initsplan.c

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/*-------------------------------------------------------------------------
 *
 * initsplan.c
 *    Target list, group by, qualification, joininfo initialization routines
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/optimizer/plan/initsplan.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "access/nbtree.h"
#include "access/sysattr.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_type.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/inherit.h"
#include "optimizer/joininfo.h"
#include "optimizer/optimizer.h"
#include "optimizer/pathnode.h"
#include "optimizer/paths.h"
#include "optimizer/placeholder.h"
#include "optimizer/planmain.h"
#include "optimizer/planner.h"
#include "optimizer/restrictinfo.h"
#include "parser/analyze.h"
#include "rewrite/rewriteManip.h"
#include "utils/lsyscache.h"
#include "utils/rel.h"
#include "utils/typcache.h"
 
/* These parameters are set by GUC */
int         from_collapse_limit;
int         join_collapse_limit;
 
 
/*
 * deconstruct_jointree requires multiple passes over the join tree, because we
 * need to finish computing JoinDomains before we start distributing quals.
 * As long as we have to do that, other information such as the relevant
 * qualscopes might as well be computed in the first pass too.
 *
 * deconstruct_recurse recursively examines the join tree and builds a List
 * (in depth-first traversal order) of JoinTreeItem structs, which are then
 * processed iteratively by deconstruct_distribute.  If there are outer
 * joins, non-degenerate outer join clauses are processed in a third pass
 * deconstruct_distribute_oj_quals.
 *
 * The JoinTreeItem structs themselves can be freed at the end of
 * deconstruct_jointree, but do not modify or free their substructure,
 * as the relid sets may also be pointed to by RestrictInfo and
 * SpecialJoinInfo nodes.
 */
typedef struct JoinTreeItem
{
    /* Fields filled during deconstruct_recurse: */
    Node       *jtnode;         /* jointree node to examine */
    JoinDomain *jdomain;        /* join domain for its ON/WHERE clauses */
    struct JoinTreeItem *jti_parent;    /* JoinTreeItem for this node's
                                         * parent, or NULL if it's the top */
    Relids      qualscope;      /* base+OJ Relids syntactically included in
                                 * this jointree node */
    Relids      inner_join_rels;    /* base+OJ Relids syntactically included
                                     * in inner joins appearing at or below
                                     * this jointree node */
    Relids      left_rels;      /* if join node, Relids of the left side */
    Relids      right_rels;     /* if join node, Relids of the right side */
    Relids      nonnullable_rels;   /* if outer join, Relids of the
                                     * non-nullable side */
    /* Fields filled during deconstruct_distribute: */
    SpecialJoinInfo *sjinfo;    /* if outer join, its SpecialJoinInfo */
    List       *oj_joinclauses; /* outer join quals not yet distributed */
    List       *lateral_clauses;    /* quals postponed from children due to
                                     * lateral references */
} JoinTreeItem;
 
 
static bool is_partial_agg_memory_risky(PlannerInfo *root);
static void create_agg_clause_infos(PlannerInfo *root);
static void create_grouping_expr_infos(PlannerInfo *root);
static EquivalenceClass *get_eclass_for_sortgroupclause(PlannerInfo *root,
                                                        SortGroupClause *sgc,
                                                        Expr *expr);
static void extract_lateral_references(PlannerInfo *root, RelOptInfo *brel,
                                       Index rtindex);
static List *deconstruct_recurse(PlannerInfo *root, Node *jtnode,
                                 JoinDomain *parent_domain,
                                 JoinTreeItem *parent_jtitem,
                                 List **item_list);
static void deconstruct_distribute(PlannerInfo *root, JoinTreeItem *jtitem);
static void process_security_barrier_quals(PlannerInfo *root,
                                           int rti, JoinTreeItem *jtitem);
static void mark_rels_nulled_by_join(PlannerInfo *root, Index ojrelid,
                                     Relids lower_rels);
static SpecialJoinInfo *make_outerjoininfo(PlannerInfo *root,
                                           Relids left_rels, Relids right_rels,
                                           Relids inner_join_rels,
                                           JoinType jointype, Index ojrelid,
                                           List *clause);
static void compute_semijoin_info(PlannerInfo *root, SpecialJoinInfo *sjinfo,
                                  List *clause);
static void deconstruct_distribute_oj_quals(PlannerInfo *root,
                                            List *jtitems,
                                            JoinTreeItem *jtitem);
static void distribute_quals_to_rels(PlannerInfo *root, List *clauses,
                                     JoinTreeItem *jtitem,
                                     SpecialJoinInfo *sjinfo,
                                     Index security_level,
                                     Relids qualscope,
                                     Relids ojscope,
                                     Relids outerjoin_nonnullable,
                                     Relids incompatible_relids,
                                     bool allow_equivalence,
                                     bool has_clone,
                                     bool is_clone,
                                     List **postponed_oj_qual_list);
static void distribute_qual_to_rels(PlannerInfo *root, Node *clause,
                                    JoinTreeItem *jtitem,
                                    SpecialJoinInfo *sjinfo,
                                    Index security_level,
                                    Relids qualscope,
                                    Relids ojscope,
                                    Relids outerjoin_nonnullable,
                                    Relids incompatible_relids,
                                    bool allow_equivalence,
                                    bool has_clone,
                                    bool is_clone,
                                    List **postponed_oj_qual_list);
static bool check_redundant_nullability_qual(PlannerInfo *root, Node *clause);
static Relids get_join_domain_min_rels(PlannerInfo *root, Relids domain_relids);
static void check_mergejoinable(RestrictInfo *restrictinfo);
static void check_hashjoinable(RestrictInfo *restrictinfo);
static void check_memoizable(RestrictInfo *restrictinfo);
 
 
/*****************************************************************************
 *
 *   JOIN TREES
 *
 *****************************************************************************/
 
/*
 * add_base_rels_to_query
 *
 *    Scan the query's jointree and create baserel RelOptInfos for all
 *    the base relations (e.g., table, subquery, and function RTEs)
 *    appearing in the jointree.
 *
 * The initial invocation must pass root->parse->jointree as the value of
 * jtnode.  Internally, the function recurses through the jointree.
 *
 * At the end of this process, there should be one baserel RelOptInfo for
 * every non-join RTE that is used in the query.  Some of the baserels
 * may be appendrel parents, which will require additional "otherrel"
 * RelOptInfos for their member rels, but those are added later.
 */
void
add_base_rels_to_query(PlannerInfo *root, Node *jtnode)
{
    if (jtnode == NULL)
        return;
    if (IsA(jtnode, RangeTblRef))
    {
        int         varno = ((RangeTblRef *) jtnode)->rtindex;
 
        (void) build_simple_rel(root, varno, NULL);
    }
    else if (IsA(jtnode, FromExpr))
    {
        FromExpr   *f = (FromExpr *) jtnode;
        ListCell   *l;
 
        foreach(l, f->fromlist)
            add_base_rels_to_query(root, lfirst(l));
    }
    else if (IsA(jtnode, JoinExpr))
    {
        JoinExpr   *j = (JoinExpr *) jtnode;
 
        add_base_rels_to_query(root, j->larg);
        add_base_rels_to_query(root, j->rarg);
    }
    else
        elog(ERROR, "unrecognized node type: %d",
             (int) nodeTag(jtnode));
}
 
/*
 * add_other_rels_to_query
 *    create "otherrel" RelOptInfos for the children of appendrel baserels
 *
 * At the end of this process, there should be RelOptInfos for all relations
 * that will be scanned by the query.
 */
void
add_other_rels_to_query(PlannerInfo *root)
{
    int         rti;
 
    for (rti = 1; rti < root->simple_rel_array_size; rti++)
    {
        RelOptInfo *rel = root->simple_rel_array[rti];
        RangeTblEntry *rte = root->simple_rte_array[rti];
 
        /* there may be empty slots corresponding to non-baserel RTEs */
        if (rel == NULL)
            continue;
 
        /* Ignore any "otherrels" that were already added. */
        if (rel->reloptkind != RELOPT_BASEREL)
            continue;
 
        /* If it's marked as inheritable, look for children. */
        if (rte->inh)
            expand_inherited_rtentry(root, rel, rte, rti);
    }
}
 
 
/*****************************************************************************
 *
 *   TARGET LISTS
 *
 *****************************************************************************/
 
/*
 * build_base_rel_tlists
 *    Add targetlist entries for each var needed in the query's final tlist
 *    (and HAVING clause, if any) to the appropriate base relations.
 *
 * We mark such vars as needed by "relation 0" to ensure that they will
 * propagate up through all join plan steps.
 */
void
build_base_rel_tlists(PlannerInfo *root, List *final_tlist)
{
    List       *tlist_vars = pull_var_clause((Node *) final_tlist,
                                             PVC_RECURSE_AGGREGATES |
                                             PVC_RECURSE_WINDOWFUNCS |
                                             PVC_INCLUDE_PLACEHOLDERS);
 
    if (tlist_vars != NIL)
    {
        add_vars_to_targetlist(root, tlist_vars, bms_make_singleton(0));
        list_free(tlist_vars);
    }
 
    /*
     * If there's a HAVING clause, we'll need the Vars it uses, too.  Note
     * that HAVING can contain Aggrefs but not WindowFuncs.
     */
    if (root->parse->havingQual)
    {
        List       *having_vars = pull_var_clause(root->parse->havingQual,
                                                  PVC_RECURSE_AGGREGATES |
                                                  PVC_INCLUDE_PLACEHOLDERS);
 
        if (having_vars != NIL)
        {
            add_vars_to_targetlist(root, having_vars,
                                   bms_make_singleton(0));
            list_free(having_vars);
        }
    }
}
 
/*
 * add_vars_to_targetlist
 *    For each variable appearing in the list, add it to the owning
 *    relation's targetlist if not already present, and mark the variable
 *    as being needed for the indicated join (or for final output if
 *    where_needed includes "relation 0").
 *
 *    The list may also contain PlaceHolderVars.  These don't necessarily
 *    have a single owning relation; we keep their attr_needed info in
 *    root->placeholder_list instead.  Find or create the associated
 *    PlaceHolderInfo entry, and update its ph_needed.
 *
 *    See also add_vars_to_attr_needed.
 */
void
add_vars_to_targetlist(PlannerInfo *root, List *vars,
                       Relids where_needed)
{
    ListCell   *temp;
 
    Assert(!bms_is_empty(where_needed));
 
    foreach(temp, vars)
    {
        Node       *node = (Node *) lfirst(temp);
 
        if (IsA(node, Var))
        {
            Var        *var = (Var *) node;
            RelOptInfo *rel = find_base_rel(root, var->varno);
            int         attno = var->varattno;
 
            if (bms_is_subset(where_needed, rel->relids))
                continue;
            Assert(attno >= rel->min_attr && attno <= rel->max_attr);
            attno -= rel->min_attr;
            if (rel->attr_needed[attno] == NULL)
            {
                /*
                 * Variable not yet requested, so add to rel's targetlist.
                 *
                 * The value available at the rel's scan level has not been
                 * nulled by any outer join, so drop its varnullingrels.
                 * (We'll put those back as we climb up the join tree.)
                 */
                var = copyObject(var);
                var->varnullingrels = NULL;
                rel->reltarget->exprs = lappend(rel->reltarget->exprs, var);
                /* reltarget cost and width will be computed later */
            }
            rel->attr_needed[attno] = bms_add_members(rel->attr_needed[attno],
                                                      where_needed);
        }
        else if (IsA(node, PlaceHolderVar))
        {
            PlaceHolderVar *phv = (PlaceHolderVar *) node;
            PlaceHolderInfo *phinfo = find_placeholder_info(root, phv);
 
            phinfo->ph_needed = bms_add_members(phinfo->ph_needed,
                                                where_needed);
        }
        else
            elog(ERROR, "unrecognized node type: %d", (int) nodeTag(node));
    }
}
 
/*
 * add_vars_to_attr_needed
 *    This does a subset of what add_vars_to_targetlist does: it just
 *    updates attr_needed for Vars and ph_needed for PlaceHolderVars.
 *    We assume the Vars are already in their relations' targetlists.
 *
 *    This is used to rebuild attr_needed/ph_needed sets after removal
 *    of a useless outer join.  The removed join clause might have been
 *    the only upper-level use of some other relation's Var, in which
 *    case we can reduce that Var's attr_needed and thereby possibly
 *    open the door to further join removals.  But we can't tell that
 *    without tedious reconstruction of the attr_needed data.
 *
 *    Note that if a Var's attr_needed is successfully reduced to empty,
 *    it will still be in the relation's targetlist even though we do
 *    not really need the scan plan node to emit it.  The extra plan
 *    inefficiency seems tiny enough to not be worth spending planner
 *    cycles to get rid of it.
 */
void
add_vars_to_attr_needed(PlannerInfo *root, List *vars,
                        Relids where_needed)
{
    ListCell   *temp;
 
    Assert(!bms_is_empty(where_needed));
 
    foreach(temp, vars)
    {
        Node       *node = (Node *) lfirst(temp);
 
        if (IsA(node, Var))
        {
            Var        *var = (Var *) node;
            RelOptInfo *rel = find_base_rel(root, var->varno);
            int         attno = var->varattno;
 
            if (bms_is_subset(where_needed, rel->relids))
                continue;
            Assert(attno >= rel->min_attr && attno <= rel->max_attr);
            attno -= rel->min_attr;
            rel->attr_needed[attno] = bms_add_members(rel->attr_needed[attno],
                                                      where_needed);
        }
        else if (IsA(node, PlaceHolderVar))
        {
            PlaceHolderVar *phv = (PlaceHolderVar *) node;
            PlaceHolderInfo *phinfo = find_placeholder_info(root, phv);
 
            phinfo->ph_needed = bms_add_members(phinfo->ph_needed,
                                                where_needed);
        }
        else
            elog(ERROR, "unrecognized node type: %d", (int) nodeTag(node));
    }
}
 
/*****************************************************************************
 *
 *    GROUP BY
 *
 *****************************************************************************/
 
/*
 * remove_useless_groupby_columns
 *      Remove any columns in the GROUP BY clause that are redundant due to
 *      being functionally dependent on other GROUP BY columns.
 *
 * Since some other DBMSes do not allow references to ungrouped columns, it's
 * not unusual to find all columns listed in GROUP BY even though listing the
 * primary-key columns, or columns of a unique constraint would be sufficient.
 * Deleting such excess columns avoids redundant sorting or hashing work, so
 * it's worth doing.
 *
 * Relcache invalidations will ensure that cached plans become invalidated
 * when the underlying supporting indexes are dropped or if a column's NOT
 * NULL attribute is removed.
 */
void
remove_useless_groupby_columns(PlannerInfo *root)
{
    Query      *parse = root->parse;
    Bitmapset **groupbyattnos;
    Bitmapset **surplusvars;
    bool        tryremove = false;
    ListCell   *lc;
    int         relid;
 
    /* No chance to do anything if there are less than two GROUP BY items */
    if (list_length(root->processed_groupClause) < 2)
        return;
 
    /* Don't fiddle with the GROUP BY clause if the query has grouping sets */
    if (parse->groupingSets)
        return;
 
    /*
     * Scan the GROUP BY clause to find GROUP BY items that are simple Vars.
     * Fill groupbyattnos[k] with a bitmapset of the column attnos of RTE k
     * that are GROUP BY items.
     */
    groupbyattnos = palloc0_array(Bitmapset *, list_length(parse->rtable) + 1);
    foreach(lc, root->processed_groupClause)
    {
        SortGroupClause *sgc = lfirst_node(SortGroupClause, lc);
        TargetEntry *tle = get_sortgroupclause_tle(sgc, parse->targetList);
        Var        *var = (Var *) tle->expr;
 
        /*
         * Ignore non-Vars and Vars from other query levels.
         *
         * XXX in principle, stable expressions containing Vars could also be
         * removed, if all the Vars are functionally dependent on other GROUP
         * BY items.  But it's not clear that such cases occur often enough to
         * be worth troubling over.
         */
        if (!IsA(var, Var) ||
            var->varlevelsup > 0)
            continue;
 
        /* OK, remember we have this Var */
        relid = var->varno;
        Assert(relid <= list_length(parse->rtable));
 
        /*
         * If this isn't the first column for this relation then we now have
         * multiple columns.  That means there might be some that can be
         * removed.
         */
        tryremove |= !bms_is_empty(groupbyattnos[relid]);
        groupbyattnos[relid] = bms_add_member(groupbyattnos[relid],
                                              var->varattno - FirstLowInvalidHeapAttributeNumber);
    }
 
    /*
     * No Vars or didn't find multiple Vars for any relation in the GROUP BY?
     * If so, nothing can be removed, so don't waste more effort trying.
     */
    if (!tryremove)
        return;
 
    /*
     * Consider each relation and see if it is possible to remove some of its
     * Vars from GROUP BY.  For simplicity and speed, we do the actual removal
     * in a separate pass.  Here, we just fill surplusvars[k] with a bitmapset
     * of the column attnos of RTE k that are removable GROUP BY items.
     */
    surplusvars = NULL;         /* don't allocate array unless required */
    relid = 0;
    foreach(lc, parse->rtable)
    {
        RangeTblEntry *rte = lfirst_node(RangeTblEntry, lc);
        RelOptInfo *rel;
        Bitmapset  *relattnos;
        Bitmapset  *best_keycolumns = NULL;
        int32       best_nkeycolumns = PG_INT32_MAX;
 
        relid++;
 
        /* Only plain relations could have primary-key constraints */
        if (rte->rtekind != RTE_RELATION)
            continue;
 
        /*
         * We must skip inheritance parent tables as some of the child rels
         * may cause duplicate rows.  This cannot happen with partitioned
         * tables, however.
         */
        if (rte->inh && rte->relkind != RELKIND_PARTITIONED_TABLE)
            continue;
 
        /* Nothing to do unless this rel has multiple Vars in GROUP BY */
        relattnos = groupbyattnos[relid];
        if (bms_membership(relattnos) != BMS_MULTIPLE)
            continue;
 
        rel = root->simple_rel_array[relid];
 
        /*
         * Now check each index for this relation to see if there are any with
         * columns which are a proper subset of the grouping columns for this
         * relation.
         */
        foreach_node(IndexOptInfo, index, rel->indexlist)
        {
            Bitmapset  *ind_attnos;
            bool        nulls_check_ok;
 
            /*
             * Skip any non-unique and deferrable indexes.  Predicate indexes
             * have not been checked yet, so we must skip those too as the
             * predOK check that's done later might fail.
             */
            if (!index->unique || !index->immediate || index->indpred != NIL)
                continue;
 
            /* For simplicity, we currently don't support expression indexes */
            if (index->indexprs != NIL)
                continue;
 
            ind_attnos = NULL;
            nulls_check_ok = true;
            for (int i = 0; i < index->nkeycolumns; i++)
            {
                /*
                 * We must insist that the index columns are all defined NOT
                 * NULL otherwise duplicate NULLs could exist.  However, we
                 * can relax this check when the index is defined with NULLS
                 * NOT DISTINCT as there can only be 1 NULL row, therefore
                 * functional dependency on the unique columns is maintained,
                 * despite the NULL.
                 */
                if (!index->nullsnotdistinct &&
                    !bms_is_member(index->indexkeys[i],
                                   rel->notnullattnums))
                {
                    nulls_check_ok = false;
                    break;
                }
 
                ind_attnos =
                    bms_add_member(ind_attnos,
                                   index->indexkeys[i] -
                                   FirstLowInvalidHeapAttributeNumber);
            }
 
            if (!nulls_check_ok)
                continue;
 
            /*
             * Skip any indexes where the indexed columns aren't a proper
             * subset of the GROUP BY.
             */
            if (bms_subset_compare(ind_attnos, relattnos) != BMS_SUBSET1)
                continue;
 
            /*
             * Record the attribute numbers from the index with the fewest
             * columns.  This allows the largest number of columns to be
             * removed from the GROUP BY clause.  In the future, we may wish
             * to consider using the narrowest set of columns and looking at
             * pg_statistic.stawidth as it might be better to use an index
             * with, say two INT4s, rather than, say, one long varlena column.
             */
            if (index->nkeycolumns < best_nkeycolumns)
            {
                best_keycolumns = ind_attnos;
                best_nkeycolumns = index->nkeycolumns;
            }
        }
 
        /* Did we find a suitable index? */
        if (!bms_is_empty(best_keycolumns))
        {
            /*
             * To easily remember whether we've found anything to do, we don't
             * allocate the surplusvars[] array until we find something.
             */
            if (surplusvars == NULL)
                surplusvars = palloc0_array(Bitmapset *, list_length(parse->rtable) + 1);
 
            /* Remember the attnos of the removable columns */
            surplusvars[relid] = bms_difference(relattnos, best_keycolumns);
        }
    }
 
    /*
     * If we found any surplus Vars, build a new GROUP BY clause without them.
     * (Note: this may leave some TLEs with unreferenced ressortgroupref
     * markings, but that's harmless.)
     */
    if (surplusvars != NULL)
    {
        List       *new_groupby = NIL;
 
        foreach(lc, root->processed_groupClause)
        {
            SortGroupClause *sgc = lfirst_node(SortGroupClause, lc);
            TargetEntry *tle = get_sortgroupclause_tle(sgc, parse->targetList);
            Var        *var = (Var *) tle->expr;
 
            /*
             * New list must include non-Vars, outer Vars, and anything not
             * marked as surplus.
             */
            if (!IsA(var, Var) ||
                var->varlevelsup > 0 ||
                !bms_is_member(var->varattno - FirstLowInvalidHeapAttributeNumber,
                               surplusvars[var->varno]))
                new_groupby = lappend(new_groupby, sgc);
        }
 
        root->processed_groupClause = new_groupby;
    }
}
 
/*
 * setup_eager_aggregation
 *    Check if eager aggregation is applicable, and if so collect suitable
 *    aggregate expressions and grouping expressions in the query.
 */
void
setup_eager_aggregation(PlannerInfo *root)
{
    /*
     * Don't apply eager aggregation if disabled by user.
     */
    if (!enable_eager_aggregate)
        return;
 
    /*
     * Don't apply eager aggregation if there are no available GROUP BY
     * clauses.
     */
    if (!root->processed_groupClause)
        return;
 
    /*
     * For now we don't try to support grouping sets.
     */
    if (root->parse->groupingSets)
        return;
 
    /*
     * For now we don't try to support DISTINCT or ORDER BY aggregates.
     */
    if (root->numOrderedAggs > 0)
        return;
 
    /*
     * If there are any aggregates that do not support partial mode, or any
     * partial aggregates that are non-serializable, do not apply eager
     * aggregation.
     */
    if (root->hasNonPartialAggs || root->hasNonSerialAggs)
        return;
 
    /*
     * We don't try to apply eager aggregation if there are set-returning
     * functions in targetlist.
     */
    if (root->parse->hasTargetSRFs)
        return;
 
    /*
     * Eager aggregation only makes sense if there are multiple base rels in
     * the query.
     */
    if (bms_membership(root->all_baserels) != BMS_MULTIPLE)
        return;
 
    /*
     * Don't apply eager aggregation if any aggregate poses a risk of
     * excessive memory usage during partial aggregation.
     */
    if (is_partial_agg_memory_risky(root))
        return;
 
    /*
     * Collect aggregate expressions and plain Vars that appear in the
     * targetlist and havingQual.
     */
    create_agg_clause_infos(root);
 
    /*
     * If there are no suitable aggregate expressions, we cannot apply eager
     * aggregation.
     */
    if (root->agg_clause_list == NIL)
        return;
 
    /*
     * Collect grouping expressions that appear in grouping clauses.
     */
    create_grouping_expr_infos(root);
}
 
/*
 * is_partial_agg_memory_risky
 *    Check if any aggregate poses a risk of excessive memory usage during
 *    partial aggregation.
 *
 * We check if any aggregate has a negative aggtransspace value, which
 * indicates that its transition state data can grow unboundedly in size.
 * Applying eager aggregation in such cases risks high memory usage since
 * partial aggregation results might be stored in join hash tables or
 * materialized nodes.
 */
static bool
is_partial_agg_memory_risky(PlannerInfo *root)
{
    ListCell   *lc;
 
    foreach(lc, root->aggtransinfos)
    {
        AggTransInfo *transinfo = lfirst_node(AggTransInfo, lc);
 
        if (transinfo->aggtransspace < 0)
            return true;
    }
 
    return false;
}
 
/*
 * create_agg_clause_infos
 *    Search the targetlist and havingQual for Aggrefs and plain Vars, and
 *    create an AggClauseInfo for each Aggref node.
 */
static void
create_agg_clause_infos(PlannerInfo *root)
{
    List       *tlist_exprs;
    List       *agg_clause_list = NIL;
    List       *tlist_vars = NIL;
    Relids      aggregate_relids = NULL;
    bool        eager_agg_applicable = true;
    ListCell   *lc;
 
    Assert(root->agg_clause_list == NIL);
    Assert(root->tlist_vars == NIL);
 
    tlist_exprs = pull_var_clause((Node *) root->processed_tlist,
                                  PVC_INCLUDE_AGGREGATES |
                                  PVC_RECURSE_WINDOWFUNCS |
                                  PVC_RECURSE_PLACEHOLDERS);
 
    /*
     * Aggregates within the HAVING clause need to be processed in the same
     * way as those in the targetlist.  Note that HAVING can contain Aggrefs
     * but not WindowFuncs.
     */
    if (root->parse->havingQual != NULL)
    {
        List       *having_exprs;
 
        having_exprs = pull_var_clause((Node *) root->parse->havingQual,
                                       PVC_INCLUDE_AGGREGATES |
                                       PVC_RECURSE_PLACEHOLDERS);
        if (having_exprs != NIL)
        {
            tlist_exprs = list_concat(tlist_exprs, having_exprs);
            list_free(having_exprs);
        }
    }
 
    foreach(lc, tlist_exprs)
    {
        Expr       *expr = (Expr *) lfirst(lc);
        Aggref     *aggref;
        Relids      agg_eval_at;
        AggClauseInfo *ac_info;
 
        /* For now we don't try to support GROUPING() expressions */
        if (IsA(expr, GroupingFunc))
        {
            eager_agg_applicable = false;
            break;
        }
 
        /* Collect plain Vars for future reference */
        if (IsA(expr, Var))
        {
            tlist_vars = list_append_unique(tlist_vars, expr);
            continue;
        }
 
        aggref = castNode(Aggref, expr);
 
        Assert(aggref->aggorder == NIL);
        Assert(aggref->aggdistinct == NIL);
 
        /*
         * We cannot push down aggregates that contain volatile functions.
         * Doing so would change the number of times the function is
         * evaluated.
         */
        if (contain_volatile_functions((Node *) aggref))
        {
            eager_agg_applicable = false;
            break;
        }
 
        /*
         * If there are any securityQuals, do not try to apply eager
         * aggregation if any non-leakproof aggregate functions are present.
         * This is overly strict, but for now...
         */
        if (root->qual_security_level > 0 &&
            !get_func_leakproof(aggref->aggfnoid))
        {
            eager_agg_applicable = false;
            break;
        }
 
        agg_eval_at = pull_varnos(root, (Node *) aggref);
 
        /*
         * If all base relations in the query are referenced by aggregate
         * functions, then eager aggregation is not applicable.
         */
        aggregate_relids = bms_add_members(aggregate_relids, agg_eval_at);
        if (bms_is_subset(root->all_baserels, aggregate_relids))
        {
            eager_agg_applicable = false;
            break;
        }
 
        /* OK, create the AggClauseInfo node */
        ac_info = makeNode(AggClauseInfo);
        ac_info->aggref = aggref;
        ac_info->agg_eval_at = agg_eval_at;
 
        /* ... and add it to the list */
        agg_clause_list = list_append_unique(agg_clause_list, ac_info);
    }
 
    list_free(tlist_exprs);
 
    if (eager_agg_applicable)
    {
        root->agg_clause_list = agg_clause_list;
        root->tlist_vars = tlist_vars;
    }
    else
    {
        list_free_deep(agg_clause_list);
        list_free(tlist_vars);
    }
}
 
/*
 * create_grouping_expr_infos
 *    Create a GroupingExprInfo for each expression usable as grouping key.
 *
 * If any grouping expression is not suitable, we will just return with
 * root->group_expr_list being NIL.
 */
static void
create_grouping_expr_infos(PlannerInfo *root)
{
    List       *exprs = NIL;
    List       *sortgrouprefs = NIL;
    List       *ecs = NIL;
    ListCell   *lc,
               *lc1,
               *lc2,
               *lc3;
 
    Assert(root->group_expr_list == NIL);
 
    foreach(lc, root->processed_groupClause)
    {
        SortGroupClause *sgc = lfirst_node(SortGroupClause, lc);
        TargetEntry *tle = get_sortgroupclause_tle(sgc, root->processed_tlist);
        TypeCacheEntry *tce;
        Oid         equalimageproc;
 
        Assert(tle->ressortgroupref > 0);
 
        /*
         * For now we only support plain Vars as grouping expressions.
         */
        if (!IsA(tle->expr, Var))
            return;
 
        /*
         * Eager aggregation is only possible if equality implies image
         * equality for each grouping key.  Otherwise, placing keys with
         * different byte images into the same group may result in the loss of
         * information that could be necessary to evaluate upper qual clauses.
         *
         * For instance, the NUMERIC data type is not supported, as values
         * that are considered equal by the equality operator (e.g., 0 and
         * 0.0) can have different scales.
         */
        tce = lookup_type_cache(exprType((Node *) tle->expr),
                                TYPECACHE_BTREE_OPFAMILY);
        if (!OidIsValid(tce->btree_opf) ||
            !OidIsValid(tce->btree_opintype))
            return;
 
        equalimageproc = get_opfamily_proc(tce->btree_opf,
                                           tce->btree_opintype,
                                           tce->btree_opintype,
                                           BTEQUALIMAGE_PROC);
 
        /*
         * If there is no BTEQUALIMAGE_PROC, eager aggregation is assumed to
         * be unsafe.  Otherwise, we call the procedure to check.  We must be
         * careful to pass the expression's actual collation, rather than the
         * data type's default collation, to ensure that non-deterministic
         * collations are correctly handled.
         */
        if (!OidIsValid(equalimageproc) ||
            !DatumGetBool(OidFunctionCall1Coll(equalimageproc,
                                               exprCollation((Node *) tle->expr),
                                               ObjectIdGetDatum(tce->btree_opintype))))
            return;
 
        exprs = lappend(exprs, tle->expr);
        sortgrouprefs = lappend_int(sortgrouprefs, tle->ressortgroupref);
        ecs = lappend(ecs, get_eclass_for_sortgroupclause(root, sgc, tle->expr));
    }
 
    /*
     * Construct a GroupingExprInfo for each expression.
     */
    forthree(lc1, exprs, lc2, sortgrouprefs, lc3, ecs)
    {
        Expr       *expr = (Expr *) lfirst(lc1);
        int         sortgroupref = lfirst_int(lc2);
        EquivalenceClass *ec = (EquivalenceClass *) lfirst(lc3);
        GroupingExprInfo *ge_info;
 
        ge_info = makeNode(GroupingExprInfo);
        ge_info->expr = (Expr *) copyObject(expr);
        ge_info->sortgroupref = sortgroupref;
        ge_info->ec = ec;
 
        root->group_expr_list = lappend(root->group_expr_list, ge_info);
    }
}
 
/*
 * get_eclass_for_sortgroupclause
 *    Given a group clause and an expression, find an existing equivalence
 *    class that the expression is a member of; return NULL if none.
 */
static EquivalenceClass *
get_eclass_for_sortgroupclause(PlannerInfo *root, SortGroupClause *sgc,
                               Expr *expr)
{
    Oid         opfamily,
                opcintype,
                collation;
    CompareType cmptype;
    Oid         equality_op;
    List       *opfamilies;
 
    /* Punt if the group clause is not sortable */
    if (!OidIsValid(sgc->sortop))
        return NULL;
 
    /* Find the operator in pg_amop --- failure shouldn't happen */
    if (!get_ordering_op_properties(sgc->sortop,
                                    &opfamily, &opcintype, &cmptype))
        elog(ERROR, "operator %u is not a valid ordering operator",
             sgc->sortop);
 
    /* Because SortGroupClause doesn't carry collation, consult the expr */
    collation = exprCollation((Node *) expr);
 
    /*
     * EquivalenceClasses need to contain opfamily lists based on the family
     * membership of mergejoinable equality operators, which could belong to
     * more than one opfamily.  So we have to look up the opfamily's equality
     * operator and get its membership.
     */
    equality_op = get_opfamily_member_for_cmptype(opfamily,
                                                  opcintype,
                                                  opcintype,
                                                  COMPARE_EQ);
    if (!OidIsValid(equality_op))   /* shouldn't happen */
        elog(ERROR, "missing operator %d(%u,%u) in opfamily %u",
             COMPARE_EQ, opcintype, opcintype, opfamily);
    opfamilies = get_mergejoin_opfamilies(equality_op);
    if (!opfamilies)            /* certainly should find some */
        elog(ERROR, "could not find opfamilies for equality operator %u",
             equality_op);
 
    /* Now find a matching EquivalenceClass */
    return get_eclass_for_sort_expr(root, expr, opfamilies, opcintype,
                                    collation, sgc->tleSortGroupRef,
                                    NULL, false);
}
 
/*****************************************************************************
 *
 *    LATERAL REFERENCES
 *
 *****************************************************************************/
 
/*
 * find_lateral_references
 *    For each LATERAL subquery, extract all its references to Vars and
 *    PlaceHolderVars of the current query level, and make sure those values
 *    will be available for evaluation of the subquery.
 *
 * While later planning steps ensure that the Var/PHV source rels are on the
 * outside of nestloops relative to the LATERAL subquery, we also need to
 * ensure that the Vars/PHVs propagate up to the nestloop join level; this
 * means setting suitable where_needed values for them.
 *
 * Note that this only deals with lateral references in unflattened LATERAL
 * subqueries.  When we flatten a LATERAL subquery, its lateral references
 * become plain Vars in the parent query, but they may have to be wrapped in
 * PlaceHolderVars if they need to be forced NULL by outer joins that don't
 * also null the LATERAL subquery.  That's all handled elsewhere.
 *
 * This has to run before deconstruct_jointree, since it might result in
 * creation of PlaceHolderInfos.
 */
void
find_lateral_references(PlannerInfo *root)
{
    Index       rti;
 
    /* We need do nothing if the query contains no LATERAL RTEs */
    if (!root->hasLateralRTEs)
        return;
 
    /*
     * Examine all baserels (the rel array has been set up by now).
     */
    for (rti = 1; rti < root->simple_rel_array_size; rti++)
    {
        RelOptInfo *brel = root->simple_rel_array[rti];
 
        /* there may be empty slots corresponding to non-baserel RTEs */
        if (brel == NULL)
            continue;
 
        Assert(brel->relid == rti); /* sanity check on array */
 
        /*
         * This bit is less obvious than it might look.  We ignore appendrel
         * otherrels and consider only their parent baserels.  In a case where
         * a LATERAL-containing UNION ALL subquery was pulled up, it is the
         * otherrel that is actually going to be in the plan.  However, we
         * want to mark all its lateral references as needed by the parent,
         * because it is the parent's relid that will be used for join
         * planning purposes.  And the parent's RTE will contain all the
         * lateral references we need to know, since the pulled-up member is
         * nothing but a copy of parts of the original RTE's subquery.  We
         * could visit the parent's children instead and transform their
         * references back to the parent's relid, but it would be much more
         * complicated for no real gain.  (Important here is that the child
         * members have not yet received any processing beyond being pulled
         * up.)  Similarly, in appendrels created by inheritance expansion,
         * it's sufficient to look at the parent relation.
         */
 
        /* ignore RTEs that are "other rels" */
        if (brel->reloptkind != RELOPT_BASEREL)
            continue;
 
        extract_lateral_references(root, brel, rti);
    }
}
 
static void
extract_lateral_references(PlannerInfo *root, RelOptInfo *brel, Index rtindex)
{
    RangeTblEntry *rte = root->simple_rte_array[rtindex];
    List       *vars;
    List       *newvars;
    Relids      where_needed;
    ListCell   *lc;
 
    /* No cross-references are possible if it's not LATERAL */
    if (!rte->lateral)
        return;
 
    /* Fetch the appropriate variables */
    if (rte->rtekind == RTE_RELATION)
        vars = pull_vars_of_level((Node *) rte->tablesample, 0);
    else if (rte->rtekind == RTE_SUBQUERY)
        vars = pull_vars_of_level((Node *) rte->subquery, 1);
    else if (rte->rtekind == RTE_FUNCTION)
        vars = pull_vars_of_level((Node *) rte->functions, 0);
    else if (rte->rtekind == RTE_TABLEFUNC)
        vars = pull_vars_of_level((Node *) rte->tablefunc, 0);
    else if (rte->rtekind == RTE_VALUES)
        vars = pull_vars_of_level((Node *) rte->values_lists, 0);
    else
    {
        Assert(false);
        return;                 /* keep compiler quiet */
    }
 
    if (vars == NIL)
        return;                 /* nothing to do */
 
    /* Copy each Var (or PlaceHolderVar) and adjust it to match our level */
    newvars = NIL;
    foreach(lc, vars)
    {
        Node       *node = (Node *) lfirst(lc);
 
        node = copyObject(node);
        if (IsA(node, Var))
        {
            Var        *var = (Var *) node;
 
            /* Adjustment is easy since it's just one node */
            var->varlevelsup = 0;
        }
        else if (IsA(node, PlaceHolderVar))
        {
            PlaceHolderVar *phv = (PlaceHolderVar *) node;
            int         levelsup = phv->phlevelsup;
 
            /* Have to work harder to adjust the contained expression too */
            if (levelsup != 0)
                IncrementVarSublevelsUp(node, -levelsup, 0);
 
            /*
             * If we pulled the PHV out of a subquery RTE, its expression
             * needs to be preprocessed.  subquery_planner() already did this
             * for level-zero PHVs in function and values RTEs, though.
             */
            if (levelsup > 0)
                phv->phexpr = preprocess_phv_expression(root, phv->phexpr);
        }
        else
            Assert(false);
        newvars = lappend(newvars, node);
    }
 
    list_free(vars);
 
    /*
     * We mark the Vars as being "needed" at the LATERAL RTE.  This is a bit
     * of a cheat: a more formal approach would be to mark each one as needed
     * at the join of the LATERAL RTE with its source RTE.  But it will work,
     * and it's much less tedious than computing a separate where_needed for
     * each Var.
     */
    where_needed = bms_make_singleton(rtindex);
 
    /*
     * Push Vars into their source relations' targetlists, and PHVs into
     * root->placeholder_list.
     */
    add_vars_to_targetlist(root, newvars, where_needed);
 
    /*
     * Remember the lateral references for rebuild_lateral_attr_needed and
     * create_lateral_join_info.
     */
    brel->lateral_vars = newvars;
}
 
/*
 * rebuild_lateral_attr_needed
 *    Put back attr_needed bits for Vars/PHVs needed for lateral references.
 *
 * This is used to rebuild attr_needed/ph_needed sets after removal of a
 * useless outer join.  It should match what find_lateral_references did,
 * except that we call add_vars_to_attr_needed not add_vars_to_targetlist.
 */
void
rebuild_lateral_attr_needed(PlannerInfo *root)
{
    Index       rti;
 
    /* We need do nothing if the query contains no LATERAL RTEs */
    if (!root->hasLateralRTEs)
        return;
 
    /* Examine the same baserels that find_lateral_references did */
    for (rti = 1; rti < root->simple_rel_array_size; rti++)
    {
        RelOptInfo *brel = root->simple_rel_array[rti];
        Relids      where_needed;
 
        if (brel == NULL)
            continue;
        if (brel->reloptkind != RELOPT_BASEREL)
            continue;
 
        /*
         * We don't need to repeat all of extract_lateral_references, since it
         * kindly saved the extracted Vars/PHVs in lateral_vars.
         */
        if (brel->lateral_vars == NIL)
            continue;
 
        where_needed = bms_make_singleton(rti);
 
        add_vars_to_attr_needed(root, brel->lateral_vars, where_needed);
    }
}
 
/*
 * create_lateral_join_info
 *    Fill in the per-base-relation direct_lateral_relids, lateral_relids
 *    and lateral_referencers sets.
 */
void
create_lateral_join_info(PlannerInfo *root)
{
    bool        found_laterals = false;
    Index       rti;
    ListCell   *lc;
 
    /* We need do nothing if the query contains no LATERAL RTEs */
    if (!root->hasLateralRTEs)
        return;
 
    /* We'll need to have the ph_eval_at values for PlaceHolderVars */
    Assert(root->placeholdersFrozen);
 
    /*
     * Examine all baserels (the rel array has been set up by now).
     */
    for (rti = 1; rti < root->simple_rel_array_size; rti++)
    {
        RelOptInfo *brel = root->simple_rel_array[rti];
        Relids      lateral_relids;
 
        /* there may be empty slots corresponding to non-baserel RTEs */
        if (brel == NULL)
            continue;
 
        Assert(brel->relid == rti); /* sanity check on array */
 
        /* ignore RTEs that are "other rels" */
        if (brel->reloptkind != RELOPT_BASEREL)
            continue;
 
        lateral_relids = NULL;
 
        /* consider each laterally-referenced Var or PHV */
        foreach(lc, brel->lateral_vars)
        {
            Node       *node = (Node *) lfirst(lc);
 
            if (IsA(node, Var))
            {
                Var        *var = (Var *) node;
 
                found_laterals = true;
                lateral_relids = bms_add_member(lateral_relids,
                                                var->varno);
            }
            else if (IsA(node, PlaceHolderVar))
            {
                PlaceHolderVar *phv = (PlaceHolderVar *) node;
                PlaceHolderInfo *phinfo = find_placeholder_info(root, phv);
 
                found_laterals = true;
                lateral_relids = bms_add_members(lateral_relids,
                                                 phinfo->ph_eval_at);
            }
            else
                Assert(false);
        }
 
        /* We now have all the simple lateral refs from this rel */
        brel->direct_lateral_relids = lateral_relids;
        brel->lateral_relids = bms_copy(lateral_relids);
    }
 
    /*
     * Now check for lateral references within PlaceHolderVars, and mark their
     * eval_at rels as having lateral references to the source rels.
     *
     * For a PHV that is due to be evaluated at a baserel, mark its source(s)
     * as direct lateral dependencies of the baserel (adding onto the ones
     * recorded above).  If it's due to be evaluated at a join, mark its
     * source(s) as indirect lateral dependencies of each baserel in the join,
     * ie put them into lateral_relids but not direct_lateral_relids.  This is
     * appropriate because we can't put any such baserel on the outside of a
     * join to one of the PHV's lateral dependencies, but on the other hand we
     * also can't yet join it directly to the dependency.
     */
    foreach(lc, root->placeholder_list)
    {
        PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(lc);
        Relids      eval_at = phinfo->ph_eval_at;
        Relids      lateral_refs;
        int         varno;
 
        if (phinfo->ph_lateral == NULL)
            continue;           /* PHV is uninteresting if no lateral refs */
 
        found_laterals = true;
 
        /*
         * Include only baserels not outer joins in the evaluation sites'
         * lateral relids.  This avoids problems when outer join order gets
         * rearranged, and it should still ensure that the lateral values are
         * available when needed.
         */
        lateral_refs = bms_intersect(phinfo->ph_lateral, root->all_baserels);
        Assert(!bms_is_empty(lateral_refs));
 
        if (bms_get_singleton_member(eval_at, &varno))
        {
            /* Evaluation site is a baserel */
            RelOptInfo *brel = find_base_rel(root, varno);
 
            brel->direct_lateral_relids =
                bms_add_members(brel->direct_lateral_relids,
                                lateral_refs);
            brel->lateral_relids =
                bms_add_members(brel->lateral_relids,
                                lateral_refs);
        }
        else
        {
            /* Evaluation site is a join */
            varno = -1;
            while ((varno = bms_next_member(eval_at, varno)) >= 0)
            {
                RelOptInfo *brel = find_base_rel_ignore_join(root, varno);
 
                if (brel == NULL)
                    continue;   /* ignore outer joins in eval_at */
                brel->lateral_relids = bms_add_members(brel->lateral_relids,
                                                       lateral_refs);
            }
        }
    }
 
    /*
     * If we found no actual lateral references, we're done; but reset the
     * hasLateralRTEs flag to avoid useless work later.
     */
    if (!found_laterals)
    {
        root->hasLateralRTEs = false;
        return;
    }
 
    /*
     * Calculate the transitive closure of the lateral_relids sets, so that
     * they describe both direct and indirect lateral references.  If relation
     * X references Y laterally, and Y references Z laterally, then we will
     * have to scan X on the inside of a nestloop with Z, so for all intents
     * and purposes X is laterally dependent on Z too.
     *
     * This code is essentially Warshall's algorithm for transitive closure.
     * The outer loop considers each baserel, and propagates its lateral
     * dependencies to those baserels that have a lateral dependency on it.
     */
    for (rti = 1; rti < root->simple_rel_array_size; rti++)
    {
        RelOptInfo *brel = root->simple_rel_array[rti];
        Relids      outer_lateral_relids;
        Index       rti2;
 
        if (brel == NULL || brel->reloptkind != RELOPT_BASEREL)
            continue;
 
        /* need not consider baserel further if it has no lateral refs */
        outer_lateral_relids = brel->lateral_relids;
        if (outer_lateral_relids == NULL)
            continue;
 
        /* else scan all baserels */
        for (rti2 = 1; rti2 < root->simple_rel_array_size; rti2++)
        {
            RelOptInfo *brel2 = root->simple_rel_array[rti2];
 
            if (brel2 == NULL || brel2->reloptkind != RELOPT_BASEREL)
                continue;
 
            /* if brel2 has lateral ref to brel, propagate brel's refs */
            if (bms_is_member(rti, brel2->lateral_relids))
                brel2->lateral_relids = bms_add_members(brel2->lateral_relids,
                                                        outer_lateral_relids);
        }
    }
 
    /*
     * Now that we've identified all lateral references, mark each baserel
     * with the set of relids of rels that reference it laterally (possibly
     * indirectly) --- that is, the inverse mapping of lateral_relids.
     */
    for (rti = 1; rti < root->simple_rel_array_size; rti++)
    {
        RelOptInfo *brel = root->simple_rel_array[rti];
        Relids      lateral_relids;
        int         rti2;
 
        if (brel == NULL || brel->reloptkind != RELOPT_BASEREL)
            continue;
 
        /* Nothing to do at rels with no lateral refs */
        lateral_relids = brel->lateral_relids;
        if (bms_is_empty(lateral_relids))
            continue;
 
        /* No rel should have a lateral dependency on itself */
        Assert(!bms_is_member(rti, lateral_relids));
 
        /* Mark this rel's referencees */
        rti2 = -1;
        while ((rti2 = bms_next_member(lateral_relids, rti2)) >= 0)
        {
            RelOptInfo *brel2 = root->simple_rel_array[rti2];
 
            if (brel2 == NULL)
                continue;       /* must be an OJ */
 
            Assert(brel2->reloptkind == RELOPT_BASEREL);
            brel2->lateral_referencers =
                bms_add_member(brel2->lateral_referencers, rti);
        }
    }
}
 
 
/*****************************************************************************
 *
 *    JOIN TREE PROCESSING
 *
 *****************************************************************************/
 
/*
 * deconstruct_jointree
 *    Recursively scan the query's join tree for WHERE and JOIN/ON qual
 *    clauses, and add these to the appropriate restrictinfo and joininfo
 *    lists belonging to base RelOptInfos.  Also, add SpecialJoinInfo nodes
 *    to root->join_info_list for any outer joins appearing in the query tree.
 *    Return a "joinlist" data structure showing the join order decisions
 *    that need to be made by make_one_rel().
 *
 * The "joinlist" result is a list of items that are either RangeTblRef
 * jointree nodes or sub-joinlists.  All the items at the same level of
 * joinlist must be joined in an order to be determined by make_one_rel()
 * (note that legal orders may be constrained by SpecialJoinInfo nodes).
 * A sub-joinlist represents a subproblem to be planned separately. Currently
 * sub-joinlists arise only from FULL OUTER JOIN or when collapsing of
 * subproblems is stopped by join_collapse_limit or from_collapse_limit.
 */
List *
deconstruct_jointree(PlannerInfo *root)
{
    List       *result;
    JoinDomain *top_jdomain;
    List       *item_list = NIL;
    ListCell   *lc;
 
    /*
     * After this point, no more PlaceHolderInfos may be made, because
     * make_outerjoininfo requires all active placeholders to be present in
     * root->placeholder_list while we crawl up the join tree.
     */
    root->placeholdersFrozen = true;
 
    /* Fetch the already-created top-level join domain for the query */
    top_jdomain = linitial_node(JoinDomain, root->join_domains);
    top_jdomain->jd_relids = NULL;  /* filled during deconstruct_recurse */
 
    /* Start recursion at top of jointree */
    Assert(root->parse->jointree != NULL &&
           IsA(root->parse->jointree, FromExpr));
 
    /* These are filled as we scan the jointree */
    root->all_baserels = NULL;
    root->outer_join_rels = NULL;
 
    /* Perform the initial scan of the jointree */
    result = deconstruct_recurse(root, (Node *) root->parse->jointree,
                                 top_jdomain, NULL,
                                 &item_list);
 
    /* Now we can form the value of all_query_rels, too */
    root->all_query_rels = bms_union(root->all_baserels, root->outer_join_rels);
 
    /* ... which should match what we computed for the top join domain */
    Assert(bms_equal(root->all_query_rels, top_jdomain->jd_relids));
 
    /* Now scan all the jointree nodes again, and distribute quals */
    foreach(lc, item_list)
    {
        JoinTreeItem *jtitem = (JoinTreeItem *) lfirst(lc);
 
        deconstruct_distribute(root, jtitem);
    }
 
    /*
     * If there were any special joins then we may have some postponed LEFT
     * JOIN clauses to deal with.
     */
    if (root->join_info_list)
    {
        foreach(lc, item_list)
        {
            JoinTreeItem *jtitem = (JoinTreeItem *) lfirst(lc);
 
            if (jtitem->oj_joinclauses != NIL)
                deconstruct_distribute_oj_quals(root, item_list, jtitem);
        }
    }
 
    /* Don't need the JoinTreeItems any more */
    list_free_deep(item_list);
 
    return result;
}
 
/*
 * deconstruct_recurse
 *    One recursion level of deconstruct_jointree's initial jointree scan.
 *
 * jtnode is the jointree node to examine, and parent_domain is the
 * enclosing join domain.  (We must add all base+OJ relids appearing
 * here or below to parent_domain.)  parent_jtitem is the JoinTreeItem
 * for the parent jointree node, or NULL at the top of the recursion.
 *
 * item_list is an in/out parameter: we add a JoinTreeItem struct to
 * that list for each jointree node, in depth-first traversal order.
 * (Hence, after each call, the last list item corresponds to its jtnode.)
 *
 * Return value is the appropriate joinlist for this jointree node.
 */
static List *
deconstruct_recurse(PlannerInfo *root, Node *jtnode,
                    JoinDomain *parent_domain,
                    JoinTreeItem *parent_jtitem,
                    List **item_list)
{
    List       *joinlist;
    JoinTreeItem *jtitem;
 
    Assert(jtnode != NULL);
 
    /* Make the new JoinTreeItem, but don't add it to item_list yet */
    jtitem = palloc0_object(JoinTreeItem);
    jtitem->jtnode = jtnode;
    jtitem->jti_parent = parent_jtitem;
 
    if (IsA(jtnode, RangeTblRef))
    {
        int         varno = ((RangeTblRef *) jtnode)->rtindex;
 
        /* Fill all_baserels as we encounter baserel jointree nodes */
        root->all_baserels = bms_add_member(root->all_baserels, varno);
        /* This node belongs to parent_domain */
        jtitem->jdomain = parent_domain;
        parent_domain->jd_relids = bms_add_member(parent_domain->jd_relids,
                                                  varno);
        /* qualscope is just the one RTE */
        jtitem->qualscope = bms_make_singleton(varno);
        /* A single baserel does not create an inner join */
        jtitem->inner_join_rels = NULL;
        joinlist = list_make1(jtnode);
    }
    else if (IsA(jtnode, FromExpr))
    {
        FromExpr   *f = (FromExpr *) jtnode;
        int         remaining;
        ListCell   *l;
 
        /* This node belongs to parent_domain, as do its children */
        jtitem->jdomain = parent_domain;
 
        /*
         * Recurse to handle child nodes, and compute output joinlist.  We
         * collapse subproblems into a single joinlist whenever the resulting
         * joinlist wouldn't exceed from_collapse_limit members.  Also, always
         * collapse one-element subproblems, since that won't lengthen the
         * joinlist anyway.
         */
        jtitem->qualscope = NULL;
        jtitem->inner_join_rels = NULL;
        joinlist = NIL;
        remaining = list_length(f->fromlist);
        foreach(l, f->fromlist)
        {
            JoinTreeItem *sub_item;
            List       *sub_joinlist;
            int         sub_members;
 
            sub_joinlist = deconstruct_recurse(root, lfirst(l),
                                               parent_domain,
                                               jtitem,
                                               item_list);
            sub_item = (JoinTreeItem *) llast(*item_list);
            jtitem->qualscope = bms_add_members(jtitem->qualscope,
                                                sub_item->qualscope);
            jtitem->inner_join_rels = sub_item->inner_join_rels;
            sub_members = list_length(sub_joinlist);
            remaining--;
            if (sub_members <= 1 ||
                list_length(joinlist) + sub_members + remaining <= from_collapse_limit)
                joinlist = list_concat(joinlist, sub_joinlist);
            else
                joinlist = lappend(joinlist, sub_joinlist);
        }
 
        /*
         * A FROM with more than one list element is an inner join subsuming
         * all below it, so we should report inner_join_rels = qualscope. If
         * there was exactly one element, we should (and already did) report
         * whatever its inner_join_rels were.  If there were no elements (is
         * that still possible?) the initialization before the loop fixed it.
         */
        if (list_length(f->fromlist) > 1)
            jtitem->inner_join_rels = jtitem->qualscope;
    }
    else if (IsA(jtnode, JoinExpr))
    {
        JoinExpr   *j = (JoinExpr *) jtnode;
        JoinDomain *child_domain,
                   *fj_domain;
        JoinTreeItem *left_item,
                   *right_item;
        List       *leftjoinlist,
                   *rightjoinlist;
 
        switch (j->jointype)
        {
            case JOIN_INNER:
                /* This node belongs to parent_domain, as do its children */
                jtitem->jdomain = parent_domain;
                /* Recurse */
                leftjoinlist = deconstruct_recurse(root, j->larg,
                                                   parent_domain,
                                                   jtitem,
                                                   item_list);
                left_item = (JoinTreeItem *) llast(*item_list);
                rightjoinlist = deconstruct_recurse(root, j->rarg,
                                                    parent_domain,
                                                    jtitem,
                                                    item_list);
                right_item = (JoinTreeItem *) llast(*item_list);
                /* Compute qualscope etc */
                jtitem->qualscope = bms_union(left_item->qualscope,
                                              right_item->qualscope);
                jtitem->inner_join_rels = jtitem->qualscope;
                jtitem->left_rels = left_item->qualscope;
                jtitem->right_rels = right_item->qualscope;
                /* Inner join adds no restrictions for quals */
                jtitem->nonnullable_rels = NULL;
                break;
            case JOIN_LEFT:
            case JOIN_ANTI:
                /* Make new join domain for my quals and the RHS */
                child_domain = makeNode(JoinDomain);
                child_domain->jd_relids = NULL; /* filled by recursion */
                root->join_domains = lappend(root->join_domains, child_domain);
                jtitem->jdomain = child_domain;
                /* Recurse */
                leftjoinlist = deconstruct_recurse(root, j->larg,
                                                   parent_domain,
                                                   jtitem,
                                                   item_list);
                left_item = (JoinTreeItem *) llast(*item_list);
                rightjoinlist = deconstruct_recurse(root, j->rarg,
                                                    child_domain,
                                                    jtitem,
                                                    item_list);
                right_item = (JoinTreeItem *) llast(*item_list);
                /* Compute join domain contents, qualscope etc */
                parent_domain->jd_relids =
                    bms_add_members(parent_domain->jd_relids,
                                    child_domain->jd_relids);
                jtitem->qualscope = bms_union(left_item->qualscope,
                                              right_item->qualscope);
                /* caution: ANTI join derived from SEMI will lack rtindex */
                if (j->rtindex != 0)
                {
                    parent_domain->jd_relids =
                        bms_add_member(parent_domain->jd_relids,
                                       j->rtindex);
                    jtitem->qualscope = bms_add_member(jtitem->qualscope,
                                                       j->rtindex);
                    root->outer_join_rels = bms_add_member(root->outer_join_rels,
                                                           j->rtindex);
                    mark_rels_nulled_by_join(root, j->rtindex,
                                             right_item->qualscope);
                }
                jtitem->inner_join_rels = bms_union(left_item->inner_join_rels,
                                                    right_item->inner_join_rels);
                jtitem->left_rels = left_item->qualscope;
                jtitem->right_rels = right_item->qualscope;
                jtitem->nonnullable_rels = left_item->qualscope;
                break;
            case JOIN_SEMI:
                /* This node belongs to parent_domain, as do its children */
                jtitem->jdomain = parent_domain;
                /* Recurse */
                leftjoinlist = deconstruct_recurse(root, j->larg,
                                                   parent_domain,
                                                   jtitem,
                                                   item_list);
                left_item = (JoinTreeItem *) llast(*item_list);
                rightjoinlist = deconstruct_recurse(root, j->rarg,
                                                    parent_domain,
                                                    jtitem,
                                                    item_list);
                right_item = (JoinTreeItem *) llast(*item_list);
                /* Compute qualscope etc */
                jtitem->qualscope = bms_union(left_item->qualscope,
                                              right_item->qualscope);
                /* SEMI join never has rtindex, so don't add to anything */
                Assert(j->rtindex == 0);
                jtitem->inner_join_rels = bms_union(left_item->inner_join_rels,
                                                    right_item->inner_join_rels);
                jtitem->left_rels = left_item->qualscope;
                jtitem->right_rels = right_item->qualscope;
                /* Semi join adds no restrictions for quals */
                jtitem->nonnullable_rels = NULL;
                break;
            case JOIN_FULL:
                /* The FULL JOIN's quals need their very own domain */
                fj_domain = makeNode(JoinDomain);
                root->join_domains = lappend(root->join_domains, fj_domain);
                jtitem->jdomain = fj_domain;
                /* Recurse, giving each side its own join domain */
                child_domain = makeNode(JoinDomain);
                child_domain->jd_relids = NULL; /* filled by recursion */
                root->join_domains = lappend(root->join_domains, child_domain);
                leftjoinlist = deconstruct_recurse(root, j->larg,
                                                   child_domain,
                                                   jtitem,
                                                   item_list);
                left_item = (JoinTreeItem *) llast(*item_list);
                fj_domain->jd_relids = bms_copy(child_domain->jd_relids);
                child_domain = makeNode(JoinDomain);
                child_domain->jd_relids = NULL; /* filled by recursion */
                root->join_domains = lappend(root->join_domains, child_domain);
                rightjoinlist = deconstruct_recurse(root, j->rarg,
                                                    child_domain,
                                                    jtitem,
                                                    item_list);
                right_item = (JoinTreeItem *) llast(*item_list);
                /* Compute qualscope etc */
                fj_domain->jd_relids = bms_add_members(fj_domain->jd_relids,
                                                       child_domain->jd_relids);
                parent_domain->jd_relids = bms_add_members(parent_domain->jd_relids,
                                                           fj_domain->jd_relids);
                jtitem->qualscope = bms_union(left_item->qualscope,
                                              right_item->qualscope);
                Assert(j->rtindex != 0);
                parent_domain->jd_relids = bms_add_member(parent_domain->jd_relids,
                                                          j->rtindex);
                jtitem->qualscope = bms_add_member(jtitem->qualscope,
                                                   j->rtindex);
                root->outer_join_rels = bms_add_member(root->outer_join_rels,
                                                       j->rtindex);
                mark_rels_nulled_by_join(root, j->rtindex,
                                         left_item->qualscope);
                mark_rels_nulled_by_join(root, j->rtindex,
                                         right_item->qualscope);
                jtitem->inner_join_rels = bms_union(left_item->inner_join_rels,
                                                    right_item->inner_join_rels);
                jtitem->left_rels = left_item->qualscope;
                jtitem->right_rels = right_item->qualscope;
                /* each side is both outer and inner */
                jtitem->nonnullable_rels = jtitem->qualscope;
                break;
            default:
                /* JOIN_RIGHT was eliminated during reduce_outer_joins() */
                elog(ERROR, "unrecognized join type: %d",
                     (int) j->jointype);
                leftjoinlist = rightjoinlist = NIL; /* keep compiler quiet */
                break;
        }
 
        /*
         * Compute the output joinlist.  We fold subproblems together except
         * at a FULL JOIN or where join_collapse_limit would be exceeded.
         */
        if (j->jointype == JOIN_FULL)
        {
            /* force the join order exactly at this node */
            joinlist = list_make1(list_make2(leftjoinlist, rightjoinlist));
        }
        else if (list_length(leftjoinlist) + list_length(rightjoinlist) <=
                 join_collapse_limit)
        {
            /* OK to combine subproblems */
            joinlist = list_concat(leftjoinlist, rightjoinlist);
        }
        else
        {
            /* can't combine, but needn't force join order above here */
            Node       *leftpart,
                       *rightpart;
 
            /* avoid creating useless 1-element sublists */
            if (list_length(leftjoinlist) == 1)
                leftpart = (Node *) linitial(leftjoinlist);
            else
                leftpart = (Node *) leftjoinlist;
            if (list_length(rightjoinlist) == 1)
                rightpart = (Node *) linitial(rightjoinlist);
            else
                rightpart = (Node *) rightjoinlist;
            joinlist = list_make2(leftpart, rightpart);
        }
    }
    else
    {
        elog(ERROR, "unrecognized node type: %d",
             (int) nodeTag(jtnode));
        joinlist = NIL;         /* keep compiler quiet */
    }
 
    /* Finally, we can add the new JoinTreeItem to item_list */
    *item_list = lappend(*item_list, jtitem);
 
    return joinlist;
}
 
/*
 * deconstruct_distribute
 *    Process one jointree node in phase 2 of deconstruct_jointree processing.
 *
 * Distribute quals of the node to appropriate restriction and join lists.
 * In addition, entries will be added to root->join_info_list for outer joins.
 */
static void
deconstruct_distribute(PlannerInfo *root, JoinTreeItem *jtitem)
{
    Node       *jtnode = jtitem->jtnode;
 
    if (IsA(jtnode, RangeTblRef))
    {
        int         varno = ((RangeTblRef *) jtnode)->rtindex;
 
        /* Deal with any securityQuals attached to the RTE */
        if (root->qual_security_level > 0)
            process_security_barrier_quals(root,
                                           varno,
                                           jtitem);
    }
    else if (IsA(jtnode, FromExpr))
    {
        FromExpr   *f = (FromExpr *) jtnode;
 
        /*
         * Process any lateral-referencing quals that were postponed to this
         * level by children.
         */
        distribute_quals_to_rels(root, jtitem->lateral_clauses,
                                 jtitem,
                                 NULL,
                                 root->qual_security_level,
                                 jtitem->qualscope,
                                 NULL, NULL, NULL,
                                 true, false, false,
                                 NULL);
 
        /*
         * Now process the top-level quals.
         */
        distribute_quals_to_rels(root, (List *) f->quals,
                                 jtitem,
                                 NULL,
                                 root->qual_security_level,
                                 jtitem->qualscope,
                                 NULL, NULL, NULL,
                                 true, false, false,
                                 NULL);
    }
    else if (IsA(jtnode, JoinExpr))
    {
        JoinExpr   *j = (JoinExpr *) jtnode;
        Relids      ojscope;
        List       *my_quals;
        SpecialJoinInfo *sjinfo;
        List      **postponed_oj_qual_list;
 
        /*
         * Include lateral-referencing quals postponed from children in
         * my_quals, so that they'll be handled properly in
         * make_outerjoininfo.  (This is destructive to
         * jtitem->lateral_clauses, but we won't use that again.)
         */
        my_quals = list_concat(jtitem->lateral_clauses,
                               (List *) j->quals);
 
        /*
         * For an OJ, form the SpecialJoinInfo now, so that we can pass it to
         * distribute_qual_to_rels.  We must compute its ojscope too.
         *
         * Semijoins are a bit of a hybrid: we build a SpecialJoinInfo, but we
         * want ojscope = NULL for distribute_qual_to_rels.
         */
        if (j->jointype != JOIN_INNER)
        {
            sjinfo = make_outerjoininfo(root,
                                        jtitem->left_rels,
                                        jtitem->right_rels,
                                        jtitem->inner_join_rels,
                                        j->jointype,
                                        j->rtindex,
                                        my_quals);
            jtitem->sjinfo = sjinfo;
            if (j->jointype == JOIN_SEMI)
                ojscope = NULL;
            else
                ojscope = bms_union(sjinfo->min_lefthand,
                                    sjinfo->min_righthand);
        }
        else
        {
            sjinfo = NULL;
            ojscope = NULL;
        }
 
        /*
         * If it's a left join with a join clause that is strict for the LHS,
         * then we need to postpone handling of any non-degenerate join
         * clauses, in case the join is able to commute with another left join
         * per identity 3.  (Degenerate clauses need not be postponed, since
         * they will drop down below this join anyway.)
         */
        if (j->jointype == JOIN_LEFT && sjinfo->lhs_strict)
        {
            postponed_oj_qual_list = &jtitem->oj_joinclauses;
 
            /*
             * Add back any commutable lower OJ relids that were removed from
             * min_lefthand or min_righthand, else the ojscope cross-check in
             * distribute_qual_to_rels will complain.  Since we are postponing
             * processing of non-degenerate clauses, this addition doesn't
             * affect anything except that cross-check.  Real clause
             * positioning decisions will be made later, when we revisit the
             * postponed clauses.
             */
            ojscope = bms_add_members(ojscope, sjinfo->commute_below_l);
            ojscope = bms_add_members(ojscope, sjinfo->commute_below_r);
        }
        else
            postponed_oj_qual_list = NULL;
 
        /* Process the JOIN's qual clauses */
        distribute_quals_to_rels(root, my_quals,
                                 jtitem,
                                 sjinfo,
                                 root->qual_security_level,
                                 jtitem->qualscope,
                                 ojscope, jtitem->nonnullable_rels,
                                 NULL,  /* incompatible_relids */
                                 true,  /* allow_equivalence */
                                 false, false,  /* not clones */
                                 postponed_oj_qual_list);
 
        /* And add the SpecialJoinInfo to join_info_list */
        if (sjinfo)
            root->join_info_list = lappend(root->join_info_list, sjinfo);
    }
    else
    {
        elog(ERROR, "unrecognized node type: %d",
             (int) nodeTag(jtnode));
    }
}
 
/*
 * process_security_barrier_quals
 *    Transfer security-barrier quals into relation's baserestrictinfo list.
 *
 * The rewriter put any relevant security-barrier conditions into the RTE's
 * securityQuals field, but it's now time to copy them into the rel's
 * baserestrictinfo.
 *
 * In inheritance cases, we only consider quals attached to the parent rel
 * here; they will be valid for all children too, so it's okay to consider
 * them for purposes like equivalence class creation.  Quals attached to
 * individual child rels will be dealt with during path creation.
 */
static void
process_security_barrier_quals(PlannerInfo *root,
                               int rti, JoinTreeItem *jtitem)
{
    RangeTblEntry *rte = root->simple_rte_array[rti];
    Index       security_level = 0;
    ListCell   *lc;
 
    /*
     * Each element of the securityQuals list has been preprocessed into an
     * implicitly-ANDed list of clauses.  All the clauses in a given sublist
     * should get the same security level, but successive sublists get higher
     * levels.
     */
    foreach(lc, rte->securityQuals)
    {
        List       *qualset = (List *) lfirst(lc);
 
        /*
         * We cheat to the extent of passing ojscope = qualscope rather than
         * its more logical value of NULL.  The only effect this has is to
         * force a Var-free qual to be evaluated at the rel rather than being
         * pushed up to top of tree, which we don't want.
         */
        distribute_quals_to_rels(root, qualset,
                                 jtitem,
                                 NULL,
                                 security_level,
                                 jtitem->qualscope,
                                 jtitem->qualscope,
                                 NULL,
                                 NULL,
                                 true,
                                 false, false,  /* not clones */
                                 NULL);
        security_level++;
    }
 
    /* Assert that qual_security_level is higher than anything we just used */
    Assert(security_level <= root->qual_security_level);
}
 
/*
 * mark_rels_nulled_by_join
 *    Fill RelOptInfo.nulling_relids of baserels nulled by this outer join
 *
 * Inputs:
 *  ojrelid: RT index of the join RTE (must not be 0)
 *  lower_rels: the base+OJ Relids syntactically below nullable side of join
 */
static void
mark_rels_nulled_by_join(PlannerInfo *root, Index ojrelid,
                         Relids lower_rels)
{
    int         relid = -1;
 
    while ((relid = bms_next_member(lower_rels, relid)) > 0)
    {
        RelOptInfo *rel = root->simple_rel_array[relid];
 
        /* ignore the RTE_GROUP RTE */
        if (relid == root->group_rtindex)
            continue;
 
        if (rel == NULL)        /* must be an outer join */
        {
            Assert(bms_is_member(relid, root->outer_join_rels));
            continue;
        }
        rel->nulling_relids = bms_add_member(rel->nulling_relids, ojrelid);
    }
}
 
/*
 * make_outerjoininfo
 *    Build a SpecialJoinInfo for the current outer join
 *
 * Inputs:
 *  left_rels: the base+OJ Relids syntactically on outer side of join
 *  right_rels: the base+OJ Relids syntactically on inner side of join
 *  inner_join_rels: base+OJ Relids participating in inner joins below this one
 *  jointype: what it says (must always be LEFT, FULL, SEMI, or ANTI)
 *  ojrelid: RT index of the join RTE (0 for SEMI, which isn't in the RT list)
 *  clause: the outer join's join condition (in implicit-AND format)
 *
 * The node should eventually be appended to root->join_info_list, but we
 * do not do that here.
 *
 * Note: we assume that this function is invoked bottom-up, so that
 * root->join_info_list already contains entries for all outer joins that are
 * syntactically below this one.
 */
static SpecialJoinInfo *
make_outerjoininfo(PlannerInfo *root,
                   Relids left_rels, Relids right_rels,
                   Relids inner_join_rels,
                   JoinType jointype, Index ojrelid,
                   List *clause)
{
    SpecialJoinInfo *sjinfo = makeNode(SpecialJoinInfo);
    Relids      clause_relids;
    Relids      strict_relids;
    Relids      min_lefthand;
    Relids      min_righthand;
    Relids      commute_below_l;
    Relids      commute_below_r;
    ListCell   *l;
 
    /*
     * We should not see RIGHT JOIN here because left/right were switched
     * earlier
     */
    Assert(jointype != JOIN_INNER);
    Assert(jointype != JOIN_RIGHT);
 
    /*
     * Presently the executor cannot support FOR [KEY] UPDATE/SHARE marking of
     * rels appearing on the nullable side of an outer join. (It's somewhat
     * unclear what that would mean, anyway: what should we mark when a result
     * row is generated from no element of the nullable relation?)  So,
     * complain if any nullable rel is FOR [KEY] UPDATE/SHARE.
     *
     * You might be wondering why this test isn't made far upstream in the
     * parser.  It's because the parser hasn't got enough info --- consider
     * FOR UPDATE applied to a view.  Only after rewriting and flattening do
     * we know whether the view contains an outer join.
     *
     * We use the original RowMarkClause list here; the PlanRowMark list would
     * list everything.
     */
    foreach(l, root->parse->rowMarks)
    {
        RowMarkClause *rc = (RowMarkClause *) lfirst(l);
 
        if (bms_is_member(rc->rti, right_rels) ||
            (jointype == JOIN_FULL && bms_is_member(rc->rti, left_rels)))
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
            /*------
             translator: %s is a SQL row locking clause such as FOR UPDATE */
                     errmsg("%s cannot be applied to the nullable side of an outer join",
                            LCS_asString(rc->strength))));
    }
 
    sjinfo->syn_lefthand = left_rels;
    sjinfo->syn_righthand = right_rels;
    sjinfo->jointype = jointype;
    sjinfo->ojrelid = ojrelid;
    /* these fields may get added to later: */
    sjinfo->commute_above_l = NULL;
    sjinfo->commute_above_r = NULL;
    sjinfo->commute_below_l = NULL;
    sjinfo->commute_below_r = NULL;
 
    compute_semijoin_info(root, sjinfo, clause);
 
    /* If it's a full join, no need to be very smart */
    if (jointype == JOIN_FULL)
    {
        sjinfo->min_lefthand = bms_copy(left_rels);
        sjinfo->min_righthand = bms_copy(right_rels);
        sjinfo->lhs_strict = false; /* don't care about this */
        return sjinfo;
    }
 
    /*
     * Retrieve all relids mentioned within the join clause.
     */
    clause_relids = pull_varnos(root, (Node *) clause);
 
    /*
     * For which relids is the clause strict, ie, it cannot succeed if the
     * rel's columns are all NULL?
     */
    strict_relids = find_nonnullable_rels((Node *) clause);
 
    /* Remember whether the clause is strict for any LHS relations */
    sjinfo->lhs_strict = bms_overlap(strict_relids, left_rels);
 
    /*
     * Required LHS always includes the LHS rels mentioned in the clause. We
     * may have to add more rels based on lower outer joins; see below.
     */
    min_lefthand = bms_intersect(clause_relids, left_rels);
 
    /*
     * Similarly for required RHS.  But here, we must also include any lower
     * inner joins, to ensure we don't try to commute with any of them.
     */
    min_righthand = bms_int_members(bms_union(clause_relids, inner_join_rels),
                                    right_rels);
 
    /*
     * Now check previous outer joins for ordering restrictions.
     *
     * commute_below_l and commute_below_r accumulate the relids of lower
     * outer joins that we think this one can commute with.  These decisions
     * are just tentative within this loop, since we might find an
     * intermediate outer join that prevents commutation.  Surviving relids
     * will get merged into the SpecialJoinInfo structs afterwards.
     */
    commute_below_l = commute_below_r = NULL;
    foreach(l, root->join_info_list)
    {
        SpecialJoinInfo *otherinfo = (SpecialJoinInfo *) lfirst(l);
        bool        have_unsafe_phvs;
 
        /*
         * A full join is an optimization barrier: we can't associate into or
         * out of it.  Hence, if it overlaps either LHS or RHS of the current
         * rel, expand that side's min relset to cover the whole full join.
         */
        if (otherinfo->jointype == JOIN_FULL)
        {
            Assert(otherinfo->ojrelid != 0);
            if (bms_overlap(left_rels, otherinfo->syn_lefthand) ||
                bms_overlap(left_rels, otherinfo->syn_righthand))
            {
                min_lefthand = bms_add_members(min_lefthand,
                                               otherinfo->syn_lefthand);
                min_lefthand = bms_add_members(min_lefthand,
                                               otherinfo->syn_righthand);
                min_lefthand = bms_add_member(min_lefthand,
                                              otherinfo->ojrelid);
            }
            if (bms_overlap(right_rels, otherinfo->syn_lefthand) ||
                bms_overlap(right_rels, otherinfo->syn_righthand))
            {
                min_righthand = bms_add_members(min_righthand,
                                                otherinfo->syn_lefthand);
                min_righthand = bms_add_members(min_righthand,
                                                otherinfo->syn_righthand);
                min_righthand = bms_add_member(min_righthand,
                                               otherinfo->ojrelid);
            }
            /* Needn't do anything else with the full join */
            continue;
        }
 
        /*
         * If our join condition contains any PlaceHolderVars that need to be
         * evaluated above the lower OJ, then we can't commute with it.
         */
        if (otherinfo->ojrelid != 0)
            have_unsafe_phvs =
                contain_placeholder_references_to(root,
                                                  (Node *) clause,
                                                  otherinfo->ojrelid);
        else
            have_unsafe_phvs = false;
 
        /*
         * For a lower OJ in our LHS, if our join condition uses the lower
         * join's RHS and is not strict for that rel, we must preserve the
         * ordering of the two OJs, so add lower OJ's full syntactic relset to
         * min_lefthand.  (We must use its full syntactic relset, not just its
         * min_lefthand + min_righthand.  This is because there might be other
         * OJs below this one that this one can commute with, but we cannot
         * commute with them if we don't with this one.)  Also, if we have
         * unsafe PHVs or the current join is a semijoin or antijoin, we must
         * preserve ordering regardless of strictness.
         *
         * Note: I believe we have to insist on being strict for at least one
         * rel in the lower OJ's min_righthand, not its whole syn_righthand.
         *
         * When we don't need to preserve ordering, check to see if outer join
         * identity 3 applies, and if so, remove the lower OJ's ojrelid from
         * our min_lefthand so that commutation is allowed.
         */
        if (bms_overlap(left_rels, otherinfo->syn_righthand))
        {
            if (bms_overlap(clause_relids, otherinfo->syn_righthand) &&
                (have_unsafe_phvs ||
                 jointype == JOIN_SEMI || jointype == JOIN_ANTI ||
                 !bms_overlap(strict_relids, otherinfo->min_righthand)))
            {
                /* Preserve ordering */
                min_lefthand = bms_add_members(min_lefthand,
                                               otherinfo->syn_lefthand);
                min_lefthand = bms_add_members(min_lefthand,
                                               otherinfo->syn_righthand);
                if (otherinfo->ojrelid != 0)
                    min_lefthand = bms_add_member(min_lefthand,
                                                  otherinfo->ojrelid);
            }
            else if (jointype == JOIN_LEFT &&
                     otherinfo->jointype == JOIN_LEFT &&
                     bms_overlap(strict_relids, otherinfo->min_righthand) &&
                     !bms_overlap(clause_relids, otherinfo->syn_lefthand))
            {
                /* Identity 3 applies, so remove the ordering restriction */
                min_lefthand = bms_del_member(min_lefthand, otherinfo->ojrelid);
                /* Record the (still tentative) commutability relationship */
                commute_below_l =
                    bms_add_member(commute_below_l, otherinfo->ojrelid);
            }
        }
 
        /*
         * For a lower OJ in our RHS, if our join condition does not use the
         * lower join's RHS and the lower OJ's join condition is strict, we
         * can interchange the ordering of the two OJs; otherwise we must add
         * the lower OJ's full syntactic relset to min_righthand.
         *
         * Also, if our join condition does not use the lower join's LHS
         * either, force the ordering to be preserved.  Otherwise we can end
         * up with SpecialJoinInfos with identical min_righthands, which can
         * confuse join_is_legal (see discussion in backend/optimizer/README).
         *
         * Also, we must preserve ordering anyway if we have unsafe PHVs, or
         * if either this join or the lower OJ is a semijoin or antijoin.
         *
         * When we don't need to preserve ordering, check to see if outer join
         * identity 3 applies, and if so, remove the lower OJ's ojrelid from
         * our min_righthand so that commutation is allowed.
         */
        if (bms_overlap(right_rels, otherinfo->syn_righthand))
        {
            if (bms_overlap(clause_relids, otherinfo->syn_righthand) ||
                !bms_overlap(clause_relids, otherinfo->min_lefthand) ||
                have_unsafe_phvs ||
                jointype == JOIN_SEMI ||
                jointype == JOIN_ANTI ||
                otherinfo->jointype == JOIN_SEMI ||
                otherinfo->jointype == JOIN_ANTI ||
                !otherinfo->lhs_strict)
            {
                /* Preserve ordering */
                min_righthand = bms_add_members(min_righthand,
                                                otherinfo->syn_lefthand);
                min_righthand = bms_add_members(min_righthand,
                                                otherinfo->syn_righthand);
                if (otherinfo->ojrelid != 0)
                    min_righthand = bms_add_member(min_righthand,
                                                   otherinfo->ojrelid);
            }
            else if (jointype == JOIN_LEFT &&
                     otherinfo->jointype == JOIN_LEFT &&
                     otherinfo->lhs_strict)
            {
                /* Identity 3 applies, so remove the ordering restriction */
                min_righthand = bms_del_member(min_righthand,
                                               otherinfo->ojrelid);
                /* Record the (still tentative) commutability relationship */
                commute_below_r =
                    bms_add_member(commute_below_r, otherinfo->ojrelid);
            }
        }
    }
 
    /*
     * Examine PlaceHolderVars.  If a PHV is supposed to be evaluated within
     * this join's nullable side, then ensure that min_righthand contains the
     * full eval_at set of the PHV.  This ensures that the PHV actually can be
     * evaluated within the RHS.  Note that this works only because we should
     * already have determined the final eval_at level for any PHV
     * syntactically within this join.
     */
    foreach(l, root->placeholder_list)
    {
        PlaceHolderInfo *phinfo = (PlaceHolderInfo *) lfirst(l);
        Relids      ph_syn_level = phinfo->ph_var->phrels;
 
        /* Ignore placeholder if it didn't syntactically come from RHS */
        if (!bms_is_subset(ph_syn_level, right_rels))
            continue;
 
        /* Else, prevent join from being formed before we eval the PHV */
        min_righthand = bms_add_members(min_righthand, phinfo->ph_eval_at);
    }
 
    /*
     * If we found nothing to put in min_lefthand, punt and make it the full
     * LHS, to avoid having an empty min_lefthand which will confuse later
     * processing. (We don't try to be smart about such cases, just correct.)
     * Likewise for min_righthand.
     */
    if (bms_is_empty(min_lefthand))
        min_lefthand = bms_copy(left_rels);
    if (bms_is_empty(min_righthand))
        min_righthand = bms_copy(right_rels);
 
    /* Now they'd better be nonempty */
    Assert(!bms_is_empty(min_lefthand));
    Assert(!bms_is_empty(min_righthand));
    /* Shouldn't overlap either */
    Assert(!bms_overlap(min_lefthand, min_righthand));
 
    sjinfo->min_lefthand = min_lefthand;
    sjinfo->min_righthand = min_righthand;
 
    /*
     * Now that we've identified the correct min_lefthand and min_righthand,
     * any commute_below_l or commute_below_r relids that have not gotten
     * added back into those sets (due to intervening outer joins) are indeed
     * commutable with this one.
     *
     * First, delete any subsequently-added-back relids (this is easier than
     * maintaining commute_below_l/r precisely through all the above).
     */
    commute_below_l = bms_del_members(commute_below_l, min_lefthand);
    commute_below_r = bms_del_members(commute_below_r, min_righthand);
 
    /* Anything left? */
    if (commute_below_l || commute_below_r)
    {
        /* Yup, so we must update the derived data in the SpecialJoinInfos */
        sjinfo->commute_below_l = commute_below_l;
        sjinfo->commute_below_r = commute_below_r;
        foreach(l, root->join_info_list)
        {
            SpecialJoinInfo *otherinfo = (SpecialJoinInfo *) lfirst(l);
 
            if (bms_is_member(otherinfo->ojrelid, commute_below_l))
                otherinfo->commute_above_l =
                    bms_add_member(otherinfo->commute_above_l, ojrelid);
            else if (bms_is_member(otherinfo->ojrelid, commute_below_r))
                otherinfo->commute_above_r =
                    bms_add_member(otherinfo->commute_above_r, ojrelid);
        }
    }
 
    return sjinfo;
}
 
/*
 * compute_semijoin_info
 *    Fill semijoin-related fields of a new SpecialJoinInfo
 *
 * Note: this relies on only the jointype and syn_righthand fields of the
 * SpecialJoinInfo; the rest may not be set yet.
 */
static void
compute_semijoin_info(PlannerInfo *root, SpecialJoinInfo *sjinfo, List *clause)
{
    List       *semi_operators;
    List       *semi_rhs_exprs;
    bool        all_btree;
    bool        all_hash;
    ListCell   *lc;
 
    /* Initialize semijoin-related fields in case we can't unique-ify */
    sjinfo->semi_can_btree = false;
    sjinfo->semi_can_hash = false;
    sjinfo->semi_operators = NIL;
    sjinfo->semi_rhs_exprs = NIL;
 
    /* Nothing more to do if it's not a semijoin */
    if (sjinfo->jointype != JOIN_SEMI)
        return;
 
    /*
     * Look to see whether the semijoin's join quals consist of AND'ed
     * equality operators, with (only) RHS variables on only one side of each
     * one.  If so, we can figure out how to enforce uniqueness for the RHS.
     *
     * Note that the input clause list is the list of quals that are
     * *syntactically* associated with the semijoin, which in practice means
     * the synthesized comparison list for an IN or the WHERE of an EXISTS.
     * Particularly in the latter case, it might contain clauses that aren't
     * *semantically* associated with the join, but refer to just one side or
     * the other.  We can ignore such clauses here, as they will just drop
     * down to be processed within one side or the other.  (It is okay to
     * consider only the syntactically-associated clauses here because for a
     * semijoin, no higher-level quals could refer to the RHS, and so there
     * can be no other quals that are semantically associated with this join.
     * We do things this way because it is useful to have the set of potential
     * unique-ification expressions before we can extract the list of quals
     * that are actually semantically associated with the particular join.)
     *
     * Note that the semi_operators list consists of the joinqual operators
     * themselves (but commuted if needed to put the RHS value on the right).
     * These could be cross-type operators, in which case the operator
     * actually needed for uniqueness is a related single-type operator. We
     * assume here that that operator will be available from the btree or hash
     * opclass when the time comes ... if not, create_unique_plan() will fail.
     */
    semi_operators = NIL;
    semi_rhs_exprs = NIL;
    all_btree = true;
    all_hash = enable_hashagg;  /* don't consider hash if not enabled */
    foreach(lc, clause)
    {
        OpExpr     *op = (OpExpr *) lfirst(lc);
        Oid         opno;
        Node       *left_expr;
        Node       *right_expr;
        Relids      left_varnos;
        Relids      right_varnos;
        Relids      all_varnos;
        Oid         opinputtype;
 
        /* Is it a binary opclause? */
        if (!IsA(op, OpExpr) ||
            list_length(op->args) != 2)
        {
            /* No, but does it reference both sides? */
            all_varnos = pull_varnos(root, (Node *) op);
            if (!bms_overlap(all_varnos, sjinfo->syn_righthand) ||
                bms_is_subset(all_varnos, sjinfo->syn_righthand))
            {
                /*
                 * Clause refers to only one rel, so ignore it --- unless it
                 * contains volatile functions, in which case we'd better
                 * punt.
                 */
                if (contain_volatile_functions((Node *) op))
                    return;
                continue;
            }
            /* Non-operator clause referencing both sides, must punt */
            return;
        }
 
        /* Extract data from binary opclause */
        opno = op->opno;
        left_expr = linitial(op->args);
        right_expr = lsecond(op->args);
        left_varnos = pull_varnos(root, left_expr);
        right_varnos = pull_varnos(root, right_expr);
        all_varnos = bms_union(left_varnos, right_varnos);
        opinputtype = exprType(left_expr);
 
        /* Does it reference both sides? */
        if (!bms_overlap(all_varnos, sjinfo->syn_righthand) ||
            bms_is_subset(all_varnos, sjinfo->syn_righthand))
        {
            /*
             * Clause refers to only one rel, so ignore it --- unless it
             * contains volatile functions, in which case we'd better punt.
             */
            if (contain_volatile_functions((Node *) op))
                return;
            continue;
        }
 
        /* check rel membership of arguments */
        if (!bms_is_empty(right_varnos) &&
            bms_is_subset(right_varnos, sjinfo->syn_righthand) &&
            !bms_overlap(left_varnos, sjinfo->syn_righthand))
        {
            /* typical case, right_expr is RHS variable */
        }
        else if (!bms_is_empty(left_varnos) &&
                 bms_is_subset(left_varnos, sjinfo->syn_righthand) &&
                 !bms_overlap(right_varnos, sjinfo->syn_righthand))
        {
            /* flipped case, left_expr is RHS variable */
            opno = get_commutator(opno);
            if (!OidIsValid(opno))
                return;
            right_expr = left_expr;
        }
        else
        {
            /* mixed membership of args, punt */
            return;
        }
 
        /* all operators must be btree equality or hash equality */
        if (all_btree)
        {
            /* oprcanmerge is considered a hint... */
            if (!op_mergejoinable(opno, opinputtype) ||
                get_mergejoin_opfamilies(opno) == NIL)
                all_btree = false;
        }
        if (all_hash)
        {
            /* ... but oprcanhash had better be correct */
            if (!op_hashjoinable(opno, opinputtype))
                all_hash = false;
        }
        if (!(all_btree || all_hash))
            return;
 
        /* so far so good, keep building lists */
        semi_operators = lappend_oid(semi_operators, opno);
        semi_rhs_exprs = lappend(semi_rhs_exprs, copyObject(right_expr));
    }
 
    /* Punt if we didn't find at least one column to unique-ify */
    if (semi_rhs_exprs == NIL)
        return;
 
    /*
     * The expressions we'd need to unique-ify mustn't be volatile.
     */
    if (contain_volatile_functions((Node *) semi_rhs_exprs))
        return;
 
    /*
     * If we get here, we can unique-ify the semijoin's RHS using at least one
     * of sorting and hashing.  Save the information about how to do that.
     */
    sjinfo->semi_can_btree = all_btree;
    sjinfo->semi_can_hash = all_hash;
    sjinfo->semi_operators = semi_operators;
    sjinfo->semi_rhs_exprs = semi_rhs_exprs;
}
 
/*
 * deconstruct_distribute_oj_quals
 *    Adjust LEFT JOIN quals to be suitable for commuted-left-join cases,
 *    then push them into the joinqual lists and EquivalenceClass structures.
 *
 * This runs immediately after we've completed the deconstruct_distribute scan.
 * jtitems contains all the JoinTreeItems (in depth-first order), and jtitem
 * is one that has postponed oj_joinclauses to deal with.
 */
static void
deconstruct_distribute_oj_quals(PlannerInfo *root,
                                List *jtitems,
                                JoinTreeItem *jtitem)
{
    SpecialJoinInfo *sjinfo = jtitem->sjinfo;
    Relids      qualscope,
                ojscope,
                nonnullable_rels;
 
    /* Recompute syntactic and semantic scopes of this left join */
    qualscope = bms_union(sjinfo->syn_lefthand, sjinfo->syn_righthand);
    qualscope = bms_add_member(qualscope, sjinfo->ojrelid);
    ojscope = bms_union(sjinfo->min_lefthand, sjinfo->min_righthand);
    nonnullable_rels = sjinfo->syn_lefthand;
 
    /*
     * If this join can commute with any other ones per outer-join identity 3,
     * and it is the one providing the join clause with flexible semantics,
     * then we have to generate variants of the join clause with different
     * nullingrels labeling.  Otherwise, just push out the postponed clause
     * as-is.
     */
    Assert(sjinfo->lhs_strict); /* else we shouldn't be here */
    if (sjinfo->commute_above_r || sjinfo->commute_below_l)
    {
        Relids      joins_above;
        Relids      joins_below;
        Relids      incompatible_joins;
        Relids      joins_so_far;
        List       *quals;
        int         save_last_rinfo_serial;
        ListCell   *lc;
 
        /* Identify the outer joins this one commutes with */
        joins_above = sjinfo->commute_above_r;
        joins_below = sjinfo->commute_below_l;
 
        /*
         * Generate qual variants with different sets of nullingrels bits.
         *
         * We only need bit-sets that correspond to the successively less
         * deeply syntactically-nested subsets of this join and its
         * commutators.  That's true first because obviously only those forms
         * of the Vars and PHVs could appear elsewhere in the query, and
         * second because the outer join identities do not provide a way to
         * re-order such joins in a way that would require different marking.
         * (That is, while the current join may commute with several others,
         * none of those others can commute with each other.)  To visit the
         * interesting joins in syntactic nesting order, we rely on the
         * jtitems list to be ordered that way.
         *
         * We first strip out all the nullingrels bits corresponding to
         * commuting joins below this one, and then successively put them back
         * as we crawl up the join stack.
         */
        quals = jtitem->oj_joinclauses;
        if (!bms_is_empty(joins_below))
            quals = (List *) remove_nulling_relids((Node *) quals,
                                                   joins_below,
                                                   NULL);
 
        /*
         * We'll need to mark the lower versions of the quals as not safe to
         * apply above not-yet-processed joins of the stack.  This prevents
         * possibly applying a cloned qual at the wrong join level.
         */
        incompatible_joins = bms_union(joins_below, joins_above);
        incompatible_joins = bms_add_member(incompatible_joins,
                                            sjinfo->ojrelid);
 
        /*
         * Each time we produce RestrictInfo(s) from these quals, reset the
         * last_rinfo_serial counter, so that the RestrictInfos for the "same"
         * qual condition get identical serial numbers.  (This relies on the
         * fact that we're not changing the qual list in any way that'd affect
         * the number of RestrictInfos built from it.) This'll allow us to
         * detect duplicative qual usage later.
         */
        save_last_rinfo_serial = root->last_rinfo_serial;
 
        joins_so_far = NULL;
        foreach(lc, jtitems)
        {
            JoinTreeItem *otherjtitem = (JoinTreeItem *) lfirst(lc);
            SpecialJoinInfo *othersj = otherjtitem->sjinfo;
            bool        below_sjinfo = false;
            bool        above_sjinfo = false;
            Relids      this_qualscope;
            Relids      this_ojscope;
            bool        allow_equivalence,
                        has_clone,
                        is_clone;
 
            if (othersj == NULL)
                continue;       /* not an outer-join item, ignore */
 
            if (bms_is_member(othersj->ojrelid, joins_below))
            {
                /* othersj commutes with sjinfo from below left */
                below_sjinfo = true;
            }
            else if (othersj == sjinfo)
            {
                /* found our join in syntactic order */
                Assert(bms_equal(joins_so_far, joins_below));
            }
            else if (bms_is_member(othersj->ojrelid, joins_above))
            {
                /* othersj commutes with sjinfo from above */
                above_sjinfo = true;
            }
            else
            {
                /* othersj is not relevant, ignore */
                continue;
            }
 
            /* Reset serial counter for this version of the quals */
            root->last_rinfo_serial = save_last_rinfo_serial;
 
            /*
             * When we are looking at joins above sjinfo, we are envisioning
             * pushing sjinfo to above othersj, so add othersj's nulling bit
             * before distributing the quals.  We should add it to Vars coming
             * from the current join's LHS: we want to transform the second
             * form of OJ identity 3 to the first form, in which Vars of
             * relation B will appear nulled by the syntactically-upper OJ
             * within the Pbc clause, but those of relation C will not.  (In
             * the notation used by optimizer/README, we're converting a qual
             * of the form Pbc to Pb*c.)  Of course, we must also remove that
             * bit from the incompatible_joins value, else we'll make a qual
             * that can't be placed anywhere.
             */
            if (above_sjinfo)
            {
                quals = (List *)
                    add_nulling_relids((Node *) quals,
                                       sjinfo->syn_lefthand,
                                       bms_make_singleton(othersj->ojrelid));
                incompatible_joins = bms_del_member(incompatible_joins,
                                                    othersj->ojrelid);
            }
 
            /* Compute qualscope and ojscope for this join level */
            this_qualscope = bms_union(qualscope, joins_so_far);
            this_ojscope = bms_union(ojscope, joins_so_far);
            if (above_sjinfo)
            {
                /* othersj is not yet in joins_so_far, but we need it */
                this_qualscope = bms_add_member(this_qualscope,
                                                othersj->ojrelid);
                this_ojscope = bms_add_member(this_ojscope,
                                              othersj->ojrelid);
                /* sjinfo is in joins_so_far, and we don't want it */
                this_ojscope = bms_del_member(this_ojscope,
                                              sjinfo->ojrelid);
            }
 
            /*
             * We generate EquivalenceClasses only from the first form of the
             * quals, with the fewest nullingrels bits set.  An EC made from
             * this version of the quals can be useful below the outer-join
             * nest, whereas versions with some nullingrels bits set would not
             * be.  We cannot generate ECs from more than one version, or
             * we'll make nonsensical conclusions that Vars with nullingrels
             * bits set are equal to their versions without.  Fortunately,
             * such ECs wouldn't be very useful anyway, because they'd equate
             * values not observable outside the join nest.  (See
             * optimizer/README.)
             *
             * The first form of the quals is also the only one marked as
             * has_clone rather than is_clone.
             */
            allow_equivalence = (joins_so_far == NULL);
            has_clone = allow_equivalence;
            is_clone = !has_clone;
 
            distribute_quals_to_rels(root, quals,
                                     otherjtitem,
                                     sjinfo,
                                     root->qual_security_level,
                                     this_qualscope,
                                     this_ojscope, nonnullable_rels,
                                     bms_copy(incompatible_joins),
                                     allow_equivalence,
                                     has_clone,
                                     is_clone,
                                     NULL); /* no more postponement */
 
            /*
             * Adjust qual nulling bits for next level up, if needed.  We
             * don't want to put sjinfo's own bit in at all, and if we're
             * above sjinfo then we did it already.  Here, we should mark all
             * Vars coming from the lower join's RHS.  (Again, we are
             * converting a qual of the form Pbc to Pb*c, but now we are
             * putting back bits that were there in the parser output and were
             * temporarily stripped above.)  Update incompatible_joins too.
             */
            if (below_sjinfo)
            {
                quals = (List *)
                    add_nulling_relids((Node *) quals,
                                       othersj->syn_righthand,
                                       bms_make_singleton(othersj->ojrelid));
                incompatible_joins = bms_del_member(incompatible_joins,
                                                    othersj->ojrelid);
            }
 
            /* ... and track joins processed so far */
            joins_so_far = bms_add_member(joins_so_far, othersj->ojrelid);
        }
    }
    else
    {
        /* No commutation possible, just process the postponed clauses */
        distribute_quals_to_rels(root, jtitem->oj_joinclauses,
                                 jtitem,
                                 sjinfo,
                                 root->qual_security_level,
                                 qualscope,
                                 ojscope, nonnullable_rels,
                                 NULL,  /* incompatible_relids */
                                 true,  /* allow_equivalence */
                                 false, false,  /* not clones */
                                 NULL); /* no more postponement */
    }
}
 
 
/*****************************************************************************
 *
 *    QUALIFICATIONS
 *
 *****************************************************************************/
 
/*
 * distribute_quals_to_rels
 *    Convenience routine to apply distribute_qual_to_rels to each element
 *    of an AND'ed list of clauses.
 */
static void
distribute_quals_to_rels(PlannerInfo *root, List *clauses,
                         JoinTreeItem *jtitem,
                         SpecialJoinInfo *sjinfo,
                         Index security_level,
                         Relids qualscope,
                         Relids ojscope,
                         Relids outerjoin_nonnullable,
                         Relids incompatible_relids,
                         bool allow_equivalence,
                         bool has_clone,
                         bool is_clone,
                         List **postponed_oj_qual_list)
{
    ListCell   *lc;
 
    foreach(lc, clauses)
    {
        Node       *clause = (Node *) lfirst(lc);
 
        distribute_qual_to_rels(root, clause,
                                jtitem,
                                sjinfo,
                                security_level,
                                qualscope,
                                ojscope,
                                outerjoin_nonnullable,
                                incompatible_relids,
                                allow_equivalence,
                                has_clone,
                                is_clone,
                                postponed_oj_qual_list);
    }
}
 
/*
 * distribute_qual_to_rels
 *    Add clause information to either the baserestrictinfo or joininfo list
 *    (depending on whether the clause is a join) of each base relation
 *    mentioned in the clause.  A RestrictInfo node is created and added to
 *    the appropriate list for each rel.  Alternatively, if the clause uses a
 *    mergejoinable operator, enter its left- and right-side expressions into
 *    the query's EquivalenceClasses.
 *
 * In some cases, quals will be added to parent jtitems' lateral_clauses
 * or to postponed_oj_qual_list instead of being processed right away.
 * These will be dealt with in later calls of deconstruct_distribute.
 *
 * 'clause': the qual clause to be distributed
 * 'jtitem': the JoinTreeItem for the containing jointree node
 * 'sjinfo': join's SpecialJoinInfo (NULL for an inner join or WHERE clause)
 * 'security_level': security_level to assign to the qual
 * 'qualscope': set of base+OJ rels the qual's syntactic scope covers
 * 'ojscope': NULL if not an outer-join qual, else the minimum set of base+OJ
 *      rels needed to form this join
 * 'outerjoin_nonnullable': NULL if not an outer-join qual, else the set of
 *      base+OJ rels appearing on the outer (nonnullable) side of the join
 *      (for FULL JOIN this includes both sides of the join, and must in fact
 *      equal qualscope)
 * 'incompatible_relids': the set of outer-join relid(s) that must not be
 *      computed below this qual.  We only bother to compute this for
 *      "clone" quals, otherwise it can be left NULL.
 * 'allow_equivalence': true if it's okay to convert clause into an
 *      EquivalenceClass
 * 'has_clone': has_clone property to assign to the qual
 * 'is_clone': is_clone property to assign to the qual
 * 'postponed_oj_qual_list': if not NULL, non-degenerate outer join clauses
 *      should be added to this list instead of being processed (list entries
 *      are just the bare clauses)
 *
 * 'qualscope' identifies what level of JOIN the qual came from syntactically.
 * 'ojscope' is needed if we decide to force the qual up to the outer-join
 * level, which will be ojscope not necessarily qualscope.
 *
 * At the time this is called, root->join_info_list must contain entries for
 * at least those special joins that are syntactically below this qual.
 * (We now need that only for detection of redundant IS NULL quals.)
 */
static void
distribute_qual_to_rels(PlannerInfo *root, Node *clause,
                        JoinTreeItem *jtitem,
                        SpecialJoinInfo *sjinfo,
                        Index security_level,
                        Relids qualscope,
                        Relids ojscope,
                        Relids outerjoin_nonnullable,
                        Relids incompatible_relids,
                        bool allow_equivalence,
                        bool has_clone,
                        bool is_clone,
                        List **postponed_oj_qual_list)
{
    Relids      relids;
    bool        is_pushed_down;
    bool        pseudoconstant = false;
    bool        maybe_equivalence;
    bool        maybe_outer_join;
    RestrictInfo *restrictinfo;
 
    /*
     * Retrieve all relids mentioned within the clause.
     */
    relids = pull_varnos(root, clause);
 
    /*
     * In ordinary SQL, a WHERE or JOIN/ON clause can't reference any rels
     * that aren't within its syntactic scope; however, if we pulled up a
     * LATERAL subquery then we might find such references in quals that have
     * been pulled up.  We need to treat such quals as belonging to the join
     * level that includes every rel they reference.  Although we could make
     * pull_up_subqueries() place such quals correctly to begin with, it's
     * easier to handle it here.  When we find a clause that contains Vars
     * outside its syntactic scope, locate the nearest parent join level that
     * includes all the required rels and add the clause to that level's
     * lateral_clauses list.  We'll process it when we reach that join level.
     */
    if (!bms_is_subset(relids, qualscope))
    {
        JoinTreeItem *pitem;
 
        Assert(root->hasLateralRTEs);   /* shouldn't happen otherwise */
        Assert(sjinfo == NULL); /* mustn't postpone past outer join */
        for (pitem = jtitem->jti_parent; pitem; pitem = pitem->jti_parent)
        {
            if (bms_is_subset(relids, pitem->qualscope))
            {
                pitem->lateral_clauses = lappend(pitem->lateral_clauses,
                                                 clause);
                return;
            }
 
            /*
             * We should not be postponing any quals past an outer join.  If
             * this Assert fires, pull_up_subqueries() messed up.
             */
            Assert(pitem->sjinfo == NULL);
        }
        elog(ERROR, "failed to postpone qual containing lateral reference");
    }
 
    /*
     * If it's an outer-join clause, also check that relids is a subset of
     * ojscope.  (This should not fail if the syntactic scope check passed.)
     */
    if (ojscope && !bms_is_subset(relids, ojscope))
        elog(ERROR, "JOIN qualification cannot refer to other relations");
 
    /*
     * If the clause is variable-free, our normal heuristic for pushing it
     * down to just the mentioned rels doesn't work, because there are none.
     *
     * If the clause is an outer-join clause, we must force it to the OJ's
     * semantic level to preserve semantics.
     *
     * Otherwise, when the clause contains volatile functions, we force it to
     * be evaluated at its original syntactic level.  This preserves the
     * expected semantics.
     *
     * When the clause contains no volatile functions either, it is actually a
     * pseudoconstant clause that will not change value during any one
     * execution of the plan, and hence can be used as a one-time qual in a
     * gating Result plan node.  We put such a clause into the regular
     * RestrictInfo lists for the moment, but eventually createplan.c will
     * pull it out and make a gating Result node immediately above whatever
     * plan node the pseudoconstant clause is assigned to.  It's usually best
     * to put a gating node as high in the plan tree as possible.
     */
    if (bms_is_empty(relids))
    {
        if (ojscope)
        {
            /* clause is attached to outer join, eval it there */
            relids = bms_copy(ojscope);
            /* mustn't use as gating qual, so don't mark pseudoconstant */
        }
        else if (contain_volatile_functions(clause))
        {
            /* eval at original syntactic level */
            relids = bms_copy(qualscope);
            /* again, can't mark pseudoconstant */
        }
        else
        {
            /*
             * If we are in the top-level join domain, we can push the qual to
             * the top of the plan tree.  Otherwise, be conservative and eval
             * it at original syntactic level.  (Ideally we'd push it to the
             * top of the current join domain in all cases, but that causes
             * problems if we later rearrange outer-join evaluation order.
             * Pseudoconstant quals below the top level are a pretty odd case,
             * so it's not clear that it's worth working hard on.)
             */
            if (jtitem->jdomain == (JoinDomain *) linitial(root->join_domains))
                relids = bms_copy(jtitem->jdomain->jd_relids);
            else
                relids = bms_copy(qualscope);
            /* mark as gating qual */
            pseudoconstant = true;
            /* tell createplan.c to check for gating quals */
            root->hasPseudoConstantQuals = true;
        }
    }
 
    /*----------
     * Check to see if clause application must be delayed by outer-join
     * considerations.
     *
     * A word about is_pushed_down: we mark the qual as "pushed down" if
     * it is (potentially) applicable at a level different from its original
     * syntactic level.  This flag is used to distinguish OUTER JOIN ON quals
     * from other quals pushed down to the same joinrel.  The rules are:
     *      WHERE quals and INNER JOIN quals: is_pushed_down = true.
     *      Non-degenerate OUTER JOIN quals: is_pushed_down = false.
     *      Degenerate OUTER JOIN quals: is_pushed_down = true.
     * A "degenerate" OUTER JOIN qual is one that doesn't mention the
     * non-nullable side, and hence can be pushed down into the nullable side
     * without changing the join result.  It is correct to treat it as a
     * regular filter condition at the level where it is evaluated.
     *
     * Note: it is not immediately obvious that a simple boolean is enough
     * for this: if for some reason we were to attach a degenerate qual to
     * its original join level, it would need to be treated as an outer join
     * qual there.  However, this cannot happen, because all the rels the
     * clause mentions must be in the outer join's min_righthand, therefore
     * the join it needs must be formed before the outer join; and we always
     * attach quals to the lowest level where they can be evaluated.  But
     * if we were ever to re-introduce a mechanism for delaying evaluation
     * of "expensive" quals, this area would need work.
     *
     * Note: generally, use of is_pushed_down has to go through the macro
     * RINFO_IS_PUSHED_DOWN, because that flag alone is not always sufficient
     * to tell whether a clause must be treated as pushed-down in context.
     * This seems like another reason why it should perhaps be rethought.
     *----------
     */
    if (bms_overlap(relids, outerjoin_nonnullable))
    {
        /*
         * The qual is attached to an outer join and mentions (some of the)
         * rels on the nonnullable side, so it's not degenerate.  If the
         * caller wants to postpone handling such clauses, just add it to
         * postponed_oj_qual_list and return.  (The work we've done up to here
         * will have to be redone later, but there's not much of it.)
         */
        if (postponed_oj_qual_list != NULL)
        {
            *postponed_oj_qual_list = lappend(*postponed_oj_qual_list, clause);
            return;
        }
 
        /*
         * We can't use such a clause to deduce equivalence (the left and
         * right sides might be unequal above the join because one of them has
         * gone to NULL) ... but we might be able to use it for more limited
         * deductions, if it is mergejoinable.  So consider adding it to the
         * lists of set-aside outer-join clauses.
         */
        is_pushed_down = false;
        maybe_equivalence = false;
        maybe_outer_join = true;
 
        /*
         * Now force the qual to be evaluated exactly at the level of joining
         * corresponding to the outer join.  We cannot let it get pushed down
         * into the nonnullable side, since then we'd produce no output rows,
         * rather than the intended single null-extended row, for any
         * nonnullable-side rows failing the qual.
         */
        Assert(ojscope);
        relids = ojscope;
        Assert(!pseudoconstant);
    }
    else
    {
        /*
         * Normal qual clause or degenerate outer-join clause.  Either way, we
         * can mark it as pushed-down.
         */
        is_pushed_down = true;
 
        /*
         * It's possible that this is an IS NULL clause that's redundant with
         * a lower antijoin; if so we can just discard it.  We need not test
         * in any of the other cases, because this will only be possible for
         * pushed-down clauses.
         */
        if (check_redundant_nullability_qual(root, clause))
            return;
 
        /* Feed qual to the equivalence machinery, if allowed by caller */
        maybe_equivalence = allow_equivalence;
 
        /*
         * Since it doesn't mention the LHS, it's certainly not useful as a
         * set-aside OJ clause, even if it's in an OJ.
         */
        maybe_outer_join = false;
    }
 
    /*
     * Build the RestrictInfo node itself.
     */
    restrictinfo = make_restrictinfo(root,
                                     (Expr *) clause,
                                     is_pushed_down,
                                     has_clone,
                                     is_clone,
                                     pseudoconstant,
                                     security_level,
                                     relids,
                                     incompatible_relids,
                                     outerjoin_nonnullable);
 
    /*
     * If it's a join clause, add vars used in the clause to targetlists of
     * their relations, so that they will be emitted by the plan nodes that
     * scan those relations (else they won't be available at the join node!).
     *
     * Normally we mark the vars as needed at the join identified by "relids".
     * However, if this is a clone clause then ignore the outer-join relids in
     * that set.  Otherwise, vars appearing in a cloned clause would end up
     * marked as having to propagate to the highest one of the commuting
     * joins, which would often be an overestimate.  For such clauses, correct
     * var propagation is ensured by making ojscope include input rels from
     * both sides of the join.
     *
     * See also rebuild_joinclause_attr_needed, which has to partially repeat
     * this work after removal of an outer join.
     *
     * Note: if the clause gets absorbed into an EquivalenceClass then this
     * may be unnecessary, but for now we have to do it to cover the case
     * where the EC becomes ec_broken and we end up reinserting the original
     * clauses into the plan.
     */
    if (bms_membership(relids) == BMS_MULTIPLE)
    {
        List       *vars = pull_var_clause(clause,
                                           PVC_RECURSE_AGGREGATES |
                                           PVC_RECURSE_WINDOWFUNCS |
                                           PVC_INCLUDE_PLACEHOLDERS);
        Relids      where_needed;
 
        if (is_clone)
            where_needed = bms_intersect(relids, root->all_baserels);
        else
            where_needed = relids;
        add_vars_to_targetlist(root, vars, where_needed);
        list_free(vars);
    }
 
    /*
     * We check "mergejoinability" of every clause, not only join clauses,
     * because we want to know about equivalences between vars of the same
     * relation, or between vars and consts.
     */
    check_mergejoinable(restrictinfo);
 
    /*
     * If it is a true equivalence clause, send it to the EquivalenceClass
     * machinery.  We do *not* attach it directly to any restriction or join
     * lists.  The EC code will propagate it to the appropriate places later.
     *
     * If the clause has a mergejoinable operator, yet isn't an equivalence
     * because it is an outer-join clause, the EC code may still be able to do
     * something with it.  We add it to appropriate lists for further
     * consideration later.  Specifically:
     *
     * If it is a left or right outer-join qualification that relates the two
     * sides of the outer join (no funny business like leftvar1 = leftvar2 +
     * rightvar), we add it to root->left_join_clauses or
     * root->right_join_clauses according to which side the nonnullable
     * variable appears on.
     *
     * If it is a full outer-join qualification, we add it to
     * root->full_join_clauses.  (Ideally we'd discard cases that aren't
     * leftvar = rightvar, as we do for left/right joins, but this routine
     * doesn't have the info needed to do that; and the current usage of the
     * full_join_clauses list doesn't require that, so it's not currently
     * worth complicating this routine's API to make it possible.)
     *
     * If none of the above hold, pass it off to
     * distribute_restrictinfo_to_rels().
     *
     * In all cases, it's important to initialize the left_ec and right_ec
     * fields of a mergejoinable clause, so that all possibly mergejoinable
     * expressions have representations in EquivalenceClasses.  If
     * process_equivalence is successful, it will take care of that;
     * otherwise, we have to call initialize_mergeclause_eclasses to do it.
     */
    if (restrictinfo->mergeopfamilies)
    {
        if (maybe_equivalence)
        {
            if (process_equivalence(root, &restrictinfo, jtitem->jdomain))
                return;
            /* EC rejected it, so set left_ec/right_ec the hard way ... */
            if (restrictinfo->mergeopfamilies)  /* EC might have changed this */
                initialize_mergeclause_eclasses(root, restrictinfo);
            /* ... and fall through to distribute_restrictinfo_to_rels */
        }
        else if (maybe_outer_join && restrictinfo->can_join)
        {
            /* we need to set up left_ec/right_ec the hard way */
            initialize_mergeclause_eclasses(root, restrictinfo);
            /* now see if it should go to any outer-join lists */
            Assert(sjinfo != NULL);
            if (bms_is_subset(restrictinfo->left_relids,
                              outerjoin_nonnullable) &&
                !bms_overlap(restrictinfo->right_relids,
                             outerjoin_nonnullable))
            {
                /* we have outervar = innervar */
                OuterJoinClauseInfo *ojcinfo = makeNode(OuterJoinClauseInfo);
 
                ojcinfo->rinfo = restrictinfo;
                ojcinfo->sjinfo = sjinfo;
                root->left_join_clauses = lappend(root->left_join_clauses,
                                                  ojcinfo);
                return;
            }
            if (bms_is_subset(restrictinfo->right_relids,
                              outerjoin_nonnullable) &&
                !bms_overlap(restrictinfo->left_relids,
                             outerjoin_nonnullable))
            {
                /* we have innervar = outervar */
                OuterJoinClauseInfo *ojcinfo = makeNode(OuterJoinClauseInfo);
 
                ojcinfo->rinfo = restrictinfo;
                ojcinfo->sjinfo = sjinfo;
                root->right_join_clauses = lappend(root->right_join_clauses,
                                                   ojcinfo);
                return;
            }
            if (sjinfo->jointype == JOIN_FULL)
            {
                /* FULL JOIN (above tests cannot match in this case) */
                OuterJoinClauseInfo *ojcinfo = makeNode(OuterJoinClauseInfo);
 
                ojcinfo->rinfo = restrictinfo;
                ojcinfo->sjinfo = sjinfo;
                root->full_join_clauses = lappend(root->full_join_clauses,
                                                  ojcinfo);
                return;
            }
            /* nope, so fall through to distribute_restrictinfo_to_rels */
        }
        else
        {
            /* we still need to set up left_ec/right_ec */
            initialize_mergeclause_eclasses(root, restrictinfo);
        }
    }
 
    /* No EC special case applies, so push it into the clause lists */
    distribute_restrictinfo_to_rels(root, restrictinfo);
}
 
/*
 * check_redundant_nullability_qual
 *    Check to see if the qual is an IS NULL qual that is redundant with
 *    a lower JOIN_ANTI join.
 *
 * We want to suppress redundant IS NULL quals, not so much to save cycles
 * as to avoid generating bogus selectivity estimates for them.  So if
 * redundancy is detected here, distribute_qual_to_rels() just throws away
 * the qual.
 */
static bool
check_redundant_nullability_qual(PlannerInfo *root, Node *clause)
{
    Var        *forced_null_var;
    ListCell   *lc;
 
    /* Check for IS NULL, and identify the Var forced to NULL */
    forced_null_var = find_forced_null_var(clause);
    if (forced_null_var == NULL)
        return false;
 
    /*
     * If the Var comes from the nullable side of a lower antijoin, the IS
     * NULL condition is necessarily true.  If it's not nulled by anything,
     * there is no point in searching the join_info_list.  Otherwise, we need
     * to find out whether the nulling rel is an antijoin.
     */
    if (forced_null_var->varnullingrels == NULL)
        return false;
 
    foreach(lc, root->join_info_list)
    {
        SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(lc);
 
        /*
         * This test will not succeed if sjinfo->ojrelid is zero, which is
         * possible for an antijoin that was converted from a semijoin; but in
         * such a case the Var couldn't have come from its nullable side.
         */
        if (sjinfo->jointype == JOIN_ANTI && sjinfo->ojrelid != 0 &&
            bms_is_member(sjinfo->ojrelid, forced_null_var->varnullingrels))
            return true;
    }
 
    return false;
}
 
/*
 * add_base_clause_to_rel
 *      Add 'restrictinfo' as a baserestrictinfo to the base relation denoted
 *      by 'relid'.  We offer some simple prechecks to try to determine if the
 *      qual is always true, in which case we ignore it rather than add it.
 *      If we detect the qual is always false, we replace it with
 *      constant-FALSE.
 */
static void
add_base_clause_to_rel(PlannerInfo *root, Index relid,
                       RestrictInfo *restrictinfo)
{
    RelOptInfo *rel = find_base_rel(root, relid);
    RangeTblEntry *rte = root->simple_rte_array[relid];
 
    Assert(bms_membership(restrictinfo->required_relids) == BMS_SINGLETON);
 
    /*
     * For inheritance parent tables, we must always record the RestrictInfo
     * in baserestrictinfo as is.  If we were to transform or skip adding it,
     * then the original wouldn't be available in apply_child_basequals. Since
     * there are two RangeTblEntries for inheritance parents, one with
     * inh==true and the other with inh==false, we're still able to apply this
     * optimization to the inh==false one.  The inh==true one is what
     * apply_child_basequals() sees, whereas the inh==false one is what's used
     * for the scan node in the final plan.
     *
     * We make an exception to this for partitioned tables.  For these, we
     * always apply the constant-TRUE and constant-FALSE transformations.  A
     * qual which is either of these for a partitioned table must also be that
     * for all of its child partitions.
     */
    if (!rte->inh || rte->relkind == RELKIND_PARTITIONED_TABLE)
    {
        /* Don't add the clause if it is always true */
        if (restriction_is_always_true(root, restrictinfo))
            return;
 
        /*
         * Substitute the origin qual with constant-FALSE if it is provably
         * always false.
         *
         * Note that we need to keep the same rinfo_serial, since it is in
         * practice the same condition.  We also need to reset the
         * last_rinfo_serial counter, which is essential to ensure that the
         * RestrictInfos for the "same" qual condition get identical serial
         * numbers (see deconstruct_distribute_oj_quals).
         */
        if (restriction_is_always_false(root, restrictinfo))
        {
            int         save_rinfo_serial = restrictinfo->rinfo_serial;
            int         save_last_rinfo_serial = root->last_rinfo_serial;
 
            restrictinfo = make_restrictinfo(root,
                                             (Expr *) makeBoolConst(false, false),
                                             restrictinfo->is_pushed_down,
                                             restrictinfo->has_clone,
                                             restrictinfo->is_clone,
                                             restrictinfo->pseudoconstant,
                                             0, /* security_level */
                                             restrictinfo->required_relids,
                                             restrictinfo->incompatible_relids,
                                             restrictinfo->outer_relids);
            restrictinfo->rinfo_serial = save_rinfo_serial;
            root->last_rinfo_serial = save_last_rinfo_serial;
        }
    }
 
    /* Add clause to rel's restriction list */
    rel->baserestrictinfo = lappend(rel->baserestrictinfo, restrictinfo);
 
    /* Update security level info */
    rel->baserestrict_min_security = Min(rel->baserestrict_min_security,
                                         restrictinfo->security_level);
}
 
/*
 * restriction_is_always_true
 *    Check to see if the RestrictInfo is always true.
 *
 * Currently we only check for NullTest quals and OR clauses that include
 * NullTest quals.  We may extend it in the future.
 */
bool
restriction_is_always_true(PlannerInfo *root,
                           RestrictInfo *restrictinfo)
{
    /*
     * For a clone clause, we don't have a reliable way to determine if the
     * input expression of a NullTest is non-nullable: nullingrel bits in
     * clone clauses may not reflect reality, so we dare not draw conclusions
     * from clones about whether Vars are guaranteed not-null.
     */
    if (restrictinfo->has_clone || restrictinfo->is_clone)
        return false;
 
    /* Check for NullTest qual */
    if (IsA(restrictinfo->clause, NullTest))
    {
        NullTest   *nulltest = (NullTest *) restrictinfo->clause;
 
        /* is this NullTest an IS_NOT_NULL qual? */
        if (nulltest->nulltesttype != IS_NOT_NULL)
            return false;
 
        /*
         * Empty rows can appear NULL in some contexts and NOT NULL in others,
         * so avoid this optimization for row expressions.
         */
        if (nulltest->argisrow)
            return false;
 
        return expr_is_nonnullable(root, nulltest->arg, NOTNULL_SOURCE_RELOPT);
    }
 
    /* If it's an OR, check its sub-clauses */
    if (restriction_is_or_clause(restrictinfo))
    {
        ListCell   *lc;
 
        Assert(is_orclause(restrictinfo->orclause));
 
        /*
         * if any of the given OR branches is provably always true then the
         * entire condition is true.
         */
        foreach(lc, ((BoolExpr *) restrictinfo->orclause)->args)
        {
            Node       *orarg = (Node *) lfirst(lc);
 
            if (!IsA(orarg, RestrictInfo))
                continue;
 
            if (restriction_is_always_true(root, (RestrictInfo *) orarg))
                return true;
        }
    }
 
    return false;
}
 
/*
 * restriction_is_always_false
 *    Check to see if the RestrictInfo is always false.
 *
 * Currently we only check for NullTest quals and OR clauses that include
 * NullTest quals.  We may extend it in the future.
 */
bool
restriction_is_always_false(PlannerInfo *root,
                            RestrictInfo *restrictinfo)
{
    /*
     * For a clone clause, we don't have a reliable way to determine if the
     * input expression of a NullTest is non-nullable: nullingrel bits in
     * clone clauses may not reflect reality, so we dare not draw conclusions
     * from clones about whether Vars are guaranteed not-null.
     */
    if (restrictinfo->has_clone || restrictinfo->is_clone)
        return false;
 
    /* Check for NullTest qual */
    if (IsA(restrictinfo->clause, NullTest))
    {
        NullTest   *nulltest = (NullTest *) restrictinfo->clause;
 
        /* is this NullTest an IS_NULL qual? */
        if (nulltest->nulltesttype != IS_NULL)
            return false;
 
        /*
         * Empty rows can appear NULL in some contexts and NOT NULL in others,
         * so avoid this optimization for row expressions.
         */
        if (nulltest->argisrow)
            return false;
 
        return expr_is_nonnullable(root, nulltest->arg, NOTNULL_SOURCE_RELOPT);
    }
 
    /* If it's an OR, check its sub-clauses */
    if (restriction_is_or_clause(restrictinfo))
    {
        ListCell   *lc;
 
        Assert(is_orclause(restrictinfo->orclause));
 
        /*
         * Currently, when processing OR expressions, we only return true when
         * all of the OR branches are always false.  This could perhaps be
         * expanded to remove OR branches that are provably false.  This may
         * be a useful thing to do as it could result in the OR being left
         * with a single arg.  That's useful as it would allow the OR
         * condition to be replaced with its single argument which may allow
         * use of an index for faster filtering on the remaining condition.
         */
        foreach(lc, ((BoolExpr *) restrictinfo->orclause)->args)
        {
            Node       *orarg = (Node *) lfirst(lc);
 
            if (!IsA(orarg, RestrictInfo) ||
                !restriction_is_always_false(root, (RestrictInfo *) orarg))
                return false;
        }
        return true;
    }
 
    return false;
}
 
/*
 * distribute_restrictinfo_to_rels
 *    Push a completed RestrictInfo into the proper restriction or join
 *    clause list(s).
 *
 * This is the last step of distribute_qual_to_rels() for ordinary qual
 * clauses.  Clauses that are interesting for equivalence-class processing
 * are diverted to the EC machinery, but may ultimately get fed back here.
 */
void
distribute_restrictinfo_to_rels(PlannerInfo *root,
                                RestrictInfo *restrictinfo)
{
    Relids      relids = restrictinfo->required_relids;
 
    if (!bms_is_empty(relids))
    {
        int         relid;
 
        if (bms_get_singleton_member(relids, &relid))
        {
            /*
             * There is only one relation participating in the clause, so it
             * is a restriction clause for that relation.
             */
            add_base_clause_to_rel(root, relid, restrictinfo);
        }
        else
        {
            /*
             * The clause is a join clause, since there is more than one rel
             * in its relid set.
             */
 
            /*
             * Check for hashjoinable operators.  (We don't bother setting the
             * hashjoin info except in true join clauses.)
             */
            check_hashjoinable(restrictinfo);
 
            /*
             * Likewise, check if the clause is suitable to be used with a
             * Memoize node to cache inner tuples during a parameterized
             * nested loop.
             */
            check_memoizable(restrictinfo);
 
            /*
             * Add clause to the join lists of all the relevant relations.
             */
            add_join_clause_to_rels(root, restrictinfo, relids);
        }
    }
    else
    {
        /*
         * clause references no rels, and therefore we have no place to attach
         * it.  Shouldn't get here if callers are working properly.
         */
        elog(ERROR, "cannot cope with variable-free clause");
    }
}
 
/*
 * process_implied_equality
 *    Create a restrictinfo item that says "item1 op item2", and push it
 *    into the appropriate lists.  (In practice opno is always a btree
 *    equality operator.)
 *
 * "qualscope" is the nominal syntactic level to impute to the restrictinfo.
 * This must contain at least all the rels used in the expressions, but it
 * is used only to set the qual application level when both exprs are
 * variable-free.  (Hence, it should usually match the join domain in which
 * the clause applies.)  Otherwise the qual is applied at the lowest join
 * level that provides all its variables.
 *
 * "security_level" is the security level to assign to the new restrictinfo.
 *
 * "both_const" indicates whether both items are known pseudo-constant;
 * in this case it is worth applying eval_const_expressions() in case we
 * can produce constant TRUE or constant FALSE.  (Otherwise it's not,
 * because the expressions went through eval_const_expressions already.)
 *
 * Returns the generated RestrictInfo, if any.  The result will be NULL
 * if both_const is true and we successfully reduced the clause to
 * constant TRUE.
 *
 * Note: this function will copy item1 and item2, but it is caller's
 * responsibility to make sure that the Relids parameters are fresh copies
 * not shared with other uses.
 *
 * Note: we do not do initialize_mergeclause_eclasses() here.  It is
 * caller's responsibility that left_ec/right_ec be set as necessary.
 */
RestrictInfo *
process_implied_equality(PlannerInfo *root,
                         Oid opno,
                         Oid collation,
                         Expr *item1,
                         Expr *item2,
                         Relids qualscope,
                         Index security_level,
                         bool both_const)
{
    RestrictInfo *restrictinfo;
    Node       *clause;
    Relids      relids;
    bool        pseudoconstant = false;
 
    /*
     * Build the new clause.  Copy to ensure it shares no substructure with
     * original (this is necessary in case there are subselects in there...)
     */
    clause = (Node *) make_opclause(opno,
                                    BOOLOID,    /* opresulttype */
                                    false,  /* opretset */
                                    copyObject(item1),
                                    copyObject(item2),
                                    InvalidOid,
                                    collation);
 
    /* If both constant, try to reduce to a boolean constant. */
    if (both_const)
    {
        clause = eval_const_expressions(root, clause);
 
        /* If we produced const TRUE, just drop the clause */
        if (clause && IsA(clause, Const))
        {
            Const      *cclause = (Const *) clause;
 
            Assert(cclause->consttype == BOOLOID);
            if (!cclause->constisnull && DatumGetBool(cclause->constvalue))
                return NULL;
        }
    }
 
    /*
     * The rest of this is a very cut-down version of distribute_qual_to_rels.
     * We can skip most of the work therein, but there are a couple of special
     * cases we still have to handle.
     *
     * Retrieve all relids mentioned within the possibly-simplified clause.
     */
    relids = pull_varnos(root, clause);
    Assert(bms_is_subset(relids, qualscope));
 
    /*
     * If the clause is variable-free, our normal heuristic for pushing it
     * down to just the mentioned rels doesn't work, because there are none.
     * Apply it as a gating qual at the appropriate level (see comments for
     * get_join_domain_min_rels).
     */
    if (bms_is_empty(relids))
    {
        /* eval at join domain's safe level */
        relids = get_join_domain_min_rels(root, qualscope);
        /* mark as gating qual */
        pseudoconstant = true;
        /* tell createplan.c to check for gating quals */
        root->hasPseudoConstantQuals = true;
    }
 
    /*
     * Build the RestrictInfo node itself.
     */
    restrictinfo = make_restrictinfo(root,
                                     (Expr *) clause,
                                     true,  /* is_pushed_down */
                                     false, /* !has_clone */
                                     false, /* !is_clone */
                                     pseudoconstant,
                                     security_level,
                                     relids,
                                     NULL,  /* incompatible_relids */
                                     NULL); /* outer_relids */
 
    /*
     * If it's a join clause, add vars used in the clause to targetlists of
     * their relations, so that they will be emitted by the plan nodes that
     * scan those relations (else they won't be available at the join node!).
     *
     * Typically, we'd have already done this when the component expressions
     * were first seen by distribute_qual_to_rels; but it is possible that
     * some of the Vars could have missed having that done because they only
     * appeared in single-relation clauses originally.  So do it here for
     * safety.
     *
     * See also rebuild_joinclause_attr_needed, which has to partially repeat
     * this work after removal of an outer join.  (Since we will put this
     * clause into the joininfo lists, that function needn't do any extra work
     * to find it.)
     */
    if (bms_membership(relids) == BMS_MULTIPLE)
    {
        List       *vars = pull_var_clause(clause,
                                           PVC_RECURSE_AGGREGATES |
                                           PVC_RECURSE_WINDOWFUNCS |
                                           PVC_INCLUDE_PLACEHOLDERS);
 
        add_vars_to_targetlist(root, vars, relids);
        list_free(vars);
    }
 
    /*
     * Check mergejoinability.  This will usually succeed, since the op came
     * from an EquivalenceClass; but we could have reduced the original clause
     * to a constant.
     */
    check_mergejoinable(restrictinfo);
 
    /*
     * Note we don't do initialize_mergeclause_eclasses(); the caller can
     * handle that much more cheaply than we can.  It's okay to call
     * distribute_restrictinfo_to_rels() before that happens.
     */
 
    /*
     * Push the new clause into all the appropriate restrictinfo lists.
     */
    distribute_restrictinfo_to_rels(root, restrictinfo);
 
    return restrictinfo;
}
 
/*
 * build_implied_join_equality --- build a RestrictInfo for a derived equality
 *
 * This overlaps the functionality of process_implied_equality(), but we
 * must not push the RestrictInfo into the joininfo tree.
 *
 * Note: this function will copy item1 and item2, but it is caller's
 * responsibility to make sure that the Relids parameters are fresh copies
 * not shared with other uses.
 *
 * Note: we do not do initialize_mergeclause_eclasses() here.  It is
 * caller's responsibility that left_ec/right_ec be set as necessary.
 */
RestrictInfo *
build_implied_join_equality(PlannerInfo *root,
                            Oid opno,
                            Oid collation,
                            Expr *item1,
                            Expr *item2,
                            Relids qualscope,
                            Index security_level)
{
    RestrictInfo *restrictinfo;
    Expr       *clause;
 
    /*
     * Build the new clause.  Copy to ensure it shares no substructure with
     * original (this is necessary in case there are subselects in there...)
     */
    clause = make_opclause(opno,
                           BOOLOID, /* opresulttype */
                           false,   /* opretset */
                           copyObject(item1),
                           copyObject(item2),
                           InvalidOid,
                           collation);
 
    /*
     * Build the RestrictInfo node itself.
     */
    restrictinfo = make_restrictinfo(root,
                                     clause,
                                     true,  /* is_pushed_down */
                                     false, /* !has_clone */
                                     false, /* !is_clone */
                                     false, /* pseudoconstant */
                                     security_level,    /* security_level */
                                     qualscope, /* required_relids */
                                     NULL,  /* incompatible_relids */
                                     NULL); /* outer_relids */
 
    /* Set mergejoinability/hashjoinability flags */
    check_mergejoinable(restrictinfo);
    check_hashjoinable(restrictinfo);
    check_memoizable(restrictinfo);
 
    return restrictinfo;
}
 
/*
 * get_join_domain_min_rels
 *    Identify the appropriate join level for derived quals belonging
 *    to the join domain with the given relids.
 *
 * When we derive a pseudoconstant (Var-free) clause from an EquivalenceClass,
 * we'd ideally apply the clause at the top level of the EC's join domain.
 * However, if there are any outer joins inside that domain that get commuted
 * with joins outside it, that leads to not finding a correct place to apply
 * the clause.  Instead, remove any lower outer joins from the relid set,
 * and apply the clause to just the remaining rels.  This still results in a
 * correct answer, since if the clause produces FALSE then the LHS of these
 * joins will be empty leading to an empty join result.
 *
 * However, there's no need to remove outer joins if this is the top-level
 * join domain of the query, since then there's nothing else to commute with.
 *
 * Note: it's tempting to use this in distribute_qual_to_rels where it's
 * dealing with pseudoconstant quals; but we can't because the necessary
 * SpecialJoinInfos aren't all formed at that point.
 *
 * The result is always freshly palloc'd; we do not modify domain_relids.
 */
static Relids
get_join_domain_min_rels(PlannerInfo *root, Relids domain_relids)
{
    Relids      result = bms_copy(domain_relids);
    ListCell   *lc;
 
    /* Top-level join domain? */
    if (bms_equal(result, root->all_query_rels))
        return result;
 
    /* Nope, look for lower outer joins that could potentially commute out */
    foreach(lc, root->join_info_list)
    {
        SpecialJoinInfo *sjinfo = (SpecialJoinInfo *) lfirst(lc);
 
        if (sjinfo->jointype == JOIN_LEFT &&
            bms_is_member(sjinfo->ojrelid, result))
        {
            result = bms_del_member(result, sjinfo->ojrelid);
            result = bms_del_members(result, sjinfo->syn_righthand);
        }
    }
    return result;
}
 
 
/*
 * rebuild_joinclause_attr_needed
 *    Put back attr_needed bits for Vars/PHVs needed for join clauses.
 *
 * This is used to rebuild attr_needed/ph_needed sets after removal of a
 * useless outer join.  It should match what distribute_qual_to_rels did,
 * except that we call add_vars_to_attr_needed not add_vars_to_targetlist.
 */
void
rebuild_joinclause_attr_needed(PlannerInfo *root)
{
    /*
     * We must examine all join clauses, but there's no value in processing
     * any join clause more than once.  So it's slightly annoying that we have
     * to find them via the per-base-relation joininfo lists.  Avoid duplicate
     * processing by tracking the rinfo_serial numbers of join clauses we've
     * already seen.  (This doesn't work for is_clone clauses, so we must
     * waste effort on them.)
     */
    Bitmapset  *seen_serials = NULL;
    Index       rti;
 
    /* Scan all baserels for join clauses */
    for (rti = 1; rti < root->simple_rel_array_size; rti++)
    {
        RelOptInfo *brel = root->simple_rel_array[rti];
        ListCell   *lc;
 
        if (brel == NULL)
            continue;
        if (brel->reloptkind != RELOPT_BASEREL)
            continue;
 
        foreach(lc, brel->joininfo)
        {
            RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc);
            Relids      relids = rinfo->required_relids;
 
            if (!rinfo->is_clone)   /* else serial number is not unique */
            {
                if (bms_is_member(rinfo->rinfo_serial, seen_serials))
                    continue;   /* saw it already */
                seen_serials = bms_add_member(seen_serials,
                                              rinfo->rinfo_serial);
            }
 
            if (bms_membership(relids) == BMS_MULTIPLE)
            {
                List       *vars = pull_var_clause((Node *) rinfo->clause,
                                                   PVC_RECURSE_AGGREGATES |
                                                   PVC_RECURSE_WINDOWFUNCS |
                                                   PVC_INCLUDE_PLACEHOLDERS);
                Relids      where_needed;
 
                if (rinfo->is_clone)
                    where_needed = bms_intersect(relids, root->all_baserels);
                else
                    where_needed = relids;
                add_vars_to_attr_needed(root, vars, where_needed);
                list_free(vars);
            }
        }
    }
}
 
 
/*
 * match_foreign_keys_to_quals
 *      Match foreign-key constraints to equivalence classes and join quals
 *
 * The idea here is to see which query join conditions match equality
 * constraints of a foreign-key relationship.  For such join conditions,
 * we can use the FK semantics to make selectivity estimates that are more
 * reliable than estimating from statistics, especially for multiple-column
 * FKs, where the normal assumption of independent conditions tends to fail.
 *
 * In this function we annotate the ForeignKeyOptInfos in root->fkey_list
 * with info about which eclasses and join qual clauses they match, and
 * discard any ForeignKeyOptInfos that are irrelevant for the query.
 */
void
match_foreign_keys_to_quals(PlannerInfo *root)
{
    List       *newlist = NIL;
    ListCell   *lc;
 
    foreach(lc, root->fkey_list)
    {
        ForeignKeyOptInfo *fkinfo = (ForeignKeyOptInfo *) lfirst(lc);
        RelOptInfo *con_rel;
        RelOptInfo *ref_rel;
        int         colno;
 
        /*
         * Either relid might identify a rel that is in the query's rtable but
         * isn't referenced by the jointree, or has been removed by join
         * removal, so that it won't have a RelOptInfo.  Hence don't use
         * find_base_rel() here.  We can ignore such FKs.
         */
        if (fkinfo->con_relid >= root->simple_rel_array_size ||
            fkinfo->ref_relid >= root->simple_rel_array_size)
            continue;           /* just paranoia */
        con_rel = root->simple_rel_array[fkinfo->con_relid];
        if (con_rel == NULL)
            continue;
        ref_rel = root->simple_rel_array[fkinfo->ref_relid];
        if (ref_rel == NULL)
            continue;
 
        /*
         * Ignore FK unless both rels are baserels.  This gets rid of FKs that
         * link to inheritance child rels (otherrels).
         */
        if (con_rel->reloptkind != RELOPT_BASEREL ||
            ref_rel->reloptkind != RELOPT_BASEREL)
            continue;
 
        /*
         * Scan the columns and try to match them to eclasses and quals.
         *
         * Note: for simple inner joins, any match should be in an eclass.
         * "Loose" quals that syntactically match an FK equality must have
         * been rejected for EC status because they are outer-join quals or
         * similar.  We can still consider them to match the FK.
         */
        for (colno = 0; colno < fkinfo->nkeys; colno++)
        {
            EquivalenceClass *ec;
            AttrNumber  con_attno,
                        ref_attno;
            Oid         fpeqop;
            ListCell   *lc2;
 
            ec = match_eclasses_to_foreign_key_col(root, fkinfo, colno);
            /* Don't bother looking for loose quals if we got an EC match */
            if (ec != NULL)
            {
                fkinfo->nmatched_ec++;
                if (ec->ec_has_const)
                    fkinfo->nconst_ec++;
                continue;
            }
 
            /*
             * Scan joininfo list for relevant clauses.  Either rel's joininfo
             * list would do equally well; we use con_rel's.
             */
            con_attno = fkinfo->conkey[colno];
            ref_attno = fkinfo->confkey[colno];
            fpeqop = InvalidOid;    /* we'll look this up only if needed */
 
            foreach(lc2, con_rel->joininfo)
            {
                RestrictInfo *rinfo = (RestrictInfo *) lfirst(lc2);
                OpExpr     *clause = (OpExpr *) rinfo->clause;
                Var        *leftvar;
                Var        *rightvar;
 
                /* Only binary OpExprs are useful for consideration */
                if (!IsA(clause, OpExpr) ||
                    list_length(clause->args) != 2)
                    continue;
                leftvar = (Var *) get_leftop((Expr *) clause);
                rightvar = (Var *) get_rightop((Expr *) clause);
 
                /* Operands must be Vars, possibly with RelabelType */
                while (leftvar && IsA(leftvar, RelabelType))
                    leftvar = (Var *) ((RelabelType *) leftvar)->arg;
                if (!(leftvar && IsA(leftvar, Var)))
                    continue;
                while (rightvar && IsA(rightvar, RelabelType))
                    rightvar = (Var *) ((RelabelType *) rightvar)->arg;
                if (!(rightvar && IsA(rightvar, Var)))
                    continue;
 
                /* Now try to match the vars to the current foreign key cols */
                if (fkinfo->ref_relid == leftvar->varno &&
                    ref_attno == leftvar->varattno &&
                    fkinfo->con_relid == rightvar->varno &&
                    con_attno == rightvar->varattno)
                {
                    /* Vars match, but is it the right operator? */
                    if (clause->opno == fkinfo->conpfeqop[colno])
                    {
                        fkinfo->rinfos[colno] = lappend(fkinfo->rinfos[colno],
                                                        rinfo);
                        fkinfo->nmatched_ri++;
                    }
                }
                else if (fkinfo->ref_relid == rightvar->varno &&
                         ref_attno == rightvar->varattno &&
                         fkinfo->con_relid == leftvar->varno &&
                         con_attno == leftvar->varattno)
                {
                    /*
                     * Reverse match, must check commutator operator.  Look it
                     * up if we didn't already.  (In the worst case we might
                     * do multiple lookups here, but that would require an FK
                     * equality operator without commutator, which is
                     * unlikely.)
                     */
                    if (!OidIsValid(fpeqop))
                        fpeqop = get_commutator(fkinfo->conpfeqop[colno]);
                    if (clause->opno == fpeqop)
                    {
                        fkinfo->rinfos[colno] = lappend(fkinfo->rinfos[colno],
                                                        rinfo);
                        fkinfo->nmatched_ri++;
                    }
                }
            }
            /* If we found any matching loose quals, count col as matched */
            if (fkinfo->rinfos[colno])
                fkinfo->nmatched_rcols++;
        }
 
        /*
         * Currently, we drop multicolumn FKs that aren't fully matched to the
         * query.  Later we might figure out how to derive some sort of
         * estimate from them, in which case this test should be weakened to
         * "if ((fkinfo->nmatched_ec + fkinfo->nmatched_rcols) > 0)".
         */
        if ((fkinfo->nmatched_ec + fkinfo->nmatched_rcols) == fkinfo->nkeys)
            newlist = lappend(newlist, fkinfo);
    }
    /* Replace fkey_list, thereby discarding any useless entries */
    root->fkey_list = newlist;
}
 
 
/*****************************************************************************
 *
 *   CHECKS FOR MERGEJOINABLE AND HASHJOINABLE CLAUSES
 *
 *****************************************************************************/
 
/*
 * check_mergejoinable
 *    If the restrictinfo's clause is mergejoinable, set the mergejoin
 *    info fields in the restrictinfo.
 *
 *    Currently, we support mergejoin for binary opclauses where
 *    the operator is a mergejoinable operator.  The arguments can be
 *    anything --- as long as there are no volatile functions in them.
 */
static void
check_mergejoinable(RestrictInfo *restrictinfo)
{
    Expr       *clause = restrictinfo->clause;
    Oid         opno;
    Node       *leftarg;
 
    if (restrictinfo->pseudoconstant)
        return;
    if (!is_opclause(clause))
        return;
    if (list_length(((OpExpr *) clause)->args) != 2)
        return;
 
    opno = ((OpExpr *) clause)->opno;
    leftarg = linitial(((OpExpr *) clause)->args);
 
    if (op_mergejoinable(opno, exprType(leftarg)) &&
        !contain_volatile_functions((Node *) restrictinfo))
        restrictinfo->mergeopfamilies = get_mergejoin_opfamilies(opno);
 
    /*
     * Note: op_mergejoinable is just a hint; if we fail to find the operator
     * in any btree opfamilies, mergeopfamilies remains NIL and so the clause
     * is not treated as mergejoinable.
     */
}
 
/*
 * check_hashjoinable
 *    If the restrictinfo's clause is hashjoinable, set the hashjoin
 *    info fields in the restrictinfo.
 *
 *    Currently, we support hashjoin for binary opclauses where
 *    the operator is a hashjoinable operator.  The arguments can be
 *    anything --- as long as there are no volatile functions in them.
 */
static void
check_hashjoinable(RestrictInfo *restrictinfo)
{
    Expr       *clause = restrictinfo->clause;
    Oid         opno;
    Node       *leftarg;
 
    if (restrictinfo->pseudoconstant)
        return;
    if (!is_opclause(clause))
        return;
    if (list_length(((OpExpr *) clause)->args) != 2)
        return;
 
    opno = ((OpExpr *) clause)->opno;
    leftarg = linitial(((OpExpr *) clause)->args);
 
    if (op_hashjoinable(opno, exprType(leftarg)) &&
        !contain_volatile_functions((Node *) restrictinfo))
        restrictinfo->hashjoinoperator = opno;
}
 
/*
 * check_memoizable
 *    If the restrictinfo's clause is suitable to be used for a Memoize node,
 *    set the left_hasheqoperator and right_hasheqoperator to the hash equality
 *    operator that will be needed during caching.
 */
static void
check_memoizable(RestrictInfo *restrictinfo)
{
    TypeCacheEntry *typentry;
    Expr       *clause = restrictinfo->clause;
    Oid         lefttype;
    Oid         righttype;
 
    if (restrictinfo->pseudoconstant)
        return;
    if (!is_opclause(clause))
        return;
    if (list_length(((OpExpr *) clause)->args) != 2)
        return;
 
    lefttype = exprType(linitial(((OpExpr *) clause)->args));
 
    typentry = lookup_type_cache(lefttype, TYPECACHE_HASH_PROC |
                                 TYPECACHE_EQ_OPR);
 
    if (OidIsValid(typentry->hash_proc) && OidIsValid(typentry->eq_opr))
        restrictinfo->left_hasheqoperator = typentry->eq_opr;
 
    righttype = exprType(lsecond(((OpExpr *) clause)->args));
 
    /*
     * Lookup the right type, unless it's the same as the left type, in which
     * case typentry is already pointing to the required TypeCacheEntry.
     */
    if (lefttype != righttype)
        typentry = lookup_type_cache(righttype, TYPECACHE_HASH_PROC |
                                     TYPECACHE_EQ_OPR);
 
    if (OidIsValid(typentry->hash_proc) && OidIsValid(typentry->eq_opr))
        restrictinfo->right_hasheqoperator = typentry->eq_opr;
}