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
 *      pull_up_sublinks
 *      inline_set_returning_functions
 *      pull_up_subqueries
 *      flatten_simple_union_all
 *      do expression preprocessing (including flattening JOIN alias vars)
 *      reduce_outer_joins
 *
 *
 * Portions Copyright (c) 1996-2013, 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 "catalog/pg_type.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/clauses.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/rewriteManip.h"


typedef struct pullup_replace_vars_context
{
    PlannerInfo *root;
    List       *targetlist;     /* tlist of subquery being pulled up */
    RangeTblEntry *target_rte;  /* RTE of subquery */
    bool       *outer_hasSubLinks;      /* -> outer query's hasSubLinks */
    int         varno;          /* varno of subquery */
    bool        need_phvs;      /* do we need PlaceHolderVars? */
    bool        wrap_non_vars;  /* do we need 'em on *all* non-Vars? */
    Node      **rv_cache;       /* cache for results with PHVs */
} pullup_replace_vars_context;

typedef struct reduce_outer_joins_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_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,
                           JoinExpr *lowest_nulling_outer_join,
                           AppendRelInfo *containing_appendrel);
static Node *pull_up_simple_subquery(PlannerInfo *root, Node *jtnode,
                        RangeTblEntry *rte,
                        JoinExpr *lowest_outer_join,
                        JoinExpr *lowest_nulling_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, Index newvarno,
                            List **translated_vars);
static bool is_simple_subquery(Query *subquery, RangeTblEntry *rte,
                   JoinExpr *lowest_outer_join);
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 void replace_vars_in_jointree(Node *jtnode,
                         pullup_replace_vars_context *context,
                         JoinExpr *lowest_nulling_outer_join);
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_state *reduce_outer_joins_pass1(Node *jtnode);
static void reduce_outer_joins_pass2(Node *jtnode,
                         reduce_outer_joins_state *state,
                         PlannerInfo *root,
                         Relids nonnullable_rels,
                         List *nonnullable_vars,
                         List *forced_null_vars);
static void substitute_multiple_relids(Node *node,
                           int varno, Relids subrelids);
static void fix_append_rel_relids(List *append_rel_list, int varno,
                      Relids subrelids);
static Node *find_jointree_node_for_rel(Node *jtnode, int relid);


/*
 * 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.  That means we need
 * to recursively search through explicit AND clauses, which are
 * probably only binary ANDs.  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)
{
    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 or JOIN_ANTI
         * nodes 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)
        {
            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 (not_clause(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 (and_clause(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;
}

/*
 * inline_set_returning_functions
 *      Attempt to "inline" set-returning functions in the FROM clause.
 *
 * 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.
 *
 * Like most of the planner, this feels free to scribble on its input data
 * structure.
 */
void
inline_set_returning_functions(PlannerInfo *root)
{
    ListCell   *rt;

    foreach(rt, root->parse->rtable)
    {
        RangeTblEntry *rte = (RangeTblEntry *) lfirst(rt);

        if (rte->rtekind == RTE_FUNCTION)
        {
            Query      *funcquery;

            /* Check safety of expansion, and expand if possible */
            funcquery = inline_set_returning_function(root, rte);
            if (funcquery)
            {
                /* Successful expansion, replace the rtable entry */
                rte->rtekind = RTE_SUBQUERY;
                rte->subquery = funcquery;
                rte->funcexpr = NULL;
                rte->funccoltypes = NIL;
                rte->funccoltypmods = NIL;
                rte->funccolcollations = NIL;
            }
        }
    }
}

/*
 * 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".
 *
 * This recursively processes the jointree and returns a modified jointree.
 */
Node *
pull_up_subqueries(PlannerInfo *root, Node *jtnode)
{
    /* Start off with no containing join nor appendrel */
    return pull_up_subqueries_recurse(root, jtnode, NULL, NULL, NULL);
}

/*
 * pull_up_subqueries_recurse
 *      Recursive guts of pull_up_subqueries.
 *
 * 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 this jointree node is within the nullable side of an outer join, then
 * lowest_nulling_outer_join references the lowest such JoinExpr node;
 * otherwise it is NULL.  This forces use of the PlaceHolderVar mechanism for
 * references to non-nullable targetlist items, but only for references above
 * that join.
 *
 * 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 not to
 * change the jointree structure while recursing: no nodes other than
 * subquery RangeTblRef entries will be replaced.  Also, we can't turn
 * pullup_replace_vars loose on the whole jointree, because it'll 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 and
 * lowest_nulling_outer_join as pointers rather than some more-indirect way
 * of identifying the lowest OJs.  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,
                           JoinExpr *lowest_nulling_outer_join,
                           AppendRelInfo *containing_appendrel)
{
    if (jtnode == NULL)
        return 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(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,
                                           lowest_nulling_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);

        /* Otherwise, do nothing at this node. */
    }
    else if (IsA(jtnode, FromExpr))
    {
        FromExpr   *f = (FromExpr *) jtnode;
        ListCell   *l;

        Assert(containing_appendrel == NULL);
        foreach(l, f->fromlist)
            lfirst(l) = pull_up_subqueries_recurse(root, lfirst(l),
                                                   lowest_outer_join,
                                                   lowest_nulling_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,
                                                     lowest_nulling_outer_join,
                                                     NULL);
                j->rarg = pull_up_subqueries_recurse(root, j->rarg,
                                                     lowest_outer_join,
                                                     lowest_nulling_outer_join,
                                                     NULL);
                break;
            case JOIN_LEFT:
            case JOIN_SEMI:
            case JOIN_ANTI:
                j->larg = pull_up_subqueries_recurse(root, j->larg,
                                                     j,
                                                     lowest_nulling_outer_join,
                                                     NULL);
                j->rarg = pull_up_subqueries_recurse(root, j->rarg,
                                                     j,
                                                     j,
                                                     NULL);
                break;
            case JOIN_FULL:
                j->larg = pull_up_subqueries_recurse(root, j->larg,
                                                     j,
                                                     j,
                                                     NULL);
                j->rarg = pull_up_subqueries_recurse(root, j->rarg,
                                                     j,
                                                     j,
                                                     NULL);
                break;
            case JOIN_RIGHT:
                j->larg = pull_up_subqueries_recurse(root, j->larg,
                                                     j,
                                                     j,
                                                     NULL);
                j->rarg = pull_up_subqueries_recurse(root, j->rarg,
                                                     j,
                                                     lowest_nulling_outer_join,
                                                     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,
                        JoinExpr *lowest_nulling_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;

    /*
     * Need a modifiable copy of the subquery to hack on.  Even if we didn't
     * sometimes choose not to pull up below, we must do this to avoid
     * problems if the same subquery is referenced from multiple jointree
     * items (which can't happen normally, but might after rule rewriting).
     */
    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->planner_cxt = CurrentMemoryContext;
    subroot->init_plans = NIL;
    subroot->cte_plan_ids = NIL;
    subroot->eq_classes = NIL;
    subroot->append_rel_list = NIL;
    subroot->rowMarks = NIL;
    subroot->hasRecursion = false;
    subroot->wt_param_id = -1;
    subroot->non_recursive_plan = NULL;

    /* No CTEs to worry about */
    Assert(subquery->cteList == NIL);

    /*
     * 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, inline any set-returning functions in its rangetable.
     */
    inline_set_returning_functions(subroot);

    /*
     * Recursively pull up the subquery's subqueries, so that
     * pull_up_subqueries' processing is complete for its jointree and
     * rangetable.
     *
     * Note: we should pass 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 say we aren't
     * handling an appendrel member.
     */
    subquery->jointree = (FromExpr *)
        pull_up_subqueries_recurse(subroot, (Node *) subquery->jointree,
                                   NULL, NULL, NULL);

    /*
     * 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(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;
    }

    /*
     * 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, but if we are under an outer join then
     * non-nullable items may have to be turned into PlaceHolderVars.  If we
     * are dealing with an appendrel member then anything that's not a simple
     * Var has to be turned into a PlaceHolderVar.  Set up appropriate context
     * data for pullup_replace_vars.
     */
    rvcontext.root = root;
    rvcontext.targetlist = subquery->targetList;
    rvcontext.target_rte = rte;
    rvcontext.outer_hasSubLinks = &parse->hasSubLinks;
    rvcontext.varno = varno;
    rvcontext.need_phvs = (lowest_nulling_outer_join != NULL ||
                           containing_appendrel != NULL);
    rvcontext.wrap_non_vars = (containing_appendrel != NULL);
    /* initialize cache array with indexes 0 .. length(tlist) */
    rvcontext.rv_cache = palloc0((list_length(subquery->targetList) + 1) *
                                 sizeof(Node *));

    /*
     * 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);
    replace_vars_in_jointree((Node *) parse->jointree, &rvcontext,
                             lowest_nulling_outer_join);
    Assert(parse->setOperations == NULL);
    parse->havingQual = pullup_replace_vars(parse->havingQual, &rvcontext);

    /*
     * Replace references in the translated_vars lists of appendrels. When
     * pulling up an appendrel member, we do not need PHVs in the list of the
     * parent appendrel --- there isn't any outer join between. Elsewhere, use
     * PHVs for safety.  (This analysis could be made tighter but it seems
     * unlikely to be worth much trouble.)
     */
    foreach(lc, root->append_rel_list)
    {
        AppendRelInfo *appinfo = (AppendRelInfo *) lfirst(lc);
        bool        save_need_phvs = rvcontext.need_phvs;

        if (appinfo == containing_appendrel)
            rvcontext.need_phvs = false;
        appinfo->translated_vars = (List *)
            pullup_replace_vars((Node *) appinfo->translated_vars, &rvcontext);
        rvcontext.need_phvs = save_need_phvs;
    }

    /*
     * Replace references in the joinaliasvars lists of join RTEs.
     *
     * You might think that we could avoid using PHVs for alias vars of joins
     * below lowest_nulling_outer_join, but that doesn't work because the
     * alias vars could be referenced above that join; we need the PHVs to be
     * present in such references after the alias vars get flattened.  (It
     * might be worth trying to be smarter here, someday.)
     */
    foreach(lc, parse->rtable)
    {
        RangeTblEntry *otherrte = (RangeTblEntry *) lfirst(lc);

        if (otherrte->rtekind == RTE_JOIN)
            otherrte->joinaliasvars = (List *)
                pullup_replace_vars((Node *) otherrte->joinaliasvars,
                                    &rvcontext);
    }

    /*
     * 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_SUBQUERY:
                case RTE_FUNCTION:
                case RTE_VALUES:
                    child_rte->lateral = true;
                    break;
                case RTE_RELATION:
                case RTE_JOIN:
                case RTE_CTE:
                    /* these can't contain any lateral references */
                    break;
            }
        }
    }

    /*
     * Now append the adjusted rtable entries to upper query. (We hold off
     * until after fixing the upper rtable entries; no point in running that
     * code on the subquery ones too.)
     */
    parse->rtable = list_concat(parse->rtable, subquery->rtable);

    /*
     * 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 (parse->hasSubLinks || root->glob->lastPHId != 0 ||
        root->append_rel_list)
    {
        Relids      subrelids;

        subrelids = get_relids_in_jointree((Node *) subquery->jointree, false);
        substitute_multiple_relids((Node *) parse, varno, subrelids);
        fix_append_rel_relids(root->append_rel_list, 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 or
     * LATERAL 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->lateral_info_list == NIL);
    Assert(subroot->lateral_info_list == NIL);
    Assert(root->placeholder_list == NIL);
    Assert(subroot->placeholder_list == NIL);

    /*
     * 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;

    /*
     * subquery won't be pulled up if it hasAggs or hasWindowFuncs, so no work
     * needed on those flags
     */

    /*
     * Return the adjusted subquery jointree to replace the RangeTblRef entry
     * in parent's jointree.
     */
    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 to parent rtable.
     */
    root->parse->rtable = list_concat(root->parse->rtable, rtable);

    /*
     * 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->translated_vars);
        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.)
         * 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.
         */
        rtr = makeNode(RangeTblRef);
        rtr->rtindex = childRTindex;
        (void) pull_up_subqueries_recurse(root, (Node *) rtr,
                                          NULL, 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.)
 */
static void
make_setop_translation_list(Query *query, Index newvarno,
                            List **translated_vars)
{
    List       *vars = NIL;
    ListCell   *l;

    foreach(l, query->targetList)
    {
        TargetEntry *tle = (TargetEntry *) lfirst(l);

        if (tle->resjunk)
            continue;

        vars = lappend(vars, makeVarFromTargetEntry(newvarno, tle));
    }

    *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(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 ||
        subquery->utilityStmt != NULL)
        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, 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->groupClause ||
        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, and we're below any outer join, and the
     * subquery contains lateral references to rels outside the outer join,
     * don't pull up.  Doing so would risk creating outer-join quals that
     * contain references to rels outside the outer join, which is a semantic
     * mess that doesn't seem worth addressing at the moment.
     */
    if (rte->lateral && lowest_outer_join != NULL)
    {
        Relids  lvarnos = pull_varnos_of_level((Node *) subquery, 1);
        Relids  jvarnos = get_relids_in_jointree((Node *) lowest_outer_join,
                                                 true);

        if (!bms_is_subset(lvarnos, jvarnos))
            return false;
    }

    /*
     * Don't pull up a subquery that has any set-returning functions in its
     * targetlist.  Otherwise we might well wind up inserting set-returning
     * functions into places where they mustn't go, such as quals of higher
     * queries.
     */
    if (expression_returns_set((Node *) subquery->targetList))
        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;

    /*
     * Hack: don't try to pull up a subquery with an empty jointree.
     * query_planner() will correctly generate a Result plan for a jointree
     * that's totally empty, but I don't think the right things happen if an
     * empty FromExpr appears lower down in a jointree.  It would pose a
     * problem for the PlaceHolderVar mechanism too, since we'd have no way to
     * identify where to evaluate a PHV coming out of the subquery. Not worth
     * working hard on this, just to collapse SubqueryScan/Result into Result;
     * especially since the SubqueryScan can often be optimized away by
     * setrefs.c anyway.
     */
    if (subquery->jointree->fromlist == NIL)
        return false;

    return true;
}

/*
 * 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 ||
        subquery->utilityStmt != NULL)
        elog(ERROR, "subquery is bogus");

    /* Is it a set-operation query at all? */
    topop = (SetOperationStmt *) subquery->setOperations;
    if (!topop)
        return false;
    Assert(IsA(topop, SetOperationStmt));

    /* 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)
{
    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, 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;
    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;
}

/*
 * Helper routine for pull_up_subqueries: do pullup_replace_vars on every
 * expression in the jointree, without changing the jointree structure itself.
 * Ugly, but there's no other way...
 *
 * If we are at or below lowest_nulling_outer_join, we can suppress use of
 * PlaceHolderVars wrapped around the replacement expressions.
 */
static void
replace_vars_in_jointree(Node *jtnode,
                         pullup_replace_vars_context *context,
                         JoinExpr *lowest_nulling_outer_join)
{
    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, for a couple of
         * reasons: we can avoid processing no-longer-referenced RTEs, and we
         * can use the appropriate setting of need_phvs depending on whether
         * the RTE is above possibly-nulling outer joins or not.
         */
        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_SUBQUERY:
                        rte->subquery =
                            pullup_replace_vars_subquery(rte->subquery,
                                                         context);
                        break;
                    case RTE_FUNCTION:
                        rte->funcexpr =
                            pullup_replace_vars(rte->funcexpr,
                                                context);
                        break;
                    case RTE_VALUES:
                        rte->values_lists = (List *)
                            pullup_replace_vars((Node *) rte->values_lists,
                                                context);
                        break;
                    case RTE_RELATION:
                    case RTE_JOIN:
                    case RTE_CTE:
                        /* 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,
                                     lowest_nulling_outer_join);
        f->quals = pullup_replace_vars(f->quals, context);
    }
    else if (IsA(jtnode, JoinExpr))
    {
        JoinExpr   *j = (JoinExpr *) jtnode;
        bool        save_need_phvs = context->need_phvs;

        if (j == lowest_nulling_outer_join)
        {
            /* no more PHVs in or below this join */
            context->need_phvs = false;
            lowest_nulling_outer_join = NULL;
        }
        replace_vars_in_jointree(j->larg, context, lowest_nulling_outer_join);
        replace_vars_in_jointree(j->rarg, context, lowest_nulling_outer_join);
        j->quals = pullup_replace_vars(j->quals, context);

        /*
         * We don't bother to update the colvars list, since it won't be used
         * again ...
         */
        context->need_phvs = save_need_phvs;
    }
    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,
                                 (void *) 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;
    Node       *newnode;

    /*
     * 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.
     */
    if (rcon->need_phvs &&
        varattno >= InvalidAttrNumber &&
        varattno <= list_length(rcon->targetlist) &&
        rcon->rv_cache[varattno] != NULL)
    {
        /* Just copy the entry and fall through to adjust its varlevelsup */
        newnode = copyObject(rcon->rv_cache[varattno]);
    }
    else if (varattno == InvalidAttrNumber)
    {
        /* Must expand whole-tuple reference into RowExpr */
        RowExpr    *rowexpr;
        List       *colnames;
        List       *fields;
        bool        save_need_phvs = rcon->need_phvs;
        int         save_sublevelsup = context->sublevels_up;

        /*
         * If generating an expansion for a var of a named rowtype (ie, this
         * is a plain relation RTE), then we must include dummy items for
         * dropped columns.  If the var is RECORD (ie, this is a JOIN), then
         * omit dropped columns. Either way, attach column names to the
         * RowExpr for use of ruleutils.c.
         *
         * In order to be able to cache the results, we always generate the
         * expansion with varlevelsup = 0, and then adjust if needed.
         */
        expandRTE(rcon->target_rte,
                  var->varno, 0 /* not varlevelsup */ , var->location,
                  (var->vartype != RECORDOID),
                  &colnames, &fields);
        /* Adjust the generated per-field Vars, but don't insert PHVs */
        rcon->need_phvs = false;
        context->sublevels_up = 0;      /* to match the expandRTE output */
        fields = (List *) replace_rte_variables_mutator((Node *) fields,
                                                        context);
        rcon->need_phvs = save_need_phvs;
        context->sublevels_up = save_sublevelsup;

        rowexpr = makeNode(RowExpr);
        rowexpr->args = fields;
        rowexpr->row_typeid = var->vartype;
        rowexpr->row_format = COERCE_IMPLICIT_CAST;
        rowexpr->colnames = colnames;
        rowexpr->location = var->location;
        newnode = (Node *) rowexpr;

        /*
         * Insert PlaceHolderVar if needed.  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.
         */
        if (rcon->need_phvs)
        {
            /* RowExpr is certainly not strict, so always need PHV */
            newnode = (Node *)
                make_placeholder_expr(rcon->root,
                                      (Expr *) newnode,
                                      bms_make_singleton(rcon->varno));
            /* cache it with the PHV, and with varlevelsup still zero */
            rcon->rv_cache[InvalidAttrNumber] = copyObject(newnode);
        }
    }
    else
    {
        /* Normal case referencing one targetlist element */
        TargetEntry *tle = get_tle_by_resno(rcon->targetlist, varattno);

        if (tle == NULL)        /* shouldn't happen */
            elog(ERROR, "could not find attribute %d in subquery targetlist",
                 varattno);

        /* Make a copy of the tlist item to return */
        newnode = copyObject(tle->expr);

        /* Insert PlaceHolderVar if needed */
        if (rcon->need_phvs)
        {
            bool        wrap;

            if (newnode && IsA(newnode, Var) &&
                ((Var *) newnode)->varlevelsup == 0)
            {
                /* Simple Vars always escape being wrapped */
                wrap = false;
            }
            else if (newnode && IsA(newnode, PlaceHolderVar) &&
                     ((PlaceHolderVar *) newnode)->phlevelsup == 0)
            {
                /* No need to wrap a PlaceHolderVar with another one, either */
                wrap = false;
            }
            else if (rcon->wrap_non_vars)
            {
                /* Wrap all non-Vars in a PlaceHolderVar */
                wrap = true;
            }
            else
            {
                /*
                 * If it contains a Var of current level, and does not contain
                 * any non-strict constructs, then it's certainly nullable so
                 * we don't need to insert a PlaceHolderVar.
                 *
                 * 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.
                 *
                 * Note: in future maybe we should insert a PlaceHolderVar
                 * anyway, if the tlist item is expensive to evaluate?
                 */
                if (contain_vars_of_level((Node *) newnode, 0) &&
                    !contain_nonstrict_functions((Node *) 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).  We can cache the value even if we
             * decided we didn't need a PHV, since this result will be
             * suitable for any request that has need_phvs.
             */
            if (varattno > InvalidAttrNumber &&
                varattno <= list_length(rcon->targetlist))
                rcon->rv_cache[varattno] = copyObject(newnode);
        }
    }

    /* Must adjust varlevelsup if tlist item is from higher query */
    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,
                                           (void *) 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 = (SetOperationStmt *) parse->setOperations;
    Assert(topop && IsA(topop, SetOperationStmt));

    /* 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,
 * but the main reason to do it is to not need to invent a JOIN_REVERSE_ANTI
 * join type.
 *
 * 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_state *state;

    /*
     * 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.
     */
    state = reduce_outer_joins_pass1((Node *) root->parse->jointree);

    /* planner.c shouldn't have called me if no outer joins */
    if (state == NULL || !state->contains_outer)
        elog(ERROR, "so where are the outer joins?");

    reduce_outer_joins_pass2((Node *) root->parse->jointree,
                             state, root, NULL, NIL, NIL);
}

/*
 * reduce_outer_joins_pass1 - phase 1 data collection
 *
 * Returns a state node describing the given jointree node.
 */
static reduce_outer_joins_state *
reduce_outer_joins_pass1(Node *jtnode)
{
    reduce_outer_joins_state *result;

    result = (reduce_outer_joins_state *)
        palloc(sizeof(reduce_outer_joins_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_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_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
 *  state: state data collected by phase 1 for this node
 *  root: toplevel planner state
 *  nonnullable_rels: set of base relids forced non-null by upper quals
 *  nonnullable_vars: list of Vars forced non-null by upper quals
 *  forced_null_vars: list of Vars forced null by upper quals
 */
static void
reduce_outer_joins_pass2(Node *jtnode,
                         reduce_outer_joins_state *state,
                         PlannerInfo *root,
                         Relids nonnullable_rels,
                         List *nonnullable_vars,
                         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_nonnullable_vars;
        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);
        /* NB: we rely on list_concat to not damage its second argument */
        pass_nonnullable_vars = find_nonnullable_vars(f->quals);
        pass_nonnullable_vars = list_concat(pass_nonnullable_vars,
                                            nonnullable_vars);
        pass_forced_null_vars = find_forced_null_vars(f->quals);
        pass_forced_null_vars = list_concat(pass_forced_null_vars,
                                            forced_null_vars);
        /* And recurse --- but only into interesting subtrees */
        Assert(list_length(f->fromlist) == list_length(state->sub_states));
        forboth(l, f->fromlist, s, state->sub_states)
        {
            reduce_outer_joins_state *sub_state = lfirst(s);

            if (sub_state->contains_outer)
                reduce_outer_joins_pass2(lfirst(l), sub_state, root,
                                         pass_nonnullable_rels,
                                         pass_nonnullable_vars,
                                         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_state *left_state = linitial(state->sub_states);
        reduce_outer_joins_state *right_state = lsecond(state->sub_states);
        List       *local_nonnullable_vars = NIL;
        bool        computed_local_nonnullable_vars = false;

        /* 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;
                }
                else
                {
                    if (bms_overlap(nonnullable_rels, right_state->relids))
                        jointype = JOIN_RIGHT;
                }
                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.
                 */
                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(state->sub_states);
            left_state = lsecond(state->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       *overlap;

            local_nonnullable_vars = find_nonnullable_vars(j->quals);
            computed_local_nonnullable_vars = true;

            /*
             * It's not sufficient to check whether local_nonnullable_vars and
             * forced_null_vars overlap: we need to know if the overlap
             * includes any RHS variables.
             */
            overlap = list_intersection(local_nonnullable_vars,
                                        forced_null_vars);
            if (overlap != NIL &&
                bms_overlap(pull_varnos((Node *) overlap),
                            right_state->relids))
                jointype = JOIN_ANTI;
        }

        /* Apply the jointype change, if any, to both jointree node and RTE */
        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;
        }
        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_nonnullable_vars;
            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);
                if (!computed_local_nonnullable_vars)
                    local_nonnullable_vars = find_nonnullable_vars(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_nonnullable_vars = list_concat(local_nonnullable_vars,
                                                         nonnullable_vars);
                    local_forced_null_vars = list_concat(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_nonnullable_vars = local_nonnullable_vars;
                    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_nonnullable_vars = nonnullable_vars;
                    pass_forced_null_vars = forced_null_vars;
                }
                else
                {
                    /* no constraints pass through JOIN_FULL */
                    pass_nonnullable_rels = NULL;
                    pass_nonnullable_vars = NIL;
                    pass_forced_null_vars = NIL;
                }
                reduce_outer_joins_pass2(j->larg, left_state, root,
                                         pass_nonnullable_rels,
                                         pass_nonnullable_vars,
                                         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_nonnullable_vars = local_nonnullable_vars;
                    pass_forced_null_vars = local_forced_null_vars;
                }
                else
                {
                    /* no constraints pass through JOIN_FULL */
                    pass_nonnullable_rels = NULL;
                    pass_nonnullable_vars = NIL;
                    pass_forced_null_vars = NIL;
                }
                reduce_outer_joins_pass2(j->rarg, right_state, root,
                                         pass_nonnullable_rels,
                                         pass_nonnullable_vars,
                                         pass_forced_null_vars);
            }
            bms_free(local_nonnullable_rels);
        }
    }
    else
        elog(ERROR, "unrecognized node type: %d",
             (int) nodeTag(jtnode));
}

/*
 * substitute_multiple_relids - adjust node relid sets after pulling up
 * a subquery
 *
 * 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_multiple_relids_context;

static bool
substitute_multiple_relids_walker(Node *node,
                                  substitute_multiple_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);
        }
        /* fall through to examine children */
    }
    if (IsA(node, Query))
    {
        /* Recurse into subselects */
        bool        result;

        context->sublevels_up++;
        result = query_tree_walker((Query *) node,
                                   substitute_multiple_relids_walker,
                                   (void *) context, 0);
        context->sublevels_up--;
        return result;
    }
    /* Shouldn't need to handle planner auxiliary nodes here */
    Assert(!IsA(node, SpecialJoinInfo));
    Assert(!IsA(node, LateralJoinInfo));
    Assert(!IsA(node, AppendRelInfo));
    Assert(!IsA(node, PlaceHolderInfo));
    Assert(!IsA(node, MinMaxAggInfo));

    return expression_tree_walker(node, substitute_multiple_relids_walker,
                                  (void *) context);
}

static void
substitute_multiple_relids(Node *node, int varno, Relids subrelids)
{
    substitute_multiple_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_multiple_relids_walker,
                                    (void *) &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_multiple_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(List *append_rel_list, 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, 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 finish fixups for its translated vars */
        substitute_multiple_relids((Node *) appinfo->translated_vars,
                                   varno, subrelids);
    }
}

/*
 * get_relids_in_jointree: get set of RT indexes present in a jointree
 *
 * If include_joins is true, join RT indexes are included; if false,
 * only base rels are included.
 */
Relids
get_relids_in_jointree(Node *jtnode, bool include_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_joins));
        }
    }
    else if (IsA(jtnode, JoinExpr))
    {
        JoinExpr   *j = (JoinExpr *) jtnode;

        result = get_relids_in_jointree(j->larg, include_joins);
        result = bms_join(result,
                          get_relids_in_jointree(j->rarg, include_joins));
        if (include_joins && j->rtindex)
            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 RT indexes making up a join
 */
Relids
get_relids_for_join(PlannerInfo *root, int joinrelid)
{
    Node       *jtnode;

    jtnode = find_jointree_node_for_rel((Node *) root->parse->jointree,
                                        joinrelid);
    if (!jtnode)
        elog(ERROR, "could not find join node %d", joinrelid);
    return get_relids_in_jointree(jtnode, 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;
}