prepjointree.c

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/*-------------------------------------------------------------------------
 *
 * prepjointree.c
 *    Planner preprocessing for subqueries and join tree manipulation.
 *
 * NOTE: the intended sequence for invoking these operations is
 *      replace_empty_jointree
 *      pull_up_sublinks
 *      preprocess_function_rtes
 *      expand_virtual_generated_columns
 *      pull_up_subqueries
 *      flatten_simple_union_all
 *      do expression preprocessing (including flattening JOIN alias vars)
 *      reduce_outer_joins
 *      remove_useless_result_rtes
 *
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/optimizer/prep/prepjointree.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "access/table.h"
#include "catalog/pg_type.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/multibitmapset.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/optimizer.h"
#include "optimizer/placeholder.h"
#include "optimizer/prep.h"
#include "optimizer/subselect.h"
#include "optimizer/tlist.h"
#include "parser/parse_relation.h"
#include "parser/parsetree.h"
#include "rewrite/rewriteHandler.h"
#include "rewrite/rewriteManip.h"
#include "utils/rel.h"
 
 
typedef struct nullingrel_info
{
    /*
     * For each leaf RTE, nullingrels[rti] is the set of relids of outer joins
     * that potentially null that RTE.
     */
    Relids     *nullingrels;
    /* Length of range table (maximum index in nullingrels[]) */
    int         rtlength;       /* used only for assertion checks */
} nullingrel_info;
 
/* Options for wrapping an expression for identification purposes */
typedef enum ReplaceWrapOption
{
    REPLACE_WRAP_NONE,          /* no expressions need to be wrapped */
    REPLACE_WRAP_ALL,           /* all expressions need to be wrapped */
    REPLACE_WRAP_VARFREE,       /* variable-free expressions need to be
                                 * wrapped */
} ReplaceWrapOption;
 
typedef struct pullup_replace_vars_context
{
    PlannerInfo *root;
    List       *targetlist;     /* tlist of subquery being pulled up */
    RangeTblEntry *target_rte;  /* RTE of subquery */
    int         result_relation;    /* the index of the result relation in the
                                     * rewritten query */
    Relids      relids;         /* relids within subquery, as numbered after
                                 * pullup (set only if target_rte->lateral) */
    nullingrel_info *nullinfo;  /* per-RTE nullingrel info (set only if
                                 * target_rte->lateral) */
    bool       *outer_hasSubLinks;  /* -> outer query's hasSubLinks */
    int         varno;          /* varno of subquery */
    ReplaceWrapOption wrap_option;  /* do we need certain outputs to be PHVs? */
    Node      **rv_cache;       /* cache for results with PHVs */
} pullup_replace_vars_context;
 
typedef struct reduce_outer_joins_pass1_state
{
    Relids      relids;         /* base relids within this subtree */
    bool        contains_outer; /* does subtree contain outer join(s)? */
    List       *sub_states;     /* List of states for subtree components */
} reduce_outer_joins_pass1_state;
 
typedef struct reduce_outer_joins_pass2_state
{
    Relids      inner_reduced;  /* OJ relids reduced to plain inner joins */
    List       *partial_reduced;    /* List of partially reduced FULL joins */
} reduce_outer_joins_pass2_state;
 
typedef struct reduce_outer_joins_partial_state
{
    int         full_join_rti;  /* RT index of a formerly-FULL join */
    Relids      unreduced_side; /* relids in its still-nullable side */
} reduce_outer_joins_partial_state;
 
static Node *pull_up_sublinks_jointree_recurse(PlannerInfo *root, Node *jtnode,
                                               Relids *relids);
static Node *pull_up_sublinks_qual_recurse(PlannerInfo *root, Node *node,
                                           Node **jtlink1, Relids available_rels1,
                                           Node **jtlink2, Relids available_rels2);
static Node *pull_up_subqueries_recurse(PlannerInfo *root, Node *jtnode,
                                        JoinExpr *lowest_outer_join,
                                        AppendRelInfo *containing_appendrel);
static Node *pull_up_simple_subquery(PlannerInfo *root, Node *jtnode,
                                     RangeTblEntry *rte,
                                     JoinExpr *lowest_outer_join,
                                     AppendRelInfo *containing_appendrel);
static Node *pull_up_simple_union_all(PlannerInfo *root, Node *jtnode,
                                      RangeTblEntry *rte);
static void pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root,
                                       int parentRTindex, Query *setOpQuery,
                                       int childRToffset);
static void make_setop_translation_list(Query *query, int newvarno,
                                        AppendRelInfo *appinfo);
static bool is_simple_subquery(PlannerInfo *root, Query *subquery,
                               RangeTblEntry *rte,
                               JoinExpr *lowest_outer_join);
static Node *pull_up_simple_values(PlannerInfo *root, Node *jtnode,
                                   RangeTblEntry *rte);
static bool is_simple_values(PlannerInfo *root, RangeTblEntry *rte);
static Node *pull_up_constant_function(PlannerInfo *root, Node *jtnode,
                                       RangeTblEntry *rte,
                                       AppendRelInfo *containing_appendrel);
static bool is_simple_union_all(Query *subquery);
static bool is_simple_union_all_recurse(Node *setOp, Query *setOpQuery,
                                        List *colTypes);
static bool is_safe_append_member(Query *subquery);
static bool jointree_contains_lateral_outer_refs(PlannerInfo *root,
                                                 Node *jtnode, bool restricted,
                                                 Relids safe_upper_varnos);
static void perform_pullup_replace_vars(PlannerInfo *root,
                                        pullup_replace_vars_context *rvcontext,
                                        AppendRelInfo *containing_appendrel);
static void replace_vars_in_jointree(Node *jtnode,
                                     pullup_replace_vars_context *context);
static Node *pullup_replace_vars(Node *expr,
                                 pullup_replace_vars_context *context);
static Node *pullup_replace_vars_callback(Var *var,
                                          replace_rte_variables_context *context);
static Query *pullup_replace_vars_subquery(Query *query,
                                           pullup_replace_vars_context *context);
static reduce_outer_joins_pass1_state *reduce_outer_joins_pass1(Node *jtnode);
static void reduce_outer_joins_pass2(Node *jtnode,
                                     reduce_outer_joins_pass1_state *state1,
                                     reduce_outer_joins_pass2_state *state2,
                                     PlannerInfo *root,
                                     Relids nonnullable_rels,
                                     List *forced_null_vars);
static void report_reduced_full_join(reduce_outer_joins_pass2_state *state2,
                                     int rtindex, Relids relids);
static Node *remove_useless_results_recurse(PlannerInfo *root, Node *jtnode,
                                            Node **parent_quals,
                                            Relids *dropped_outer_joins);
static int  get_result_relid(PlannerInfo *root, Node *jtnode);
static void remove_result_refs(PlannerInfo *root, int varno, Node *newjtloc);
static bool find_dependent_phvs(PlannerInfo *root, int varno);
static bool find_dependent_phvs_in_jointree(PlannerInfo *root,
                                            Node *node, int varno);
static void substitute_phv_relids(Node *node,
                                  int varno, Relids subrelids);
static void fix_append_rel_relids(PlannerInfo *root, int varno,
                                  Relids subrelids);
static Node *find_jointree_node_for_rel(Node *jtnode, int relid);
static nullingrel_info *get_nullingrels(Query *parse);
static void get_nullingrels_recurse(Node *jtnode, Relids upper_nullingrels,
                                    nullingrel_info *info);
 
 
/*
 * transform_MERGE_to_join
 *      Replace a MERGE's jointree to also include the target relation.
 */
void
transform_MERGE_to_join(Query *parse)
{
    RangeTblEntry *joinrte;
    JoinExpr   *joinexpr;
    bool        have_action[NUM_MERGE_MATCH_KINDS];
    JoinType    jointype;
    int         joinrti;
    List       *vars;
    RangeTblRef *rtr;
    FromExpr   *target;
    Node       *source;
    int         sourcerti;
 
    if (parse->commandType != CMD_MERGE)
        return;
 
    /* XXX probably bogus */
    vars = NIL;
 
    /*
     * Work out what kind of join is required.  If there any WHEN NOT MATCHED
     * BY SOURCE/TARGET actions, an outer join is required so that we process
     * all unmatched tuples from the source and/or target relations.
     * Otherwise, we can use an inner join.
     */
    have_action[MERGE_WHEN_MATCHED] = false;
    have_action[MERGE_WHEN_NOT_MATCHED_BY_SOURCE] = false;
    have_action[MERGE_WHEN_NOT_MATCHED_BY_TARGET] = false;
 
    foreach_node(MergeAction, action, parse->mergeActionList)
    {
        if (action->commandType != CMD_NOTHING)
            have_action[action->matchKind] = true;
    }
 
    if (have_action[MERGE_WHEN_NOT_MATCHED_BY_SOURCE] &&
        have_action[MERGE_WHEN_NOT_MATCHED_BY_TARGET])
        jointype = JOIN_FULL;
    else if (have_action[MERGE_WHEN_NOT_MATCHED_BY_SOURCE])
        jointype = JOIN_LEFT;
    else if (have_action[MERGE_WHEN_NOT_MATCHED_BY_TARGET])
        jointype = JOIN_RIGHT;
    else
        jointype = JOIN_INNER;
 
    /* Manufacture a join RTE to use. */
    joinrte = makeNode(RangeTblEntry);
    joinrte->rtekind = RTE_JOIN;
    joinrte->jointype = jointype;
    joinrte->joinmergedcols = 0;
    joinrte->joinaliasvars = vars;
    joinrte->joinleftcols = NIL;    /* MERGE does not allow JOIN USING */
    joinrte->joinrightcols = NIL;   /* ditto */
    joinrte->join_using_alias = NULL;
 
    joinrte->alias = NULL;
    joinrte->eref = makeAlias("*MERGE*", NIL);
    joinrte->lateral = false;
    joinrte->inh = false;
    joinrte->inFromCl = true;
 
    /*
     * Add completed RTE to pstate's range table list, so that we know its
     * index.
     */
    parse->rtable = lappend(parse->rtable, joinrte);
    joinrti = list_length(parse->rtable);
 
    /*
     * Create a JOIN between the target and the source relation.
     *
     * Here the target is identified by parse->mergeTargetRelation.  For a
     * regular table, this will equal parse->resultRelation, but for a
     * trigger-updatable view, it will be the expanded view subquery that we
     * need to pull data from.
     *
     * The source relation is in parse->jointree->fromlist, but any quals in
     * parse->jointree->quals are restrictions on the target relation (if the
     * target relation is an auto-updatable view).
     */
    /* target rel, with any quals */
    rtr = makeNode(RangeTblRef);
    rtr->rtindex = parse->mergeTargetRelation;
    target = makeFromExpr(list_make1(rtr), parse->jointree->quals);
 
    /* source rel (expect exactly one -- see transformMergeStmt()) */
    Assert(list_length(parse->jointree->fromlist) == 1);
    source = linitial(parse->jointree->fromlist);
 
    /*
     * index of source rel (expect either a RangeTblRef or a JoinExpr -- see
     * transformFromClauseItem()).
     */
    if (IsA(source, RangeTblRef))
        sourcerti = ((RangeTblRef *) source)->rtindex;
    else if (IsA(source, JoinExpr))
        sourcerti = ((JoinExpr *) source)->rtindex;
    else
    {
        elog(ERROR, "unrecognized source node type: %d",
             (int) nodeTag(source));
        sourcerti = 0;          /* keep compiler quiet */
    }
 
    /* Join the source and target */
    joinexpr = makeNode(JoinExpr);
    joinexpr->jointype = jointype;
    joinexpr->isNatural = false;
    joinexpr->larg = (Node *) target;
    joinexpr->rarg = source;
    joinexpr->usingClause = NIL;
    joinexpr->join_using_alias = NULL;
    joinexpr->quals = parse->mergeJoinCondition;
    joinexpr->alias = NULL;
    joinexpr->rtindex = joinrti;
 
    /* Make the new join be the sole entry in the query's jointree */
    parse->jointree->fromlist = list_make1(joinexpr);
    parse->jointree->quals = NULL;
 
    /*
     * If necessary, mark parse->targetlist entries that refer to the target
     * as nullable by the join.  Normally the targetlist will be empty for a
     * MERGE, but if the target is a trigger-updatable view, it will contain a
     * whole-row Var referring to the expanded view query.
     */
    if (parse->targetList != NIL &&
        (jointype == JOIN_RIGHT || jointype == JOIN_FULL))
        parse->targetList = (List *)
            add_nulling_relids((Node *) parse->targetList,
                               bms_make_singleton(parse->mergeTargetRelation),
                               bms_make_singleton(joinrti));
 
    /*
     * If the source relation is on the outer side of the join, mark any
     * source relation Vars in the join condition, actions, and RETURNING list
     * as nullable by the join.  These Vars will be added to the targetlist by
     * preprocess_targetlist(), so it's important to mark them correctly here.
     *
     * It might seem that this is not necessary for Vars in the join
     * condition, since it is inside the join, but it is also needed above the
     * join (in the ModifyTable node) to distinguish between the MATCHED and
     * NOT MATCHED BY SOURCE cases -- see ExecMergeMatched().  Note that this
     * creates a modified copy of the join condition, for use above the join,
     * without modifying the original join condition, inside the join.
     */
    if (jointype == JOIN_LEFT || jointype == JOIN_FULL)
    {
        parse->mergeJoinCondition =
            add_nulling_relids(parse->mergeJoinCondition,
                               bms_make_singleton(sourcerti),
                               bms_make_singleton(joinrti));
 
        foreach_node(MergeAction, action, parse->mergeActionList)
        {
            action->qual =
                add_nulling_relids(action->qual,
                                   bms_make_singleton(sourcerti),
                                   bms_make_singleton(joinrti));
 
            action->targetList = (List *)
                add_nulling_relids((Node *) action->targetList,
                                   bms_make_singleton(sourcerti),
                                   bms_make_singleton(joinrti));
        }
 
        parse->returningList = (List *)
            add_nulling_relids((Node *) parse->returningList,
                               bms_make_singleton(sourcerti),
                               bms_make_singleton(joinrti));
    }
 
    /*
     * If there are any WHEN NOT MATCHED BY SOURCE actions, the executor will
     * use the join condition to distinguish between MATCHED and NOT MATCHED
     * BY SOURCE cases.  Otherwise, it's no longer needed, and we set it to
     * NULL, saving cycles during planning and execution.
     *
     * We need to be careful though: the executor evaluates this condition
     * using the output of the join subplan node, which nulls the output from
     * the source relation when the join condition doesn't match.  That risks
     * producing incorrect results when rechecking using a "non-strict" join
     * condition, such as "src.col IS NOT DISTINCT FROM tgt.col".  To guard
     * against that, we add an additional "src IS NOT NULL" check to the join
     * condition, so that it does the right thing when performing a recheck
     * based on the output of the join subplan.
     */
    if (have_action[MERGE_WHEN_NOT_MATCHED_BY_SOURCE])
    {
        Var        *var;
        NullTest   *ntest;
 
        /* source wholerow Var (nullable by the new join) */
        var = makeWholeRowVar(rt_fetch(sourcerti, parse->rtable),
                              sourcerti, 0, false);
        var->varnullingrels = bms_make_singleton(joinrti);
 
        /* "src IS NOT NULL" check */
        ntest = makeNode(NullTest);
        ntest->arg = (Expr *) var;
        ntest->nulltesttype = IS_NOT_NULL;
        ntest->argisrow = false;
        ntest->location = -1;
 
        /* combine it with the original join condition */
        parse->mergeJoinCondition =
            (Node *) make_and_qual((Node *) ntest, parse->mergeJoinCondition);
    }
    else
        parse->mergeJoinCondition = NULL;   /* join condition not needed */
}
 
/*
 * replace_empty_jointree
 *      If the Query's jointree is empty, replace it with a dummy RTE_RESULT
 *      relation.
 *
 * By doing this, we can avoid a bunch of corner cases that formerly existed
 * for SELECTs with omitted FROM clauses.  An example is that a subquery
 * with empty jointree previously could not be pulled up, because that would
 * have resulted in an empty relid set, making the subquery not uniquely
 * identifiable for join or PlaceHolderVar processing.
 *
 * Unlike most other functions in this file, this function doesn't recurse;
 * we rely on other processing to invoke it on sub-queries at suitable times.
 */
void
replace_empty_jointree(Query *parse)
{
    RangeTblEntry *rte;
    Index       rti;
    RangeTblRef *rtr;
 
    /* Nothing to do if jointree is already nonempty */
    if (parse->jointree->fromlist != NIL)
        return;
 
    /* We mustn't change it in the top level of a setop tree, either */
    if (parse->setOperations)
        return;
 
    /* Create suitable RTE */
    rte = makeNode(RangeTblEntry);
    rte->rtekind = RTE_RESULT;
    rte->eref = makeAlias("*RESULT*", NIL);
 
    /* Add it to rangetable */
    parse->rtable = lappend(parse->rtable, rte);
    rti = list_length(parse->rtable);
 
    /* And jam a reference into the jointree */
    rtr = makeNode(RangeTblRef);
    rtr->rtindex = rti;
    parse->jointree->fromlist = list_make1(rtr);
}
 
/*
 * pull_up_sublinks
 *      Attempt to pull up ANY and EXISTS SubLinks to be treated as
 *      semijoins or anti-semijoins.
 *
 * A clause "foo op ANY (sub-SELECT)" can be processed by pulling the
 * sub-SELECT up to become a rangetable entry and treating the implied
 * comparisons as quals of a semijoin.  However, this optimization *only*
 * works at the top level of WHERE or a JOIN/ON clause, because we cannot
 * distinguish whether the ANY ought to return FALSE or NULL in cases
 * involving NULL inputs.  Also, in an outer join's ON clause we can only
 * do this if the sublink is degenerate (ie, references only the nullable
 * side of the join).  In that case it is legal to push the semijoin
 * down into the nullable side of the join.  If the sublink references any
 * nonnullable-side variables then it would have to be evaluated as part
 * of the outer join, which makes things way too complicated.
 *
 * Under similar conditions, EXISTS and NOT EXISTS clauses can be handled
 * by pulling up the sub-SELECT and creating a semijoin or anti-semijoin.
 *
 * This routine searches for such clauses and does the necessary parsetree
 * transformations if any are found.
 *
 * This routine has to run before preprocess_expression(), so the quals
 * clauses are not yet reduced to implicit-AND format, and are not guaranteed
 * to be AND/OR-flat either.  That means we need to recursively search through
 * explicit AND clauses.  We stop as soon as we hit a non-AND item.
 */
void
pull_up_sublinks(PlannerInfo *root)
{
    Node       *jtnode;
    Relids      relids;
 
    /* Begin recursion through the jointree */
    jtnode = pull_up_sublinks_jointree_recurse(root,
                                               (Node *) root->parse->jointree,
                                               &relids);
 
    /*
     * root->parse->jointree must always be a FromExpr, so insert a dummy one
     * if we got a bare RangeTblRef or JoinExpr out of the recursion.
     */
    if (IsA(jtnode, FromExpr))
        root->parse->jointree = (FromExpr *) jtnode;
    else
        root->parse->jointree = makeFromExpr(list_make1(jtnode), NULL);
}
 
/*
 * Recurse through jointree nodes for pull_up_sublinks()
 *
 * In addition to returning the possibly-modified jointree node, we return
 * a relids set of the contained rels into *relids.
 */
static Node *
pull_up_sublinks_jointree_recurse(PlannerInfo *root, Node *jtnode,
                                  Relids *relids)
{
    /* Since this function recurses, it could be driven to stack overflow. */
    check_stack_depth();
 
    if (jtnode == NULL)
    {
        *relids = NULL;
    }
    else if (IsA(jtnode, RangeTblRef))
    {
        int         varno = ((RangeTblRef *) jtnode)->rtindex;
 
        *relids = bms_make_singleton(varno);
        /* jtnode is returned unmodified */
    }
    else if (IsA(jtnode, FromExpr))
    {
        FromExpr   *f = (FromExpr *) jtnode;
        List       *newfromlist = NIL;
        Relids      frelids = NULL;
        FromExpr   *newf;
        Node       *jtlink;
        ListCell   *l;
 
        /* First, recurse to process children and collect their relids */
        foreach(l, f->fromlist)
        {
            Node       *newchild;
            Relids      childrelids;
 
            newchild = pull_up_sublinks_jointree_recurse(root,
                                                         lfirst(l),
                                                         &childrelids);
            newfromlist = lappend(newfromlist, newchild);
            frelids = bms_join(frelids, childrelids);
        }
        /* Build the replacement FromExpr; no quals yet */
        newf = makeFromExpr(newfromlist, NULL);
        /* Set up a link representing the rebuilt jointree */
        jtlink = (Node *) newf;
        /* Now process qual --- all children are available for use */
        newf->quals = pull_up_sublinks_qual_recurse(root, f->quals,
                                                    &jtlink, frelids,
                                                    NULL, NULL);
 
        /*
         * Note that the result will be either newf, or a stack of JoinExprs
         * with newf at the base.  We rely on subsequent optimization steps to
         * flatten this and rearrange the joins as needed.
         *
         * Although we could include the pulled-up subqueries in the returned
         * relids, there's no need since upper quals couldn't refer to their
         * outputs anyway.
         */
        *relids = frelids;
        jtnode = jtlink;
    }
    else if (IsA(jtnode, JoinExpr))
    {
        JoinExpr   *j;
        Relids      leftrelids;
        Relids      rightrelids;
        Node       *jtlink;
 
        /*
         * Make a modifiable copy of join node, but don't bother copying its
         * subnodes (yet).
         */
        j = (JoinExpr *) palloc(sizeof(JoinExpr));
        memcpy(j, jtnode, sizeof(JoinExpr));
        jtlink = (Node *) j;
 
        /* Recurse to process children and collect their relids */
        j->larg = pull_up_sublinks_jointree_recurse(root, j->larg,
                                                    &leftrelids);
        j->rarg = pull_up_sublinks_jointree_recurse(root, j->rarg,
                                                    &rightrelids);
 
        /*
         * Now process qual, showing appropriate child relids as available,
         * and attach any pulled-up jointree items at the right place. In the
         * inner-join case we put new JoinExprs above the existing one (much
         * as for a FromExpr-style join).  In outer-join cases the new
         * JoinExprs must go into the nullable side of the outer join. The
         * point of the available_rels machinations is to ensure that we only
         * pull up quals for which that's okay.
         *
         * We don't expect to see any pre-existing JOIN_SEMI, JOIN_ANTI,
         * JOIN_RIGHT_SEMI, or JOIN_RIGHT_ANTI jointypes here.
         */
        switch (j->jointype)
        {
            case JOIN_INNER:
                j->quals = pull_up_sublinks_qual_recurse(root, j->quals,
                                                         &jtlink,
                                                         bms_union(leftrelids,
                                                                   rightrelids),
                                                         NULL, NULL);
                break;
            case JOIN_LEFT:
                j->quals = pull_up_sublinks_qual_recurse(root, j->quals,
                                                         &j->rarg,
                                                         rightrelids,
                                                         NULL, NULL);
                break;
            case JOIN_FULL:
                /* can't do anything with full-join quals */
                break;
            case JOIN_RIGHT:
                j->quals = pull_up_sublinks_qual_recurse(root, j->quals,
                                                         &j->larg,
                                                         leftrelids,
                                                         NULL, NULL);
                break;
            default:
                elog(ERROR, "unrecognized join type: %d",
                     (int) j->jointype);
                break;
        }
 
        /*
         * Although we could include the pulled-up subqueries in the returned
         * relids, there's no need since upper quals couldn't refer to their
         * outputs anyway.  But we *do* need to include the join's own rtindex
         * because we haven't yet collapsed join alias variables, so upper
         * levels would mistakenly think they couldn't use references to this
         * join.
         */
        *relids = bms_join(leftrelids, rightrelids);
        if (j->rtindex)
            *relids = bms_add_member(*relids, j->rtindex);
        jtnode = jtlink;
    }
    else
        elog(ERROR, "unrecognized node type: %d",
             (int) nodeTag(jtnode));
    return jtnode;
}
 
/*
 * Recurse through top-level qual nodes for pull_up_sublinks()
 *
 * jtlink1 points to the link in the jointree where any new JoinExprs should
 * be inserted if they reference available_rels1 (i.e., available_rels1
 * denotes the relations present underneath jtlink1).  Optionally, jtlink2 can
 * point to a second link where new JoinExprs should be inserted if they
 * reference available_rels2 (pass NULL for both those arguments if not used).
 * Note that SubLinks referencing both sets of variables cannot be optimized.
 * If we find multiple pull-up-able SubLinks, they'll get stacked onto jtlink1
 * and/or jtlink2 in the order we encounter them.  We rely on subsequent
 * optimization to rearrange the stack if appropriate.
 *
 * Returns the replacement qual node, or NULL if the qual should be removed.
 */
static Node *
pull_up_sublinks_qual_recurse(PlannerInfo *root, Node *node,
                              Node **jtlink1, Relids available_rels1,
                              Node **jtlink2, Relids available_rels2)
{
    if (node == NULL)
        return NULL;
    if (IsA(node, SubLink))
    {
        SubLink    *sublink = (SubLink *) node;
        JoinExpr   *j;
        Relids      child_rels;
 
        /* Is it a convertible ANY or EXISTS clause? */
        if (sublink->subLinkType == ANY_SUBLINK)
        {
            ScalarArrayOpExpr *saop;
 
            if ((saop = convert_VALUES_to_ANY(root,
                                              sublink->testexpr,
                                              (Query *) sublink->subselect)) != NULL)
 
                /*
                 * The VALUES sequence was simplified.  Nothing more to do
                 * here.
                 */
                return (Node *) saop;
 
            if ((j = convert_ANY_sublink_to_join(root, sublink,
                                                 available_rels1)) != NULL)
            {
                /* Yes; insert the new join node into the join tree */
                j->larg = *jtlink1;
                *jtlink1 = (Node *) j;
                /* Recursively process pulled-up jointree nodes */
                j->rarg = pull_up_sublinks_jointree_recurse(root,
                                                            j->rarg,
                                                            &child_rels);
 
                /*
                 * Now recursively process the pulled-up quals.  Any inserted
                 * joins can get stacked onto either j->larg or j->rarg,
                 * depending on which rels they reference.
                 */
                j->quals = pull_up_sublinks_qual_recurse(root,
                                                         j->quals,
                                                         &j->larg,
                                                         available_rels1,
                                                         &j->rarg,
                                                         child_rels);
                /* Return NULL representing constant TRUE */
                return NULL;
            }
            if (available_rels2 != NULL &&
                (j = convert_ANY_sublink_to_join(root, sublink,
                                                 available_rels2)) != NULL)
            {
                /* Yes; insert the new join node into the join tree */
                j->larg = *jtlink2;
                *jtlink2 = (Node *) j;
                /* Recursively process pulled-up jointree nodes */
                j->rarg = pull_up_sublinks_jointree_recurse(root,
                                                            j->rarg,
                                                            &child_rels);
 
                /*
                 * Now recursively process the pulled-up quals.  Any inserted
                 * joins can get stacked onto either j->larg or j->rarg,
                 * depending on which rels they reference.
                 */
                j->quals = pull_up_sublinks_qual_recurse(root,
                                                         j->quals,
                                                         &j->larg,
                                                         available_rels2,
                                                         &j->rarg,
                                                         child_rels);
                /* Return NULL representing constant TRUE */
                return NULL;
            }
        }
        else if (sublink->subLinkType == EXISTS_SUBLINK)
        {
            if ((j = convert_EXISTS_sublink_to_join(root, sublink, false,
                                                    available_rels1)) != NULL)
            {
                /* Yes; insert the new join node into the join tree */
                j->larg = *jtlink1;
                *jtlink1 = (Node *) j;
                /* Recursively process pulled-up jointree nodes */
                j->rarg = pull_up_sublinks_jointree_recurse(root,
                                                            j->rarg,
                                                            &child_rels);
 
                /*
                 * Now recursively process the pulled-up quals.  Any inserted
                 * joins can get stacked onto either j->larg or j->rarg,
                 * depending on which rels they reference.
                 */
                j->quals = pull_up_sublinks_qual_recurse(root,
                                                         j->quals,
                                                         &j->larg,
                                                         available_rels1,
                                                         &j->rarg,
                                                         child_rels);
                /* Return NULL representing constant TRUE */
                return NULL;
            }
            if (available_rels2 != NULL &&
                (j = convert_EXISTS_sublink_to_join(root, sublink, false,
                                                    available_rels2)) != NULL)
            {
                /* Yes; insert the new join node into the join tree */
                j->larg = *jtlink2;
                *jtlink2 = (Node *) j;
                /* Recursively process pulled-up jointree nodes */
                j->rarg = pull_up_sublinks_jointree_recurse(root,
                                                            j->rarg,
                                                            &child_rels);
 
                /*
                 * Now recursively process the pulled-up quals.  Any inserted
                 * joins can get stacked onto either j->larg or j->rarg,
                 * depending on which rels they reference.
                 */
                j->quals = pull_up_sublinks_qual_recurse(root,
                                                         j->quals,
                                                         &j->larg,
                                                         available_rels2,
                                                         &j->rarg,
                                                         child_rels);
                /* Return NULL representing constant TRUE */
                return NULL;
            }
        }
        /* Else return it unmodified */
        return node;
    }
    if (is_notclause(node))
    {
        /* If the immediate argument of NOT is EXISTS, try to convert */
        SubLink    *sublink = (SubLink *) get_notclausearg((Expr *) node);
        JoinExpr   *j;
        Relids      child_rels;
 
        if (sublink && IsA(sublink, SubLink))
        {
            if (sublink->subLinkType == EXISTS_SUBLINK)
            {
                if ((j = convert_EXISTS_sublink_to_join(root, sublink, true,
                                                        available_rels1)) != NULL)
                {
                    /* Yes; insert the new join node into the join tree */
                    j->larg = *jtlink1;
                    *jtlink1 = (Node *) j;
                    /* Recursively process pulled-up jointree nodes */
                    j->rarg = pull_up_sublinks_jointree_recurse(root,
                                                                j->rarg,
                                                                &child_rels);
 
                    /*
                     * Now recursively process the pulled-up quals.  Because
                     * we are underneath a NOT, we can't pull up sublinks that
                     * reference the left-hand stuff, but it's still okay to
                     * pull up sublinks referencing j->rarg.
                     */
                    j->quals = pull_up_sublinks_qual_recurse(root,
                                                             j->quals,
                                                             &j->rarg,
                                                             child_rels,
                                                             NULL, NULL);
                    /* Return NULL representing constant TRUE */
                    return NULL;
                }
                if (available_rels2 != NULL &&
                    (j = convert_EXISTS_sublink_to_join(root, sublink, true,
                                                        available_rels2)) != NULL)
                {
                    /* Yes; insert the new join node into the join tree */
                    j->larg = *jtlink2;
                    *jtlink2 = (Node *) j;
                    /* Recursively process pulled-up jointree nodes */
                    j->rarg = pull_up_sublinks_jointree_recurse(root,
                                                                j->rarg,
                                                                &child_rels);
 
                    /*
                     * Now recursively process the pulled-up quals.  Because
                     * we are underneath a NOT, we can't pull up sublinks that
                     * reference the left-hand stuff, but it's still okay to
                     * pull up sublinks referencing j->rarg.
                     */
                    j->quals = pull_up_sublinks_qual_recurse(root,
                                                             j->quals,
                                                             &j->rarg,
                                                             child_rels,
                                                             NULL, NULL);
                    /* Return NULL representing constant TRUE */
                    return NULL;
                }
            }
        }
        /* Else return it unmodified */
        return node;
    }
    if (is_andclause(node))
    {
        /* Recurse into AND clause */
        List       *newclauses = NIL;
        ListCell   *l;
 
        foreach(l, ((BoolExpr *) node)->args)
        {
            Node       *oldclause = (Node *) lfirst(l);
            Node       *newclause;
 
            newclause = pull_up_sublinks_qual_recurse(root,
                                                      oldclause,
                                                      jtlink1,
                                                      available_rels1,
                                                      jtlink2,
                                                      available_rels2);
            if (newclause)
                newclauses = lappend(newclauses, newclause);
        }
        /* We might have got back fewer clauses than we started with */
        if (newclauses == NIL)
            return NULL;
        else if (list_length(newclauses) == 1)
            return (Node *) linitial(newclauses);
        else
            return (Node *) make_andclause(newclauses);
    }
    /* Stop if not an AND */
    return node;
}
 
/*
 * preprocess_function_rtes
 *      Constant-simplify any FUNCTION RTEs in the FROM clause, and then
 *      attempt to "inline" any that are set-returning functions.
 *
 * If an RTE_FUNCTION rtable entry invokes a set-returning function that
 * contains just a simple SELECT, we can convert the rtable entry to an
 * RTE_SUBQUERY entry exposing the SELECT directly.  This is especially
 * useful if the subquery can then be "pulled up" for further optimization,
 * but we do it even if not, to reduce executor overhead.
 *
 * This has to be done before we have started to do any optimization of
 * subqueries, else any such steps wouldn't get applied to subqueries
 * obtained via inlining.  However, we do it after pull_up_sublinks
 * so that we can inline any functions used in SubLink subselects.
 *
 * The reason for applying const-simplification at this stage is that
 * (a) we'd need to do it anyway to inline a SRF, and (b) by doing it now,
 * we can be sure that pull_up_constant_function() will see constants
 * if there are constants to be seen.  This approach also guarantees
 * that every FUNCTION RTE has been const-simplified, allowing planner.c's
 * preprocess_expression() to skip doing it again.
 *
 * Like most of the planner, this feels free to scribble on its input data
 * structure.
 */
void
preprocess_function_rtes(PlannerInfo *root)
{
    ListCell   *rt;
 
    foreach(rt, root->parse->rtable)
    {
        RangeTblEntry *rte = (RangeTblEntry *) lfirst(rt);
 
        if (rte->rtekind == RTE_FUNCTION)
        {
            Query      *funcquery;
 
            /* Apply const-simplification */
            rte->functions = (List *)
                eval_const_expressions(root, (Node *) rte->functions);
 
            /* Check safety of expansion, and expand if possible */
            funcquery = inline_set_returning_function(root, rte);
            if (funcquery)
            {
                /* Successful expansion, convert the RTE to a subquery */
                rte->rtekind = RTE_SUBQUERY;
                rte->subquery = funcquery;
                rte->security_barrier = false;
 
                /*
                 * Clear fields that should not be set in a subquery RTE.
                 * However, we leave rte->functions filled in for the moment,
                 * in case makeWholeRowVar needs to consult it.  We'll clear
                 * it in setrefs.c (see add_rte_to_flat_rtable) so that this
                 * abuse of the data structure doesn't escape the planner.
                 */
                rte->funcordinality = false;
            }
        }
    }
}
 
/*
 * expand_virtual_generated_columns
 *      Expand all virtual generated column references in a query.
 *
 * This scans the rangetable for relations with virtual generated columns, and
 * replaces all Var nodes in the query that reference these columns with the
 * generation expressions.  Note that we do not descend into subqueries; that
 * is taken care of when the subqueries are planned.
 *
 * This has to be done after we have pulled up any SubLinks within the query's
 * quals; otherwise any virtual generated column references within the SubLinks
 * that should be transformed into joins wouldn't get expanded.
 *
 * Returns a modified copy of the query tree, if any relations with virtual
 * generated columns are present.
 */
Query *
expand_virtual_generated_columns(PlannerInfo *root)
{
    Query      *parse = root->parse;
    int         rt_index;
    ListCell   *lc;
 
    rt_index = 0;
    foreach(lc, parse->rtable)
    {
        RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc);
        Relation    rel;
        TupleDesc   tupdesc;
 
        ++rt_index;
 
        /*
         * Only normal relations can have virtual generated columns.
         */
        if (rte->rtekind != RTE_RELATION)
            continue;
 
        rel = table_open(rte->relid, NoLock);
 
        tupdesc = RelationGetDescr(rel);
        if (tupdesc->constr && tupdesc->constr->has_generated_virtual)
        {
            List       *tlist = NIL;
            pullup_replace_vars_context rvcontext;
 
            for (int i = 0; i < tupdesc->natts; i++)
            {
                Form_pg_attribute attr = TupleDescAttr(tupdesc, i);
                TargetEntry *tle;
 
                if (attr->attgenerated == ATTRIBUTE_GENERATED_VIRTUAL)
                {
                    Node       *defexpr;
 
                    defexpr = build_generation_expression(rel, i + 1);
                    ChangeVarNodes(defexpr, 1, rt_index, 0);
 
                    tle = makeTargetEntry((Expr *) defexpr, i + 1, 0, false);
                    tlist = lappend(tlist, tle);
                }
                else
                {
                    Var        *var;
 
                    var = makeVar(rt_index,
                                  i + 1,
                                  attr->atttypid,
                                  attr->atttypmod,
                                  attr->attcollation,
                                  0);
 
                    tle = makeTargetEntry((Expr *) var, i + 1, 0, false);
                    tlist = lappend(tlist, tle);
                }
            }
 
            Assert(list_length(tlist) > 0);
            Assert(!rte->lateral);
 
            /*
             * The relation's targetlist items are now in the appropriate form
             * to insert into the query, except that we may need to wrap them
             * in PlaceHolderVars.  Set up required context data for
             * pullup_replace_vars.
             */
            rvcontext.root = root;
            rvcontext.targetlist = tlist;
            rvcontext.target_rte = rte;
            rvcontext.result_relation = parse->resultRelation;
            /* won't need these values */
            rvcontext.relids = NULL;
            rvcontext.nullinfo = NULL;
            /* pass NULL for outer_hasSubLinks */
            rvcontext.outer_hasSubLinks = NULL;
            rvcontext.varno = rt_index;
            /* this flag will be set below, if needed */
            rvcontext.wrap_option = REPLACE_WRAP_NONE;
            /* initialize cache array with indexes 0 .. length(tlist) */
            rvcontext.rv_cache = palloc0((list_length(tlist) + 1) *
                                         sizeof(Node *));
 
            /*
             * If the query uses grouping sets, we need a PlaceHolderVar for
             * each expression of the relation's targetlist items.  (See
             * comments in pull_up_simple_subquery().)
             */
            if (parse->groupingSets)
                rvcontext.wrap_option = REPLACE_WRAP_ALL;
 
            /*
             * Apply pullup variable replacement throughout the query tree.
             */
            parse = (Query *) pullup_replace_vars((Node *) parse, &rvcontext);
        }
 
        table_close(rel, NoLock);
    }
 
    return parse;
}
 
/*
 * pull_up_subqueries
 *      Look for subqueries in the rangetable that can be pulled up into
 *      the parent query.  If the subquery has no special features like
 *      grouping/aggregation then we can merge it into the parent's jointree.
 *      Also, subqueries that are simple UNION ALL structures can be
 *      converted into "append relations".
 */
void
pull_up_subqueries(PlannerInfo *root)
{
    /* Top level of jointree must always be a FromExpr */
    Assert(IsA(root->parse->jointree, FromExpr));
    /* Recursion starts with no containing join nor appendrel */
    root->parse->jointree = (FromExpr *)
        pull_up_subqueries_recurse(root, (Node *) root->parse->jointree,
                                   NULL, NULL);
    /* We should still have a FromExpr */
    Assert(IsA(root->parse->jointree, FromExpr));
}
 
/*
 * pull_up_subqueries_recurse
 *      Recursive guts of pull_up_subqueries.
 *
 * This recursively processes the jointree and returns a modified jointree.
 *
 * If this jointree node is within either side of an outer join, then
 * lowest_outer_join references the lowest such JoinExpr node; otherwise
 * it is NULL.  We use this to constrain the effects of LATERAL subqueries.
 *
 * If we are looking at a member subquery of an append relation,
 * containing_appendrel describes that relation; else it is NULL.
 * This forces use of the PlaceHolderVar mechanism for all non-Var targetlist
 * items, and puts some additional restrictions on what can be pulled up.
 *
 * A tricky aspect of this code is that if we pull up a subquery we have
 * to replace Vars that reference the subquery's outputs throughout the
 * parent query, including quals attached to jointree nodes above the one
 * we are currently processing!  We handle this by being careful to maintain
 * validity of the jointree structure while recursing, in the following sense:
 * whenever we recurse, all qual expressions in the tree must be reachable
 * from the top level, in case the recursive call needs to modify them.
 *
 * Notice also that we can't turn pullup_replace_vars loose on the whole
 * jointree, because it'd return a mutated copy of the tree; we have to
 * invoke it just on the quals, instead.  This behavior is what makes it
 * reasonable to pass lowest_outer_join as a pointer rather than some
 * more-indirect way of identifying the lowest OJ.  Likewise, we don't
 * replace append_rel_list members but only their substructure, so the
 * containing_appendrel reference is safe to use.
 */
static Node *
pull_up_subqueries_recurse(PlannerInfo *root, Node *jtnode,
                           JoinExpr *lowest_outer_join,
                           AppendRelInfo *containing_appendrel)
{
    /* Since this function recurses, it could be driven to stack overflow. */
    check_stack_depth();
    /* Also, since it's a bit expensive, let's check for query cancel. */
    CHECK_FOR_INTERRUPTS();
 
    Assert(jtnode != NULL);
    if (IsA(jtnode, RangeTblRef))
    {
        int         varno = ((RangeTblRef *) jtnode)->rtindex;
        RangeTblEntry *rte = rt_fetch(varno, root->parse->rtable);
 
        /*
         * Is this a subquery RTE, and if so, is the subquery simple enough to
         * pull up?
         *
         * If we are looking at an append-relation member, we can't pull it up
         * unless is_safe_append_member says so.
         */
        if (rte->rtekind == RTE_SUBQUERY &&
            is_simple_subquery(root, rte->subquery, rte, lowest_outer_join) &&
            (containing_appendrel == NULL ||
             is_safe_append_member(rte->subquery)))
            return pull_up_simple_subquery(root, jtnode, rte,
                                           lowest_outer_join,
                                           containing_appendrel);
 
        /*
         * Alternatively, is it a simple UNION ALL subquery?  If so, flatten
         * into an "append relation".
         *
         * It's safe to do this regardless of whether this query is itself an
         * appendrel member.  (If you're thinking we should try to flatten the
         * two levels of appendrel together, you're right; but we handle that
         * in set_append_rel_pathlist, not here.)
         */
        if (rte->rtekind == RTE_SUBQUERY &&
            is_simple_union_all(rte->subquery))
            return pull_up_simple_union_all(root, jtnode, rte);
 
        /*
         * Or perhaps it's a simple VALUES RTE?
         *
         * We don't allow VALUES pullup below an outer join nor into an
         * appendrel (such cases are impossible anyway at the moment).
         */
        if (rte->rtekind == RTE_VALUES &&
            lowest_outer_join == NULL &&
            containing_appendrel == NULL &&
            is_simple_values(root, rte))
            return pull_up_simple_values(root, jtnode, rte);
 
        /*
         * Or perhaps it's a FUNCTION RTE that we could inline?
         */
        if (rte->rtekind == RTE_FUNCTION)
            return pull_up_constant_function(root, jtnode, rte,
                                             containing_appendrel);
 
        /* Otherwise, do nothing at this node. */
    }
    else if (IsA(jtnode, FromExpr))
    {
        FromExpr   *f = (FromExpr *) jtnode;
        ListCell   *l;
 
        Assert(containing_appendrel == NULL);
        /* Recursively transform all the child nodes */
        foreach(l, f->fromlist)
        {
            lfirst(l) = pull_up_subqueries_recurse(root, lfirst(l),
                                                   lowest_outer_join,
                                                   NULL);
        }
    }
    else if (IsA(jtnode, JoinExpr))
    {
        JoinExpr   *j = (JoinExpr *) jtnode;
 
        Assert(containing_appendrel == NULL);
        /* Recurse, being careful to tell myself when inside outer join */
        switch (j->jointype)
        {
            case JOIN_INNER:
                j->larg = pull_up_subqueries_recurse(root, j->larg,
                                                     lowest_outer_join,
                                                     NULL);
                j->rarg = pull_up_subqueries_recurse(root, j->rarg,
                                                     lowest_outer_join,
                                                     NULL);
                break;
            case JOIN_LEFT:
            case JOIN_SEMI:
            case JOIN_ANTI:
                j->larg = pull_up_subqueries_recurse(root, j->larg,
                                                     j,
                                                     NULL);
                j->rarg = pull_up_subqueries_recurse(root, j->rarg,
                                                     j,
                                                     NULL);
                break;
            case JOIN_FULL:
                j->larg = pull_up_subqueries_recurse(root, j->larg,
                                                     j,
                                                     NULL);
                j->rarg = pull_up_subqueries_recurse(root, j->rarg,
                                                     j,
                                                     NULL);
                break;
            case JOIN_RIGHT:
                j->larg = pull_up_subqueries_recurse(root, j->larg,
                                                     j,
                                                     NULL);
                j->rarg = pull_up_subqueries_recurse(root, j->rarg,
                                                     j,
                                                     NULL);
                break;
            default:
                elog(ERROR, "unrecognized join type: %d",
                     (int) j->jointype);
                break;
        }
    }
    else
        elog(ERROR, "unrecognized node type: %d",
             (int) nodeTag(jtnode));
    return jtnode;
}
 
/*
 * pull_up_simple_subquery
 *      Attempt to pull up a single simple subquery.
 *
 * jtnode is a RangeTblRef that has been tentatively identified as a simple
 * subquery by pull_up_subqueries.  We return the replacement jointree node,
 * or jtnode itself if we determine that the subquery can't be pulled up
 * after all.
 *
 * rte is the RangeTblEntry referenced by jtnode.  Remaining parameters are
 * as for pull_up_subqueries_recurse.
 */
static Node *
pull_up_simple_subquery(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte,
                        JoinExpr *lowest_outer_join,
                        AppendRelInfo *containing_appendrel)
{
    Query      *parse = root->parse;
    int         varno = ((RangeTblRef *) jtnode)->rtindex;
    Query      *subquery;
    PlannerInfo *subroot;
    int         rtoffset;
    pullup_replace_vars_context rvcontext;
    ListCell   *lc;
 
    /*
     * Make a modifiable copy of the subquery to hack on, so that the RTE will
     * be left unchanged in case we decide below that we can't pull it up
     * after all.
     */
    subquery = copyObject(rte->subquery);
 
    /*
     * Create a PlannerInfo data structure for this subquery.
     *
     * NOTE: the next few steps should match the first processing in
     * subquery_planner().  Can we refactor to avoid code duplication, or
     * would that just make things uglier?
     */
    subroot = makeNode(PlannerInfo);
    subroot->parse = subquery;
    subroot->glob = root->glob;
    subroot->query_level = root->query_level;
    subroot->parent_root = root->parent_root;
    subroot->plan_params = NIL;
    subroot->outer_params = NULL;
    subroot->planner_cxt = CurrentMemoryContext;
    subroot->init_plans = NIL;
    subroot->cte_plan_ids = NIL;
    subroot->multiexpr_params = NIL;
    subroot->join_domains = NIL;
    subroot->eq_classes = NIL;
    subroot->ec_merging_done = false;
    subroot->last_rinfo_serial = 0;
    subroot->all_result_relids = NULL;
    subroot->leaf_result_relids = NULL;
    subroot->append_rel_list = NIL;
    subroot->row_identity_vars = NIL;
    subroot->rowMarks = NIL;
    memset(subroot->upper_rels, 0, sizeof(subroot->upper_rels));
    memset(subroot->upper_targets, 0, sizeof(subroot->upper_targets));
    subroot->processed_groupClause = NIL;
    subroot->processed_distinctClause = NIL;
    subroot->processed_tlist = NIL;
    subroot->update_colnos = NIL;
    subroot->grouping_map = NULL;
    subroot->minmax_aggs = NIL;
    subroot->qual_security_level = 0;
    subroot->placeholdersFrozen = false;
    subroot->hasRecursion = false;
    subroot->wt_param_id = -1;
    subroot->non_recursive_path = NULL;
    /* We don't currently need a top JoinDomain for the subroot */
 
    /* No CTEs to worry about */
    Assert(subquery->cteList == NIL);
 
    /*
     * If the FROM clause is empty, replace it with a dummy RTE_RESULT RTE, so
     * that we don't need so many special cases to deal with that situation.
     */
    replace_empty_jointree(subquery);
 
    /*
     * Pull up any SubLinks within the subquery's quals, so that we don't
     * leave unoptimized SubLinks behind.
     */
    if (subquery->hasSubLinks)
        pull_up_sublinks(subroot);
 
    /*
     * Similarly, preprocess its function RTEs to inline any set-returning
     * functions in its rangetable.
     */
    preprocess_function_rtes(subroot);
 
    /*
     * Scan the rangetable for relations with virtual generated columns, and
     * replace all Var nodes in the query that reference these columns with
     * the generation expressions.
     */
    subquery = subroot->parse = expand_virtual_generated_columns(subroot);
 
    /*
     * Recursively pull up the subquery's subqueries, so that
     * pull_up_subqueries' processing is complete for its jointree and
     * rangetable.
     *
     * Note: it's okay that the subquery's recursion starts with NULL for
     * containing-join info, even if we are within an outer join in the upper
     * query; the lower query starts with a clean slate for outer-join
     * semantics.  Likewise, we needn't pass down appendrel state.
     */
    pull_up_subqueries(subroot);
 
    /*
     * Now we must recheck whether the subquery is still simple enough to pull
     * up.  If not, abandon processing it.
     *
     * We don't really need to recheck all the conditions involved, but it's
     * easier just to keep this "if" looking the same as the one in
     * pull_up_subqueries_recurse.
     */
    if (is_simple_subquery(root, subquery, rte, lowest_outer_join) &&
        (containing_appendrel == NULL || is_safe_append_member(subquery)))
    {
        /* good to go */
    }
    else
    {
        /*
         * Give up, return unmodified RangeTblRef.
         *
         * Note: The work we just did will be redone when the subquery gets
         * planned on its own.  Perhaps we could avoid that by storing the
         * modified subquery back into the rangetable, but I'm not gonna risk
         * it now.
         */
        return jtnode;
    }
 
    /*
     * We must flatten any join alias Vars in the subquery's targetlist,
     * because pulling up the subquery's subqueries might have changed their
     * expansions into arbitrary expressions, which could affect
     * pullup_replace_vars' decisions about whether PlaceHolderVar wrappers
     * are needed for tlist entries.  (Likely it'd be better to do
     * flatten_join_alias_vars on the whole query tree at some earlier stage,
     * maybe even in the rewriter; but for now let's just fix this case here.)
     */
    subquery->targetList = (List *)
        flatten_join_alias_vars(subroot, subroot->parse,
                                (Node *) subquery->targetList);
 
    /*
     * Adjust level-0 varnos in subquery so that we can append its rangetable
     * to upper query's.  We have to fix the subquery's append_rel_list as
     * well.
     */
    rtoffset = list_length(parse->rtable);
    OffsetVarNodes((Node *) subquery, rtoffset, 0);
    OffsetVarNodes((Node *) subroot->append_rel_list, rtoffset, 0);
 
    /*
     * Upper-level vars in subquery are now one level closer to their parent
     * than before.
     */
    IncrementVarSublevelsUp((Node *) subquery, -1, 1);
    IncrementVarSublevelsUp((Node *) subroot->append_rel_list, -1, 1);
 
    /*
     * The subquery's targetlist items are now in the appropriate form to
     * insert into the top query, except that we may need to wrap them in
     * PlaceHolderVars.  Set up required context data for pullup_replace_vars.
     * (Note that we should include the subquery's inner joins in relids,
     * since it may include join alias vars referencing them.)
     */
    rvcontext.root = root;
    rvcontext.targetlist = subquery->targetList;
    rvcontext.target_rte = rte;
    rvcontext.result_relation = 0;
    if (rte->lateral)
    {
        rvcontext.relids = get_relids_in_jointree((Node *) subquery->jointree,
                                                  true, true);
        rvcontext.nullinfo = get_nullingrels(parse);
    }
    else                        /* won't need these values */
    {
        rvcontext.relids = NULL;
        rvcontext.nullinfo = NULL;
    }
    rvcontext.outer_hasSubLinks = &parse->hasSubLinks;
    rvcontext.varno = varno;
    /* this flag will be set below, if needed */
    rvcontext.wrap_option = REPLACE_WRAP_NONE;
    /* initialize cache array with indexes 0 .. length(tlist) */
    rvcontext.rv_cache = palloc0((list_length(subquery->targetList) + 1) *
                                 sizeof(Node *));
 
    /*
     * If the parent query uses grouping sets, we need a PlaceHolderVar for
     * each expression of the subquery's targetlist items.  This ensures that
     * expressions retain their separate identity so that they will match
     * grouping set columns when appropriate.  (It'd be sufficient to wrap
     * values used in grouping set columns, and do so only in non-aggregated
     * portions of the tlist and havingQual, but that would require a lot of
     * infrastructure that pullup_replace_vars hasn't currently got.)
     */
    if (parse->groupingSets)
        rvcontext.wrap_option = REPLACE_WRAP_ALL;
 
    /*
     * Replace all of the top query's references to the subquery's outputs
     * with copies of the adjusted subtlist items, being careful not to
     * replace any of the jointree structure.
     */
    perform_pullup_replace_vars(root, &rvcontext,
                                containing_appendrel);
 
    /*
     * If the subquery had a LATERAL marker, propagate that to any of its
     * child RTEs that could possibly now contain lateral cross-references.
     * The children might or might not contain any actual lateral
     * cross-references, but we have to mark the pulled-up child RTEs so that
     * later planner stages will check for such.
     */
    if (rte->lateral)
    {
        foreach(lc, subquery->rtable)
        {
            RangeTblEntry *child_rte = (RangeTblEntry *) lfirst(lc);
 
            switch (child_rte->rtekind)
            {
                case RTE_RELATION:
                    if (child_rte->tablesample)
                        child_rte->lateral = true;
                    break;
                case RTE_SUBQUERY:
                case RTE_FUNCTION:
                case RTE_VALUES:
                case RTE_TABLEFUNC:
                    child_rte->lateral = true;
                    break;
                case RTE_JOIN:
                case RTE_CTE:
                case RTE_NAMEDTUPLESTORE:
                case RTE_RESULT:
                case RTE_GROUP:
                    /* these can't contain any lateral references */
                    break;
            }
        }
    }
 
    /*
     * Now append the adjusted rtable entries and their perminfos to upper
     * query. (We hold off until after fixing the upper rtable entries; no
     * point in running that code on the subquery ones too.)
     */
    CombineRangeTables(&parse->rtable, &parse->rteperminfos,
                       subquery->rtable, subquery->rteperminfos);
 
    /*
     * Pull up any FOR UPDATE/SHARE markers, too.  (OffsetVarNodes already
     * adjusted the marker rtindexes, so just concat the lists.)
     */
    parse->rowMarks = list_concat(parse->rowMarks, subquery->rowMarks);
 
    /*
     * We also have to fix the relid sets of any PlaceHolderVar nodes in the
     * parent query.  (This could perhaps be done by pullup_replace_vars(),
     * but it seems cleaner to use two passes.)  Note in particular that any
     * PlaceHolderVar nodes just created by pullup_replace_vars() will be
     * adjusted, so having created them with the subquery's varno is correct.
     *
     * Likewise, relids appearing in AppendRelInfo nodes have to be fixed. We
     * already checked that this won't require introducing multiple subrelids
     * into the single-slot AppendRelInfo structs.
     */
    if (root->glob->lastPHId != 0 || root->append_rel_list)
    {
        Relids      subrelids;
 
        subrelids = get_relids_in_jointree((Node *) subquery->jointree,
                                           true, false);
        if (root->glob->lastPHId != 0)
            substitute_phv_relids((Node *) parse, varno, subrelids);
        fix_append_rel_relids(root, varno, subrelids);
    }
 
    /*
     * And now add subquery's AppendRelInfos to our list.
     */
    root->append_rel_list = list_concat(root->append_rel_list,
                                        subroot->append_rel_list);
 
    /*
     * We don't have to do the equivalent bookkeeping for outer-join info,
     * because that hasn't been set up yet.  placeholder_list likewise.
     */
    Assert(root->join_info_list == NIL);
    Assert(subroot->join_info_list == NIL);
    Assert(root->placeholder_list == NIL);
    Assert(subroot->placeholder_list == NIL);
 
    /*
     * We no longer need the RTE's copy of the subquery's query tree.  Getting
     * rid of it saves nothing in particular so far as this level of query is
     * concerned; but if this query level is in turn pulled up into a parent,
     * we'd waste cycles copying the now-unused query tree.
     */
    rte->subquery = NULL;
 
    /*
     * Miscellaneous housekeeping.
     *
     * Although replace_rte_variables() faithfully updated parse->hasSubLinks
     * if it copied any SubLinks out of the subquery's targetlist, we still
     * could have SubLinks added to the query in the expressions of FUNCTION
     * and VALUES RTEs copied up from the subquery.  So it's necessary to copy
     * subquery->hasSubLinks anyway.  Perhaps this can be improved someday.
     */
    parse->hasSubLinks |= subquery->hasSubLinks;
 
    /* If subquery had any RLS conditions, now main query does too */
    parse->hasRowSecurity |= subquery->hasRowSecurity;
 
    /*
     * subquery won't be pulled up if it hasAggs, hasWindowFuncs, or
     * hasTargetSRFs, so no work needed on those flags
     */
 
    /*
     * Return the adjusted subquery jointree to replace the RangeTblRef entry
     * in parent's jointree; or, if the FromExpr is degenerate, just return
     * its single member.
     */
    Assert(IsA(subquery->jointree, FromExpr));
    Assert(subquery->jointree->fromlist != NIL);
    if (subquery->jointree->quals == NULL &&
        list_length(subquery->jointree->fromlist) == 1)
        return (Node *) linitial(subquery->jointree->fromlist);
 
    return (Node *) subquery->jointree;
}
 
/*
 * pull_up_simple_union_all
 *      Pull up a single simple UNION ALL subquery.
 *
 * jtnode is a RangeTblRef that has been identified as a simple UNION ALL
 * subquery by pull_up_subqueries.  We pull up the leaf subqueries and
 * build an "append relation" for the union set.  The result value is just
 * jtnode, since we don't actually need to change the query jointree.
 */
static Node *
pull_up_simple_union_all(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte)
{
    int         varno = ((RangeTblRef *) jtnode)->rtindex;
    Query      *subquery = rte->subquery;
    int         rtoffset = list_length(root->parse->rtable);
    List       *rtable;
 
    /*
     * Make a modifiable copy of the subquery's rtable, so we can adjust
     * upper-level Vars in it.  There are no such Vars in the setOperations
     * tree proper, so fixing the rtable should be sufficient.
     */
    rtable = copyObject(subquery->rtable);
 
    /*
     * Upper-level vars in subquery are now one level closer to their parent
     * than before.  We don't have to worry about offsetting varnos, though,
     * because the UNION leaf queries can't cross-reference each other.
     */
    IncrementVarSublevelsUp_rtable(rtable, -1, 1);
 
    /*
     * If the UNION ALL subquery had a LATERAL marker, propagate that to all
     * its children.  The individual children might or might not contain any
     * actual lateral cross-references, but we have to mark the pulled-up
     * child RTEs so that later planner stages will check for such.
     */
    if (rte->lateral)
    {
        ListCell   *rt;
 
        foreach(rt, rtable)
        {
            RangeTblEntry *child_rte = (RangeTblEntry *) lfirst(rt);
 
            Assert(child_rte->rtekind == RTE_SUBQUERY);
            child_rte->lateral = true;
        }
    }
 
    /*
     * Append child RTEs (and their perminfos) to parent rtable.
     */
    CombineRangeTables(&root->parse->rtable, &root->parse->rteperminfos,
                       rtable, subquery->rteperminfos);
 
    /*
     * Recursively scan the subquery's setOperations tree and add
     * AppendRelInfo nodes for leaf subqueries to the parent's
     * append_rel_list.  Also apply pull_up_subqueries to the leaf subqueries.
     */
    Assert(subquery->setOperations);
    pull_up_union_leaf_queries(subquery->setOperations, root, varno, subquery,
                               rtoffset);
 
    /*
     * Mark the parent as an append relation.
     */
    rte->inh = true;
 
    return jtnode;
}
 
/*
 * pull_up_union_leaf_queries -- recursive guts of pull_up_simple_union_all
 *
 * Build an AppendRelInfo for each leaf query in the setop tree, and then
 * apply pull_up_subqueries to the leaf query.
 *
 * Note that setOpQuery is the Query containing the setOp node, whose tlist
 * contains references to all the setop output columns.  When called from
 * pull_up_simple_union_all, this is *not* the same as root->parse, which is
 * the parent Query we are pulling up into.
 *
 * parentRTindex is the appendrel parent's index in root->parse->rtable.
 *
 * The child RTEs have already been copied to the parent.  childRToffset
 * tells us where in the parent's range table they were copied.  When called
 * from flatten_simple_union_all, childRToffset is 0 since the child RTEs
 * were already in root->parse->rtable and no RT index adjustment is needed.
 */
static void
pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root, int parentRTindex,
                           Query *setOpQuery, int childRToffset)
{
    if (IsA(setOp, RangeTblRef))
    {
        RangeTblRef *rtr = (RangeTblRef *) setOp;
        int         childRTindex;
        AppendRelInfo *appinfo;
 
        /*
         * Calculate the index in the parent's range table
         */
        childRTindex = childRToffset + rtr->rtindex;
 
        /*
         * Build a suitable AppendRelInfo, and attach to parent's list.
         */
        appinfo = makeNode(AppendRelInfo);
        appinfo->parent_relid = parentRTindex;
        appinfo->child_relid = childRTindex;
        appinfo->parent_reltype = InvalidOid;
        appinfo->child_reltype = InvalidOid;
        make_setop_translation_list(setOpQuery, childRTindex, appinfo);
        appinfo->parent_reloid = InvalidOid;
        root->append_rel_list = lappend(root->append_rel_list, appinfo);
 
        /*
         * Recursively apply pull_up_subqueries to the new child RTE.  (We
         * must build the AppendRelInfo first, because this will modify it;
         * indeed, that's the only part of the upper query where Vars
         * referencing childRTindex can exist at this point.)
         *
         * Note that we can pass NULL for containing-join info even if we're
         * actually under an outer join, because the child's expressions
         * aren't going to propagate up to the join.  Also, we ignore the
         * possibility that pull_up_subqueries_recurse() returns a different
         * jointree node than what we pass it; if it does, the important thing
         * is that it replaced the child relid in the AppendRelInfo node.
         */
        rtr = makeNode(RangeTblRef);
        rtr->rtindex = childRTindex;
        (void) pull_up_subqueries_recurse(root, (Node *) rtr,
                                          NULL, appinfo);
    }
    else if (IsA(setOp, SetOperationStmt))
    {
        SetOperationStmt *op = (SetOperationStmt *) setOp;
 
        /* Recurse to reach leaf queries */
        pull_up_union_leaf_queries(op->larg, root, parentRTindex, setOpQuery,
                                   childRToffset);
        pull_up_union_leaf_queries(op->rarg, root, parentRTindex, setOpQuery,
                                   childRToffset);
    }
    else
    {
        elog(ERROR, "unrecognized node type: %d",
             (int) nodeTag(setOp));
    }
}
 
/*
 * make_setop_translation_list
 *    Build the list of translations from parent Vars to child Vars for
 *    a UNION ALL member.  (At this point it's just a simple list of
 *    referencing Vars, but if we succeed in pulling up the member
 *    subquery, the Vars will get replaced by pulled-up expressions.)
 *    Also create the rather trivial reverse-translation array.
 */
static void
make_setop_translation_list(Query *query, int newvarno,
                            AppendRelInfo *appinfo)
{
    List       *vars = NIL;
    AttrNumber *pcolnos;
    ListCell   *l;
 
    /* Initialize reverse-translation array with all entries zero */
    /* (entries for resjunk columns will stay that way) */
    appinfo->num_child_cols = list_length(query->targetList);
    appinfo->parent_colnos = pcolnos =
        (AttrNumber *) palloc0(appinfo->num_child_cols * sizeof(AttrNumber));
 
    foreach(l, query->targetList)
    {
        TargetEntry *tle = (TargetEntry *) lfirst(l);
 
        if (tle->resjunk)
            continue;
 
        vars = lappend(vars, makeVarFromTargetEntry(newvarno, tle));
        pcolnos[tle->resno - 1] = tle->resno;
    }
 
    appinfo->translated_vars = vars;
}
 
/*
 * is_simple_subquery
 *    Check a subquery in the range table to see if it's simple enough
 *    to pull up into the parent query.
 *
 * rte is the RTE_SUBQUERY RangeTblEntry that contained the subquery.
 * (Note subquery is not necessarily equal to rte->subquery; it could be a
 * processed copy of that.)
 * lowest_outer_join is the lowest outer join above the subquery, or NULL.
 */
static bool
is_simple_subquery(PlannerInfo *root, Query *subquery, RangeTblEntry *rte,
                   JoinExpr *lowest_outer_join)
{
    /*
     * Let's just make sure it's a valid subselect ...
     */
    if (!IsA(subquery, Query) ||
        subquery->commandType != CMD_SELECT)
        elog(ERROR, "subquery is bogus");
 
    /*
     * Can't currently pull up a query with setops (unless it's simple UNION
     * ALL, which is handled by a different code path). Maybe after querytree
     * redesign...
     */
    if (subquery->setOperations)
        return false;
 
    /*
     * Can't pull up a subquery involving grouping, aggregation, SRFs,
     * sorting, limiting, or WITH.  (XXX WITH could possibly be allowed later)
     *
     * We also don't pull up a subquery that has explicit FOR UPDATE/SHARE
     * clauses, because pullup would cause the locking to occur semantically
     * higher than it should.  Implicit FOR UPDATE/SHARE is okay because in
     * that case the locking was originally declared in the upper query
     * anyway.
     */
    if (subquery->hasAggs ||
        subquery->hasWindowFuncs ||
        subquery->hasTargetSRFs ||
        subquery->groupClause ||
        subquery->groupingSets ||
        subquery->havingQual ||
        subquery->sortClause ||
        subquery->distinctClause ||
        subquery->limitOffset ||
        subquery->limitCount ||
        subquery->hasForUpdate ||
        subquery->cteList)
        return false;
 
    /*
     * Don't pull up if the RTE represents a security-barrier view; we
     * couldn't prevent information leakage once the RTE's Vars are scattered
     * about in the upper query.
     */
    if (rte->security_barrier)
        return false;
 
    /*
     * If the subquery is LATERAL, check for pullup restrictions from that.
     */
    if (rte->lateral)
    {
        bool        restricted;
        Relids      safe_upper_varnos;
 
        /*
         * The subquery's WHERE and JOIN/ON quals mustn't contain any lateral
         * references to rels outside a higher outer join (including the case
         * where the outer join is within the subquery itself).  In such a
         * case, pulling up would result in a situation where we need to
         * postpone quals from below an outer join to above it, which is
         * probably completely wrong and in any case is a complication that
         * doesn't seem worth addressing at the moment.
         */
        if (lowest_outer_join != NULL)
        {
            restricted = true;
            safe_upper_varnos = get_relids_in_jointree((Node *) lowest_outer_join,
                                                       true, true);
        }
        else
        {
            restricted = false;
            safe_upper_varnos = NULL;   /* doesn't matter */
        }
 
        if (jointree_contains_lateral_outer_refs(root,
                                                 (Node *) subquery->jointree,
                                                 restricted, safe_upper_varnos))
            return false;
 
        /*
         * If there's an outer join above the LATERAL subquery, also disallow
         * pullup if the subquery's targetlist has any references to rels
         * outside the outer join, since these might get pulled into quals
         * above the subquery (but in or below the outer join) and then lead
         * to qual-postponement issues similar to the case checked for above.
         * (We wouldn't need to prevent pullup if no such references appear in
         * outer-query quals, but we don't have enough info here to check
         * that.  Also, maybe this restriction could be removed if we forced
         * such refs to be wrapped in PlaceHolderVars, even when they're below
         * the nearest outer join?  But it's a pretty hokey usage, so not
         * clear this is worth sweating over.)
         *
         * If you change this, see also the comments about lateral references
         * in pullup_replace_vars_callback().
         */
        if (lowest_outer_join != NULL)
        {
            Relids      lvarnos = pull_varnos_of_level(root,
                                                       (Node *) subquery->targetList,
                                                       1);
 
            if (!bms_is_subset(lvarnos, safe_upper_varnos))
                return false;
        }
    }
 
    /*
     * Don't pull up a subquery that has any volatile functions in its
     * targetlist.  Otherwise we might introduce multiple evaluations of these
     * functions, if they get copied to multiple places in the upper query,
     * leading to surprising results.  (Note: the PlaceHolderVar mechanism
     * doesn't quite guarantee single evaluation; else we could pull up anyway
     * and just wrap such items in PlaceHolderVars ...)
     */
    if (contain_volatile_functions((Node *) subquery->targetList))
        return false;
 
    return true;
}
 
/*
 * pull_up_simple_values
 *      Pull up a single simple VALUES RTE.
 *
 * jtnode is a RangeTblRef that has been identified as a simple VALUES RTE
 * by pull_up_subqueries.  We always return a RangeTblRef representing a
 * RESULT RTE to replace it (all failure cases should have been detected by
 * is_simple_values()).  Actually, what we return is just jtnode, because
 * we replace the VALUES RTE in the rangetable with the RESULT RTE.
 *
 * rte is the RangeTblEntry referenced by jtnode.  Because of the limited
 * possible usage of VALUES RTEs, we do not need the remaining parameters
 * of pull_up_subqueries_recurse.
 */
static Node *
pull_up_simple_values(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte)
{
    Query      *parse = root->parse;
    int         varno = ((RangeTblRef *) jtnode)->rtindex;
    List       *values_list;
    List       *tlist;
    AttrNumber  attrno;
    pullup_replace_vars_context rvcontext;
    ListCell   *lc;
 
    Assert(rte->rtekind == RTE_VALUES);
    Assert(list_length(rte->values_lists) == 1);
 
    /*
     * Need a modifiable copy of the VALUES list to hack on, just in case it's
     * multiply referenced.
     */
    values_list = copyObject(linitial(rte->values_lists));
 
    /*
     * The VALUES RTE can't contain any Vars of level zero, let alone any that
     * are join aliases, so no need to flatten join alias Vars.
     */
    Assert(!contain_vars_of_level((Node *) values_list, 0));
 
    /*
     * Set up required context data for pullup_replace_vars.  In particular,
     * we have to make the VALUES list look like a subquery targetlist.
     */
    tlist = NIL;
    attrno = 1;
    foreach(lc, values_list)
    {
        tlist = lappend(tlist,
                        makeTargetEntry((Expr *) lfirst(lc),
                                        attrno,
                                        NULL,
                                        false));
        attrno++;
    }
    rvcontext.root = root;
    rvcontext.targetlist = tlist;
    rvcontext.target_rte = rte;
    rvcontext.result_relation = 0;
    rvcontext.relids = NULL;    /* can't be any lateral references here */
    rvcontext.nullinfo = NULL;
    rvcontext.outer_hasSubLinks = &parse->hasSubLinks;
    rvcontext.varno = varno;
    rvcontext.wrap_option = REPLACE_WRAP_NONE;
    /* initialize cache array with indexes 0 .. length(tlist) */
    rvcontext.rv_cache = palloc0((list_length(tlist) + 1) *
                                 sizeof(Node *));
 
    /*
     * Replace all of the top query's references to the RTE's outputs with
     * copies of the adjusted VALUES expressions, being careful not to replace
     * any of the jointree structure.  We can assume there's no outer joins or
     * appendrels in the dummy Query that surrounds a VALUES RTE.
     */
    perform_pullup_replace_vars(root, &rvcontext, NULL);
 
    /*
     * There should be no appendrels to fix, nor any outer joins and hence no
     * PlaceHolderVars.
     */
    Assert(root->append_rel_list == NIL);
    Assert(root->join_info_list == NIL);
    Assert(root->placeholder_list == NIL);
 
    /*
     * Replace the VALUES RTE with a RESULT RTE.  The VALUES RTE is the only
     * rtable entry in the current query level, so this is easy.
     */
    Assert(list_length(parse->rtable) == 1);
 
    /* Create suitable RTE */
    rte = makeNode(RangeTblEntry);
    rte->rtekind = RTE_RESULT;
    rte->eref = makeAlias("*RESULT*", NIL);
 
    /* Replace rangetable */
    parse->rtable = list_make1(rte);
 
    /* We could manufacture a new RangeTblRef, but the one we have is fine */
    Assert(varno == 1);
 
    return jtnode;
}
 
/*
 * is_simple_values
 *    Check a VALUES RTE in the range table to see if it's simple enough
 *    to pull up into the parent query.
 *
 * rte is the RTE_VALUES RangeTblEntry to check.
 */
static bool
is_simple_values(PlannerInfo *root, RangeTblEntry *rte)
{
    Assert(rte->rtekind == RTE_VALUES);
 
    /*
     * There must be exactly one VALUES list, else it's not semantically
     * correct to replace the VALUES RTE with a RESULT RTE, nor would we have
     * a unique set of expressions to substitute into the parent query.
     */
    if (list_length(rte->values_lists) != 1)
        return false;
 
    /*
     * Because VALUES can't appear under an outer join (or at least, we won't
     * try to pull it up if it does), we need not worry about LATERAL, nor
     * about validity of PHVs for the VALUES' outputs.
     */
 
    /*
     * Don't pull up a VALUES that contains any set-returning or volatile
     * functions.  The considerations here are basically identical to the
     * restrictions on a pull-able subquery's targetlist.
     */
    if (expression_returns_set((Node *) rte->values_lists) ||
        contain_volatile_functions((Node *) rte->values_lists))
        return false;
 
    /*
     * Do not pull up a VALUES that's not the only RTE in its parent query.
     * This is actually the only case that the parser will generate at the
     * moment, and assuming this is true greatly simplifies
     * pull_up_simple_values().
     */
    if (list_length(root->parse->rtable) != 1 ||
        rte != (RangeTblEntry *) linitial(root->parse->rtable))
        return false;
 
    return true;
}
 
/*
 * pull_up_constant_function
 *      Pull up an RTE_FUNCTION expression that was simplified to a constant.
 *
 * jtnode is a RangeTblRef that has been identified as a FUNCTION RTE by
 * pull_up_subqueries.  If its expression is just a Const, hoist that value
 * up into the parent query, and replace the RTE_FUNCTION with RTE_RESULT.
 *
 * In principle we could pull up any immutable expression, but we don't.
 * That might result in multiple evaluations of the expression, which could
 * be costly if it's not just a Const.  Also, the main value of this is
 * to let the constant participate in further const-folding, and of course
 * that won't happen for a non-Const.
 *
 * The pulled-up value might need to be wrapped in a PlaceHolderVar if the
 * RTE is below an outer join or is part of an appendrel; the extra
 * parameters show whether that's needed.
 */
static Node *
pull_up_constant_function(PlannerInfo *root, Node *jtnode,
                          RangeTblEntry *rte,
                          AppendRelInfo *containing_appendrel)
{
    Query      *parse = root->parse;
    RangeTblFunction *rtf;
    TypeFuncClass functypclass;
    Oid         funcrettype;
    TupleDesc   tupdesc;
    pullup_replace_vars_context rvcontext;
 
    /* Fail if the RTE has ORDINALITY - we don't implement that here. */
    if (rte->funcordinality)
        return jtnode;
 
    /* Fail if RTE isn't a single, simple Const expr */
    if (list_length(rte->functions) != 1)
        return jtnode;
    rtf = linitial_node(RangeTblFunction, rte->functions);
    if (!IsA(rtf->funcexpr, Const))
        return jtnode;
 
    /*
     * If the function's result is not a scalar, we punt.  In principle we
     * could break the composite constant value apart into per-column
     * constants, but for now it seems not worth the work.
     */
    if (rtf->funccolcount != 1)
        return jtnode;          /* definitely composite */
 
    /* If it has a coldeflist, it certainly returns RECORD */
    if (rtf->funccolnames != NIL)
        return jtnode;          /* must be a one-column RECORD type */
 
    functypclass = get_expr_result_type(rtf->funcexpr,
                                        &funcrettype,
                                        &tupdesc);
    if (functypclass != TYPEFUNC_SCALAR)
        return jtnode;          /* must be a one-column composite type */
 
    /* Create context for applying pullup_replace_vars */
    rvcontext.root = root;
    rvcontext.targetlist = list_make1(makeTargetEntry((Expr *) rtf->funcexpr,
                                                      1,    /* resno */
                                                      NULL, /* resname */
                                                      false));  /* resjunk */
    rvcontext.target_rte = rte;
    rvcontext.result_relation = 0;
 
    /*
     * Since this function was reduced to a Const, it doesn't contain any
     * lateral references, even if it's marked as LATERAL.  This means we
     * don't need to fill relids or nullinfo.
     */
    rvcontext.relids = NULL;
    rvcontext.nullinfo = NULL;
 
    rvcontext.outer_hasSubLinks = &parse->hasSubLinks;
    rvcontext.varno = ((RangeTblRef *) jtnode)->rtindex;
    /* this flag will be set below, if needed */
    rvcontext.wrap_option = REPLACE_WRAP_NONE;
    /* initialize cache array with indexes 0 .. length(tlist) */
    rvcontext.rv_cache = palloc0((list_length(rvcontext.targetlist) + 1) *
                                 sizeof(Node *));
 
    /*
     * If the parent query uses grouping sets, we need a PlaceHolderVar for
     * each expression of the subquery's targetlist items.  (See comments in
     * pull_up_simple_subquery().)
     */
    if (parse->groupingSets)
        rvcontext.wrap_option = REPLACE_WRAP_ALL;
 
    /*
     * Replace all of the top query's references to the RTE's output with
     * copies of the funcexpr, being careful not to replace any of the
     * jointree structure.
     */
    perform_pullup_replace_vars(root, &rvcontext,
                                containing_appendrel);
 
    /*
     * We don't need to bother with changing PlaceHolderVars in the parent
     * query.  Their references to the RT index are still good for now, and
     * will get removed later if we're able to drop the RTE_RESULT.
     */
 
    /*
     * Convert the RTE to be RTE_RESULT type, signifying that we don't need to
     * scan it anymore, and zero out RTE_FUNCTION-specific fields.  Also make
     * sure the RTE is not marked LATERAL, since elsewhere we don't expect
     * RTE_RESULTs to be LATERAL.
     */
    rte->rtekind = RTE_RESULT;
    rte->functions = NIL;
    rte->lateral = false;
 
    /*
     * We can reuse the RangeTblRef node.
     */
    return jtnode;
}
 
/*
 * is_simple_union_all
 *    Check a subquery to see if it's a simple UNION ALL.
 *
 * We require all the setops to be UNION ALL (no mixing) and there can't be
 * any datatype coercions involved, ie, all the leaf queries must emit the
 * same datatypes.
 */
static bool
is_simple_union_all(Query *subquery)
{
    SetOperationStmt *topop;
 
    /* Let's just make sure it's a valid subselect ... */
    if (!IsA(subquery, Query) ||
        subquery->commandType != CMD_SELECT)
        elog(ERROR, "subquery is bogus");
 
    /* Is it a set-operation query at all? */
    topop = castNode(SetOperationStmt, subquery->setOperations);
    if (!topop)
        return false;
 
    /* Can't handle ORDER BY, LIMIT/OFFSET, locking, or WITH */
    if (subquery->sortClause ||
        subquery->limitOffset ||
        subquery->limitCount ||
        subquery->rowMarks ||
        subquery->cteList)
        return false;
 
    /* Recursively check the tree of set operations */
    return is_simple_union_all_recurse((Node *) topop, subquery,
                                       topop->colTypes);
}
 
static bool
is_simple_union_all_recurse(Node *setOp, Query *setOpQuery, List *colTypes)
{
    /* Since this function recurses, it could be driven to stack overflow. */
    check_stack_depth();
 
    if (IsA(setOp, RangeTblRef))
    {
        RangeTblRef *rtr = (RangeTblRef *) setOp;
        RangeTblEntry *rte = rt_fetch(rtr->rtindex, setOpQuery->rtable);
        Query      *subquery = rte->subquery;
 
        Assert(subquery != NULL);
 
        /* Leaf nodes are OK if they match the toplevel column types */
        /* We don't have to compare typmods or collations here */
        return tlist_same_datatypes(subquery->targetList, colTypes, true);
    }
    else if (IsA(setOp, SetOperationStmt))
    {
        SetOperationStmt *op = (SetOperationStmt *) setOp;
 
        /* Must be UNION ALL */
        if (op->op != SETOP_UNION || !op->all)
            return false;
 
        /* Recurse to check inputs */
        return is_simple_union_all_recurse(op->larg, setOpQuery, colTypes) &&
            is_simple_union_all_recurse(op->rarg, setOpQuery, colTypes);
    }
    else
    {
        elog(ERROR, "unrecognized node type: %d",
             (int) nodeTag(setOp));
        return false;           /* keep compiler quiet */
    }
}
 
/*
 * is_safe_append_member
 *    Check a subquery that is a leaf of a UNION ALL appendrel to see if it's
 *    safe to pull up.
 */
static bool
is_safe_append_member(Query *subquery)
{
    FromExpr   *jtnode;
 
    /*
     * It's only safe to pull up the child if its jointree contains exactly
     * one RTE, else the AppendRelInfo data structure breaks. The one base RTE
     * could be buried in several levels of FromExpr, however.  Also, if the
     * child's jointree is completely empty, we can pull up because
     * pull_up_simple_subquery will insert a single RTE_RESULT RTE instead.
     *
     * Also, the child can't have any WHERE quals because there's no place to
     * put them in an appendrel.  (This is a bit annoying...) If we didn't
     * need to check this, we'd just test whether get_relids_in_jointree()
     * yields a singleton set, to be more consistent with the coding of
     * fix_append_rel_relids().
     */
    jtnode = subquery->jointree;
    Assert(IsA(jtnode, FromExpr));
    /* Check the completely-empty case */
    if (jtnode->fromlist == NIL && jtnode->quals == NULL)
        return true;
    /* Check the more general case */
    while (IsA(jtnode, FromExpr))
    {
        if (jtnode->quals != NULL)
            return false;
        if (list_length(jtnode->fromlist) != 1)
            return false;
        jtnode = linitial(jtnode->fromlist);
    }
    if (!IsA(jtnode, RangeTblRef))
        return false;
 
    return true;
}
 
/*
 * jointree_contains_lateral_outer_refs
 *      Check for disallowed lateral references in a jointree's quals
 *
 * If restricted is false, all level-1 Vars are allowed (but we still must
 * search the jointree, since it might contain outer joins below which there
 * will be restrictions).  If restricted is true, return true when any qual
 * in the jointree contains level-1 Vars coming from outside the rels listed
 * in safe_upper_varnos.
 */
static bool
jointree_contains_lateral_outer_refs(PlannerInfo *root, Node *jtnode,
                                     bool restricted,
                                     Relids safe_upper_varnos)
{
    if (jtnode == NULL)
        return false;
    if (IsA(jtnode, RangeTblRef))
        return false;
    else if (IsA(jtnode, FromExpr))
    {
        FromExpr   *f = (FromExpr *) jtnode;
        ListCell   *l;
 
        /* First, recurse to check child joins */
        foreach(l, f->fromlist)
        {
            if (jointree_contains_lateral_outer_refs(root,
                                                     lfirst(l),
                                                     restricted,
                                                     safe_upper_varnos))
                return true;
        }
 
        /* Then check the top-level quals */
        if (restricted &&
            !bms_is_subset(pull_varnos_of_level(root, f->quals, 1),
                           safe_upper_varnos))
            return true;
    }
    else if (IsA(jtnode, JoinExpr))
    {
        JoinExpr   *j = (JoinExpr *) jtnode;
 
        /*
         * If this is an outer join, we mustn't allow any upper lateral
         * references in or below it.
         */
        if (j->jointype != JOIN_INNER)
        {
            restricted = true;
            safe_upper_varnos = NULL;
        }
 
        /* Check the child joins */
        if (jointree_contains_lateral_outer_refs(root,
                                                 j->larg,
                                                 restricted,
                                                 safe_upper_varnos))
            return true;
        if (jointree_contains_lateral_outer_refs(root,
                                                 j->rarg,
                                                 restricted,
                                                 safe_upper_varnos))
            return true;
 
        /* Check the JOIN's qual clauses */
        if (restricted &&
            !bms_is_subset(pull_varnos_of_level(root, j->quals, 1),
                           safe_upper_varnos))
            return true;
    }
    else
        elog(ERROR, "unrecognized node type: %d",
             (int) nodeTag(jtnode));
    return false;
}
 
/*
 * Perform pullup_replace_vars everyplace it's needed in the query tree.
 *
 * Caller has already filled *rvcontext with data describing what to
 * substitute for Vars referencing the target subquery.  In addition
 * we need the identity of the containing appendrel if any.
 */
static void
perform_pullup_replace_vars(PlannerInfo *root,
                            pullup_replace_vars_context *rvcontext,
                            AppendRelInfo *containing_appendrel)
{
    Query      *parse = root->parse;
    ListCell   *lc;
 
    /*
     * If we are considering an appendrel child subquery (that is, a UNION ALL
     * member query that we're pulling up), then the only part of the upper
     * query that could reference the child yet is the translated_vars list of
     * the associated AppendRelInfo.  Furthermore, we do not want to force use
     * of PHVs in the AppendRelInfo --- there isn't any outer join between.
     */
    if (containing_appendrel)
    {
        ReplaceWrapOption save_wrap_option = rvcontext->wrap_option;
 
        rvcontext->wrap_option = REPLACE_WRAP_NONE;
        containing_appendrel->translated_vars = (List *)
            pullup_replace_vars((Node *) containing_appendrel->translated_vars,
                                rvcontext);
        rvcontext->wrap_option = save_wrap_option;
        return;
    }
 
    /*
     * Replace all of the top query's references to the subquery's outputs
     * with copies of the adjusted subtlist items, being careful not to
     * replace any of the jointree structure.  (This'd be a lot cleaner if we
     * could use query_tree_mutator.)  We have to use PHVs in the targetList,
     * returningList, and havingQual, since those are certainly above any
     * outer join.  replace_vars_in_jointree tracks its location in the
     * jointree and uses PHVs or not appropriately.
     */
    parse->targetList = (List *)
        pullup_replace_vars((Node *) parse->targetList, rvcontext);
    parse->returningList = (List *)
        pullup_replace_vars((Node *) parse->returningList, rvcontext);
 
    if (parse->onConflict)
    {
        parse->onConflict->onConflictSet = (List *)
            pullup_replace_vars((Node *) parse->onConflict->onConflictSet,
                                rvcontext);
        parse->onConflict->onConflictWhere =
            pullup_replace_vars(parse->onConflict->onConflictWhere,
                                rvcontext);
 
        /*
         * We assume ON CONFLICT's arbiterElems, arbiterWhere, exclRelTlist
         * can't contain any references to a subquery.
         */
    }
    if (parse->mergeActionList)
    {
        foreach(lc, parse->mergeActionList)
        {
            MergeAction *action = lfirst(lc);
 
            action->qual = pullup_replace_vars(action->qual, rvcontext);
            action->targetList = (List *)
                pullup_replace_vars((Node *) action->targetList, rvcontext);
        }
    }
    parse->mergeJoinCondition = pullup_replace_vars(parse->mergeJoinCondition,
                                                    rvcontext);
    replace_vars_in_jointree((Node *) parse->jointree, rvcontext);
    Assert(parse->setOperations == NULL);
    parse->havingQual = pullup_replace_vars(parse->havingQual, rvcontext);
 
    /*
     * Replace references in the translated_vars lists of appendrels.
     */
    foreach(lc, root->append_rel_list)
    {
        AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(lc);
 
        appinfo->translated_vars = (List *)
            pullup_replace_vars((Node *) appinfo->translated_vars, rvcontext);
    }
 
    /*
     * Replace references in the joinaliasvars lists of join RTEs and the
     * groupexprs list of group RTE.
     */
    foreach(lc, parse->rtable)
    {
        RangeTblEntry *otherrte = (RangeTblEntry *) lfirst(lc);
 
        if (otherrte->rtekind == RTE_JOIN)
            otherrte->joinaliasvars = (List *)
                pullup_replace_vars((Node *) otherrte->joinaliasvars,
                                    rvcontext);
        else if (otherrte->rtekind == RTE_GROUP)
            otherrte->groupexprs = (List *)
                pullup_replace_vars((Node *) otherrte->groupexprs,
                                    rvcontext);
    }
}
 
/*
 * Helper routine for perform_pullup_replace_vars: do pullup_replace_vars on
 * every expression in the jointree, without changing the jointree structure
 * itself.  Ugly, but there's no other way...
 */
static void
replace_vars_in_jointree(Node *jtnode,
                         pullup_replace_vars_context *context)
{
    if (jtnode == NULL)
        return;
    if (IsA(jtnode, RangeTblRef))
    {
        /*
         * If the RangeTblRef refers to a LATERAL subquery (that isn't the
         * same subquery we're pulling up), it might contain references to the
         * target subquery, which we must replace.  We drive this from the
         * jointree scan, rather than a scan of the rtable, so that we can
         * avoid processing no-longer-referenced RTEs.
         */
        int         varno = ((RangeTblRef *) jtnode)->rtindex;
 
        if (varno != context->varno)    /* ignore target subquery itself */
        {
            RangeTblEntry *rte = rt_fetch(varno, context->root->parse->rtable);
 
            Assert(rte != context->target_rte);
            if (rte->lateral)
            {
                switch (rte->rtekind)
                {
                    case RTE_RELATION:
                        /* shouldn't be marked LATERAL unless tablesample */
                        Assert(rte->tablesample);
                        rte->tablesample = (TableSampleClause *)
                            pullup_replace_vars((Node *) rte->tablesample,
                                                context);
                        break;
                    case RTE_SUBQUERY:
                        rte->subquery =
                            pullup_replace_vars_subquery(rte->subquery,
                                                         context);
                        break;
                    case RTE_FUNCTION:
                        rte->functions = (List *)
                            pullup_replace_vars((Node *) rte->functions,
                                                context);
                        break;
                    case RTE_TABLEFUNC:
                        rte->tablefunc = (TableFunc *)
                            pullup_replace_vars((Node *) rte->tablefunc,
                                                context);
                        break;
                    case RTE_VALUES:
                        rte->values_lists = (List *)
                            pullup_replace_vars((Node *) rte->values_lists,
                                                context);
                        break;
                    case RTE_JOIN:
                    case RTE_CTE:
                    case RTE_NAMEDTUPLESTORE:
                    case RTE_RESULT:
                    case RTE_GROUP:
                        /* these shouldn't be marked LATERAL */
                        Assert(false);
                        break;
                }
            }
        }
    }
    else if (IsA(jtnode, FromExpr))
    {
        FromExpr   *f = (FromExpr *) jtnode;
        ListCell   *l;
 
        foreach(l, f->fromlist)
            replace_vars_in_jointree(lfirst(l), context);
        f->quals = pullup_replace_vars(f->quals, context);
    }
    else if (IsA(jtnode, JoinExpr))
    {
        JoinExpr   *j = (JoinExpr *) jtnode;
        ReplaceWrapOption save_wrap_option = context->wrap_option;
 
        replace_vars_in_jointree(j->larg, context);
        replace_vars_in_jointree(j->rarg, context);
 
        /*
         * Use PHVs within the join quals of a full join for variable-free
         * expressions.  Otherwise, we cannot identify which side of the join
         * a pulled-up variable-free expression came from, which can lead to
         * failure to make a plan at all because none of the quals appear to
         * be mergeable or hashable conditions.
         */
        if (j->jointype == JOIN_FULL)
            context->wrap_option = REPLACE_WRAP_VARFREE;
 
        j->quals = pullup_replace_vars(j->quals, context);
 
        context->wrap_option = save_wrap_option;
    }
    else
        elog(ERROR, "unrecognized node type: %d",
             (int) nodeTag(jtnode));
}
 
/*
 * Apply pullup variable replacement throughout an expression tree
 *
 * Returns a modified copy of the tree, so this can't be used where we
 * need to do in-place replacement.
 */
static Node *
pullup_replace_vars(Node *expr, pullup_replace_vars_context *context)
{
    return replace_rte_variables(expr,
                                 context->varno, 0,
                                 pullup_replace_vars_callback,
                                 context,
                                 context->outer_hasSubLinks);
}
 
static Node *
pullup_replace_vars_callback(Var *var,
                             replace_rte_variables_context *context)
{
    pullup_replace_vars_context *rcon = (pullup_replace_vars_context *) context->callback_arg;
    int         varattno = var->varattno;
    bool        need_phv;
    Node       *newnode;
 
    /* System columns are not replaced. */
    if (varattno < InvalidAttrNumber)
        return (Node *) copyObject(var);
 
    /*
     * We need a PlaceHolderVar if the Var-to-be-replaced has nonempty
     * varnullingrels (unless we find below that the replacement expression is
     * a Var or PlaceHolderVar that we can just add the nullingrels to).  We
     * also need one if the caller has instructed us that certain expression
     * replacements need to be wrapped for identification purposes.
     */
    need_phv = (var->varnullingrels != NULL) ||
        (rcon->wrap_option != REPLACE_WRAP_NONE);
 
    /*
     * If PlaceHolderVars are needed, we cache the modified expressions in
     * rcon->rv_cache[].  This is not in hopes of any material speed gain
     * within this function, but to avoid generating identical PHVs with
     * different IDs.  That would result in duplicate evaluations at runtime,
     * and possibly prevent optimizations that rely on recognizing different
     * references to the same subquery output as being equal().  So it's worth
     * a bit of extra effort to avoid it.
     *
     * The cached items have phlevelsup = 0 and phnullingrels = NULL; we'll
     * copy them and adjust those values for this reference site below.
     */
    if (need_phv &&
        varattno >= InvalidAttrNumber &&
        varattno <= list_length(rcon->targetlist) &&
        rcon->rv_cache[varattno] != NULL)
    {
        /* Just copy the entry and fall through to adjust phlevelsup etc */
        newnode = copyObject(rcon->rv_cache[varattno]);
    }
    else
    {
        /*
         * Generate the replacement expression.  This takes care of expanding
         * wholerow references and dealing with non-default varreturningtype.
         */
        newnode = ReplaceVarFromTargetList(var,
                                           rcon->target_rte,
                                           rcon->targetlist,
                                           rcon->result_relation,
                                           REPLACEVARS_REPORT_ERROR,
                                           0);
 
        /* Insert PlaceHolderVar if needed */
        if (need_phv)
        {
            bool        wrap;
 
            if (rcon->wrap_option == REPLACE_WRAP_ALL)
            {
                /* Caller told us to wrap all expressions in a PlaceHolderVar */
                wrap = true;
            }
            else if (varattno == InvalidAttrNumber)
            {
                /*
                 * Insert PlaceHolderVar for whole-tuple reference.  Notice
                 * that we are wrapping one PlaceHolderVar around the whole
                 * RowExpr, rather than putting one around each element of the
                 * row.  This is because we need the expression to yield NULL,
                 * not ROW(NULL,NULL,...) when it is forced to null by an
                 * outer join.
                 */
                wrap = true;
            }
            else if (newnode && IsA(newnode, Var) &&
                     ((Var *) newnode)->varlevelsup == 0)
            {
                /*
                 * Simple Vars always escape being wrapped, unless they are
                 * lateral references to something outside the subquery being
                 * pulled up and the referenced rel is not under the same
                 * lowest nulling outer join.
                 */
                wrap = false;
                if (rcon->target_rte->lateral &&
                    !bms_is_member(((Var *) newnode)->varno, rcon->relids))
                {
                    nullingrel_info *nullinfo = rcon->nullinfo;
                    int         lvarno = ((Var *) newnode)->varno;
 
                    Assert(lvarno > 0 && lvarno <= nullinfo->rtlength);
                    if (!bms_is_subset(nullinfo->nullingrels[rcon->varno],
                                       nullinfo->nullingrels[lvarno]))
                        wrap = true;
                }
            }
            else if (newnode && IsA(newnode, PlaceHolderVar) &&
                     ((PlaceHolderVar *) newnode)->phlevelsup == 0)
            {
                /* The same rules apply for a PlaceHolderVar */
                wrap = false;
                if (rcon->target_rte->lateral &&
                    !bms_is_subset(((PlaceHolderVar *) newnode)->phrels,
                                   rcon->relids))
                {
                    nullingrel_info *nullinfo = rcon->nullinfo;
                    Relids      lvarnos = ((PlaceHolderVar *) newnode)->phrels;
                    int         lvarno;
 
                    lvarno = -1;
                    while ((lvarno = bms_next_member(lvarnos, lvarno)) >= 0)
                    {
                        Assert(lvarno > 0 && lvarno <= nullinfo->rtlength);
                        if (!bms_is_subset(nullinfo->nullingrels[rcon->varno],
                                           nullinfo->nullingrels[lvarno]))
                        {
                            wrap = true;
                            break;
                        }
                    }
                }
            }
            else
            {
                /*
                 * If the node contains Var(s) or PlaceHolderVar(s) of the
                 * subquery being pulled up, or of rels that are under the
                 * same lowest nulling outer join as the subquery, and does
                 * not contain any non-strict constructs, then instead of
                 * adding a PHV on top we can add the required nullingrels to
                 * those Vars/PHVs.  (This is fundamentally a generalization
                 * of the above cases for bare Vars and PHVs.)
                 *
                 * This test is somewhat expensive, but it avoids pessimizing
                 * the plan in cases where the nullingrels get removed again
                 * later by outer join reduction.
                 *
                 * Note that we don't force wrapping of expressions containing
                 * lateral references, so long as they also contain Vars/PHVs
                 * of the subquery, or of rels that are under the same lowest
                 * nulling outer join as the subquery.  This is okay because
                 * of the restriction to strict constructs: if those Vars/PHVs
                 * have been forced to NULL by an outer join then the end
                 * result of the expression will be NULL too, regardless of
                 * the lateral references.  So it's not necessary to force the
                 * expression to be evaluated below the outer join.  This can
                 * be a very valuable optimization, because it may allow us to
                 * avoid using a nested loop to pass the lateral reference
                 * down.
                 *
                 * This analysis could be tighter: in particular, a non-strict
                 * construct hidden within a lower-level PlaceHolderVar is not
                 * reason to add another PHV.  But for now it doesn't seem
                 * worth the code to be more exact.  This is also why it's
                 * preferable to handle bare PHVs in the above branch, rather
                 * than this branch.  We also prefer to handle bare Vars in a
                 * separate branch, as it's cheaper this way and parallels the
                 * handling of PHVs.
                 *
                 * For a LATERAL subquery, we have to check the actual var
                 * membership of the node, but if it's non-lateral then any
                 * level-zero var must belong to the subquery.
                 */
                bool        contain_nullable_vars = false;
 
                if (!rcon->target_rte->lateral)
                {
                    if (contain_vars_of_level(newnode, 0))
                        contain_nullable_vars = true;
                }
                else
                {
                    Relids      all_varnos;
 
                    all_varnos = pull_varnos(rcon->root, newnode);
                    if (bms_overlap(all_varnos, rcon->relids))
                        contain_nullable_vars = true;
                    else
                    {
                        nullingrel_info *nullinfo = rcon->nullinfo;
                        int         varno;
 
                        varno = -1;
                        while ((varno = bms_next_member(all_varnos, varno)) >= 0)
                        {
                            Assert(varno > 0 && varno <= nullinfo->rtlength);
                            if (bms_is_subset(nullinfo->nullingrels[rcon->varno],
                                              nullinfo->nullingrels[varno]))
                            {
                                contain_nullable_vars = true;
                                break;
                            }
                        }
                    }
                }
 
                if (contain_nullable_vars &&
                    !contain_nonstrict_functions(newnode))
                {
                    /* No wrap needed */
                    wrap = false;
                }
                else
                {
                    /* Else wrap it in a PlaceHolderVar */
                    wrap = true;
                }
            }
 
            if (wrap)
            {
                newnode = (Node *)
                    make_placeholder_expr(rcon->root,
                                          (Expr *) newnode,
                                          bms_make_singleton(rcon->varno));
 
                /*
                 * Cache it if possible (ie, if the attno is in range, which
                 * it probably always should be).
                 */
                if (varattno >= InvalidAttrNumber &&
                    varattno <= list_length(rcon->targetlist))
                    rcon->rv_cache[varattno] = copyObject(newnode);
            }
        }
    }
 
    /* Propagate any varnullingrels into the replacement expression */
    if (var->varnullingrels != NULL)
    {
        if (IsA(newnode, Var))
        {
            Var        *newvar = (Var *) newnode;
 
            Assert(newvar->varlevelsup == 0);
            newvar->varnullingrels = bms_add_members(newvar->varnullingrels,
                                                     var->varnullingrels);
        }
        else if (IsA(newnode, PlaceHolderVar))
        {
            PlaceHolderVar *newphv = (PlaceHolderVar *) newnode;
 
            Assert(newphv->phlevelsup == 0);
            newphv->phnullingrels = bms_add_members(newphv->phnullingrels,
                                                    var->varnullingrels);
        }
        else
        {
            /*
             * There should be Vars/PHVs within the expression that we can
             * modify.  Vars/PHVs of the subquery should have the full
             * var->varnullingrels added to them, but if there are lateral
             * references within the expression, those must be marked with
             * only the nullingrels that potentially apply to them.  (This
             * corresponds to the fact that the expression will now be
             * evaluated at the join level of the Var that we are replacing:
             * the lateral references may have bubbled up through fewer outer
             * joins than the subquery's Vars have.  Per the discussion above,
             * we'll still get the right answers.)  That relid set could be
             * different for different lateral relations, so we have to do
             * this work for each one.
             *
             * (Currently, the restrictions in is_simple_subquery() mean that
             * at most we have to remove the lowest outer join's relid from
             * the nullingrels of a lateral reference.  However, we might
             * relax those restrictions someday, so let's do this right.)
             */
            if (rcon->target_rte->lateral)
            {
                nullingrel_info *nullinfo = rcon->nullinfo;
                Relids      lvarnos;
                int         lvarno;
 
                /*
                 * Identify lateral varnos used within newnode.  We must do
                 * this before injecting var->varnullingrels into the tree.
                 */
                lvarnos = pull_varnos(rcon->root, newnode);
                lvarnos = bms_del_members(lvarnos, rcon->relids);
                /* For each one, add relevant nullingrels if any */
                lvarno = -1;
                while ((lvarno = bms_next_member(lvarnos, lvarno)) >= 0)
                {
                    Relids      lnullingrels;
 
                    Assert(lvarno > 0 && lvarno <= nullinfo->rtlength);
                    lnullingrels = bms_intersect(var->varnullingrels,
                                                 nullinfo->nullingrels[lvarno]);
                    if (!bms_is_empty(lnullingrels))
                        newnode = add_nulling_relids(newnode,
                                                     bms_make_singleton(lvarno),
                                                     lnullingrels);
                }
            }
 
            /* Finally, deal with Vars/PHVs of the subquery itself */
            newnode = add_nulling_relids(newnode,
                                         rcon->relids,
                                         var->varnullingrels);
            /* Assert we did put the varnullingrels into the expression */
            Assert(bms_is_subset(var->varnullingrels,
                                 pull_varnos(rcon->root, newnode)));
        }
    }
 
    /* Must adjust varlevelsup if replaced Var is within a subquery */
    if (var->varlevelsup > 0)
        IncrementVarSublevelsUp(newnode, var->varlevelsup, 0);
 
    return newnode;
}
 
/*
 * Apply pullup variable replacement to a subquery
 *
 * This needs to be different from pullup_replace_vars() because
 * replace_rte_variables will think that it shouldn't increment sublevels_up
 * before entering the Query; so we need to call it with sublevels_up == 1.
 */
static Query *
pullup_replace_vars_subquery(Query *query,
                             pullup_replace_vars_context *context)
{
    Assert(IsA(query, Query));
    return (Query *) replace_rte_variables((Node *) query,
                                           context->varno, 1,
                                           pullup_replace_vars_callback,
                                           context,
                                           NULL);
}
 
 
/*
 * flatten_simple_union_all
 *      Try to optimize top-level UNION ALL structure into an appendrel
 *
 * If a query's setOperations tree consists entirely of simple UNION ALL
 * operations, flatten it into an append relation, which we can process more
 * intelligently than the general setops case.  Otherwise, do nothing.
 *
 * In most cases, this can succeed only for a top-level query, because for a
 * subquery in FROM, the parent query's invocation of pull_up_subqueries would
 * already have flattened the UNION via pull_up_simple_union_all.  But there
 * are a few cases we can support here but not in that code path, for example
 * when the subquery also contains ORDER BY.
 */
void
flatten_simple_union_all(PlannerInfo *root)
{
    Query      *parse = root->parse;
    SetOperationStmt *topop;
    Node       *leftmostjtnode;
    int         leftmostRTI;
    RangeTblEntry *leftmostRTE;
    int         childRTI;
    RangeTblEntry *childRTE;
    RangeTblRef *rtr;
 
    /* Shouldn't be called unless query has setops */
    topop = castNode(SetOperationStmt, parse->setOperations);
    Assert(topop);
 
    /* Can't optimize away a recursive UNION */
    if (root->hasRecursion)
        return;
 
    /*
     * Recursively check the tree of set operations.  If not all UNION ALL
     * with identical column types, punt.
     */
    if (!is_simple_union_all_recurse((Node *) topop, parse, topop->colTypes))
        return;
 
    /*
     * Locate the leftmost leaf query in the setops tree.  The upper query's
     * Vars all refer to this RTE (see transformSetOperationStmt).
     */
    leftmostjtnode = topop->larg;
    while (leftmostjtnode && IsA(leftmostjtnode, SetOperationStmt))
        leftmostjtnode = ((SetOperationStmt *) leftmostjtnode)->larg;
    Assert(leftmostjtnode && IsA(leftmostjtnode, RangeTblRef));
    leftmostRTI = ((RangeTblRef *) leftmostjtnode)->rtindex;
    leftmostRTE = rt_fetch(leftmostRTI, parse->rtable);
    Assert(leftmostRTE->rtekind == RTE_SUBQUERY);
 
    /*
     * Make a copy of the leftmost RTE and add it to the rtable.  This copy
     * will represent the leftmost leaf query in its capacity as a member of
     * the appendrel.  The original will represent the appendrel as a whole.
     * (We must do things this way because the upper query's Vars have to be
     * seen as referring to the whole appendrel.)
     */
    childRTE = copyObject(leftmostRTE);
    parse->rtable = lappend(parse->rtable, childRTE);
    childRTI = list_length(parse->rtable);
 
    /* Modify the setops tree to reference the child copy */
    ((RangeTblRef *) leftmostjtnode)->rtindex = childRTI;
 
    /* Modify the formerly-leftmost RTE to mark it as an appendrel parent */
    leftmostRTE->inh = true;
 
    /*
     * Form a RangeTblRef for the appendrel, and insert it into FROM.  The top
     * Query of a setops tree should have had an empty FromClause initially.
     */
    rtr = makeNode(RangeTblRef);
    rtr->rtindex = leftmostRTI;
    Assert(parse->jointree->fromlist == NIL);
    parse->jointree->fromlist = list_make1(rtr);
 
    /*
     * Now pretend the query has no setops.  We must do this before trying to
     * do subquery pullup, because of Assert in pull_up_simple_subquery.
     */
    parse->setOperations = NULL;
 
    /*
     * Build AppendRelInfo information, and apply pull_up_subqueries to the
     * leaf queries of the UNION ALL.  (We must do that now because they
     * weren't previously referenced by the jointree, and so were missed by
     * the main invocation of pull_up_subqueries.)
     */
    pull_up_union_leaf_queries((Node *) topop, root, leftmostRTI, parse, 0);
}
 
 
/*
 * reduce_outer_joins
 *      Attempt to reduce outer joins to plain inner joins.
 *
 * The idea here is that given a query like
 *      SELECT ... FROM a LEFT JOIN b ON (...) WHERE b.y = 42;
 * we can reduce the LEFT JOIN to a plain JOIN if the "=" operator in WHERE
 * is strict.  The strict operator will always return NULL, causing the outer
 * WHERE to fail, on any row where the LEFT JOIN filled in NULLs for b's
 * columns.  Therefore, there's no need for the join to produce null-extended
 * rows in the first place --- which makes it a plain join not an outer join.
 * (This scenario may not be very likely in a query written out by hand, but
 * it's reasonably likely when pushing quals down into complex views.)
 *
 * More generally, an outer join can be reduced in strength if there is a
 * strict qual above it in the qual tree that constrains a Var from the
 * nullable side of the join to be non-null.  (For FULL joins this applies
 * to each side separately.)
 *
 * Another transformation we apply here is to recognize cases like
 *      SELECT ... FROM a LEFT JOIN b ON (a.x = b.y) WHERE b.y IS NULL;
 * If the join clause is strict for b.y, then only null-extended rows could
 * pass the upper WHERE, and we can conclude that what the query is really
 * specifying is an anti-semijoin.  We change the join type from JOIN_LEFT
 * to JOIN_ANTI.  The IS NULL clause then becomes redundant, and must be
 * removed to prevent bogus selectivity calculations, but we leave it to
 * distribute_qual_to_rels to get rid of such clauses.
 *
 * Also, we get rid of JOIN_RIGHT cases by flipping them around to become
 * JOIN_LEFT.  This saves some code here and in some later planner routines;
 * the main benefit is to reduce the number of jointypes that can appear in
 * SpecialJoinInfo nodes.  Note that we can still generate Paths and Plans
 * that use JOIN_RIGHT (or JOIN_RIGHT_ANTI) by switching the inputs again.
 *
 * To ease recognition of strict qual clauses, we require this routine to be
 * run after expression preprocessing (i.e., qual canonicalization and JOIN
 * alias-var expansion).
 */
void
reduce_outer_joins(PlannerInfo *root)
{
    reduce_outer_joins_pass1_state *state1;
    reduce_outer_joins_pass2_state state2;
    ListCell   *lc;
 
    /*
     * To avoid doing strictness checks on more quals than necessary, we want
     * to stop descending the jointree as soon as there are no outer joins
     * below our current point.  This consideration forces a two-pass process.
     * The first pass gathers information about which base rels appear below
     * each side of each join clause, and about whether there are outer
     * join(s) below each side of each join clause. The second pass examines
     * qual clauses and changes join types as it descends the tree.
     */
    state1 = reduce_outer_joins_pass1((Node *) root->parse->jointree);
 
    /* planner.c shouldn't have called me if no outer joins */
    if (state1 == NULL || !state1->contains_outer)
        elog(ERROR, "so where are the outer joins?");
 
    state2.inner_reduced = NULL;
    state2.partial_reduced = NIL;
 
    reduce_outer_joins_pass2((Node *) root->parse->jointree,
                             state1, &state2,
                             root, NULL, NIL);
 
    /*
     * If we successfully reduced the strength of any outer joins, we must
     * remove references to those joins as nulling rels.  This is handled as
     * an additional pass, for simplicity and because we can handle all
     * fully-reduced joins in a single pass over the parse tree.
     */
    if (!bms_is_empty(state2.inner_reduced))
    {
        root->parse = (Query *)
            remove_nulling_relids((Node *) root->parse,
                                  state2.inner_reduced,
                                  NULL);
        /* There could be references in the append_rel_list, too */
        root->append_rel_list = (List *)
            remove_nulling_relids((Node *) root->append_rel_list,
                                  state2.inner_reduced,
                                  NULL);
    }
 
    /*
     * Partially-reduced full joins have to be done one at a time, since
     * they'll each need a different setting of except_relids.
     */
    foreach(lc, state2.partial_reduced)
    {
        reduce_outer_joins_partial_state *statep = lfirst(lc);
        Relids      full_join_relids = bms_make_singleton(statep->full_join_rti);
 
        root->parse = (Query *)
            remove_nulling_relids((Node *) root->parse,
                                  full_join_relids,
                                  statep->unreduced_side);
        root->append_rel_list = (List *)
            remove_nulling_relids((Node *) root->append_rel_list,
                                  full_join_relids,
                                  statep->unreduced_side);
    }
}
 
/*
 * reduce_outer_joins_pass1 - phase 1 data collection
 *
 * Returns a state node describing the given jointree node.
 */
static reduce_outer_joins_pass1_state *
reduce_outer_joins_pass1(Node *jtnode)
{
    reduce_outer_joins_pass1_state *result;
 
    result = (reduce_outer_joins_pass1_state *)
        palloc(sizeof(reduce_outer_joins_pass1_state));
    result->relids = NULL;
    result->contains_outer = false;
    result->sub_states = NIL;
 
    if (jtnode == NULL)
        return result;
    if (IsA(jtnode, RangeTblRef))
    {
        int         varno = ((RangeTblRef *) jtnode)->rtindex;
 
        result->relids = bms_make_singleton(varno);
    }
    else if (IsA(jtnode, FromExpr))
    {
        FromExpr   *f = (FromExpr *) jtnode;
        ListCell   *l;
 
        foreach(l, f->fromlist)
        {
            reduce_outer_joins_pass1_state *sub_state;
 
            sub_state = reduce_outer_joins_pass1(lfirst(l));
            result->relids = bms_add_members(result->relids,
                                             sub_state->relids);
            result->contains_outer |= sub_state->contains_outer;
            result->sub_states = lappend(result->sub_states, sub_state);
        }
    }
    else if (IsA(jtnode, JoinExpr))
    {
        JoinExpr   *j = (JoinExpr *) jtnode;
        reduce_outer_joins_pass1_state *sub_state;
 
        /* join's own RT index is not wanted in result->relids */
        if (IS_OUTER_JOIN(j->jointype))
            result->contains_outer = true;
 
        sub_state = reduce_outer_joins_pass1(j->larg);
        result->relids = bms_add_members(result->relids,
                                         sub_state->relids);
        result->contains_outer |= sub_state->contains_outer;
        result->sub_states = lappend(result->sub_states, sub_state);
 
        sub_state = reduce_outer_joins_pass1(j->rarg);
        result->relids = bms_add_members(result->relids,
                                         sub_state->relids);
        result->contains_outer |= sub_state->contains_outer;
        result->sub_states = lappend(result->sub_states, sub_state);
    }
    else
        elog(ERROR, "unrecognized node type: %d",
             (int) nodeTag(jtnode));
    return result;
}
 
/*
 * reduce_outer_joins_pass2 - phase 2 processing
 *
 *  jtnode: current jointree node
 *  state1: state data collected by phase 1 for this node
 *  state2: where to accumulate info about successfully-reduced joins
 *  root: toplevel planner state
 *  nonnullable_rels: set of base relids forced non-null by upper quals
 *  forced_null_vars: multibitmapset of Vars forced null by upper quals
 *
 * Returns info in state2 about outer joins that were successfully simplified.
 * Joins that were fully reduced to inner joins are all added to
 * state2->inner_reduced.  If a full join is reduced to a left join,
 * it needs its own entry in state2->partial_reduced, since that will
 * require custom processing to remove only the correct nullingrel markers.
 */
static void
reduce_outer_joins_pass2(Node *jtnode,
                         reduce_outer_joins_pass1_state *state1,
                         reduce_outer_joins_pass2_state *state2,
                         PlannerInfo *root,
                         Relids nonnullable_rels,
                         List *forced_null_vars)
{
    /*
     * pass 2 should never descend as far as an empty subnode or base rel,
     * because it's only called on subtrees marked as contains_outer.
     */
    if (jtnode == NULL)
        elog(ERROR, "reached empty jointree");
    if (IsA(jtnode, RangeTblRef))
        elog(ERROR, "reached base rel");
    else if (IsA(jtnode, FromExpr))
    {
        FromExpr   *f = (FromExpr *) jtnode;
        ListCell   *l;
        ListCell   *s;
        Relids      pass_nonnullable_rels;
        List       *pass_forced_null_vars;
 
        /* Scan quals to see if we can add any constraints */
        pass_nonnullable_rels = find_nonnullable_rels(f->quals);
        pass_nonnullable_rels = bms_add_members(pass_nonnullable_rels,
                                                nonnullable_rels);
        pass_forced_null_vars = find_forced_null_vars(f->quals);
        pass_forced_null_vars = mbms_add_members(pass_forced_null_vars,
                                                 forced_null_vars);
        /* And recurse --- but only into interesting subtrees */
        Assert(list_length(f->fromlist) == list_length(state1->sub_states));
        forboth(l, f->fromlist, s, state1->sub_states)
        {
            reduce_outer_joins_pass1_state *sub_state = lfirst(s);
 
            if (sub_state->contains_outer)
                reduce_outer_joins_pass2(lfirst(l), sub_state,
                                         state2, root,
                                         pass_nonnullable_rels,
                                         pass_forced_null_vars);
        }
        bms_free(pass_nonnullable_rels);
        /* can't so easily clean up var lists, unfortunately */
    }
    else if (IsA(jtnode, JoinExpr))
    {
        JoinExpr   *j = (JoinExpr *) jtnode;
        int         rtindex = j->rtindex;
        JoinType    jointype = j->jointype;
        reduce_outer_joins_pass1_state *left_state = linitial(state1->sub_states);
        reduce_outer_joins_pass1_state *right_state = lsecond(state1->sub_states);
 
        /* Can we simplify this join? */
        switch (jointype)
        {
            case JOIN_INNER:
                break;
            case JOIN_LEFT:
                if (bms_overlap(nonnullable_rels, right_state->relids))
                    jointype = JOIN_INNER;
                break;
            case JOIN_RIGHT:
                if (bms_overlap(nonnullable_rels, left_state->relids))
                    jointype = JOIN_INNER;
                break;
            case JOIN_FULL:
                if (bms_overlap(nonnullable_rels, left_state->relids))
                {
                    if (bms_overlap(nonnullable_rels, right_state->relids))
                        jointype = JOIN_INNER;
                    else
                    {
                        jointype = JOIN_LEFT;
                        /* Also report partial reduction in state2 */
                        report_reduced_full_join(state2, rtindex,
                                                 right_state->relids);
                    }
                }
                else
                {
                    if (bms_overlap(nonnullable_rels, right_state->relids))
                    {
                        jointype = JOIN_RIGHT;
                        /* Also report partial reduction in state2 */
                        report_reduced_full_join(state2, rtindex,
                                                 left_state->relids);
                    }
                }
                break;
            case JOIN_SEMI:
            case JOIN_ANTI:
 
                /*
                 * These could only have been introduced by pull_up_sublinks,
                 * so there's no way that upper quals could refer to their
                 * righthand sides, and no point in checking.  We don't expect
                 * to see JOIN_RIGHT_SEMI or JOIN_RIGHT_ANTI yet.
                 */
                break;
            default:
                elog(ERROR, "unrecognized join type: %d",
                     (int) jointype);
                break;
        }
 
        /*
         * Convert JOIN_RIGHT to JOIN_LEFT.  Note that in the case where we
         * reduced JOIN_FULL to JOIN_RIGHT, this will mean the JoinExpr no
         * longer matches the internal ordering of any CoalesceExpr's built to
         * represent merged join variables.  We don't care about that at
         * present, but be wary of it ...
         */
        if (jointype == JOIN_RIGHT)
        {
            Node       *tmparg;
 
            tmparg = j->larg;
            j->larg = j->rarg;
            j->rarg = tmparg;
            jointype = JOIN_LEFT;
            right_state = linitial(state1->sub_states);
            left_state = lsecond(state1->sub_states);
        }
 
        /*
         * See if we can reduce JOIN_LEFT to JOIN_ANTI.  This is the case if
         * the join's own quals are strict for any var that was forced null by
         * higher qual levels.  NOTE: there are other ways that we could
         * detect an anti-join, in particular if we were to check whether Vars
         * coming from the RHS must be non-null because of table constraints.
         * That seems complicated and expensive though (in particular, one
         * would have to be wary of lower outer joins). For the moment this
         * seems sufficient.
         */
        if (jointype == JOIN_LEFT)
        {
            List       *nonnullable_vars;
            Bitmapset  *overlap;
 
            /* Find Vars in j->quals that must be non-null in joined rows */
            nonnullable_vars = find_nonnullable_vars(j->quals);
 
            /*
             * It's not sufficient to check whether nonnullable_vars and
             * forced_null_vars overlap: we need to know if the overlap
             * includes any RHS variables.
             */
            overlap = mbms_overlap_sets(nonnullable_vars, forced_null_vars);
            if (bms_overlap(overlap, right_state->relids))
                jointype = JOIN_ANTI;
        }
 
        /*
         * Apply the jointype change, if any, to both jointree node and RTE.
         * Also, if we changed an RTE to INNER, add its RTI to inner_reduced.
         */
        if (rtindex && jointype != j->jointype)
        {
            RangeTblEntry *rte = rt_fetch(rtindex, root->parse->rtable);
 
            Assert(rte->rtekind == RTE_JOIN);
            Assert(rte->jointype == j->jointype);
            rte->jointype = jointype;
            if (jointype == JOIN_INNER)
                state2->inner_reduced = bms_add_member(state2->inner_reduced,
                                                       rtindex);
        }
        j->jointype = jointype;
 
        /* Only recurse if there's more to do below here */
        if (left_state->contains_outer || right_state->contains_outer)
        {
            Relids      local_nonnullable_rels;
            List       *local_forced_null_vars;
            Relids      pass_nonnullable_rels;
            List       *pass_forced_null_vars;
 
            /*
             * If this join is (now) inner, we can add any constraints its
             * quals provide to those we got from above.  But if it is outer,
             * we can pass down the local constraints only into the nullable
             * side, because an outer join never eliminates any rows from its
             * non-nullable side.  Also, there is no point in passing upper
             * constraints into the nullable side, since if there were any
             * we'd have been able to reduce the join.  (In the case of upper
             * forced-null constraints, we *must not* pass them into the
             * nullable side --- they either applied here, or not.) The upshot
             * is that we pass either the local or the upper constraints,
             * never both, to the children of an outer join.
             *
             * Note that a SEMI join works like an inner join here: it's okay
             * to pass down both local and upper constraints.  (There can't be
             * any upper constraints affecting its inner side, but it's not
             * worth having a separate code path to avoid passing them.)
             *
             * At a FULL join we just punt and pass nothing down --- is it
             * possible to be smarter?
             */
            if (jointype != JOIN_FULL)
            {
                local_nonnullable_rels = find_nonnullable_rels(j->quals);
                local_forced_null_vars = find_forced_null_vars(j->quals);
                if (jointype == JOIN_INNER || jointype == JOIN_SEMI)
                {
                    /* OK to merge upper and local constraints */
                    local_nonnullable_rels = bms_add_members(local_nonnullable_rels,
                                                             nonnullable_rels);
                    local_forced_null_vars = mbms_add_members(local_forced_null_vars,
                                                              forced_null_vars);
                }
            }
            else
            {
                /* no use in calculating these */
                local_nonnullable_rels = NULL;
                local_forced_null_vars = NIL;
            }
 
            if (left_state->contains_outer)
            {
                if (jointype == JOIN_INNER || jointype == JOIN_SEMI)
                {
                    /* pass union of local and upper constraints */
                    pass_nonnullable_rels = local_nonnullable_rels;
                    pass_forced_null_vars = local_forced_null_vars;
                }
                else if (jointype != JOIN_FULL) /* ie, LEFT or ANTI */
                {
                    /* can't pass local constraints to non-nullable side */
                    pass_nonnullable_rels = nonnullable_rels;
                    pass_forced_null_vars = forced_null_vars;
                }
                else
                {
                    /* no constraints pass through JOIN_FULL */
                    pass_nonnullable_rels = NULL;
                    pass_forced_null_vars = NIL;
                }
                reduce_outer_joins_pass2(j->larg, left_state,
                                         state2, root,
                                         pass_nonnullable_rels,
                                         pass_forced_null_vars);
            }
 
            if (right_state->contains_outer)
            {
                if (jointype != JOIN_FULL)  /* ie, INNER/LEFT/SEMI/ANTI */
                {
                    /* pass appropriate constraints, per comment above */
                    pass_nonnullable_rels = local_nonnullable_rels;
                    pass_forced_null_vars = local_forced_null_vars;
                }
                else
                {
                    /* no constraints pass through JOIN_FULL */
                    pass_nonnullable_rels = NULL;
                    pass_forced_null_vars = NIL;
                }
                reduce_outer_joins_pass2(j->rarg, right_state,
                                         state2, root,
                                         pass_nonnullable_rels,
                                         pass_forced_null_vars);
            }
            bms_free(local_nonnullable_rels);
        }
    }
    else
        elog(ERROR, "unrecognized node type: %d",
             (int) nodeTag(jtnode));
}
 
/* Helper for reduce_outer_joins_pass2 */
static void
report_reduced_full_join(reduce_outer_joins_pass2_state *state2,
                         int rtindex, Relids relids)
{
    reduce_outer_joins_partial_state *statep;
 
    statep = palloc(sizeof(reduce_outer_joins_partial_state));
    statep->full_join_rti = rtindex;
    statep->unreduced_side = relids;
    state2->partial_reduced = lappend(state2->partial_reduced, statep);
}
 
 
/*
 * remove_useless_result_rtes
 *      Attempt to remove RTE_RESULT RTEs from the join tree.
 *      Also, elide single-child FromExprs where possible.
 *
 * We can remove RTE_RESULT entries from the join tree using the knowledge
 * that RTE_RESULT returns exactly one row and has no output columns.  Hence,
 * if one is inner-joined to anything else, we can delete it.  Optimizations
 * are also possible for some outer-join cases, as detailed below.
 *
 * This pass also replaces single-child FromExprs with their child node
 * where possible.  It's appropriate to do that here and not earlier because
 * RTE_RESULT removal might reduce a multiple-child FromExpr to have only one
 * child.  We can remove such a FromExpr if its quals are empty, or if it's
 * semantically valid to merge the quals into those of the parent node.
 * While removing unnecessary join tree nodes has some micro-efficiency value,
 * the real reason to do this is to eliminate cases where the nullable side of
 * an outer join node is a FromExpr whose single child is another outer join.
 * To correctly determine whether the two outer joins can commute,
 * deconstruct_jointree() must treat any quals of such a FromExpr as being
 * degenerate quals of the upper outer join.  The best way to do that is to
 * make them actually *be* quals of the upper join, by dropping the FromExpr
 * and hoisting the quals up into the upper join's quals.  (Note that there is
 * no hazard when the intermediate FromExpr has multiple children, since then
 * it represents an inner join that cannot commute with the upper outer join.)
 * As long as we have to do that, we might as well elide such FromExprs
 * everywhere.
 *
 * Some of these optimizations depend on recognizing empty (constant-true)
 * quals for FromExprs and JoinExprs.  That makes it useful to apply this
 * optimization pass after expression preprocessing, since that will have
 * eliminated constant-true quals, allowing more cases to be recognized as
 * optimizable.  What's more, the usual reason for an RTE_RESULT to be present
 * is that we pulled up a subquery or VALUES clause, thus very possibly
 * replacing Vars with constants, making it more likely that a qual can be
 * reduced to constant true.  Also, because some optimizations depend on
 * the outer-join type, it's best to have done reduce_outer_joins() first.
 *
 * A PlaceHolderVar referencing an RTE_RESULT RTE poses an obstacle to this
 * process: we must remove the RTE_RESULT's relid from the PHV's phrels, but
 * we must not reduce the phrels set to empty.  If that would happen, and
 * the RTE_RESULT is an immediate child of an outer join, we have to give up
 * and not remove the RTE_RESULT: there is noplace else to evaluate the
 * PlaceHolderVar.  (That is, in such cases the RTE_RESULT *does* have output
 * columns.)  But if the RTE_RESULT is an immediate child of an inner join,
 * we can usually change the PlaceHolderVar's phrels so as to evaluate it at
 * the inner join instead.  This is OK because we really only care that PHVs
 * are evaluated above or below the correct outer joins.  We can't, however,
 * postpone the evaluation of a PHV to above where it is used; so there are
 * some checks below on whether output PHVs are laterally referenced in the
 * other join input rel(s).
 *
 * We used to try to do this work as part of pull_up_subqueries() where the
 * potentially-optimizable cases get introduced; but it's way simpler, and
 * more effective, to do it separately.
 */
void
remove_useless_result_rtes(PlannerInfo *root)
{
    Relids      dropped_outer_joins = NULL;
    ListCell   *cell;
 
    /* Top level of jointree must always be a FromExpr */
    Assert(IsA(root->parse->jointree, FromExpr));
    /* Recurse ... */
    root->parse->jointree = (FromExpr *)
        remove_useless_results_recurse(root,
                                       (Node *) root->parse->jointree,
                                       NULL,
                                       &dropped_outer_joins);
    /* We should still have a FromExpr */
    Assert(IsA(root->parse->jointree, FromExpr));
 
    /*
     * If we removed any outer-join nodes from the jointree, run around and
     * remove references to those joins as nulling rels.  (There could be such
     * references in PHVs that we pulled up out of the original subquery that
     * the RESULT rel replaced.  This is kosher on the grounds that we now
     * know that such an outer join wouldn't really have nulled anything.)  We
     * don't do this during the main recursion, for simplicity and because we
     * can handle all such joins in a single pass over the parse tree.
     */
    if (!bms_is_empty(dropped_outer_joins))
    {
        root->parse = (Query *)
            remove_nulling_relids((Node *) root->parse,
                                  dropped_outer_joins,
                                  NULL);
        /* There could be references in the append_rel_list, too */
        root->append_rel_list = (List *)
            remove_nulling_relids((Node *) root->append_rel_list,
                                  dropped_outer_joins,
                                  NULL);
    }
 
    /*
     * Remove any PlanRowMark referencing an RTE_RESULT RTE.  We obviously
     * must do that for any RTE_RESULT that we just removed.  But one for a
     * RTE that we did not remove can be dropped anyway: since the RTE has
     * only one possible output row, there is no need for EPQ to mark and
     * restore that row.
     *
     * It's necessary, not optional, to remove the PlanRowMark for a surviving
     * RTE_RESULT RTE; otherwise we'll generate a whole-row Var for the
     * RTE_RESULT, which the executor has no support for.
     */
    foreach(cell, root->rowMarks)
    {
        PlanRowMark *rc = (PlanRowMark *) lfirst(cell);
 
        if (rt_fetch(rc->rti, root->parse->rtable)->rtekind == RTE_RESULT)
            root->rowMarks = foreach_delete_current(root->rowMarks, cell);
    }
}
 
/*
 * remove_useless_results_recurse
 *      Recursive guts of remove_useless_result_rtes.
 *
 * This recursively processes the jointree and returns a modified jointree.
 * In addition, the RT indexes of any removed outer-join nodes are added to
 * *dropped_outer_joins.
 *
 * jtnode is the current jointree node.  If it could be valid to merge
 * its quals into those of the parent node, parent_quals should point to
 * the parent's quals list; otherwise, pass NULL for parent_quals.
 * (Note that in some cases, parent_quals points to the quals of a parent
 * more than one level up in the tree.)
 */
static Node *
remove_useless_results_recurse(PlannerInfo *root, Node *jtnode,
                               Node **parent_quals,
                               Relids *dropped_outer_joins)
{
    Assert(jtnode != NULL);
    if (IsA(jtnode, RangeTblRef))
    {
        /* Can't immediately do anything with a RangeTblRef */
    }
    else if (IsA(jtnode, FromExpr))
    {
        FromExpr   *f = (FromExpr *) jtnode;
        Relids      result_relids = NULL;
        ListCell   *cell;
 
        /*
         * We can drop RTE_RESULT rels from the fromlist so long as at least
         * one child remains, since joining to a one-row table changes
         * nothing.  (But we can't drop a RTE_RESULT that computes PHV(s) that
         * are needed by some sibling.  The cleanup transformation below would
         * reassign the PHVs to be computed at the join, which is too late for
         * the sibling's use.)  The easiest way to mechanize this rule is to
         * modify the list in-place.
         */
        foreach(cell, f->fromlist)
        {
            Node       *child = (Node *) lfirst(cell);
            int         varno;
 
            /* Recursively transform child, allowing it to push up quals ... */
            child = remove_useless_results_recurse(root, child,
                                                   &f->quals,
                                                   dropped_outer_joins);
            /* ... and stick it back into the tree */
            lfirst(cell) = child;
 
            /*
             * If it's an RTE_RESULT with at least one sibling, and no sibling
             * references dependent PHVs, we can drop it.  We don't yet know
             * what the inner join's final relid set will be, so postpone
             * cleanup of PHVs etc till after this loop.
             */
            if (list_length(f->fromlist) > 1 &&
                (varno = get_result_relid(root, child)) != 0 &&
                !find_dependent_phvs_in_jointree(root, (Node *) f, varno))
            {
                f->fromlist = foreach_delete_current(f->fromlist, cell);
                result_relids = bms_add_member(result_relids, varno);
            }
        }
 
        /*
         * Clean up if we dropped any RTE_RESULT RTEs.  This is a bit
         * inefficient if there's more than one, but it seems better to
         * optimize the support code for the single-relid case.
         */
        if (result_relids)
        {
            int         varno = -1;
 
            while ((varno = bms_next_member(result_relids, varno)) >= 0)
                remove_result_refs(root, varno, (Node *) f);
        }
 
        /*
         * If the FromExpr now has only one child, see if we can elide it.
         * This is always valid if there are no quals, except at the top of
         * the jointree (since Query.jointree is required to point to a
         * FromExpr).  Otherwise, we can do it if we can push the quals up to
         * the parent node.
         *
         * Note: while it would not be terribly hard to generalize this
         * transformation to merge multi-child FromExprs into their parent
         * FromExpr, that risks making the parent join too expensive to plan.
         * We leave it to later processing to decide heuristically whether
         * that's a good idea.  Pulling up a single child is always OK,
         * however.
         */
        if (list_length(f->fromlist) == 1 &&
            f != root->parse->jointree &&
            (f->quals == NULL || parent_quals != NULL))
        {
            /*
             * Merge any quals up to parent.  They should be in implicit-AND
             * format by now, so we just need to concatenate lists.  Put the
             * child quals at the front, on the grounds that they should
             * nominally be evaluated earlier.
             */
            if (f->quals != NULL)
                *parent_quals = (Node *)
                    list_concat(castNode(List, f->quals),
                                castNode(List, *parent_quals));
            return (Node *) linitial(f->fromlist);
        }
    }
    else if (IsA(jtnode, JoinExpr))
    {
        JoinExpr   *j = (JoinExpr *) jtnode;
        int         varno;
 
        /*
         * First, recurse.  We can absorb pushed-up FromExpr quals from either
         * child into this node if the jointype is INNER, since then this is
         * equivalent to a FromExpr.  When the jointype is LEFT, we can absorb
         * quals from the RHS child into the current node, as they're
         * essentially degenerate quals of the outer join.  Moreover, if we've
         * been passed down a parent_quals pointer then we can allow quals of
         * the LHS child to be absorbed into the parent.  (This is important
         * to ensure we remove single-child FromExprs immediately below
         * commutable left joins.)  For other jointypes, we can't move child
         * quals up, or at least there's no particular reason to.
         */
        j->larg = remove_useless_results_recurse(root, j->larg,
                                                 (j->jointype == JOIN_INNER) ?
                                                 &j->quals :
                                                 (j->jointype == JOIN_LEFT) ?
                                                 parent_quals : NULL,
                                                 dropped_outer_joins);
        j->rarg = remove_useless_results_recurse(root, j->rarg,
                                                 (j->jointype == JOIN_INNER ||
                                                  j->jointype == JOIN_LEFT) ?
                                                 &j->quals : NULL,
                                                 dropped_outer_joins);
 
        /* Apply join-type-specific optimization rules */
        switch (j->jointype)
        {
            case JOIN_INNER:
 
                /*
                 * An inner join is equivalent to a FromExpr, so if either
                 * side was simplified to an RTE_RESULT rel, we can replace
                 * the join with a FromExpr with just the other side.
                 * Furthermore, we can elide that FromExpr according to the
                 * same rules as above.
                 *
                 * Just as in the FromExpr case, we can't simplify if the
                 * other input rel references any PHVs that are marked as to
                 * be evaluated at the RTE_RESULT rel, because we can't
                 * postpone their evaluation in that case.  But we only have
                 * to check this in cases where it's syntactically legal for
                 * the other input to have a LATERAL reference to the
                 * RTE_RESULT rel.  Only RHSes of inner and left joins are
                 * allowed to have such refs.
                 */
                if ((varno = get_result_relid(root, j->larg)) != 0 &&
                    !find_dependent_phvs_in_jointree(root, j->rarg, varno))
                {
                    remove_result_refs(root, varno, j->rarg);
                    if (j->quals != NULL && parent_quals == NULL)
                        jtnode = (Node *)
                            makeFromExpr(list_make1(j->rarg), j->quals);
                    else
                    {
                        /* Merge any quals up to parent */
                        if (j->quals != NULL)
                            *parent_quals = (Node *)
                                list_concat(castNode(List, j->quals),
                                            castNode(List, *parent_quals));
                        jtnode = j->rarg;
                    }
                }
                else if ((varno = get_result_relid(root, j->rarg)) != 0)
                {
                    remove_result_refs(root, varno, j->larg);
                    if (j->quals != NULL && parent_quals == NULL)
                        jtnode = (Node *)
                            makeFromExpr(list_make1(j->larg), j->quals);
                    else
                    {
                        /* Merge any quals up to parent */
                        if (j->quals != NULL)
                            *parent_quals = (Node *)
                                list_concat(castNode(List, j->quals),
                                            castNode(List, *parent_quals));
                        jtnode = j->larg;
                    }
                }
                break;
            case JOIN_LEFT:
 
                /*
                 * We can simplify this case if the RHS is an RTE_RESULT, with
                 * two different possibilities:
                 *
                 * If the qual is empty (JOIN ON TRUE), then the join can be
                 * strength-reduced to a plain inner join, since each LHS row
                 * necessarily has exactly one join partner.  So we can always
                 * discard the RHS, much as in the JOIN_INNER case above.
                 * (Again, the LHS could not contain a lateral reference to
                 * the RHS.)
                 *
                 * Otherwise, it's still true that each LHS row should be
                 * returned exactly once, and since the RHS returns no columns
                 * (unless there are PHVs that have to be evaluated there), we
                 * don't much care if it's null-extended or not.  So in this
                 * case also, we can just ignore the qual and discard the left
                 * join.
                 */
                if ((varno = get_result_relid(root, j->rarg)) != 0 &&
                    (j->quals == NULL ||
                     !find_dependent_phvs(root, varno)))
                {
                    remove_result_refs(root, varno, j->larg);
                    *dropped_outer_joins = bms_add_member(*dropped_outer_joins,
                                                          j->rtindex);
                    jtnode = j->larg;
                }
                break;
            case JOIN_SEMI:
 
                /*
                 * We may simplify this case if the RHS is an RTE_RESULT; the
                 * join qual becomes effectively just a filter qual for the
                 * LHS, since we should either return the LHS row or not.  The
                 * filter clause must go into a new FromExpr if we can't push
                 * it up to the parent.
                 *
                 * There is a fine point about PHVs that are supposed to be
                 * evaluated at the RHS.  Such PHVs could only appear in the
                 * semijoin's qual, since the rest of the query cannot
                 * reference any outputs of the semijoin's RHS.  Therefore,
                 * they can't actually go to null before being examined, and
                 * it'd be OK to just remove the PHV wrapping.  We don't have
                 * infrastructure for that, but remove_result_refs() will
                 * relabel them as to be evaluated at the LHS, which is fine.
                 *
                 * Also, we don't need to worry about removing traces of the
                 * join's rtindex, since it hasn't got one.
                 */
                if ((varno = get_result_relid(root, j->rarg)) != 0)
                {
                    Assert(j->rtindex == 0);
                    remove_result_refs(root, varno, j->larg);
                    if (j->quals != NULL && parent_quals == NULL)
                        jtnode = (Node *)
                            makeFromExpr(list_make1(j->larg), j->quals);
                    else
                    {
                        /* Merge any quals up to parent */
                        if (j->quals != NULL)
                            *parent_quals = (Node *)
                                list_concat(castNode(List, j->quals),
                                            castNode(List, *parent_quals));
                        jtnode = j->larg;
                    }
                }
                break;
            case JOIN_FULL:
            case JOIN_ANTI:
                /* We have no special smarts for these cases */
                break;
            default:
                /* Note: JOIN_RIGHT should be gone at this point */
                elog(ERROR, "unrecognized join type: %d",
                     (int) j->jointype);
                break;
        }
    }
    else
        elog(ERROR, "unrecognized node type: %d",
             (int) nodeTag(jtnode));
    return jtnode;
}
 
/*
 * get_result_relid
 *      If jtnode is a RangeTblRef for an RTE_RESULT RTE, return its relid;
 *      otherwise return 0.
 */
static int
get_result_relid(PlannerInfo *root, Node *jtnode)
{
    int         varno;
 
    if (!IsA(jtnode, RangeTblRef))
        return 0;
    varno = ((RangeTblRef *) jtnode)->rtindex;
    if (rt_fetch(varno, root->parse->rtable)->rtekind != RTE_RESULT)
        return 0;
    return varno;
}
 
/*
 * remove_result_refs
 *      Helper routine for dropping an unneeded RTE_RESULT RTE.
 *
 * This doesn't physically remove the RTE from the jointree, because that's
 * more easily handled in remove_useless_results_recurse.  What it does do
 * is the necessary cleanup in the rest of the tree: we must adjust any PHVs
 * that may reference the RTE.  Be sure to call this at a point where the
 * jointree is valid (no disconnected nodes).
 *
 * Note that we don't need to process the append_rel_list, since RTEs
 * referenced directly in the jointree won't be appendrel members.
 *
 * varno is the RTE_RESULT's relid.
 * newjtloc is the jointree location at which any PHVs referencing the
 * RTE_RESULT should be evaluated instead.
 */
static void
remove_result_refs(PlannerInfo *root, int varno, Node *newjtloc)
{
    /* Fix up PlaceHolderVars as needed */
    /* If there are no PHVs anywhere, we can skip this bit */
    if (root->glob->lastPHId != 0)
    {
        Relids      subrelids;
 
        subrelids = get_relids_in_jointree(newjtloc, true, false);
        Assert(!bms_is_empty(subrelids));
        substitute_phv_relids((Node *) root->parse, varno, subrelids);
        fix_append_rel_relids(root, varno, subrelids);
    }
 
    /*
     * We also need to remove any PlanRowMark referencing the RTE, but we
     * postpone that work until we return to remove_useless_result_rtes.
     */
}
 
 
/*
 * find_dependent_phvs - are there any PlaceHolderVars whose relids are
 * exactly the given varno?
 *
 * find_dependent_phvs should be used when we want to see if there are
 * any such PHVs anywhere in the Query.  Another use-case is to see if
 * a subtree of the join tree contains such PHVs; but for that, we have
 * to look not only at the join tree nodes themselves but at the
 * referenced RTEs.  For that, use find_dependent_phvs_in_jointree.
 */
 
typedef struct
{
    Relids      relids;
    int         sublevels_up;
} find_dependent_phvs_context;
 
static bool
find_dependent_phvs_walker(Node *node,
                           find_dependent_phvs_context *context)
{
    if (node == NULL)
        return false;
    if (IsA(node, PlaceHolderVar))
    {
        PlaceHolderVar *phv = (PlaceHolderVar *) node;
 
        if (phv->phlevelsup == context->sublevels_up &&
            bms_equal(context->relids, phv->phrels))
            return true;
        /* fall through to examine children */
    }
    if (IsA(node, Query))
    {
        /* Recurse into subselects */
        bool        result;
 
        context->sublevels_up++;
        result = query_tree_walker((Query *) node,
                                   find_dependent_phvs_walker,
                                   context, 0);
        context->sublevels_up--;
        return result;
    }
    /* Shouldn't need to handle most planner auxiliary nodes here */
    Assert(!IsA(node, SpecialJoinInfo));
    Assert(!IsA(node, PlaceHolderInfo));
    Assert(!IsA(node, MinMaxAggInfo));
 
    return expression_tree_walker(node, find_dependent_phvs_walker, context);
}
 
static bool
find_dependent_phvs(PlannerInfo *root, int varno)
{
    find_dependent_phvs_context context;
 
    /* If there are no PHVs anywhere, we needn't work hard */
    if (root->glob->lastPHId == 0)
        return false;
 
    context.relids = bms_make_singleton(varno);
    context.sublevels_up = 0;
 
    if (query_tree_walker(root->parse, find_dependent_phvs_walker, &context, 0))
        return true;
    /* The append_rel_list could be populated already, so check it too */
    if (expression_tree_walker((Node *) root->append_rel_list,
                               find_dependent_phvs_walker,
                               &context))
        return true;
    return false;
}
 
static bool
find_dependent_phvs_in_jointree(PlannerInfo *root, Node *node, int varno)
{
    find_dependent_phvs_context context;
    Relids      subrelids;
    int         relid;
 
    /* If there are no PHVs anywhere, we needn't work hard */
    if (root->glob->lastPHId == 0)
        return false;
 
    context.relids = bms_make_singleton(varno);
    context.sublevels_up = 0;
 
    /*
     * See if the jointree fragment itself contains references (in join quals)
     */
    if (find_dependent_phvs_walker(node, &context))
        return true;
 
    /*
     * Otherwise, identify the set of referenced RTEs (we can ignore joins,
     * since they should be flattened already, so their join alias lists no
     * longer matter), and tediously check each RTE.  We can ignore RTEs that
     * are not marked LATERAL, though, since they couldn't possibly contain
     * any cross-references to other RTEs.
     */
    subrelids = get_relids_in_jointree(node, false, false);
    relid = -1;
    while ((relid = bms_next_member(subrelids, relid)) >= 0)
    {
        RangeTblEntry *rte = rt_fetch(relid, root->parse->rtable);
 
        if (rte->lateral &&
            range_table_entry_walker(rte, find_dependent_phvs_walker, &context, 0))
            return true;
    }
 
    return false;
}
 
/*
 * substitute_phv_relids - adjust PlaceHolderVar relid sets after pulling up
 * a subquery or removing an RTE_RESULT jointree item
 *
 * Find any PlaceHolderVar nodes in the given tree that reference the
 * pulled-up relid, and change them to reference the replacement relid(s).
 *
 * NOTE: although this has the form of a walker, we cheat and modify the
 * nodes in-place.  This should be OK since the tree was copied by
 * pullup_replace_vars earlier.  Avoid scribbling on the original values of
 * the bitmapsets, though, because expression_tree_mutator doesn't copy those.
 */
 
typedef struct
{
    int         varno;
    int         sublevels_up;
    Relids      subrelids;
} substitute_phv_relids_context;
 
static bool
substitute_phv_relids_walker(Node *node,
                             substitute_phv_relids_context *context)
{
    if (node == NULL)
        return false;
    if (IsA(node, PlaceHolderVar))
    {
        PlaceHolderVar *phv = (PlaceHolderVar *) node;
 
        if (phv->phlevelsup == context->sublevels_up &&
            bms_is_member(context->varno, phv->phrels))
        {
            phv->phrels = bms_union(phv->phrels,
                                    context->subrelids);
            phv->phrels = bms_del_member(phv->phrels,
                                         context->varno);
            /* Assert we haven't broken the PHV */
            Assert(!bms_is_empty(phv->phrels));
        }
        /* fall through to examine children */
    }
    if (IsA(node, Query))
    {
        /* Recurse into subselects */
        bool        result;
 
        context->sublevels_up++;
        result = query_tree_walker((Query *) node,
                                   substitute_phv_relids_walker,
                                   context, 0);
        context->sublevels_up--;
        return result;
    }
    /* Shouldn't need to handle planner auxiliary nodes here */
    Assert(!IsA(node, SpecialJoinInfo));
    Assert(!IsA(node, AppendRelInfo));
    Assert(!IsA(node, PlaceHolderInfo));
    Assert(!IsA(node, MinMaxAggInfo));
 
    return expression_tree_walker(node, substitute_phv_relids_walker, context);
}
 
static void
substitute_phv_relids(Node *node, int varno, Relids subrelids)
{
    substitute_phv_relids_context context;
 
    context.varno = varno;
    context.sublevels_up = 0;
    context.subrelids = subrelids;
 
    /*
     * Must be prepared to start with a Query or a bare expression tree.
     */
    query_or_expression_tree_walker(node,
                                    substitute_phv_relids_walker,
                                    &context,
                                    0);
}
 
/*
 * fix_append_rel_relids: update RT-index fields of AppendRelInfo nodes
 *
 * When we pull up a subquery, any AppendRelInfo references to the subquery's
 * RT index have to be replaced by the substituted relid (and there had better
 * be only one).  We also need to apply substitute_phv_relids to their
 * translated_vars lists, since those might contain PlaceHolderVars.
 *
 * We assume we may modify the AppendRelInfo nodes in-place.
 */
static void
fix_append_rel_relids(PlannerInfo *root, int varno, Relids subrelids)
{
    ListCell   *l;
    int         subvarno = -1;
 
    /*
     * We only want to extract the member relid once, but we mustn't fail
     * immediately if there are multiple members; it could be that none of the
     * AppendRelInfo nodes refer to it.  So compute it on first use. Note that
     * bms_singleton_member will complain if set is not singleton.
     */
    foreach(l, root->append_rel_list)
    {
        AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(l);
 
        /* The parent_relid shouldn't ever be a pullup target */
        Assert(appinfo->parent_relid != varno);
 
        if (appinfo->child_relid == varno)
        {
            if (subvarno < 0)
                subvarno = bms_singleton_member(subrelids);
            appinfo->child_relid = subvarno;
        }
 
        /* Also fix up any PHVs in its translated vars */
        if (root->glob->lastPHId != 0)
            substitute_phv_relids((Node *) appinfo->translated_vars,
                                  varno, subrelids);
    }
}
 
/*
 * get_relids_in_jointree: get set of RT indexes present in a jointree
 *
 * Base-relation relids are always included in the result.
 * If include_outer_joins is true, outer-join RT indexes are included.
 * If include_inner_joins is true, inner-join RT indexes are included.
 *
 * Note that for most purposes in the planner, outer joins are included
 * in standard relid sets.  Setting include_inner_joins true is only
 * appropriate for special purposes during subquery flattening.
 */
Relids
get_relids_in_jointree(Node *jtnode, bool include_outer_joins,
                       bool include_inner_joins)
{
    Relids      result = NULL;
 
    if (jtnode == NULL)
        return result;
    if (IsA(jtnode, RangeTblRef))
    {
        int         varno = ((RangeTblRef *) jtnode)->rtindex;
 
        result = bms_make_singleton(varno);
    }
    else if (IsA(jtnode, FromExpr))
    {
        FromExpr   *f = (FromExpr *) jtnode;
        ListCell   *l;
 
        foreach(l, f->fromlist)
        {
            result = bms_join(result,
                              get_relids_in_jointree(lfirst(l),
                                                     include_outer_joins,
                                                     include_inner_joins));
        }
    }
    else if (IsA(jtnode, JoinExpr))
    {
        JoinExpr   *j = (JoinExpr *) jtnode;
 
        result = get_relids_in_jointree(j->larg,
                                        include_outer_joins,
                                        include_inner_joins);
        result = bms_join(result,
                          get_relids_in_jointree(j->rarg,
                                                 include_outer_joins,
                                                 include_inner_joins));
        if (j->rtindex)
        {
            if (j->jointype == JOIN_INNER)
            {
                if (include_inner_joins)
                    result = bms_add_member(result, j->rtindex);
            }
            else
            {
                if (include_outer_joins)
                    result = bms_add_member(result, j->rtindex);
            }
        }
    }
    else
        elog(ERROR, "unrecognized node type: %d",
             (int) nodeTag(jtnode));
    return result;
}
 
/*
 * get_relids_for_join: get set of base+OJ RT indexes making up a join
 */
Relids
get_relids_for_join(Query *query, int joinrelid)
{
    Node       *jtnode;
 
    jtnode = find_jointree_node_for_rel((Node *) query->jointree,
                                        joinrelid);
    if (!jtnode)
        elog(ERROR, "could not find join node %d", joinrelid);
    return get_relids_in_jointree(jtnode, true, false);
}
 
/*
 * find_jointree_node_for_rel: locate jointree node for a base or join RT index
 *
 * Returns NULL if not found
 */
static Node *
find_jointree_node_for_rel(Node *jtnode, int relid)
{
    if (jtnode == NULL)
        return NULL;
    if (IsA(jtnode, RangeTblRef))
    {
        int         varno = ((RangeTblRef *) jtnode)->rtindex;
 
        if (relid == varno)
            return jtnode;
    }
    else if (IsA(jtnode, FromExpr))
    {
        FromExpr   *f = (FromExpr *) jtnode;
        ListCell   *l;
 
        foreach(l, f->fromlist)
        {
            jtnode = find_jointree_node_for_rel(lfirst(l), relid);
            if (jtnode)
                return jtnode;
        }
    }
    else if (IsA(jtnode, JoinExpr))
    {
        JoinExpr   *j = (JoinExpr *) jtnode;
 
        if (relid == j->rtindex)
            return jtnode;
        jtnode = find_jointree_node_for_rel(j->larg, relid);
        if (jtnode)
            return jtnode;
        jtnode = find_jointree_node_for_rel(j->rarg, relid);
        if (jtnode)
            return jtnode;
    }
    else
        elog(ERROR, "unrecognized node type: %d",
             (int) nodeTag(jtnode));
    return NULL;
}
 
/*
 * get_nullingrels: collect info about which outer joins null which relations
 *
 * The result struct contains, for each leaf relation used in the query,
 * the set of relids of outer joins that potentially null that rel.
 */
static nullingrel_info *
get_nullingrels(Query *parse)
{
    nullingrel_info *result = palloc_object(nullingrel_info);
 
    result->rtlength = list_length(parse->rtable);
    result->nullingrels = palloc0_array(Relids, result->rtlength + 1);
    get_nullingrels_recurse((Node *) parse->jointree, NULL, result);
    return result;
}
 
/*
 * Recursive guts of get_nullingrels().
 *
 * Note: at any recursion level, the passed-down upper_nullingrels must be
 * treated as a constant, but it can be stored directly into *info
 * if we're at leaf level.  Upper recursion levels do not free their mutated
 * copies of the nullingrels, because those are probably referenced by
 * at least one leaf rel.
 */
static void
get_nullingrels_recurse(Node *jtnode, Relids upper_nullingrels,
                        nullingrel_info *info)
{
    if (jtnode == NULL)
        return;
    if (IsA(jtnode, RangeTblRef))
    {
        int         varno = ((RangeTblRef *) jtnode)->rtindex;
 
        Assert(varno > 0 && varno <= info->rtlength);
        info->nullingrels[varno] = upper_nullingrels;
    }
    else if (IsA(jtnode, FromExpr))
    {
        FromExpr   *f = (FromExpr *) jtnode;
        ListCell   *l;
 
        foreach(l, f->fromlist)
        {
            get_nullingrels_recurse(lfirst(l), upper_nullingrels, info);
        }
    }
    else if (IsA(jtnode, JoinExpr))
    {
        JoinExpr   *j = (JoinExpr *) jtnode;
        Relids      local_nullingrels;
 
        switch (j->jointype)
        {
            case JOIN_INNER:
                get_nullingrels_recurse(j->larg, upper_nullingrels, info);
                get_nullingrels_recurse(j->rarg, upper_nullingrels, info);
                break;
            case JOIN_LEFT:
            case JOIN_SEMI:
            case JOIN_ANTI:
                local_nullingrels = bms_add_member(bms_copy(upper_nullingrels),
                                                   j->rtindex);
                get_nullingrels_recurse(j->larg, upper_nullingrels, info);
                get_nullingrels_recurse(j->rarg, local_nullingrels, info);
                break;
            case JOIN_FULL:
                local_nullingrels = bms_add_member(bms_copy(upper_nullingrels),
                                                   j->rtindex);
                get_nullingrels_recurse(j->larg, local_nullingrels, info);
                get_nullingrels_recurse(j->rarg, local_nullingrels, info);
                break;
            case JOIN_RIGHT:
                local_nullingrels = bms_add_member(bms_copy(upper_nullingrels),
                                                   j->rtindex);
                get_nullingrels_recurse(j->larg, local_nullingrels, info);
                get_nullingrels_recurse(j->rarg, upper_nullingrels, info);
                break;
            default:
                elog(ERROR, "unrecognized join type: %d",
                     (int) j->jointype);
                break;
        }
    }
    else
        elog(ERROR, "unrecognized node type: %d",
             (int) nodeTag(jtnode));
}