, prelid);
    } while (rel->reloptkind == RELOPT_OTHER_MEMBER_REL);
 
    Assert(rel->reloptkind == RELOPT_BASEREL);
 
    return result;
}
 
 
/*
 * get_baserel_parampathinfo
 *      Get the ParamPathInfo for a parameterized path for a base relation,
 *      constructing one if we don't have one already.
 *
 * This centralizes estimating the rowcounts for parameterized paths.
 * We need to cache those to be sure we use the same rowcount for all paths
 * of the same parameterization for a given rel.  This is also a convenient
 * place to determine which movable join clauses the parameterized path will
 * be responsible for evaluating.
 */
ParamPathInfo *
get_baserel_parampathinfo(PlannerInfo *root, RelOptInfo *baserel,
                          Relids required_outer)
{
    ParamPathInfo *ppi;
    Relids      joinrelids;
    List       *pclauses;
    List       *eqclauses;
    Bitmapset  *pserials;
    double      rows;
    ListCell   *lc;
 
    /* If rel has LATERAL refs, every path for it should account for them */
    Assert(bms_is_subset(baserel->lateral_relids, required_outer));
 
    /* Unparameterized paths have no ParamPathInfo */
    if (bms_is_empty(required_outer))
        return NULL;
 
    Assert(!bms_overlap(baserel->relids, required_outer));
 
    /* If we already have a PPI for this parameterization, just return it */
    if ((ppi = find_param_path_info(baserel, required_outer)))
        return ppi;
 
    /*
     * Identify all joinclauses that are movable to this base rel given this
     * parameterization.
     */
    joinrelids = bms_union(baserel->relids, required_outer);
    pclauses = NIL;
    foreach(lc, baserel->joininfo)
    {
        RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
 
        if (join_clause_is_movable_into(rinfo,
                                        baserel->relids,
                                        joinrelids))
            pclauses = lappend(pclauses, rinfo);
    }
 
    /*
     * Add in joinclauses generated by EquivalenceClasses, too.  (These
     * necessarily satisfy join_clause_is_movable_into; but in assert-enabled
     * builds, let's verify that.)
     */
    eqclauses = generate_join_implied_equalities(root,
                                                 joinrelids,
                                                 required_outer,
                                                 baserel,
                                                 NULL);
#ifdef USE_ASSERT_CHECKING
    foreach(lc, eqclauses)
    {
        RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
 
        Assert(join_clause_is_movable_into(rinfo,
                                           baserel->relids,
                                           joinrelids));
    }
#endif
    pclauses = list_concat(pclauses, eqclauses);
 
    /* Compute set of serial numbers of the enforced clauses */
    pserials = NULL;
    foreach(lc, pclauses)
    {
        RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
 
        pserials = bms_add_member(pserials, rinfo->rinfo_serial);
    }
 
    /* Estimate the number of rows returned by the parameterized scan */
    rows = get_parameterized_baserel_size(root, baserel, pclauses);
 
    /* And now we can build the ParamPathInfo */
    ppi = makeNode(ParamPathInfo);
    ppi->ppi_req_outer = required_outer;
    ppi->ppi_rows = rows;
    ppi->ppi_clauses = pclauses;
    ppi->ppi_serials = pserials;
    baserel->ppilist = lappend(baserel->ppilist, ppi);
 
    return ppi;
}
 
/*
 * get_joinrel_parampathinfo
 *      Get the ParamPathInfo for a parameterized path for a join relation,
 *      constructing one if we don't have one already.
 *
 * This centralizes estimating the rowcounts for parameterized paths.
 * We need to cache those to be sure we use the same rowcount for all paths
 * of the same parameterization for a given rel.  This is also a convenient
 * place to determine which movable join clauses the parameterized path will
 * be responsible for evaluating.
 *
 * outer_path and inner_path are a pair of input paths that can be used to
 * construct the join, and restrict_clauses is the list of regular join
 * clauses (including clauses derived from EquivalenceClasses) that must be
 * applied at the join node when using these inputs.
 *
 * Unlike the situation for base rels, the set of movable join clauses to be
 * enforced at a join varies with the selected pair of input paths, so we
 * must calculate that and pass it back, even if we already have a matching
 * ParamPathInfo.  We handle this by adding any clauses moved down to this
 * join to *restrict_clauses, which is an in/out parameter.  (The addition
 * is done in such a way as to not modify the passed-in List structure.)
 *
 * Note: when considering a nestloop join, the caller must have removed from
 * restrict_clauses any movable clauses that are themselves scheduled to be
 * pushed into the right-hand path.  We do not do that here since it's
 * unnecessary for other join types.
 */
ParamPathInfo *
get_joinrel_parampathinfo(PlannerInfo *root, RelOptInfo *joinrel,
                          Path *outer_path,
                          Path *inner_path,
                          SpecialJoinInfo *sjinfo,
                          Relids required_outer,
                          List **restrict_clauses)
{
    ParamPathInfo *ppi;
    Relids      join_and_req;
    Relids      outer_and_req;
    Relids      inner_and_req;
    List       *pclauses;
    List       *eclauses;
    List       *dropped_ecs;
    double      rows;
    ListCell   *lc;
 
    /* If rel has LATERAL refs, every path for it should account for them */
    Assert(bms_is_subset(joinrel->lateral_relids, required_outer));
 
    /* Unparameterized paths have no ParamPathInfo or extra join clauses */
    if (bms_is_empty(required_outer))
        return NULL;
 
    Assert(!bms_overlap(joinrel->relids, required_outer));
 
    /*
     * Identify all joinclauses that are movable to this join rel given this
     * parameterization.  These are the clauses that are movable into this
     * join, but not movable into either input path.  Treat an unparameterized
     * input path as not accepting parameterized clauses (because it won't,
     * per the shortcut exit above), even though the joinclause movement rules
     * might allow the same clauses to be moved into a parameterized path for
     * that rel.
     */
    join_and_req = bms_union(joinrel->relids, required_outer);
    if (outer_path->param_info)
        outer_and_req = bms_union(outer_path->parent->relids,
                                  PATH_REQ_OUTER(outer_path));
    else
        outer_and_req = NULL;   /* outer path does not accept parameters */
    if (inner_path->param_info)
        inner_and_req = bms_union(inner_path->parent->relids,
                                  PATH_REQ_OUTER(inner_path));
    else
        inner_and_req = NULL;   /* inner path does not accept parameters */
 
    pclauses = NIL;
    foreach(lc, joinrel->joininfo)
    {
        RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
 
        if (join_clause_is_movable_into(rinfo,
                                        joinrel->relids,
                                        join_and_req) &&
            !join_clause_is_movable_into(rinfo,
                                         outer_path->parent->relids,
                                         outer_and_req) &&
            !join_clause_is_movable_into(rinfo,
                                         inner_path->parent->relids,
                                         inner_and_req))
            pclauses = lappend(pclauses, rinfo);
    }
 
    /* Consider joinclauses generated by EquivalenceClasses, too */
    eclauses = generate_join_implied_equalities(root,
                                                join_and_req,
                                                required_outer,
                                                joinrel,
                                                NULL);
    /* We only want ones that aren't movable to lower levels */
    dropped_ecs = NIL;
    foreach(lc, eclauses)
    {
        RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
 
        Assert(join_clause_is_movable_into(rinfo,
                                           joinrel->relids,
                                           join_and_req));
        if (join_clause_is_movable_into(rinfo,
                                        outer_path->parent->relids,
                                        outer_and_req))
            continue;           /* drop if movable into LHS */
        if (join_clause_is_movable_into(rinfo,
                                        inner_path->parent->relids,
                                        inner_and_req))
        {
            /* drop if movable into RHS, but remember EC for use below */
            Assert(rinfo->left_ec == rinfo->right_ec);
            dropped_ecs = lappend(dropped_ecs, rinfo->left_ec);
            continue;
        }
        pclauses = lappend(pclauses, rinfo);
    }
 
    /*
     * EquivalenceClasses are harder to deal with than we could wish, because
     * of the fact that a given EC can generate different clauses depending on
     * context.  Suppose we have an EC {X.X, Y.Y, Z.Z} where X and Y are the
     * LHS and RHS of the current join and Z is in required_outer, and further
     * suppose that the inner_path is parameterized by both X and Z.  The code
     * above will have produced either Z.Z = X.X or Z.Z = Y.Y from that EC,
     * and in the latter case will have discarded it as being movable into the
     * RHS.  However, the EC machinery might have produced either Y.Y = X.X or
     * Y.Y = Z.Z as the EC enforcement clause within the inner_path; it will
     * not have produced both, and we can't readily tell from here which one
     * it did pick.  If we add no clause to this join, we'll end up with
     * insufficient enforcement of the EC; either Z.Z or X.X will fail to be
     * constrained to be equal to the other members of the EC.  (When we come
     * to join Z to this X/Y path, we will certainly drop whichever EC clause
     * is generated at that join, so this omission won't get fixed later.)
     *
     * To handle this, for each EC we discarded such a clause from, try to
     * generate a clause connecting the required_outer rels to the join's LHS
     * ("Z.Z = X.X" in the terms of the above example).  If successful, and if
     * the clause can't be moved to the LHS, add it to the current join's
     * restriction clauses.  (If an EC cannot generate such a clause then it
     * has nothing that needs to be enforced here, while if the clause can be
     * moved into the LHS then it should have been enforced within that path.)
     *
     * Note that we don't need similar processing for ECs whose clause was
     * considered to be movable into the LHS, because the LHS can't refer to
     * the RHS so there is no comparable ambiguity about what it might
     * actually be enforcing internally.
     */
    if (dropped_ecs)
    {
        Relids      real_outer_and_req;
 
        real_outer_and_req = bms_union(outer_path->parent->relids,
                                       required_outer);
        eclauses =
            generate_join_implied_equalities_for_ecs(root,
                                                     dropped_ecs,
                                                     real_outer_and_req,
                                                     required_outer,
                                                     outer_path->parent);
        foreach(lc, eclauses)
        {
            RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
 
            Assert(join_clause_is_movable_into(rinfo,
                                               outer_path->parent->relids,
                                               real_outer_and_req));
            if (!join_clause_is_movable_into(rinfo,
                                             outer_path->parent->relids,
                                             outer_and_req))
                pclauses = lappend(pclauses, rinfo);
        }
    }
 
    /*
     * Now, attach the identified moved-down clauses to the caller's
     * restrict_clauses list.  By using list_concat in this order, we leave
     * the original list structure of restrict_clauses undamaged.
     */
    *restrict_clauses = list_concat(pclauses, *restrict_clauses);
 
    /* If we already have a PPI for this parameterization, just return it */
    if ((ppi = find_param_path_info(joinrel, required_outer)))
        return ppi;
 
    /* Estimate the number of rows returned by the parameterized join */
    rows = get_parameterized_joinrel_size(root, joinrel,
                                          outer_path,
                                          inner_path,
                                          sjinfo,
                                          *restrict_clauses);
 
    /*
     * And now we can build the ParamPathInfo.  No point in saving the
     * input-pair-dependent clause list, though.
     *
     * Note: in GEQO mode, we'll be called in a temporary memory context, but
     * the joinrel structure is there too, so no problem.
     */
    ppi = makeNode(ParamPathInfo);
    ppi->ppi_req_outer = required_outer;
    ppi->ppi_rows = rows;
    ppi->ppi_clauses = NIL;
    ppi->ppi_serials = NULL;
    joinrel->ppilist = lappend(joinrel->ppilist, ppi);
 
    return ppi;
}
 
/*
 * get_appendrel_parampathinfo
 *      Get the ParamPathInfo for a parameterized path for an append relation.
 *
 * For an append relation, the rowcount estimate will just be the sum of
 * the estimates for its children.  However, we still need a ParamPathInfo
 * to flag the fact that the path requires parameters.  So this just creates
 * a suitable struct with zero ppi_rows (and no ppi_clauses either, since
 * the Append node isn't responsible for checking quals).
 */
ParamPathInfo *
get_appendrel_parampathinfo(RelOptInfo *appendrel, Relids required_outer)
{
    ParamPathInfo *ppi;
 
    /* If rel has LATERAL refs, every path for it should account for them */
    Assert(bms_is_subset(appendrel->lateral_relids, required_outer));
 
    /* Unparameterized paths have no ParamPathInfo */
    if (bms_is_empty(required_outer))
        return NULL;
 
    Assert(!bms_overlap(appendrel->relids, required_outer));
 
    /* If we already have a PPI for this parameterization, just return it */
    if ((ppi = find_param_path_info(appendrel, required_outer)))
        return ppi;
 
    /* Else build the ParamPathInfo */
    ppi = makeNode(ParamPathInfo);
    ppi->ppi_req_outer = required_outer;
    ppi->ppi_rows = 0;
    ppi->ppi_clauses = NIL;
    ppi->ppi_serials = NULL;
    appendrel->ppilist = lappend(appendrel->ppilist, ppi);
 
    return ppi;
}
 
/*
 * Returns a ParamPathInfo for the parameterization given by required_outer, if
 * already available in the given rel. Returns NULL otherwise.
 */
ParamPathInfo *
find_param_path_info(RelOptInfo *rel, Relids required_outer)
{
    ListCell   *lc;
 
    foreach(lc, rel->ppilist)
    {
        ParamPathInfo *ppi = (ParamPathInfo *) lfirst(lc);
 
        if (bms_equal(ppi->ppi_req_outer, required_outer))
            return ppi;
    }
 
    return NULL;
}
 
/*
 * get_param_path_clause_serials
 *      Given a parameterized Path, return the set of pushed-down clauses
 *      (identified by rinfo_serial numbers) enforced within the Path.
 */
Bitmapset *
get_param_path_clause_serials(Path *path)
{
    if (path->param_info == NULL)
        return NULL;            /* not parameterized */
 
    /*
     * We don't currently support parameterized MergeAppend paths, as
     * explained in the comments for generate_orderedappend_paths.
     */
    Assert(!IsA(path, MergeAppendPath));
 
    if (IsA(path, NestPath) ||
        IsA(path, MergePath) ||
        IsA(path, HashPath))
    {
        /*
         * For a join path, combine clauses enforced within either input path
         * with those enforced as joinrestrictinfo in this path.  Note that
         * joinrestrictinfo may include some non-pushed-down clauses, but for
         * current purposes it's okay if we include those in the result. (To
         * be more careful, we could check for clause_relids overlapping the
         * path parameterization, but it's not worth the cycles for now.)
         */
        JoinPath   *jpath = (JoinPath *) path;
        Bitmapset  *pserials;
        ListCell   *lc;
 
        pserials = NULL;
        pserials = bms_add_members(pserials,
                                   get_param_path_clause_serials(jpath->outerjoinpath));
        pserials = bms_add_members(pserials,
                                   get_param_path_clause_serials(jpath->innerjoinpath));
        foreach(lc, jpath->joinrestrictinfo)
        {
            RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
 
            pserials = bms_add_member(pserials, rinfo->rinfo_serial);
        }
        return pserials;
    }
    else if (IsA(path, AppendPath))
    {
        /*
         * For an appendrel, take the intersection of the sets of clauses
         * enforced in each input path.
         */
        AppendPath *apath = (AppendPath *) path;
        Bitmapset  *pserials;
        ListCell   *lc;
 
        pserials = NULL;
        foreach(lc, apath->subpaths)
        {
            Path       *subpath = (Path *) lfirst(lc);
            Bitmapset  *subserials;
 
            subserials = get_param_path_clause_serials(subpath);
            if (lc == list_head(apath->subpaths))
                pserials = bms_copy(subserials);
            else
                pserials = bms_int_members(pserials, subserials);
        }
        return pserials;
    }
    else
    {
        /*
         * Otherwise, it's a baserel path and we can use the
         * previously-computed set of serial numbers.
         */
        return path->param_info->ppi_serials;
    }
}
 
/*
 * build_joinrel_partition_info
 *      Checks if the two relations being joined can use partitionwise join
 *      and if yes, initialize partitioning information of the resulting
 *      partitioned join relation.
 */
static void
build_joinrel_partition_info(PlannerInfo *root,
                             RelOptInfo *joinrel, RelOptInfo *outer_rel,
                             RelOptInfo *inner_rel, SpecialJoinInfo *sjinfo,
                             List *restrictlist)
{
    PartitionScheme part_scheme;
 
    /* Nothing to do if partitionwise join technique is disabled. */
    if ((joinrel->pgs_mask & PGS_CONSIDER_PARTITIONWISE) == 0)
    {
        Assert(!IS_PARTITIONED_REL(joinrel));
        return;
    }
 
    /*
     * We can only consider this join as an input to further partitionwise
     * joins if (a) the input relations are partitioned and have
     * consider_partitionwise_join=true, (b) the partition schemes match, and
     * (c) we can identify an equi-join between the partition keys.  Note that
     * if it were possible for have_partkey_equi_join to return different
     * answers for the same joinrel depending on which join ordering we try
     * first, this logic would break.  That shouldn't happen, though, because
     * of the way the query planner deduces implied equalities and reorders
     * the joins.  Please see optimizer/README for details.
     */
    if (outer_rel->part_scheme == NULL || inner_rel->part_scheme == NULL ||
        !outer_rel->consider_partitionwise_join ||
        !inner_rel->consider_partitionwise_join ||
        outer_rel->part_scheme != inner_rel->part_scheme ||
        !have_partkey_equi_join(root, joinrel, outer_rel, inner_rel,
                                sjinfo->jointype, restrictlist))
    {
        Assert(!IS_PARTITIONED_REL(joinrel));
        return;
    }
 
    part_scheme = outer_rel->part_scheme;
 
    /*
     * This function will be called only once for each joinrel, hence it
     * should not have partitioning fields filled yet.
     */
    Assert(!joinrel->part_scheme && !joinrel->partexprs &&
           !joinrel->nullable_partexprs && !joinrel->part_rels &&
           !joinrel->boundinfo);
 
    /*
     * If the join relation is partitioned, it uses the same partitioning
     * scheme as the joining relations.
     *
     * Note: we calculate the partition bounds, number of partitions, and
     * child-join relations of the join relation in try_partitionwise_join().
     */
    joinrel->part_scheme = part_scheme;
    set_joinrel_partition_key_exprs(joinrel, outer_rel, inner_rel,
                                    sjinfo->jointype);
 
    /*
     * Set the consider_partitionwise_join flag.
     */
    Assert(outer_rel->consider_partitionwise_join);
    Assert(inner_rel->consider_partitionwise_join);
    joinrel->consider_partitionwise_join = true;
}
 
/*
 * have_partkey_equi_join
 *
 * Returns true if there exist equi-join conditions involving pairs
 * of matching partition keys of the relations being joined for all
 * partition keys.
 */
static bool
have_partkey_equi_join(PlannerInfo *root, RelOptInfo *joinrel,
                       RelOptInfo *rel1, RelOptInfo *rel2,
                       JoinType jointype, List *restrictlist)
{
    PartitionScheme part_scheme = rel1->part_scheme;
    bool        pk_known_equal[PARTITION_MAX_KEYS];
    int         num_equal_pks;
    ListCell   *lc;
 
    /*
     * This function must only be called when the joined relations have same
     * partitioning scheme.
     */
    Assert(rel1->part_scheme == rel2->part_scheme);
    Assert(part_scheme);
 
    /* We use a bool array to track which partkey columns are known equal */
    memset(pk_known_equal, 0, sizeof(pk_known_equal));
    /* ... as well as a count of how many are known equal */
    num_equal_pks = 0;
 
    /* First, look through the join's restriction clauses */
    foreach(lc, restrictlist)
    {
        RestrictInfo *rinfo = lfirst_node(RestrictInfo, lc);
        OpExpr     *opexpr;
        Expr       *expr1;
        Expr       *expr2;
        bool        strict_op;
        int         ipk1;
        int         ipk2;
 
        /* If processing an outer join, only use its own join clauses. */
        if (IS_OUTER_JOIN(jointype) &&
            RINFO_IS_PUSHED_DOWN(rinfo, joinrel->relids))
            continue;
 
        /* Skip clauses which can not be used for a join. */
        if (!rinfo->can_join)
            continue;
 
        /* Skip clauses which are not equality conditions. */
        if (!rinfo->mergeopfamilies && !OidIsValid(rinfo->hashjoinoperator))
            continue;
 
        /* Should be OK to assume it's an OpExpr. */
        opexpr = castNode(OpExpr, rinfo->clause);
 
        /* Match the operands to the relation. */
        if (bms_is_subset(rinfo->left_relids, rel1->relids) &&
            bms_is_subset(rinfo->right_relids, rel2->relids))
        {
            expr1 = linitial(opexpr->args);
            expr2 = lsecond(opexpr->args);
        }
        else if (bms_is_subset(rinfo->left_relids, rel2->relids) &&
                 bms_is_subset(rinfo->right_relids, rel1->relids))
        {
            expr1 = lsecond(opexpr->args);
            expr2 = linitial(opexpr->args);
        }
        else
            continue;
 
        /*
         * Now we need to know whether the join operator is strict; see
         * comments in pathnodes.h.
         */
        strict_op = op_strict(opexpr->opno);
 
        /*
         * Vars appearing in the relation's partition keys will not have any
         * varnullingrels, but those in expr1 and expr2 will if we're above
         * outer joins that could null the respective rels.  It's okay to
         * match anyway, if the join operator is strict.
         */
        if (strict_op)
        {
            if (bms_overlap(rel1->relids, root->outer_join_rels))
                expr1 = (Expr *) remove_nulling_relids((Node *) expr1,
                                                       root->outer_join_rels,
                                                       NULL);
            if (bms_overlap(rel2->relids, root->outer_join_rels))
                expr2 = (Expr *) remove_nulling_relids((Node *) expr2,
                                                       root->outer_join_rels,
                                                       NULL);
        }
 
        /*
         * Only clauses referencing the partition keys are useful for
         * partitionwise join.
         */
        ipk1 = match_expr_to_partition_keys(expr1, rel1, strict_op);
        if (ipk1 < 0)
            continue;
        ipk2 = match_expr_to_partition_keys(expr2, rel2, strict_op);
        if (ipk2 < 0)
            continue;
 
        /*
         * If the clause refers to keys at different ordinal positions, it can
         * not be used for partitionwise join.
         */
        if (ipk1 != ipk2)
            continue;
 
        /* Ignore clause if we already proved these keys equal. */
        if (pk_known_equal[ipk1])
            continue;
 
        /* Reject if the partition key collation differs from the clause's. */
        if (rel1->part_scheme->partcollation[ipk1] != opexpr->inputcollid)
            return false;
 
        /*
         * The clause allows partitionwise join only if it uses the same
         * operator family as that specified by the partition key.
         */
        if (part_scheme->strategy == PARTITION_STRATEGY_HASH)
        {
            if (!OidIsValid(rinfo->hashjoinoperator) ||
                !op_in_opfamily(rinfo->hashjoinoperator,
                                part_scheme->partopfamily[ipk1]))
                continue;
        }
        else if (!list_member_oid(rinfo->mergeopfamilies,
                                  part_scheme->partopfamily[ipk1]))
            continue;
 
        /* Mark the partition key as having an equi-join clause. */
        pk_known_equal[ipk1] = true;
 
        /* We can stop examining clauses once we prove all keys equal. */
        if (++num_equal_pks == part_scheme->partnatts)
            return true;
    }
 
    /*
     * Also check to see if any keys are known equal by equivclass.c.  In most
     * cases there would have been a join restriction clause generated from
     * any EC that had such knowledge, but there might be no such clause, or
     * it might happen to constrain other members of the ECs than the ones we
     * are looking for.
     */
    for (int ipk = 0; ipk < part_scheme->partnatts; ipk++)
    {
        Oid         btree_opfamily;
 
        /* Ignore if we already proved these keys equal. */
        if (pk_known_equal[ipk])
            continue;
 
        /*
         * We need a btree opfamily to ask equivclass.c about.  If the
         * partopfamily is a hash opfamily, look up its equality operator, and
         * select some btree opfamily that that operator is part of.  (Any
         * such opfamily should be good enough, since equivclass.c will track
         * multiple opfamilies as appropriate.)
         */
        if (part_scheme->strategy == PARTITION_STRATEGY_HASH)
        {
            Oid         eq_op;
            List       *eq_opfamilies;
 
            eq_op = get_opfamily_member(part_scheme->partopfamily[ipk],
                                        part_scheme->partopcintype[ipk],
                                        part_scheme->partopcintype[ipk],
                                        HTEqualStrategyNumber);
            if (!OidIsValid(eq_op))
                break;          /* we're not going to succeed */
            eq_opfamilies = get_mergejoin_opfamilies(eq_op);
            if (eq_opfamilies == NIL)
                break;          /* we're not going to succeed */
            btree_opfamily = linitial_oid(eq_opfamilies);
        }
        else
            btree_opfamily = part_scheme->partopfamily[ipk];
 
        /*
         * We consider only non-nullable partition keys here; nullable ones
         * would not be treated as part of the same equivalence classes as
         * non-nullable ones.
         */
        foreach(lc, rel1->partexprs[ipk])
        {
            Node       *expr1 = (Node *) lfirst(lc);
            ListCell   *lc2;
            Oid         partcoll1 = rel1->part_scheme->partcollation[ipk];
            Oid         exprcoll1 = exprCollation(expr1);
 
            foreach(lc2, rel2->partexprs[ipk])
            {
                Node       *expr2 = (Node *) lfirst(lc2);
 
                if (exprs_known_equal(root, expr1, expr2, btree_opfamily))
                {
                    /*
                     * Ensure that the collation of the expression matches
                     * that of the partition key. Checking just one collation
                     * (partcoll1 and exprcoll1) suffices because partcoll1
                     * and partcoll2, as well as exprcoll1 and exprcoll2,
                     * should be identical. This holds because both rel1 and
                     * rel2 use the same PartitionScheme and expr1 and expr2
                     * are equal.
                     */
                    if (partcoll1 == exprcoll1)
                    {
                        Oid         partcoll2 PG_USED_FOR_ASSERTS_ONLY =
                            rel2->part_scheme->partcollation[ipk];
                        Oid         exprcoll2 PG_USED_FOR_ASSERTS_ONLY =
                            exprCollation(expr2);
 
                        Assert(partcoll2 == exprcoll2);
                        pk_known_equal[ipk] = true;
                        break;
                    }
                }
            }
            if (pk_known_equal[ipk])
                break;
        }
 
        if (pk_known_equal[ipk])
        {
            /* We can stop examining keys once we prove all keys equal. */
            if (++num_equal_pks == part_scheme->partnatts)
                return true;
        }
        else
            break;              /* no chance to succeed, give up */
    }
 
    return false;
}
 
/*
 * match_expr_to_partition_keys
 *
 * Tries to match an expression to one of the nullable or non-nullable
 * partition keys of "rel".  Returns the matched key's ordinal position,
 * or -1 if the expression could not be matched to any of the keys.
 *
 * strict_op must be true if the expression will be compared with the
 * partition key using a strict operator.  This allows us to consider
 * nullable as well as nonnullable partition keys.
 */
static int
match_expr_to_partition_keys(Expr *expr, RelOptInfo *rel, bool strict_op)
{
    int         cnt;
 
    /* This function should be called only for partitioned relations. */
    Assert(rel->part_scheme);
    Assert(rel->partexprs);
    Assert(rel->nullable_partexprs);
 
    /* Remove any relabel decorations. */
    while (IsA(expr, RelabelType))
        expr = (Expr *) (castNode(RelabelType, expr))->arg;
 
    for (cnt = 0; cnt < rel->part_scheme->partnatts; cnt++)
    {
        ListCell   *lc;
 
        /* We can always match to the non-nullable partition keys. */
        foreach(lc, rel->partexprs[cnt])
        {
            if (equal(lfirst(lc), expr))
                return cnt;
        }
 
        if (!strict_op)
            continue;
 
        /*
         * If it's a strict join operator then a NULL partition key on one
         * side will not join to any partition key on the other side, and in
         * particular such a row can't join to a row from a different
         * partition on the other side.  So, it's okay to search the nullable
         * partition keys as well.
         */
        foreach(lc, rel->nullable_partexprs[cnt])
        {
            if (equal(lfirst(lc), expr))
                return cnt;
        }
    }
 
    return -1;
}
 
/*
 * set_joinrel_partition_key_exprs
 *      Initialize partition key expressions for a partitioned joinrel.
 */
static void
set_joinrel_partition_key_exprs(RelOptInfo *joinrel,
                                RelOptInfo *outer_rel, RelOptInfo *inner_rel,
                                JoinType jointype)
{
    PartitionScheme part_scheme = joinrel->part_scheme;
    int         partnatts = part_scheme->partnatts;
 
    joinrel->partexprs = palloc0_array(List *, partnatts);
    joinrel->nullable_partexprs = palloc0_array(List *, partnatts);
 
    /*
     * The joinrel's partition expressions are the same as those of the input
     * rels, but we must properly classify them as nullable or not in the
     * joinrel's output.  (Also, we add some more partition expressions if
     * it's a FULL JOIN.)
     */
    for (int cnt = 0; cnt < partnatts; cnt++)
    {
        /* mark these const to enforce that we copy them properly */
        const List *outer_expr = outer_rel->partexprs[cnt];
        const List *outer_null_expr = outer_rel->nullable_partexprs[cnt];
        const List *inner_expr = inner_rel->partexprs[cnt];
        const List *inner_null_expr = inner_rel->nullable_partexprs[cnt];
        List       *partexpr = NIL;
        List       *nullable_partexpr = NIL;
        ListCell   *lc;
 
        switch (jointype)
        {
                /*
                 * A join relation resulting from an INNER join may be
                 * regarded as partitioned by either of the inner and outer
                 * relation keys.  For example, A INNER JOIN B ON A.a = B.b
                 * can be regarded as partitioned on either A.a or B.b.  So we
                 * add both keys to the joinrel's partexpr lists.  However,
                 * anything that was already nullable still has to be treated
                 * as nullable.
                 */
            case JOIN_INNER:
                partexpr = list_concat_copy(outer_expr, inner_expr);
                nullable_partexpr = list_concat_copy(outer_null_expr,
                                                     inner_null_expr);
                break;
 
                /*
                 * A join relation resulting from a SEMI or ANTI join may be
                 * regarded as partitioned by the outer relation keys.  The
                 * inner relation's keys are no longer interesting; since they
                 * aren't visible in the join output, nothing could join to
                 * them.
                 */
            case JOIN_SEMI:
            case JOIN_ANTI:
                partexpr = list_copy(outer_expr);
                nullable_partexpr = list_copy(outer_null_expr);
                break;
 
                /*
                 * A join relation resulting from a LEFT OUTER JOIN likewise
                 * may be regarded as partitioned on the (non-nullable) outer
                 * relation keys.  The inner (nullable) relation keys are okay
                 * as partition keys for further joins as long as they involve
                 * strict join operators.
                 */
            case JOIN_LEFT:
                partexpr = list_copy(outer_expr);
                nullable_partexpr = list_concat_copy(inner_expr,
                                                     outer_null_expr);
                nullable_partexpr = list_concat(nullable_partexpr,
                                                inner_null_expr);
                break;
 
                /*
                 * For FULL OUTER JOINs, both relations are nullable, so the
                 * resulting join relation may be regarded as partitioned on
                 * either of inner and outer relation keys, but only for joins
                 * that involve strict join operators.
                 */
            case JOIN_FULL:
                nullable_partexpr = list_concat_copy(outer_expr,
                                                     inner_expr);
                nullable_partexpr = list_concat(nullable_partexpr,
                                                outer_null_expr);
                nullable_partexpr = list_concat(nullable_partexpr,
                                                inner_null_expr);
 
                /*
                 * Also add CoalesceExprs corresponding to each possible
                 * full-join output variable (that is, left side coalesced to
                 * right side), so that we can match equijoin expressions
                 * using those variables.  We really only need these for
                 * columns merged by JOIN USING, and only with the pairs of
                 * input items that correspond to the data structures that
                 * parse analysis would build for such variables.  But it's
                 * hard to tell which those are, so just make all the pairs.
                 * Extra items in the nullable_partexprs list won't cause big
                 * problems.  (It's possible that such items will get matched
                 * to user-written COALESCEs, but it should still be valid to
                 * partition on those, since they're going to be either the
                 * partition column or NULL; it's the same argument as for
                 * partitionwise nesting of any outer join.)  We assume no
                 * type coercions are needed to make the coalesce expressions,
                 * since columns of different types won't have gotten
                 * classified as the same PartitionScheme.  Note that we
                 * intentionally leave out the varnullingrels decoration that
                 * would ordinarily appear on the Vars inside these
                 * CoalesceExprs, because have_partkey_equi_join will strip
                 * varnullingrels from the expressions it will compare to the
                 * partexprs.
                 */
                foreach(lc, list_concat_copy(outer_expr, outer_null_expr))
                {
                    Node       *larg = (Node *) lfirst(lc);
                    ListCell   *lc2;
 
                    foreach(lc2, list_concat_copy(inner_expr, inner_null_expr))
                    {
                        Node       *rarg = (Node *) lfirst(lc2);
                        CoalesceExpr *c = makeNode(CoalesceExpr);
 
                        c->coalescetype = exprType(larg);
                        c->coalescecollid = exprCollation(larg);
                        c->args = list_make2(larg, rarg);
                        c->location = -1;
                        nullable_partexpr = lappend(nullable_partexpr, c);
                    }
                }
                break;
 
            default:
                elog(ERROR, "unrecognized join type: %d", (int) jointype);
        }
 
        joinrel->partexprs[cnt] = partexpr;
        joinrel->nullable_partexprs[cnt] = nullable_partexpr;
    }
}
 
/*
 * build_child_join_reltarget
 *    Set up a child-join relation's reltarget from a parent-join relation.
 */
static void
build_child_join_reltarget(PlannerInfo *root,
                           RelOptInfo *parentrel,
                           RelOptInfo *childrel,
                           int nappinfos,
                           AppendRelInfo **appinfos)
{
    /* Build the targetlist */
    childrel->reltarget->exprs = (List *)
        adjust_appendrel_attrs(root,
                               (Node *) parentrel->reltarget->exprs,
                               nappinfos, appinfos);
 
    /* Set the cost and width fields */
    childrel->reltarget->cost.startup = parentrel->reltarget->cost.startup;
    childrel->reltarget->cost.per_tuple = parentrel->reltarget->cost.per_tuple;
    childrel->reltarget->width = parentrel->reltarget->width;
}
 
/*
 * create_rel_agg_info
 *    Create the RelAggInfo structure for the given relation if it can produce
 *    grouped paths.  The given relation is the non-grouped one which has the
 *    reltarget already constructed.
 *
 * calculate_grouped_rows: if true, calculate the estimated number of grouped
 * rows for the relation.  If false, skip the estimation to avoid unnecessary
 * planning overhead.
 */
RelAggInfo *
create_rel_agg_info(PlannerInfo *root, RelOptInfo *rel,
                    bool calculate_grouped_rows)
{
    ListCell   *lc;
    RelAggInfo *result;
    PathTarget *agg_input;
    PathTarget *target;
    List       *group_clauses = NIL;
    List       *group_exprs = NIL;
 
    /*
     * The lists of aggregate expressions and grouping expressions should have
     * been constructed.
     */
    Assert(root->agg_clause_list != NIL);
    Assert(root->group_expr_list != NIL);
 
    /*
     * If this is a child rel, the grouped rel for its parent rel must have
     * been created if it can.  So we can just use parent's RelAggInfo if
     * there is one, with appropriate variable substitutions.
     */
    if (IS_OTHER_REL(rel))
    {
        RelOptInfo *grouped_rel;
        RelAggInfo *agg_info;
 
        grouped_rel = rel->top_parent->grouped_rel;
        if (grouped_rel == NULL)
            return NULL;
 
        Assert(IS_GROUPED_REL(grouped_rel));
 
        /* Must do multi-level transformation */
        agg_info = (RelAggInfo *)
            adjust_appendrel_attrs_multilevel(root,
                                              (Node *) grouped_rel->agg_info,
                                              rel,
                                              rel->top_parent);
 
        agg_info->apply_agg_at = NULL;  /* caller will change this later */
 
        if (calculate_grouped_rows)
        {
            agg_info->grouped_rows =
                estimate_num_groups(root, agg_info->group_exprs,
                                    rel->rows, NULL, NULL);
 
            /*
             * The grouped paths for the given relation are considered useful
             * iff the average group size is no less than
             * min_eager_agg_group_size.
             */
            agg_info->agg_useful =
                (rel->rows / agg_info->grouped_rows) >= min_eager_agg_group_size;
        }
 
        return agg_info;
    }
 
    /* Check if it's possible to produce grouped paths for this relation. */
    if (!eager_aggregation_possible_for_relation(root, rel))
        return NULL;
 
    /*
     * Create targets for the grouped paths and for the input paths of the
     * grouped paths.
     */
    target = create_empty_pathtarget();
    agg_input = create_empty_pathtarget();
 
    /* ... and initialize these targets */
    if (!init_grouping_targets(root, rel, target, agg_input,
                               &group_clauses, &group_exprs))
        return NULL;
 
    /*
     * Eager aggregation is not applicable if there are no available grouping
     * expressions.
     */
    if (group_clauses == NIL)
        return NULL;
 
    /* Add aggregates to the grouping target */
    foreach(lc, root->agg_clause_list)
    {
        AggClauseInfo *ac_info = lfirst_node(AggClauseInfo, lc);
        Aggref     *aggref;
 
        Assert(IsA(ac_info->aggref, Aggref));
 
        aggref = (Aggref *) copyObject(ac_info->aggref);
        mark_partial_aggref(aggref, AGGSPLIT_INITIAL_SERIAL);
 
        add_column_to_pathtarget(target, (Expr *) aggref, 0);
    }
 
    /* Set the estimated eval cost and output width for both targets */
    set_pathtarget_cost_width(root, target);
    set_pathtarget_cost_width(root, agg_input);
 
    /* build the RelAggInfo result */
    result = makeNode(RelAggInfo);
    result->target = target;
    result->agg_input = agg_input;
    result->group_clauses = group_clauses;
    result->group_exprs = group_exprs;
    result->apply_agg_at = NULL;    /* caller will change this later */
 
    if (calculate_grouped_rows)
    {
        result->grouped_rows = estimate_num_groups(root, result->group_exprs,
                                                   rel->rows, NULL, NULL);
 
        /*
         * The grouped paths for the given relation are considered useful iff
         * the average group size is no less than min_eager_agg_group_size.
         */
        result->agg_useful =
            (rel->rows / result->grouped_rows) >= min_eager_agg_group_size;
    }
 
    return result;
}
 
/*
 * eager_aggregation_possible_for_relation
 *    Check if it's possible to produce grouped paths for the given relation.
 */
static bool
eager_aggregation_possible_for_relation(PlannerInfo *root, RelOptInfo *rel)
{
    ListCell   *lc;
    int         cur_relid;
 
    /*
     * Check to see if the given relation is in the nullable side of an outer
     * join.  In this case, we cannot push a partial aggregation down to the
     * relation, because the NULL-extended rows produced by the outer join
     * would not be available when we perform the partial aggregation, while
     * with a non-eager-aggregation plan these rows are available for the
     * top-level aggregation.  Doing so may result in the rows being grouped
     * differently than expected, or produce incorrect values from the
     * aggregate functions.
     */
    cur_relid = -1;
    while ((cur_relid = bms_next_member(rel->relids, cur_relid)) >= 0)
    {
        RelOptInfo *baserel = find_base_rel_ignore_join(root, cur_relid);
 
        if (baserel == NULL)
            continue;           /* ignore outer joins in rel->relids */
 
        if (!bms_is_subset(baserel->nulling_relids, rel->relids))
            return false;
    }
 
    /*
     * For now we don't try to support PlaceHolderVars.
     */
    foreach(lc, rel->reltarget->exprs)
    {
        Expr       *expr = lfirst(lc);
 
        if (IsA(expr, PlaceHolderVar))
            return false;
    }
 
    /* Caller should only pass base relations or joins. */
    Assert(rel->reloptkind == RELOPT_BASEREL ||
           rel->reloptkind == RELOPT_JOINREL);
 
    /*
     * Check if all aggregate expressions can be evaluated on this relation
     * level.
     */
    foreach(lc, root->agg_clause_list)
    {
        AggClauseInfo *ac_info = lfirst_node(AggClauseInfo, lc);
 
        Assert(IsA(ac_info->aggref, Aggref));
 
        /*
         * Give up if any aggregate requires relations other than the current
         * one.  If the aggregate requires the current relation plus
         * additional relations, grouping the current relation could make some
         * input rows unavailable for the higher aggregate and may reduce the
         * number of input rows it receives.  If the aggregate does not
         * require the current relation at all, it should not be grouped, as
         * we do not support joining two grouped relations.
         */
        if (!bms_is_subset(ac_info->agg_eval_at, rel->relids))
            return false;
    }
 
    return true;
}
 
/*
 * init_grouping_targets
 *    Initialize the target for grouped paths (target) as well as the target
 *    for paths that generate input for the grouped paths (agg_input).
 *
 * We also construct the list of SortGroupClauses and the list of grouping
 * expressions for the partial aggregation, and return them in *group_clause
 * and *group_exprs.
 *
 * Return true if the targets could be initialized, false otherwise.
 */
static bool
init_grouping_targets(PlannerInfo *root, RelOptInfo *rel,
                      PathTarget *target, PathTarget *agg_input,
                      List **group_clauses, List **group_exprs)
{
    ListCell   *lc;
    List       *possibly_dependent = NIL;
    Index       maxSortGroupRef;
 
    /* Identify the max sortgroupref */
    maxSortGroupRef = 0;
    foreach(lc, root->processed_tlist)
    {
        Index       ref = ((TargetEntry *) lfirst(lc))->ressortgroupref;
 
        if (ref > maxSortGroupRef)
            maxSortGroupRef = ref;
    }
 
    /*
     * At this point, all Vars from this relation that are needed by upper
     * joins or are required in the final targetlist should already be present
     * in its reltarget.  Therefore, we can safely iterate over this
     * relation's reltarget->exprs to construct the PathTarget and grouping
     * clauses for the grouped paths.
     */
    foreach(lc, rel->reltarget->exprs)
    {
        Expr       *expr = (Expr *) lfirst(lc);
        Index       sortgroupref;
 
        /*
         * Given that PlaceHolderVar currently prevents us from doing eager
         * aggregation, the source target cannot contain anything more complex
         * than a Var.
         */
        Assert(IsA(expr, Var));
 
        /*
         * Get the sortgroupref of the expr if it is found among, or can be
         * deduced from, the original grouping expressions.
         */
        sortgroupref = get_expression_sortgroupref(root, expr);
        if (sortgroupref > 0)
        {
            SortGroupClause *sgc;
 
            /* Find the matching SortGroupClause */
            sgc = get_sortgroupref_clause(sortgroupref, root->processed_groupClause);
            Assert(sgc->tleSortGroupRef <= maxSortGroupRef);
 
            /*
             * If the target expression is to be used as a grouping key, it
             * should be emitted by the grouped paths that have been pushed
             * down to this relation level.
             */
            add_column_to_pathtarget(target, expr, sortgroupref);
 
            /*
             * ... and it also should be emitted by the input paths.
             */
            add_column_to_pathtarget(agg_input, expr, sortgroupref);
 
            /*
             * Record this SortGroupClause and grouping expression.  Note that
             * this SortGroupClause might have already been recorded.
             */
            if (!list_member(*group_clauses, sgc))
            {
                *group_clauses = lappend(*group_clauses, sgc);
                *group_exprs = lappend(*group_exprs, expr);
            }
        }
        else if (is_var_needed_by_join(root, (Var *) expr, rel))
        {
            /*
             * The expression is needed for an upper join but is neither in
             * the GROUP BY clause nor derivable from it using EC (otherwise,
             * it would have already been included in the targets above).  We
             * need to create a special SortGroupClause for this expression.
             *
             * It is important to include such expressions in the grouping
             * keys.  This is essential to ensure that an aggregated row from
             * the partial aggregation matches the other side of the join if
             * and only if each row in the partial group does.  This ensures
             * that all rows within the same partial group share the same
             * 'destiny', which is crucial for maintaining correctness.
             */
            SortGroupClause *sgc;
            TypeCacheEntry *tce;
            Oid         equalimageproc;
 
            /*
             * But first, check if equality implies image equality for this
             * expression.  If not, we cannot use it as a grouping key.  See
             * comments in create_grouping_expr_infos().
             */
            tce = lookup_type_cache(exprType((Node *) expr),
                                    TYPECACHE_BTREE_OPFAMILY);
            if (!OidIsValid(tce->btree_opf) ||
                !OidIsValid(tce->btree_opintype))
                return false;
 
            equalimageproc = get_opfamily_proc(tce->btree_opf,
                                               tce->btree_opintype,
                                               tce->btree_opintype,
                                               BTEQUALIMAGE_PROC);
            if (!OidIsValid(equalimageproc) ||
                !DatumGetBool(OidFunctionCall1Coll(equalimageproc,
                                                   tce->typcollation,
                                                   ObjectIdGetDatum(tce->btree_opintype))))
                return false;
 
            /* Create the SortGroupClause. */
            sgc = makeNode(SortGroupClause);
 
            /* Initialize the SortGroupClause. */
            sgc->tleSortGroupRef = ++maxSortGroupRef;
            get_sort_group_operators(exprType((Node *) expr),
                                     false, true, false,
                                     &sgc->sortop, &sgc->eqop, NULL,
                                     &sgc->hashable);
 
            /* This expression should be emitted by the grouped paths */
            add_column_to_pathtarget(target, expr, sgc->tleSortGroupRef);
 
            /* ... and it also should be emitted by the input paths. */
            add_column_to_pathtarget(agg_input, expr, sgc->tleSortGroupRef);
 
            /* Record this SortGroupClause and grouping expression */
            *group_clauses = lappend(*group_clauses, sgc);
            *group_exprs = lappend(*group_exprs, expr);
        }
        else if (is_var_in_aggref_only(root, (Var *) expr))
        {
            /*
             * The expression is referenced by an aggregate function pushed
             * down to this relation and does not appear elsewhere in the
             * targetlist or havingQual.  Add it to 'agg_input' but not to
             * 'target'.
             */
            add_new_column_to_pathtarget(agg_input, expr);
        }
        else
        {
            /*
             * The expression may be functionally dependent on other
             * expressions in the target, but we cannot verify this until all
             * target expressions have been constructed.
             */
            possibly_dependent = lappend(possibly_dependent, expr);
        }
    }
 
    /*
     * Now we can verify whether an expression is functionally dependent on
     * others.
     */
    foreach(lc, possibly_dependent)
    {
        Var        *tvar;
        List       *deps = NIL;
        RangeTblEntry *rte;
 
        tvar = lfirst_node(Var, lc);
        rte = root->simple_rte_array[tvar->varno];
 
        if (check_functional_grouping(rte->relid, tvar->varno,
                                      tvar->varlevelsup,
                                      target->exprs, &deps))
        {
            /*
             * The expression is functionally dependent on other target
             * expressions, so it can be included in the targets.  Since it
             * will not be used as a grouping key, a sortgroupref is not
             * needed for it.
             */
            add_new_column_to_pathtarget(target, (Expr *) tvar);
            add_new_column_to_pathtarget(agg_input, (Expr *) tvar);
        }
        else
        {
            /*
             * We may arrive here with a grouping expression that is proven
             * redundant by EquivalenceClass processing, such as 't1.a' in the
             * query below.
             *
             * select max(t1.c) from t t1, t t2 where t1.a = 1 group by t1.a,
             * t1.b;
             *
             * For now we just give up in this case.
             */
            return false;
        }
    }
 
    return true;
}
 
/*
 * is_var_in_aggref_only
 *    Check whether the given Var appears in aggregate expressions and not
 *    elsewhere in the targetlist or havingQual.
 */
static bool
is_var_in_aggref_only(PlannerInfo *root, Var *var)
{
    ListCell   *lc;
 
    /*
     * Search the list of aggregate expressions for the Var.
     */
    foreach(lc, root->agg_clause_list)
    {
        AggClauseInfo *ac_info = lfirst_node(AggClauseInfo, lc);
        List       *vars;
 
        Assert(IsA(ac_info->aggref, Aggref));
 
        if (!bms_is_member(var->varno, ac_info->agg_eval_at))
            continue;
 
        vars = pull_var_clause((Node *) ac_info->aggref,
                               PVC_RECURSE_AGGREGATES |
                               PVC_RECURSE_WINDOWFUNCS |
                               PVC_RECURSE_PLACEHOLDERS);
 
        if (list_member(vars, var))
        {
            list_free(vars);
            break;
        }
 
        list_free(vars);
    }
 
    return (lc != NULL && !list_member(root->tlist_vars, var));
}
 
/*
 * is_var_needed_by_join
 *    Check if the given Var is needed by joins above the current rel.
 */
static bool
is_var_needed_by_join(PlannerInfo *root, Var *var, RelOptInfo *rel)
{
    Relids      relids;
    int         attno;
    RelOptInfo *baserel;
 
    /*
     * Note that when checking if the Var is needed by joins above, we want to
     * exclude cases where the Var is only needed in the final targetlist.  So
     * include "relation 0" in the check.
     */
    relids = bms_copy(rel->relids);
    relids = bms_add_member(relids, 0);
 
    baserel = find_base_rel(root, var->varno);
    attno = var->varattno - baserel->min_attr;
 
    return bms_nonempty_difference(baserel->attr_needed[attno], relids);
}
 
/*
 * get_expression_sortgroupref
 *    Return the sortgroupref of the given "expr" if it is found among the
 *    original grouping expressions, or is known equal to any of the original
 *    grouping expressions due to equivalence relationships.  Return 0 if no
 *    match is found.
 */
static Index
get_expression_sortgroupref(PlannerInfo *root, Expr *expr)
{
    ListCell   *lc;
 
    Assert(IsA(expr, Var));
 
    foreach(lc, root->group_expr_list)
    {
        GroupingExprInfo *ge_info = lfirst_node(GroupingExprInfo, lc);
        ListCell   *lc1;
 
        Assert(IsA(ge_info->expr, Var));
        Assert(ge_info->sortgroupref > 0);
 
        if (equal(expr, ge_info->expr))
            return ge_info->sortgroupref;
 
        if (ge_info->ec == NULL ||
            !bms_is_member(((Var *) expr)->varno, ge_info->ec->ec_relids))
            continue;
 
        /*
         * Scan the EquivalenceClass, looking for a match to the given
         * expression.  We ignore child members here.
         */
        foreach(lc1, ge_info->ec->ec_members)
        {
            EquivalenceMember *em = (EquivalenceMember *) lfirst(lc1);
 
            /* Child members should not exist in ec_members */
            Assert(!em->em_is_child);
 
            if (equal(expr, em->em_expr))
                return ge_info->sortgroupref;
        }
    }
 
    /* no match is found */
    return 0;
}