Split the processing of INSERT/UPDATE/DELETE operations out of execMain.c.

[postgresql] / src / backend / optimizer / plan / subselect.c

/*-------------------------------------------------------------------------
 *
 * subselect.c
 *        Planning routines for subselects and parameters.
 *
 * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *        $PostgreSQL: pgsql/src/backend/optimizer/plan/subselect.c,v 1.154 2009/10/10 01:43:49 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "catalog/pg_operator.h"
#include "catalog/pg_type.h"
#include "executor/executor.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/cost.h"
#include "optimizer/planmain.h"
#include "optimizer/planner.h"
#include "optimizer/prep.h"
#include "optimizer/subselect.h"
#include "optimizer/var.h"
#include "parser/parse_relation.h"
#include "parser/parsetree.h"
#include "rewrite/rewriteManip.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"


typedef struct convert_testexpr_context
{
        PlannerInfo *root;
        List       *subst_nodes;        /* Nodes to substitute for Params */
} convert_testexpr_context;

typedef struct process_sublinks_context
{
        PlannerInfo *root;
        bool            isTopQual;
} process_sublinks_context;

typedef struct finalize_primnode_context
{
        PlannerInfo *root;
        Bitmapset  *paramids;           /* Non-local PARAM_EXEC paramids found */
} finalize_primnode_context;


static Node *build_subplan(PlannerInfo *root, Plan *plan, List *rtable,
                          SubLinkType subLinkType, Node *testexpr,
                          bool adjust_testexpr, bool unknownEqFalse);
static List *generate_subquery_params(PlannerInfo *root, List *tlist,
                                                 List **paramIds);
static List *generate_subquery_vars(PlannerInfo *root, List *tlist,
                                           Index varno);
static Node *convert_testexpr(PlannerInfo *root,
                                 Node *testexpr,
                                 List *subst_nodes);
static Node *convert_testexpr_mutator(Node *node,
                                                 convert_testexpr_context *context);
static bool subplan_is_hashable(Plan *plan);
static bool testexpr_is_hashable(Node *testexpr);
static bool hash_ok_operator(OpExpr *expr);
static bool simplify_EXISTS_query(Query *query);
static Query *convert_EXISTS_to_ANY(PlannerInfo *root, Query *subselect,
                                          Node **testexpr, List **paramIds);
static Node *replace_correlation_vars_mutator(Node *node, PlannerInfo *root);
static Node *process_sublinks_mutator(Node *node,
                                                 process_sublinks_context *context);
static Bitmapset *finalize_plan(PlannerInfo *root,
                          Plan *plan,
                          Bitmapset *valid_params);
static bool finalize_primnode(Node *node, finalize_primnode_context *context);


/*
 * Generate a Param node to replace the given Var,
 * which is expected to have varlevelsup > 0 (ie, it is not local).
 */
static Param *
replace_outer_var(PlannerInfo *root, Var *var)
{
        Param      *retval;
        ListCell   *ppl;
        PlannerParamItem *pitem;
        Index           abslevel;
        int                     i;

        Assert(var->varlevelsup > 0 && var->varlevelsup < root->query_level);
        abslevel = root->query_level - var->varlevelsup;

        /*
         * If there's already a paramlist entry for this same Var, just use it.
         * NOTE: in sufficiently complex querytrees, it is possible for the same
         * varno/abslevel to refer to different RTEs in different parts of the
         * parsetree, so that different fields might end up sharing the same Param
         * number.      As long as we check the vartype/typmod as well, I believe that
         * this sort of aliasing will cause no trouble.  The correct field should
         * get stored into the Param slot at execution in each part of the tree.
         */
        i = 0;
        foreach(ppl, root->glob->paramlist)
        {
                pitem = (PlannerParamItem *) lfirst(ppl);
                if (pitem->abslevel == abslevel && IsA(pitem->item, Var))
                {
                        Var                *pvar = (Var *) pitem->item;

                        if (pvar->varno == var->varno &&
                                pvar->varattno == var->varattno &&
                                pvar->vartype == var->vartype &&
                                pvar->vartypmod == var->vartypmod)
                                break;
                }
                i++;
        }

        if (!ppl)
        {
                /* Nope, so make a new one */
                var = (Var *) copyObject(var);
                var->varlevelsup = 0;

                pitem = makeNode(PlannerParamItem);
                pitem->item = (Node *) var;
                pitem->abslevel = abslevel;

                root->glob->paramlist = lappend(root->glob->paramlist, pitem);
                /* i is already the correct index for the new item */
        }

        retval = makeNode(Param);
        retval->paramkind = PARAM_EXEC;
        retval->paramid = i;
        retval->paramtype = var->vartype;
        retval->paramtypmod = var->vartypmod;
        retval->location = -1;

        return retval;
}

/*
 * Generate a Param node to replace the given Aggref
 * which is expected to have agglevelsup > 0 (ie, it is not local).
 */
static Param *
replace_outer_agg(PlannerInfo *root, Aggref *agg)
{
        Param      *retval;
        PlannerParamItem *pitem;
        Index           abslevel;
        int                     i;

        Assert(agg->agglevelsup > 0 && agg->agglevelsup < root->query_level);
        abslevel = root->query_level - agg->agglevelsup;

        /*
         * It does not seem worthwhile to try to match duplicate outer aggs. Just
         * make a new slot every time.
         */
        agg = (Aggref *) copyObject(agg);
        IncrementVarSublevelsUp((Node *) agg, -((int) agg->agglevelsup), 0);
        Assert(agg->agglevelsup == 0);

        pitem = makeNode(PlannerParamItem);
        pitem->item = (Node *) agg;
        pitem->abslevel = abslevel;

        root->glob->paramlist = lappend(root->glob->paramlist, pitem);
        i = list_length(root->glob->paramlist) - 1;

        retval = makeNode(Param);
        retval->paramkind = PARAM_EXEC;
        retval->paramid = i;
        retval->paramtype = agg->aggtype;
        retval->paramtypmod = -1;
        retval->location = -1;

        return retval;
}

/*
 * Generate a new Param node that will not conflict with any other.
 *
 * This is used to allocate PARAM_EXEC slots for subplan outputs.
 */
static Param *
generate_new_param(PlannerInfo *root, Oid paramtype, int32 paramtypmod)
{
        Param      *retval;
        PlannerParamItem *pitem;

        retval = makeNode(Param);
        retval->paramkind = PARAM_EXEC;
        retval->paramid = list_length(root->glob->paramlist);
        retval->paramtype = paramtype;
        retval->paramtypmod = paramtypmod;
        retval->location = -1;

        pitem = makeNode(PlannerParamItem);
        pitem->item = (Node *) retval;
        pitem->abslevel = root->query_level;

        root->glob->paramlist = lappend(root->glob->paramlist, pitem);

        return retval;
}

/*
 * Assign a (nonnegative) PARAM_EXEC ID for a recursive query's worktable.
 */
int
SS_assign_worktable_param(PlannerInfo *root)
{
        Param      *param;

        /* We generate a Param of datatype INTERNAL */
        param = generate_new_param(root, INTERNALOID, -1);
        /* ... but the caller only cares about its ID */
        return param->paramid;
}

/*
 * Get the datatype of the first column of the plan's output.
 *
 * This is stored for ARRAY_SUBLINK execution and for exprType()/exprTypmod(),
 * which have no way to get at the plan associated with a SubPlan node.
 * We really only need the info for EXPR_SUBLINK and ARRAY_SUBLINK subplans,
 * but for consistency we save it always.
 */
static void
get_first_col_type(Plan *plan, Oid *coltype, int32 *coltypmod)
{
        /* In cases such as EXISTS, tlist might be empty; arbitrarily use VOID */
        if (plan->targetlist)
        {
                TargetEntry *tent = (TargetEntry *) linitial(plan->targetlist);

                Assert(IsA(tent, TargetEntry));
                if (!tent->resjunk)
                {
                        *coltype = exprType((Node *) tent->expr);
                        *coltypmod = exprTypmod((Node *) tent->expr);
                        return;
                }
        }
        *coltype = VOIDOID;
        *coltypmod = -1;
}

/*
 * Convert a SubLink (as created by the parser) into a SubPlan.
 *
 * We are given the SubLink's contained query, type, and testexpr.  We are
 * also told if this expression appears at top level of a WHERE/HAVING qual.
 *
 * Note: we assume that the testexpr has been AND/OR flattened (actually,
 * it's been through eval_const_expressions), but not converted to
 * implicit-AND form; and any SubLinks in it should already have been
 * converted to SubPlans.  The subquery is as yet untouched, however.
 *
 * The result is whatever we need to substitute in place of the SubLink
 * node in the executable expression.  This will be either the SubPlan
 * node (if we have to do the subplan as a subplan), or a Param node
 * representing the result of an InitPlan, or a row comparison expression
 * tree containing InitPlan Param nodes.
 */
static Node *
make_subplan(PlannerInfo *root, Query *orig_subquery, SubLinkType subLinkType,
                         Node *testexpr, bool isTopQual)
{
        Query      *subquery;
        bool            simple_exists = false;
        double          tuple_fraction;
        Plan       *plan;
        PlannerInfo *subroot;
        Node       *result;

        /*
         * Copy the source Query node.  This is a quick and dirty kluge to resolve
         * the fact that the parser can generate trees with multiple links to the
         * same sub-Query node, but the planner wants to scribble on the Query.
         * Try to clean this up when we do querytree redesign...
         */
        subquery = (Query *) copyObject(orig_subquery);

        /*
         * If it's an EXISTS subplan, we might be able to simplify it.
         */
        if (subLinkType == EXISTS_SUBLINK)
                simple_exists = simplify_EXISTS_query(subquery);

        /*
         * For an EXISTS subplan, tell lower-level planner to expect that only the
         * first tuple will be retrieved.  For ALL and ANY subplans, we will be
         * able to stop evaluating if the test condition fails or matches, so very
         * often not all the tuples will be retrieved; for lack of a better idea,
         * specify 50% retrieval.  For EXPR and ROWCOMPARE subplans, use default
         * behavior (we're only expecting one row out, anyway).
         *
         * NOTE: if you change these numbers, also change cost_subplan() in
         * path/costsize.c.
         *
         * XXX If an ANY subplan is uncorrelated, build_subplan may decide to hash
         * its output.  In that case it would've been better to specify full
         * retrieval.  At present, however, we can only check hashability after
         * we've made the subplan :-(.  (Determining whether it'll fit in work_mem
         * is the really hard part.)  Therefore, we don't want to be too
         * optimistic about the percentage of tuples retrieved, for fear of
         * selecting a plan that's bad for the materialization case.
         */
        if (subLinkType == EXISTS_SUBLINK)
                tuple_fraction = 1.0;   /* just like a LIMIT 1 */
        else if (subLinkType == ALL_SUBLINK ||
                         subLinkType == ANY_SUBLINK)
                tuple_fraction = 0.5;   /* 50% */
        else
                tuple_fraction = 0.0;   /* default behavior */

        /*
         * Generate the plan for the subquery.
         */
        plan = subquery_planner(root->glob, subquery,
                                                        root,
                                                        false, tuple_fraction,
                                                        &subroot);

        /* And convert to SubPlan or InitPlan format. */
        result = build_subplan(root, plan, subroot->parse->rtable,
                                                   subLinkType, testexpr, true, isTopQual);

        /*
         * If it's a correlated EXISTS with an unimportant targetlist, we might be
         * able to transform it to the equivalent of an IN and then implement it
         * by hashing.  We don't have enough information yet to tell which way is
         * likely to be better (it depends on the expected number of executions of
         * the EXISTS qual, and we are much too early in planning the outer query
         * to be able to guess that).  So we generate both plans, if possible, and
         * leave it to the executor to decide which to use.
         */
        if (simple_exists && IsA(result, SubPlan))
        {
                Node       *newtestexpr;
                List       *paramIds;

                /* Make a second copy of the original subquery */
                subquery = (Query *) copyObject(orig_subquery);
                /* and re-simplify */
                simple_exists = simplify_EXISTS_query(subquery);
                Assert(simple_exists);
                /* See if it can be converted to an ANY query */
                subquery = convert_EXISTS_to_ANY(root, subquery,
                                                                                 &newtestexpr, &paramIds);
                if (subquery)
                {
                        /* Generate the plan for the ANY subquery; we'll need all rows */
                        plan = subquery_planner(root->glob, subquery,
                                                                        root,
                                                                        false, 0.0,
                                                                        &subroot);

                        /* Now we can check if it'll fit in work_mem */
                        if (subplan_is_hashable(plan))
                        {
                                SubPlan    *hashplan;
                                AlternativeSubPlan *asplan;

                                /* OK, convert to SubPlan format. */
                                hashplan = (SubPlan *) build_subplan(root, plan,
                                                                                                         subroot->parse->rtable,
                                                                                                         ANY_SUBLINK, newtestexpr,
                                                                                                         false, true);
                                /* Check we got what we expected */
                                Assert(IsA(hashplan, SubPlan));
                                Assert(hashplan->parParam == NIL);
                                Assert(hashplan->useHashTable);
                                /* build_subplan won't have filled in paramIds */
                                hashplan->paramIds = paramIds;

                                /* Leave it to the executor to decide which plan to use */
                                asplan = makeNode(AlternativeSubPlan);
                                asplan->subplans = list_make2(result, hashplan);
                                result = (Node *) asplan;
                        }
                }
        }

        return result;
}

/*
 * Build a SubPlan node given the raw inputs --- subroutine for make_subplan
 *
 * Returns either the SubPlan, or an expression using initplan output Params,
 * as explained in the comments for make_subplan.
 */
static Node *
build_subplan(PlannerInfo *root, Plan *plan, List *rtable,
                          SubLinkType subLinkType, Node *testexpr,
                          bool adjust_testexpr, bool unknownEqFalse)
{
        Node       *result;
        SubPlan    *splan;
        bool            isInitPlan;
        Bitmapset  *tmpset;
        int                     paramid;

        /*
         * Initialize the SubPlan node.  Note plan_id, plan_name, and cost fields
         * are set further down.
         */
        splan = makeNode(SubPlan);
        splan->subLinkType = subLinkType;
        splan->testexpr = NULL;
        splan->paramIds = NIL;
        get_first_col_type(plan, &splan->firstColType, &splan->firstColTypmod);
        splan->useHashTable = false;
        splan->unknownEqFalse = unknownEqFalse;
        splan->setParam = NIL;
        splan->parParam = NIL;
        splan->args = NIL;

        /*
         * Make parParam and args lists of param IDs and expressions that current
         * query level will pass to this child plan.
         */
        tmpset = bms_copy(plan->extParam);
        while ((paramid = bms_first_member(tmpset)) >= 0)
        {
                PlannerParamItem *pitem = list_nth(root->glob->paramlist, paramid);

                if (pitem->abslevel == root->query_level)
                {
                        Node       *arg;

                        /*
                         * The Var or Aggref has already been adjusted to have the correct
                         * varlevelsup or agglevelsup.  We probably don't even need to
                         * copy it again, but be safe.
                         */
                        arg = copyObject(pitem->item);

                        /*
                         * If it's an Aggref, its arguments might contain SubLinks, which
                         * have not yet been processed.  Do that now.
                         */
                        if (IsA(arg, Aggref))
                                arg = SS_process_sublinks(root, arg, false);

                        splan->parParam = lappend_int(splan->parParam, paramid);
                        splan->args = lappend(splan->args, arg);
                }
        }
        bms_free(tmpset);

        /*
         * Un-correlated or undirect correlated plans of EXISTS, EXPR, ARRAY, or
         * ROWCOMPARE types can be used as initPlans.  For EXISTS, EXPR, or ARRAY,
         * we just produce a Param referring to the result of evaluating the
         * initPlan.  For ROWCOMPARE, we must modify the testexpr tree to contain
         * PARAM_EXEC Params instead of the PARAM_SUBLINK Params emitted by the
         * parser.
         */
        if (splan->parParam == NIL && subLinkType == EXISTS_SUBLINK)
        {
                Param      *prm;

                Assert(testexpr == NULL);
                prm = generate_new_param(root, BOOLOID, -1);
                splan->setParam = list_make1_int(prm->paramid);
                isInitPlan = true;
                result = (Node *) prm;
        }
        else if (splan->parParam == NIL && subLinkType == EXPR_SUBLINK)
        {
                TargetEntry *te = linitial(plan->targetlist);
                Param      *prm;

                Assert(!te->resjunk);
                Assert(testexpr == NULL);
                prm = generate_new_param(root,
                                                                 exprType((Node *) te->expr),
                                                                 exprTypmod((Node *) te->expr));
                splan->setParam = list_make1_int(prm->paramid);
                isInitPlan = true;
                result = (Node *) prm;
        }
        else if (splan->parParam == NIL && subLinkType == ARRAY_SUBLINK)
        {
                TargetEntry *te = linitial(plan->targetlist);
                Oid                     arraytype;
                Param      *prm;

                Assert(!te->resjunk);
                Assert(testexpr == NULL);
                arraytype = get_array_type(exprType((Node *) te->expr));
                if (!OidIsValid(arraytype))
                        elog(ERROR, "could not find array type for datatype %s",
                                 format_type_be(exprType((Node *) te->expr)));
                prm = generate_new_param(root,
                                                                 arraytype,
                                                                 exprTypmod((Node *) te->expr));
                splan->setParam = list_make1_int(prm->paramid);
                isInitPlan = true;
                result = (Node *) prm;
        }
        else if (splan->parParam == NIL && subLinkType == ROWCOMPARE_SUBLINK)
        {
                /* Adjust the Params */
                List       *params;

                Assert(testexpr != NULL);
                params = generate_subquery_params(root,
                                                                                  plan->targetlist,
                                                                                  &splan->paramIds);
                result = convert_testexpr(root,
                                                                  testexpr,
                                                                  params);
                splan->setParam = list_copy(splan->paramIds);
                isInitPlan = true;

                /*
                 * The executable expression is returned to become part of the outer
                 * plan's expression tree; it is not kept in the initplan node.
                 */
        }
        else
        {
                /*
                 * Adjust the Params in the testexpr, unless caller said it's not
                 * needed.
                 */
                if (testexpr && adjust_testexpr)
                {
                        List       *params;

                        params = generate_subquery_params(root,
                                                                                          plan->targetlist,
                                                                                          &splan->paramIds);
                        splan->testexpr = convert_testexpr(root,
                                                                                           testexpr,
                                                                                           params);
                }
                else
                        splan->testexpr = testexpr;

                /*
                 * We can't convert subplans of ALL_SUBLINK or ANY_SUBLINK types to
                 * initPlans, even when they are uncorrelated or undirect correlated,
                 * because we need to scan the output of the subplan for each outer
                 * tuple.  But if it's a not-direct-correlated IN (= ANY) test, we
                 * might be able to use a hashtable to avoid comparing all the tuples.
                 */
                if (subLinkType == ANY_SUBLINK &&
                        splan->parParam == NIL &&
                        subplan_is_hashable(plan) &&
                        testexpr_is_hashable(splan->testexpr))
                        splan->useHashTable = true;

                /*
                 * Otherwise, we have the option to tack a Material node onto the top
                 * of the subplan, to reduce the cost of reading it repeatedly.  This
                 * is pointless for a direct-correlated subplan, since we'd have to
                 * recompute its results each time anyway.      For uncorrelated/undirect
                 * correlated subplans, we add Material unless the subplan's top plan
                 * node would materialize its output anyway.
                 */
                else if (splan->parParam == NIL &&
                                 !ExecMaterializesOutput(nodeTag(plan)))
                        plan = materialize_finished_plan(plan);

                result = (Node *) splan;
                isInitPlan = false;
        }

        /*
         * Add the subplan and its rtable to the global lists.
         */
        root->glob->subplans = lappend(root->glob->subplans, plan);
        root->glob->subrtables = lappend(root->glob->subrtables, rtable);
        splan->plan_id = list_length(root->glob->subplans);

        if (isInitPlan)
                root->init_plans = lappend(root->init_plans, splan);

        /*
         * A parameterless subplan (not initplan) should be prepared to handle
         * REWIND efficiently.  If it has direct parameters then there's no point
         * since it'll be reset on each scan anyway; and if it's an initplan then
         * there's no point since it won't get re-run without parameter changes
         * anyway.      The input of a hashed subplan doesn't need REWIND either.
         */
        if (splan->parParam == NIL && !isInitPlan && !splan->useHashTable)
                root->glob->rewindPlanIDs = bms_add_member(root->glob->rewindPlanIDs,
                                                                                                   splan->plan_id);

        /* Label the subplan for EXPLAIN purposes */
        if (isInitPlan)
        {
                ListCell   *lc;
                int                     offset;

                splan->plan_name = palloc(32 + 12 * list_length(splan->setParam));
                sprintf(splan->plan_name, "InitPlan %d (returns ", splan->plan_id);
                offset = strlen(splan->plan_name);
                foreach(lc, splan->setParam)
                {
                        sprintf(splan->plan_name + offset, "$%d%s",
                                        lfirst_int(lc),
                                        lnext(lc) ? "," : "");
                        offset += strlen(splan->plan_name + offset);
                }
                sprintf(splan->plan_name + offset, ")");
        }
        else
        {
                splan->plan_name = palloc(32);
                sprintf(splan->plan_name, "SubPlan %d", splan->plan_id);
        }

        /* Lastly, fill in the cost estimates for use later */
        cost_subplan(root, splan, plan);

        return result;
}

/*
 * generate_subquery_params: build a list of Params representing the output
 * columns of a sublink's sub-select, given the sub-select's targetlist.
 *
 * We also return an integer list of the paramids of the Params.
 */
static List *
generate_subquery_params(PlannerInfo *root, List *tlist, List **paramIds)
{
        List       *result;
        List       *ids;
        ListCell   *lc;

        result = ids = NIL;
        foreach(lc, tlist)
        {
                TargetEntry *tent = (TargetEntry *) lfirst(lc);
                Param      *param;

                if (tent->resjunk)
                        continue;

                param = generate_new_param(root,
                                                                   exprType((Node *) tent->expr),
                                                                   exprTypmod((Node *) tent->expr));
                result = lappend(result, param);
                ids = lappend_int(ids, param->paramid);
        }

        *paramIds = ids;
        return result;
}

/*
 * generate_subquery_vars: build a list of Vars representing the output
 * columns of a sublink's sub-select, given the sub-select's targetlist.
 * The Vars have the specified varno (RTE index).
 */
static List *
generate_subquery_vars(PlannerInfo *root, List *tlist, Index varno)
{
        List       *result;
        ListCell   *lc;

        result = NIL;
        foreach(lc, tlist)
        {
                TargetEntry *tent = (TargetEntry *) lfirst(lc);
                Var                *var;

                if (tent->resjunk)
                        continue;

                var = makeVar(varno,
                                          tent->resno,
                                          exprType((Node *) tent->expr),
                                          exprTypmod((Node *) tent->expr),
                                          0);
                result = lappend(result, var);
        }

        return result;
}

/*
 * convert_testexpr: convert the testexpr given by the parser into
 * actually executable form.  This entails replacing PARAM_SUBLINK Params
 * with Params or Vars representing the results of the sub-select.      The
 * nodes to be substituted are passed in as the List result from
 * generate_subquery_params or generate_subquery_vars.
 *
 * The given testexpr has already been recursively processed by
 * process_sublinks_mutator.  Hence it can no longer contain any
 * PARAM_SUBLINK Params for lower SubLink nodes; we can safely assume that
 * any we find are for our own level of SubLink.
 */
static Node *
convert_testexpr(PlannerInfo *root,
                                 Node *testexpr,
                                 List *subst_nodes)
{
        convert_testexpr_context context;

        context.root = root;
        context.subst_nodes = subst_nodes;
        return convert_testexpr_mutator(testexpr, &context);
}

static Node *
convert_testexpr_mutator(Node *node,
                                                 convert_testexpr_context *context)
{
        if (node == NULL)
                return NULL;
        if (IsA(node, Param))
        {
                Param      *param = (Param *) node;

                if (param->paramkind == PARAM_SUBLINK)
                {
                        if (param->paramid <= 0 ||
                                param->paramid > list_length(context->subst_nodes))
                                elog(ERROR, "unexpected PARAM_SUBLINK ID: %d", param->paramid);

                        /*
                         * We copy the list item to avoid having doubly-linked
                         * substructure in the modified parse tree.  This is probably
                         * unnecessary when it's a Param, but be safe.
                         */
                        return (Node *) copyObject(list_nth(context->subst_nodes,
                                                                                                param->paramid - 1));
                }
        }
        return expression_tree_mutator(node,
                                                                   convert_testexpr_mutator,
                                                                   (void *) context);
}

/*
 * subplan_is_hashable: can we implement an ANY subplan by hashing?
 */
static bool
subplan_is_hashable(Plan *plan)
{
        double          subquery_size;

        /*
         * The estimated size of the subquery result must fit in work_mem. (Note:
         * we use sizeof(HeapTupleHeaderData) here even though the tuples will
         * actually be stored as MinimalTuples; this provides some fudge factor
         * for hashtable overhead.)
         */
        subquery_size = plan->plan_rows *
                (MAXALIGN(plan->plan_width) + MAXALIGN(sizeof(HeapTupleHeaderData)));
        if (subquery_size > work_mem * 1024L)
                return false;

        return true;
}

/*
 * testexpr_is_hashable: is an ANY SubLink's test expression hashable?
 */
static bool
testexpr_is_hashable(Node *testexpr)
{
        /*
         * The testexpr must be a single OpExpr, or an AND-clause containing only
         * OpExprs.
         *
         * The combining operators must be hashable and strict. The need for
         * hashability is obvious, since we want to use hashing. Without
         * strictness, behavior in the presence of nulls is too unpredictable.  We
         * actually must assume even more than plain strictness: they can't yield
         * NULL for non-null inputs, either (see nodeSubplan.c).  However, hash
         * indexes and hash joins assume that too.
         */
        if (testexpr && IsA(testexpr, OpExpr))
        {
                if (hash_ok_operator((OpExpr *) testexpr))
                        return true;
        }
        else if (and_clause(testexpr))
        {
                ListCell   *l;

                foreach(l, ((BoolExpr *) testexpr)->args)
                {
                        Node       *andarg = (Node *) lfirst(l);

                        if (!IsA(andarg, OpExpr))
                                return false;
                        if (!hash_ok_operator((OpExpr *) andarg))
                                return false;
                }
                return true;
        }

        return false;
}

static bool
hash_ok_operator(OpExpr *expr)
{
        Oid                     opid = expr->opno;
        HeapTuple       tup;
        Form_pg_operator optup;

        /* quick out if not a binary operator */
        if (list_length(expr->args) != 2)
                return false;
        /* else must look up the operator properties */
        tup = SearchSysCache(OPEROID,
                                                 ObjectIdGetDatum(opid),
                                                 0, 0, 0);
        if (!HeapTupleIsValid(tup))
                elog(ERROR, "cache lookup failed for operator %u", opid);
        optup = (Form_pg_operator) GETSTRUCT(tup);
        if (!optup->oprcanhash || !func_strict(optup->oprcode))
        {
                ReleaseSysCache(tup);
                return false;
        }
        ReleaseSysCache(tup);
        return true;
}


/*
 * SS_process_ctes: process a query's WITH list
 *
 * We plan each interesting WITH item and convert it to an initplan.
 * A side effect is to fill in root->cte_plan_ids with a list that
 * parallels root->parse->cteList and provides the subplan ID for
 * each CTE's initplan.
 */
void
SS_process_ctes(PlannerInfo *root)
{
        ListCell   *lc;

        Assert(root->cte_plan_ids == NIL);

        foreach(lc, root->parse->cteList)
        {
                CommonTableExpr *cte = (CommonTableExpr *) lfirst(lc);
                Query      *subquery;
                Plan       *plan;
                PlannerInfo *subroot;
                SubPlan    *splan;
                Bitmapset  *tmpset;
                int                     paramid;
                Param      *prm;

                /*
                 * Ignore CTEs that are not actually referenced anywhere.
                 */
                if (cte->cterefcount == 0)
                {
                        /* Make a dummy entry in cte_plan_ids */
                        root->cte_plan_ids = lappend_int(root->cte_plan_ids, -1);
                        continue;
                }

                /*
                 * Copy the source Query node.  Probably not necessary, but let's keep
                 * this similar to make_subplan.
                 */
                subquery = (Query *) copyObject(cte->ctequery);

                /*
                 * Generate the plan for the CTE query.  Always plan for full
                 * retrieval --- we don't have enough info to predict otherwise.
                 */
                plan = subquery_planner(root->glob, subquery,
                                                                root,
                                                                cte->cterecursive, 0.0,
                                                                &subroot);

                /*
                 * Make a SubPlan node for it.  This is just enough unlike
                 * build_subplan that we can't share code.
                 *
                 * Note plan_id, plan_name, and cost fields are set further down.
                 */
                splan = makeNode(SubPlan);
                splan->subLinkType = CTE_SUBLINK;
                splan->testexpr = NULL;
                splan->paramIds = NIL;
                get_first_col_type(plan, &splan->firstColType, &splan->firstColTypmod);
                splan->useHashTable = false;
                splan->unknownEqFalse = false;
                splan->setParam = NIL;
                splan->parParam = NIL;
                splan->args = NIL;

                /*
                 * Make parParam and args lists of param IDs and expressions that
                 * current query level will pass to this child plan.  Even though this
                 * is an initplan, there could be side-references to earlier
                 * initplan's outputs, specifically their CTE output parameters.
                 */
                tmpset = bms_copy(plan->extParam);
                while ((paramid = bms_first_member(tmpset)) >= 0)
                {
                        PlannerParamItem *pitem = list_nth(root->glob->paramlist, paramid);

                        if (pitem->abslevel == root->query_level)
                        {
                                prm = (Param *) pitem->item;
                                if (!IsA(prm, Param) ||
                                        prm->paramtype != INTERNALOID)
                                        elog(ERROR, "bogus local parameter passed to WITH query");

                                splan->parParam = lappend_int(splan->parParam, paramid);
                                splan->args = lappend(splan->args, copyObject(prm));
                        }
                }
                bms_free(tmpset);

                /*
                 * Assign a param to represent the query output.  We only really care
                 * about reserving a parameter ID number.
                 */
                prm = generate_new_param(root, INTERNALOID, -1);
                splan->setParam = list_make1_int(prm->paramid);

                /*
                 * Add the subplan and its rtable to the global lists.
                 */
                root->glob->subplans = lappend(root->glob->subplans, plan);
                root->glob->subrtables = lappend(root->glob->subrtables,
                                                                                 subroot->parse->rtable);
                splan->plan_id = list_length(root->glob->subplans);

                root->init_plans = lappend(root->init_plans, splan);

                root->cte_plan_ids = lappend_int(root->cte_plan_ids, splan->plan_id);

                /* Label the subplan for EXPLAIN purposes */
                splan->plan_name = palloc(4 + strlen(cte->ctename) + 1);
                sprintf(splan->plan_name, "CTE %s", cte->ctename);

                /* Lastly, fill in the cost estimates for use later */
                cost_subplan(root, splan, plan);
        }
}

/*
 * convert_ANY_sublink_to_join: try to convert an ANY SubLink to a join
 *
 * The caller has found an ANY SubLink at the top level of one of the query's
 * qual clauses, but has not checked the properties of the SubLink further.
 * Decide whether it is appropriate to process this SubLink in join style.
 * If so, form a JoinExpr and return it.  Return NULL if the SubLink cannot
 * be converted to a join.
 *
 * The only non-obvious input parameter is available_rels: this is the set
 * of query rels that can safely be referenced in the sublink expression.
 * (We must restrict this to avoid changing the semantics when a sublink
 * is present in an outer join's ON qual.)  The conversion must fail if
 * the converted qual would reference any but these parent-query relids.
 *
 * On success, the returned JoinExpr has larg = NULL and rarg = the jointree
 * item representing the pulled-up subquery.  The caller must set larg to
 * represent the relation(s) on the lefthand side of the new join, and insert
 * the JoinExpr into the upper query's jointree at an appropriate place
 * (typically, where the lefthand relation(s) had been).  Note that the
 * passed-in SubLink must also be removed from its original position in the
 * query quals, since the quals of the returned JoinExpr replace it.
 * (Notionally, we replace the SubLink with a constant TRUE, then elide the
 * redundant constant from the qual.)
 *
 * Side effects of a successful conversion include adding the SubLink's
 * subselect to the query's rangetable, so that it can be referenced in
 * the JoinExpr's rarg.
 */
JoinExpr *
convert_ANY_sublink_to_join(PlannerInfo *root, SubLink *sublink,
                                                        Relids available_rels)
{
        JoinExpr   *result;
        Query      *parse = root->parse;
        Query      *subselect = (Query *) sublink->subselect;
        Relids          upper_varnos;
        int                     rtindex;
        RangeTblEntry *rte;
        RangeTblRef *rtr;
        List       *subquery_vars;
        Node       *quals;

        Assert(sublink->subLinkType == ANY_SUBLINK);

        /*
         * The sub-select must not refer to any Vars of the parent query. (Vars of
         * higher levels should be okay, though.)
         */
        if (contain_vars_of_level((Node *) subselect, 1))
                return NULL;

        /*
         * The test expression must contain some Vars of the parent query, else
         * it's not gonna be a join.  (Note that it won't have Vars referring to
         * the subquery, rather Params.)
         */
        upper_varnos = pull_varnos(sublink->testexpr);
        if (bms_is_empty(upper_varnos))
                return NULL;

        /*
         * However, it can't refer to anything outside available_rels.
         */
        if (!bms_is_subset(upper_varnos, available_rels))
                return NULL;

        /*
         * The combining operators and left-hand expressions mustn't be volatile.
         */
        if (contain_volatile_functions(sublink->testexpr))
                return NULL;

        /*
         * Okay, pull up the sub-select into upper range table.
         *
         * We rely here on the assumption that the outer query has no references
         * to the inner (necessarily true, other than the Vars that we build
         * below). Therefore this is a lot easier than what pull_up_subqueries has
         * to go through.
         */
        rte = addRangeTableEntryForSubquery(NULL,
                                                                                subselect,
                                                                                makeAlias("ANY_subquery", NIL),
                                                                                false);
        parse->rtable = lappend(parse->rtable, rte);
        rtindex = list_length(parse->rtable);

        /*
         * Form a RangeTblRef for the pulled-up sub-select.
         */
        rtr = makeNode(RangeTblRef);
        rtr->rtindex = rtindex;

        /*
         * Build a list of Vars representing the subselect outputs.
         */
        subquery_vars = generate_subquery_vars(root,
                                                                                   subselect->targetList,
                                                                                   rtindex);

        /*
         * Build the new join's qual expression, replacing Params with these Vars.
         */
        quals = convert_testexpr(root, sublink->testexpr, subquery_vars);

        /*
         * And finally, build the JoinExpr node.
         */
        result = makeNode(JoinExpr);
        result->jointype = JOIN_SEMI;
        result->isNatural = false;
        result->larg = NULL;            /* caller must fill this in */
        result->rarg = (Node *) rtr;
        result->usingClause = NIL;
        result->quals = quals;
        result->alias = NULL;
        result->rtindex = 0;            /* we don't need an RTE for it */

        return result;
}

/*
 * convert_EXISTS_sublink_to_join: try to convert an EXISTS SubLink to a join
 *
 * The API of this function is identical to convert_ANY_sublink_to_join's,
 * except that we also support the case where the caller has found NOT EXISTS,
 * so we need an additional input parameter "under_not".
 */
JoinExpr *
convert_EXISTS_sublink_to_join(PlannerInfo *root, SubLink *sublink,
                                                           bool under_not, Relids available_rels)
{
        JoinExpr   *result;
        Query      *parse = root->parse;
        Query      *subselect = (Query *) sublink->subselect;
        Node       *whereClause;
        int                     rtoffset;
        int                     varno;
        Relids          clause_varnos;
        Relids          upper_varnos;

        Assert(sublink->subLinkType == EXISTS_SUBLINK);

        /*
         * Copy the subquery so we can modify it safely (see comments in
         * make_subplan).
         */
        subselect = (Query *) copyObject(subselect);

        /*
         * See if the subquery can be simplified based on the knowledge that it's
         * being used in EXISTS().      If we aren't able to get rid of its
         * targetlist, we have to fail, because the pullup operation leaves us
         * with noplace to evaluate the targetlist.
         */
        if (!simplify_EXISTS_query(subselect))
                return NULL;

        /*
         * The subquery must have a nonempty jointree, else we won't have a join.
         */
        if (subselect->jointree->fromlist == NIL)
                return NULL;

        /*
         * Separate out the WHERE clause.  (We could theoretically also remove
         * top-level plain JOIN/ON clauses, but it's probably not worth the
         * trouble.)
         */
        whereClause = subselect->jointree->quals;
        subselect->jointree->quals = NULL;

        /*
         * The rest of the sub-select must not refer to any Vars of the parent
         * query.  (Vars of higher levels should be okay, though.)
         */
        if (contain_vars_of_level((Node *) subselect, 1))
                return NULL;

        /*
         * On the other hand, the WHERE clause must contain some Vars of the
         * parent query, else it's not gonna be a join.
         */
        if (!contain_vars_of_level(whereClause, 1))
                return NULL;

        /*
         * We don't risk optimizing if the WHERE clause is volatile, either.
         */
        if (contain_volatile_functions(whereClause))
                return NULL;

        /*
         * Prepare to pull up the sub-select into top range table.
         *
         * We rely here on the assumption that the outer query has no references
         * to the inner (necessarily true). Therefore this is a lot easier than
         * what pull_up_subqueries has to go through.
         *
         * In fact, it's even easier than what convert_ANY_sublink_to_join has to
         * do.  The machinations of simplify_EXISTS_query ensured that there is
         * nothing interesting in the subquery except an rtable and jointree, and
         * even the jointree FromExpr no longer has quals.      So we can just append
         * the rtable to our own and use the FromExpr in our jointree. But first,
         * adjust all level-zero varnos in the subquery to account for the rtable
         * merger.
         */
        rtoffset = list_length(parse->rtable);
        OffsetVarNodes((Node *) subselect, rtoffset, 0);
        OffsetVarNodes(whereClause, rtoffset, 0);

        /*
         * Upper-level vars in subquery will now be one level closer to their
         * parent than before; in particular, anything that had been level 1
         * becomes level zero.
         */
        IncrementVarSublevelsUp((Node *) subselect, -1, 1);
        IncrementVarSublevelsUp(whereClause, -1, 1);

        /*
         * Now that the WHERE clause is adjusted to match the parent query
         * environment, we can easily identify all the level-zero rels it uses.
         * The ones <= rtoffset belong to the upper query; the ones > rtoffset do
         * not.
         */
        clause_varnos = pull_varnos(whereClause);
        upper_varnos = NULL;
        while ((varno = bms_first_member(clause_varnos)) >= 0)
        {
                if (varno <= rtoffset)
                        upper_varnos = bms_add_member(upper_varnos, varno);
        }
        bms_free(clause_varnos);
        Assert(!bms_is_empty(upper_varnos));

        /*
         * Now that we've got the set of upper-level varnos, we can make the last
         * check: only available_rels can be referenced.
         */
        if (!bms_is_subset(upper_varnos, available_rels))
                return NULL;

        /* Now we can attach the modified subquery rtable to the parent */
        parse->rtable = list_concat(parse->rtable, subselect->rtable);

        /*
         * And finally, build the JoinExpr node.
         */
        result = makeNode(JoinExpr);
        result->jointype = under_not ? JOIN_ANTI : JOIN_SEMI;
        result->isNatural = false;
        result->larg = NULL;            /* caller must fill this in */
        /* flatten out the FromExpr node if it's useless */
        if (list_length(subselect->jointree->fromlist) == 1)
                result->rarg = (Node *) linitial(subselect->jointree->fromlist);
        else
                result->rarg = (Node *) subselect->jointree;
        result->usingClause = NIL;
        result->quals = whereClause;
        result->alias = NULL;
        result->rtindex = 0;            /* we don't need an RTE for it */

        return result;
}

/*
 * simplify_EXISTS_query: remove any useless stuff in an EXISTS's subquery
 *
 * The only thing that matters about an EXISTS query is whether it returns
 * zero or more than zero rows.  Therefore, we can remove certain SQL features
 * that won't affect that.  The only part that is really likely to matter in
 * typical usage is simplifying the targetlist: it's a common habit to write
 * "SELECT * FROM" even though there is no need to evaluate any columns.
 *
 * Note: by suppressing the targetlist we could cause an observable behavioral
 * change, namely that any errors that might occur in evaluating the tlist
 * won't occur, nor will other side-effects of volatile functions.  This seems
 * unlikely to bother anyone in practice.
 *
 * Returns TRUE if was able to discard the targetlist, else FALSE.
 */
static bool
simplify_EXISTS_query(Query *query)
{
        /*
         * We don't try to simplify at all if the query uses set operations,
         * aggregates, HAVING, LIMIT/OFFSET, or FOR UPDATE/SHARE; none of these
         * seem likely in normal usage and their possible effects are complex.
         */
        if (query->commandType != CMD_SELECT ||
                query->intoClause ||
                query->setOperations ||
                query->hasAggs ||
                query->hasWindowFuncs ||
                query->havingQual ||
                query->limitOffset ||
                query->limitCount ||
                query->rowMarks)
                return false;

        /*
         * Mustn't throw away the targetlist if it contains set-returning
         * functions; those could affect whether zero rows are returned!
         */
        if (expression_returns_set((Node *) query->targetList))
                return false;

        /*
         * Otherwise, we can throw away the targetlist, as well as any GROUP,
         * WINDOW, DISTINCT, and ORDER BY clauses; none of those clauses will
         * change a nonzero-rows result to zero rows or vice versa.  (Furthermore,
         * since our parsetree representation of these clauses depends on the
         * targetlist, we'd better throw them away if we drop the targetlist.)
         */
        query->targetList = NIL;
        query->groupClause = NIL;
        query->windowClause = NIL;
        query->distinctClause = NIL;
        query->sortClause = NIL;
        query->hasDistinctOn = false;

        return true;
}

/*
 * convert_EXISTS_to_ANY: try to convert EXISTS to a hashable ANY sublink
 *
 * The subselect is expected to be a fresh copy that we can munge up,
 * and to have been successfully passed through simplify_EXISTS_query.
 *
 * On success, the modified subselect is returned, and we store a suitable
 * upper-level test expression at *testexpr, plus a list of the subselect's
 * output Params at *paramIds.  (The test expression is already Param-ified
 * and hence need not go through convert_testexpr, which is why we have to
 * deal with the Param IDs specially.)
 *
 * On failure, returns NULL.
 */
static Query *
convert_EXISTS_to_ANY(PlannerInfo *root, Query *subselect,
                                          Node **testexpr, List **paramIds)
{
        Node       *whereClause;
        List       *leftargs,
                           *rightargs,
                           *opids,
                           *newWhere,
                           *tlist,
                           *testlist,
                           *paramids;
        ListCell   *lc,
                           *rc,
                           *oc;
        AttrNumber      resno;

        /*
         * Query must not require a targetlist, since we have to insert a new one.
         * Caller should have dealt with the case already.
         */
        Assert(subselect->targetList == NIL);

        /*
         * Separate out the WHERE clause.  (We could theoretically also remove
         * top-level plain JOIN/ON clauses, but it's probably not worth the
         * trouble.)
         */
        whereClause = subselect->jointree->quals;
        subselect->jointree->quals = NULL;

        /*
         * The rest of the sub-select must not refer to any Vars of the parent
         * query.  (Vars of higher levels should be okay, though.)
         *
         * Note: we need not check for Aggrefs separately because we know the
         * sub-select is as yet unoptimized; any uplevel Aggref must therefore
         * contain an uplevel Var reference.  This is not the case below ...
         */
        if (contain_vars_of_level((Node *) subselect, 1))
                return NULL;

        /*
         * We don't risk optimizing if the WHERE clause is volatile, either.
         */
        if (contain_volatile_functions(whereClause))
                return NULL;

        /*
         * Clean up the WHERE clause by doing const-simplification etc on it.
         * Aside from simplifying the processing we're about to do, this is
         * important for being able to pull chunks of the WHERE clause up into the
         * parent query.  Since we are invoked partway through the parent's
         * preprocess_expression() work, earlier steps of preprocess_expression()
         * wouldn't get applied to the pulled-up stuff unless we do them here. For
         * the parts of the WHERE clause that get put back into the child query,
         * this work is partially duplicative, but it shouldn't hurt.
         *
         * Note: we do not run flatten_join_alias_vars.  This is OK because any
         * parent aliases were flattened already, and we're not going to pull any
         * child Vars (of any description) into the parent.
         *
         * Note: passing the parent's root to eval_const_expressions is
         * technically wrong, but we can get away with it since only the
         * boundParams (if any) are used, and those would be the same in a
         * subroot.
         */
        whereClause = eval_const_expressions(root, whereClause);
        whereClause = (Node *) canonicalize_qual((Expr *) whereClause);
        whereClause = (Node *) make_ands_implicit((Expr *) whereClause);

        /*
         * We now have a flattened implicit-AND list of clauses, which we try to
         * break apart into "outervar = innervar" hash clauses. Anything that
         * can't be broken apart just goes back into the newWhere list.  Note that
         * we aren't trying hard yet to ensure that we have only outer or only
         * inner on each side; we'll check that if we get to the end.
         */
        leftargs = rightargs = opids = newWhere = NIL;
        foreach(lc, (List *) whereClause)
        {
                OpExpr     *expr = (OpExpr *) lfirst(lc);

                if (IsA(expr, OpExpr) &&
                        hash_ok_operator(expr))
                {
                        Node       *leftarg = (Node *) linitial(expr->args);
                        Node       *rightarg = (Node *) lsecond(expr->args);

                        if (contain_vars_of_level(leftarg, 1))
                        {
                                leftargs = lappend(leftargs, leftarg);
                                rightargs = lappend(rightargs, rightarg);
                                opids = lappend_oid(opids, expr->opno);
                                continue;
                        }
                        if (contain_vars_of_level(rightarg, 1))
                        {
                                /*
                                 * We must commute the clause to put the outer var on the
                                 * left, because the hashing code in nodeSubplan.c expects
                                 * that.  This probably shouldn't ever fail, since hashable
                                 * operators ought to have commutators, but be paranoid.
                                 */
                                expr->opno = get_commutator(expr->opno);
                                if (OidIsValid(expr->opno) && hash_ok_operator(expr))
                                {
                                        leftargs = lappend(leftargs, rightarg);
                                        rightargs = lappend(rightargs, leftarg);
                                        opids = lappend_oid(opids, expr->opno);
                                        continue;
                                }
                                /* If no commutator, no chance to optimize the WHERE clause */
                                return NULL;
                        }
                }
                /* Couldn't handle it as a hash clause */
                newWhere = lappend(newWhere, expr);
        }

        /*
         * If we didn't find anything we could convert, fail.
         */
        if (leftargs == NIL)
                return NULL;

        /*
         * There mustn't be any parent Vars or Aggs in the stuff that we intend to
         * put back into the child query.  Note: you might think we don't need to
         * check for Aggs separately, because an uplevel Agg must contain an
         * uplevel Var in its argument.  But it is possible that the uplevel Var
         * got optimized away by eval_const_expressions.  Consider
         *
         * SUM(CASE WHEN false THEN uplevelvar ELSE 0 END)
         */
        if (contain_vars_of_level((Node *) newWhere, 1) ||
                contain_vars_of_level((Node *) rightargs, 1))
                return NULL;
        if (root->parse->hasAggs &&
                (contain_aggs_of_level((Node *) newWhere, 1) ||
                 contain_aggs_of_level((Node *) rightargs, 1)))
                return NULL;

        /*
         * And there can't be any child Vars in the stuff we intend to pull up.
         * (Note: we'd need to check for child Aggs too, except we know the child
         * has no aggs at all because of simplify_EXISTS_query's check. The same
         * goes for window functions.)
         */
        if (contain_vars_of_level((Node *) leftargs, 0))
                return NULL;

        /*
         * Also reject sublinks in the stuff we intend to pull up.      (It might be
         * possible to support this, but doesn't seem worth the complication.)
         */
        if (contain_subplans((Node *) leftargs))
                return NULL;

        /*
         * Okay, adjust the sublevelsup in the stuff we're pulling up.
         */
        IncrementVarSublevelsUp((Node *) leftargs, -1, 1);

        /*
         * Put back any child-level-only WHERE clauses.
         */
        if (newWhere)
                subselect->jointree->quals = (Node *) make_ands_explicit(newWhere);

        /*
         * Build a new targetlist for the child that emits the expressions we
         * need.  Concurrently, build a testexpr for the parent using Params to
         * reference the child outputs.  (Since we generate Params directly here,
         * there will be no need to convert the testexpr in build_subplan.)
         */
        tlist = testlist = paramids = NIL;
        resno = 1;
        /* there's no "for3" so we have to chase one of the lists manually */
        oc = list_head(opids);
        forboth(lc, leftargs, rc, rightargs)
        {
                Node       *leftarg = (Node *) lfirst(lc);
                Node       *rightarg = (Node *) lfirst(rc);
                Oid                     opid = lfirst_oid(oc);
                Param      *param;

                oc = lnext(oc);
                param = generate_new_param(root,
                                                                   exprType(rightarg),
                                                                   exprTypmod(rightarg));
                tlist = lappend(tlist,
                                                makeTargetEntry((Expr *) rightarg,
                                                                                resno++,
                                                                                NULL,
                                                                                false));
                testlist = lappend(testlist,
                                                   make_opclause(opid, BOOLOID, false,
                                                                                 (Expr *) leftarg, (Expr *) param));
                paramids = lappend_int(paramids, param->paramid);
        }

        /* Put everything where it should go, and we're done */
        subselect->targetList = tlist;
        *testexpr = (Node *) make_ands_explicit(testlist);
        *paramIds = paramids;

        return subselect;
}


/*
 * Replace correlation vars (uplevel vars) with Params.
 *
 * Uplevel aggregates are replaced, too.
 *
 * Note: it is critical that this runs immediately after SS_process_sublinks.
 * Since we do not recurse into the arguments of uplevel aggregates, they will
 * get copied to the appropriate subplan args list in the parent query with
 * uplevel vars not replaced by Params, but only adjusted in level (see
 * replace_outer_agg).  That's exactly what we want for the vars of the parent
 * level --- but if an aggregate's argument contains any further-up variables,
 * they have to be replaced with Params in their turn.  That will happen when
 * the parent level runs SS_replace_correlation_vars.  Therefore it must do
 * so after expanding its sublinks to subplans.  And we don't want any steps
 * in between, else those steps would never get applied to the aggregate
 * argument expressions, either in the parent or the child level.
 *
 * Another fairly tricky thing going on here is the handling of SubLinks in
 * the arguments of uplevel aggregates.  Those are not touched inside the
 * intermediate query level, either.  Instead, SS_process_sublinks recurses
 * on them after copying the Aggref expression into the parent plan level
 * (this is actually taken care of in build_subplan).
 */
Node *
SS_replace_correlation_vars(PlannerInfo *root, Node *expr)
{
        /* No setup needed for tree walk, so away we go */
        return replace_correlation_vars_mutator(expr, root);
}

static Node *
replace_correlation_vars_mutator(Node *node, PlannerInfo *root)
{
        if (node == NULL)
                return NULL;
        if (IsA(node, Var))
        {
                if (((Var *) node)->varlevelsup > 0)
                        return (Node *) replace_outer_var(root, (Var *) node);
        }
        if (IsA(node, Aggref))
        {
                if (((Aggref *) node)->agglevelsup > 0)
                        return (Node *) replace_outer_agg(root, (Aggref *) node);
        }
        return expression_tree_mutator(node,
                                                                   replace_correlation_vars_mutator,
                                                                   (void *) root);
}

/*
 * Expand SubLinks to SubPlans in the given expression.
 *
 * The isQual argument tells whether or not this expression is a WHERE/HAVING
 * qualifier expression.  If it is, any sublinks appearing at top level need
 * not distinguish FALSE from UNKNOWN return values.
 */
Node *
SS_process_sublinks(PlannerInfo *root, Node *expr, bool isQual)
{
        process_sublinks_context context;

        context.root = root;
        context.isTopQual = isQual;
        return process_sublinks_mutator(expr, &context);
}

static Node *
process_sublinks_mutator(Node *node, process_sublinks_context *context)
{
        process_sublinks_context locContext;

        locContext.root = context->root;

        if (node == NULL)
                return NULL;
        if (IsA(node, SubLink))
        {
                SubLink    *sublink = (SubLink *) node;
                Node       *testexpr;

                /*
                 * First, recursively process the lefthand-side expressions, if any.
                 * They're not top-level anymore.
                 */
                locContext.isTopQual = false;
                testexpr = process_sublinks_mutator(sublink->testexpr, &locContext);

                /*
                 * Now build the SubPlan node and make the expr to return.
                 */
                return make_subplan(context->root,
                                                        (Query *) sublink->subselect,
                                                        sublink->subLinkType,
                                                        testexpr,
                                                        context->isTopQual);
        }

        /*
         * Don't recurse into the arguments of an outer aggregate here. Any
         * SubLinks in the arguments have to be dealt with at the outer query
         * level; they'll be handled when build_subplan collects the Aggref into
         * the arguments to be passed down to the current subplan.
         */
        if (IsA(node, Aggref))
        {
                if (((Aggref *) node)->agglevelsup > 0)
                        return node;
        }

        /*
         * We should never see a SubPlan expression in the input (since this is
         * the very routine that creates 'em to begin with).  We shouldn't find
         * ourselves invoked directly on a Query, either.
         */
        Assert(!IsA(node, SubPlan));
        Assert(!IsA(node, AlternativeSubPlan));
        Assert(!IsA(node, Query));

        /*
         * Because make_subplan() could return an AND or OR clause, we have to
         * take steps to preserve AND/OR flatness of a qual.  We assume the input
         * has been AND/OR flattened and so we need no recursion here.
         *
         * (Due to the coding here, we will not get called on the List subnodes of
         * an AND; and the input is *not* yet in implicit-AND format.  So no check
         * is needed for a bare List.)
         *
         * Anywhere within the top-level AND/OR clause structure, we can tell
         * make_subplan() that NULL and FALSE are interchangeable.      So isTopQual
         * propagates down in both cases.  (Note that this is unlike the meaning
         * of "top level qual" used in most other places in Postgres.)
         */
        if (and_clause(node))
        {
                List       *newargs = NIL;
                ListCell   *l;

                /* Still at qual top-level */
                locContext.isTopQual = context->isTopQual;

                foreach(l, ((BoolExpr *) node)->args)
                {
                        Node       *newarg;

                        newarg = process_sublinks_mutator(lfirst(l), &locContext);
                        if (and_clause(newarg))
                                newargs = list_concat(newargs, ((BoolExpr *) newarg)->args);
                        else
                                newargs = lappend(newargs, newarg);
                }
                return (Node *) make_andclause(newargs);
        }

        if (or_clause(node))
        {
                List       *newargs = NIL;
                ListCell   *l;

                /* Still at qual top-level */
                locContext.isTopQual = context->isTopQual;

                foreach(l, ((BoolExpr *) node)->args)
                {
                        Node       *newarg;

                        newarg = process_sublinks_mutator(lfirst(l), &locContext);
                        if (or_clause(newarg))
                                newargs = list_concat(newargs, ((BoolExpr *) newarg)->args);
                        else
                                newargs = lappend(newargs, newarg);
                }
                return (Node *) make_orclause(newargs);
        }

        /*
         * If we recurse down through anything other than an AND or OR node, we
         * are definitely not at top qual level anymore.
         */
        locContext.isTopQual = false;

        return expression_tree_mutator(node,
                                                                   process_sublinks_mutator,
                                                                   (void *) &locContext);
}

/*
 * SS_finalize_plan - do final sublink processing for a completed Plan.
 *
 * This recursively computes the extParam and allParam sets for every Plan
 * node in the given plan tree.  It also optionally attaches any previously
 * generated InitPlans to the top plan node.  (Any InitPlans should already
 * have been put through SS_finalize_plan.)
 */
void
SS_finalize_plan(PlannerInfo *root, Plan *plan, bool attach_initplans)
{
        Bitmapset  *valid_params,
                           *initExtParam,
                           *initSetParam;
        Cost            initplan_cost;
        int                     paramid;
        ListCell   *l;

        /*
         * Examine any initPlans to determine the set of external params they
         * reference, the set of output params they supply, and their total cost.
         * We'll use at least some of this info below.  (Note we are assuming that
         * finalize_plan doesn't touch the initPlans.)
         *
         * In the case where attach_initplans is false, we are assuming that the
         * existing initPlans are siblings that might supply params needed by the
         * current plan.
         */
        initExtParam = initSetParam = NULL;
        initplan_cost = 0;
        foreach(l, root->init_plans)
        {
                SubPlan    *initsubplan = (SubPlan *) lfirst(l);
                Plan       *initplan = planner_subplan_get_plan(root, initsubplan);
                ListCell   *l2;

                initExtParam = bms_add_members(initExtParam, initplan->extParam);
                foreach(l2, initsubplan->setParam)
                {
                        initSetParam = bms_add_member(initSetParam, lfirst_int(l2));
                }
                initplan_cost += initsubplan->startup_cost + initsubplan->per_call_cost;
        }

        /*
         * Now determine the set of params that are validly referenceable in this
         * query level; to wit, those available from outer query levels plus the
         * output parameters of any initPlans.  (We do not include output
         * parameters of regular subplans.      Those should only appear within the
         * testexpr of SubPlan nodes, and are taken care of locally within
         * finalize_primnode.)
         *
         * Note: this is a bit overly generous since some parameters of upper
         * query levels might belong to query subtrees that don't include this
         * query.  However, valid_params is only a debugging crosscheck, so it
         * doesn't seem worth expending lots of cycles to try to be exact.
         */
        valid_params = bms_copy(initSetParam);
        paramid = 0;
        foreach(l, root->glob->paramlist)
        {
                PlannerParamItem *pitem = (PlannerParamItem *) lfirst(l);

                if (pitem->abslevel < root->query_level)
                {
                        /* valid outer-level parameter */
                        valid_params = bms_add_member(valid_params, paramid);
                }

                paramid++;
        }
        /* Also include the recursion working table, if any */
        if (root->wt_param_id >= 0)
                valid_params = bms_add_member(valid_params, root->wt_param_id);

        /*
         * Now recurse through plan tree.
         */
        (void) finalize_plan(root, plan, valid_params);

        bms_free(valid_params);

        /*
         * Finally, attach any initPlans to the topmost plan node, and add their
         * extParams to the topmost node's, too.  However, any setParams of the
         * initPlans should not be present in the topmost node's extParams, only
         * in its allParams.  (As of PG 8.1, it's possible that some initPlans
         * have extParams that are setParams of other initPlans, so we have to
         * take care of this situation explicitly.)
         *
         * We also add the eval cost of each initPlan to the startup cost of the
         * top node.  This is a conservative overestimate, since in fact each
         * initPlan might be executed later than plan startup, or even not at all.
         */
        if (attach_initplans)
        {
                plan->initPlan = root->init_plans;
                root->init_plans = NIL; /* make sure they're not attached twice */

                /* allParam must include all these params */
                plan->allParam = bms_add_members(plan->allParam, initExtParam);
                plan->allParam = bms_add_members(plan->allParam, initSetParam);
                /* extParam must include any child extParam */
                plan->extParam = bms_add_members(plan->extParam, initExtParam);
                /* but extParam shouldn't include any setParams */
                plan->extParam = bms_del_members(plan->extParam, initSetParam);
                /* ensure extParam is exactly NULL if it's empty */
                if (bms_is_empty(plan->extParam))
                        plan->extParam = NULL;

                plan->startup_cost += initplan_cost;
                plan->total_cost += initplan_cost;
        }
}

/*
 * Recursive processing of all nodes in the plan tree
 *
 * The return value is the computed allParam set for the given Plan node.
 * This is just an internal notational convenience.
 */
static Bitmapset *
finalize_plan(PlannerInfo *root, Plan *plan, Bitmapset *valid_params)
{
        finalize_primnode_context context;

        if (plan == NULL)
                return NULL;

        context.root = root;
        context.paramids = NULL;        /* initialize set to empty */

        /*
         * When we call finalize_primnode, context.paramids sets are automatically
         * merged together.  But when recursing to self, we have to do it the hard
         * way.  We want the paramids set to include params in subplans as well as
         * at this level.
         */

        /* Find params in targetlist and qual */
        finalize_primnode((Node *) plan->targetlist, &context);
        finalize_primnode((Node *) plan->qual, &context);

        /* Check additional node-type-specific fields */
        switch (nodeTag(plan))
        {
                case T_Result:
                        finalize_primnode(((Result *) plan)->resconstantqual,
                                                          &context);
                        break;

                case T_IndexScan:
                        finalize_primnode((Node *) ((IndexScan *) plan)->indexqual,
                                                          &context);

                        /*
                         * we need not look at indexqualorig, since it will have the same
                         * param references as indexqual.
                         */
                        break;

                case T_BitmapIndexScan:
                        finalize_primnode((Node *) ((BitmapIndexScan *) plan)->indexqual,
                                                          &context);

                        /*
                         * we need not look at indexqualorig, since it will have the same
                         * param references as indexqual.
                         */
                        break;

                case T_BitmapHeapScan:
                        finalize_primnode((Node *) ((BitmapHeapScan *) plan)->bitmapqualorig,
                                                          &context);
                        break;

                case T_TidScan:
                        finalize_primnode((Node *) ((TidScan *) plan)->tidquals,
                                                          &context);
                        break;

                case T_SubqueryScan:

                        /*
                         * In a SubqueryScan, SS_finalize_plan has already been run on the
                         * subplan by the inner invocation of subquery_planner, so there's
                         * no need to do it again.      Instead, just pull out the subplan's
                         * extParams list, which represents the params it needs from my
                         * level and higher levels.
                         */
                        context.paramids = bms_add_members(context.paramids,
                                                                 ((SubqueryScan *) plan)->subplan->extParam);
                        break;

                case T_FunctionScan:
                        finalize_primnode(((FunctionScan *) plan)->funcexpr,
                                                          &context);
                        break;

                case T_ValuesScan:
                        finalize_primnode((Node *) ((ValuesScan *) plan)->values_lists,
                                                          &context);
                        break;

                case T_CteScan:
                        {
                                /*
                                 * You might think we should add the node's cteParam to
                                 * paramids, but we shouldn't because that param is just a
                                 * linkage mechanism for multiple CteScan nodes for the same
                                 * CTE; it is never used for changed-param signaling.  What
                                 * we have to do instead is to find the referenced CTE plan
                                 * and incorporate its external paramids, so that the correct
                                 * things will happen if the CTE references outer-level
                                 * variables.  See test cases for bug #4902.
                                 */
                                int             plan_id = ((CteScan *) plan)->ctePlanId;
                                Plan   *cteplan;

                                /* so, do this ... */
                                if (plan_id < 1 || plan_id > list_length(root->glob->subplans))
                                        elog(ERROR, "could not find plan for CteScan referencing plan ID %d",
                                                 plan_id);
                                cteplan = (Plan *) list_nth(root->glob->subplans, plan_id - 1);
                                context.paramids =
                                        bms_add_members(context.paramids, cteplan->extParam);

#ifdef NOT_USED
                                /* ... but not this */
                                context.paramids =
                                        bms_add_member(context.paramids,
                                                                   ((CteScan *) plan)->cteParam);
#endif
                        }
                        break;

                case T_WorkTableScan:
                        context.paramids =
                                bms_add_member(context.paramids,
                                                           ((WorkTableScan *) plan)->wtParam);
                        break;

                case T_ModifyTable:
                        {
                                ListCell   *l;

                                finalize_primnode((Node *) ((ModifyTable *) plan)->returningLists,
                                                                  &context);
                                foreach(l, ((ModifyTable *) plan)->plans)
                                {
                                        context.paramids =
                                                bms_add_members(context.paramids,
                                                                                finalize_plan(root,
                                                                                                          (Plan *) lfirst(l),
                                                                                                          valid_params));
                                }
                        }
                        break;

                case T_Append:
                        {
                                ListCell   *l;

                                foreach(l, ((Append *) plan)->appendplans)
                                {
                                        context.paramids =
                                                bms_add_members(context.paramids,
                                                                                finalize_plan(root,
                                                                                                          (Plan *) lfirst(l),
                                                                                                          valid_params));
                                }
                        }
                        break;

                case T_BitmapAnd:
                        {
                                ListCell   *l;

                                foreach(l, ((BitmapAnd *) plan)->bitmapplans)
                                {
                                        context.paramids =
                                                bms_add_members(context.paramids,
                                                                                finalize_plan(root,
                                                                                                          (Plan *) lfirst(l),
                                                                                                          valid_params));
                                }
                        }
                        break;

                case T_BitmapOr:
                        {
                                ListCell   *l;

                                foreach(l, ((BitmapOr *) plan)->bitmapplans)
                                {
                                        context.paramids =
                                                bms_add_members(context.paramids,
                                                                                finalize_plan(root,
                                                                                                          (Plan *) lfirst(l),
                                                                                                          valid_params));
                                }
                        }
                        break;

                case T_NestLoop:
                        finalize_primnode((Node *) ((Join *) plan)->joinqual,
                                                          &context);
                        break;

                case T_MergeJoin:
                        finalize_primnode((Node *) ((Join *) plan)->joinqual,
                                                          &context);
                        finalize_primnode((Node *) ((MergeJoin *) plan)->mergeclauses,
                                                          &context);
                        break;

                case T_HashJoin:
                        finalize_primnode((Node *) ((Join *) plan)->joinqual,
                                                          &context);
                        finalize_primnode((Node *) ((HashJoin *) plan)->hashclauses,
                                                          &context);
                        break;

                case T_Limit:
                        finalize_primnode(((Limit *) plan)->limitOffset,
                                                          &context);
                        finalize_primnode(((Limit *) plan)->limitCount,
                                                          &context);
                        break;

                case T_RecursiveUnion:
                case T_Hash:
                case T_Agg:
                case T_WindowAgg:
                case T_SeqScan:
                case T_Material:
                case T_Sort:
                case T_Unique:
                case T_SetOp:
                case T_Group:
                        break;

                default:
                        elog(ERROR, "unrecognized node type: %d",
                                 (int) nodeTag(plan));
        }

        /* Process left and right child plans, if any */
        context.paramids = bms_add_members(context.paramids,
                                                                           finalize_plan(root,
                                                                                                         plan->lefttree,
                                                                                                         valid_params));

        context.paramids = bms_add_members(context.paramids,
                                                                           finalize_plan(root,
                                                                                                         plan->righttree,
                                                                                                         valid_params));

        /*
         * RecursiveUnion *generates* its worktable param, so don't bubble that up
         */
        if (IsA(plan, RecursiveUnion))
        {
                context.paramids = bms_del_member(context.paramids,
                                                                                  ((RecursiveUnion *) plan)->wtParam);
        }

        /* Now we have all the paramids */

        if (!bms_is_subset(context.paramids, valid_params))
                elog(ERROR, "plan should not reference subplan's variable");

        /*
         * Note: by definition, extParam and allParam should have the same value
         * in any plan node that doesn't have child initPlans.  We set them equal
         * here, and later SS_finalize_plan will update them properly in node(s)
         * that it attaches initPlans to.
         *
         * For speed at execution time, make sure extParam/allParam are actually
         * NULL if they are empty sets.
         */
        if (bms_is_empty(context.paramids))
        {
                plan->extParam = NULL;
                plan->allParam = NULL;
        }
        else
        {
                plan->extParam = context.paramids;
                plan->allParam = bms_copy(context.paramids);
        }

        return plan->allParam;
}

/*
 * finalize_primnode: add IDs of all PARAM_EXEC params appearing in the given
 * expression tree to the result set.
 */
static bool
finalize_primnode(Node *node, finalize_primnode_context *context)
{
        if (node == NULL)
                return false;
        if (IsA(node, Param))
        {
                if (((Param *) node)->paramkind == PARAM_EXEC)
                {
                        int                     paramid = ((Param *) node)->paramid;

                        context->paramids = bms_add_member(context->paramids, paramid);
                }
                return false;                   /* no more to do here */
        }
        if (IsA(node, SubPlan))
        {
                SubPlan    *subplan = (SubPlan *) node;
                Plan       *plan = planner_subplan_get_plan(context->root, subplan);
                ListCell   *lc;
                Bitmapset  *subparamids;

                /* Recurse into the testexpr, but not into the Plan */
                finalize_primnode(subplan->testexpr, context);

                /*
                 * Remove any param IDs of output parameters of the subplan that were
                 * referenced in the testexpr.  These are not interesting for
                 * parameter change signaling since we always re-evaluate the subplan.
                 * Note that this wouldn't work too well if there might be uses of the
                 * same param IDs elsewhere in the plan, but that can't happen because
                 * generate_new_param never tries to merge params.
                 */
                foreach(lc, subplan->paramIds)
                {
                        context->paramids = bms_del_member(context->paramids,
                                                                                           lfirst_int(lc));
                }

                /* Also examine args list */
                finalize_primnode((Node *) subplan->args, context);

                /*
                 * Add params needed by the subplan to paramids, but excluding those
                 * we will pass down to it.
                 */
                subparamids = bms_copy(plan->extParam);
                foreach(lc, subplan->parParam)
                {
                        subparamids = bms_del_member(subparamids, lfirst_int(lc));
                }
                context->paramids = bms_join(context->paramids, subparamids);

                return false;                   /* no more to do here */
        }
        return expression_tree_walker(node, finalize_primnode,
                                                                  (void *) context);
}

/*
 * SS_make_initplan_from_plan - given a plan tree, make it an InitPlan
 *
 * The plan is expected to return a scalar value of the indicated type.
 * We build an EXPR_SUBLINK SubPlan node and put it into the initplan
 * list for the current query level.  A Param that represents the initplan's
 * output is returned.
 *
 * We assume the plan hasn't been put through SS_finalize_plan.
 */
Param *
SS_make_initplan_from_plan(PlannerInfo *root, Plan *plan,
                                                   Oid resulttype, int32 resulttypmod)
{
        SubPlan    *node;
        Param      *prm;

        /*
         * We must run SS_finalize_plan(), since that's normally done before a
         * subplan gets put into the initplan list.  Tell it not to attach any
         * pre-existing initplans to this one, since they are siblings not
         * children of this initplan.  (This is something else that could perhaps
         * be cleaner if we did extParam/allParam processing in setrefs.c instead
         * of here?  See notes for materialize_finished_plan.)
         */

        /*
         * Build extParam/allParam sets for plan nodes.
         */
        SS_finalize_plan(root, plan, false);

        /*
         * Add the subplan and its rtable to the global lists.
         */
        root->glob->subplans = lappend(root->glob->subplans,
                                                                   plan);
        root->glob->subrtables = lappend(root->glob->subrtables,
                                                                         root->parse->rtable);

        /*
         * Create a SubPlan node and add it to the outer list of InitPlans. Note
         * it has to appear after any other InitPlans it might depend on (see
         * comments in ExecReScan).
         */
        node = makeNode(SubPlan);
        node->subLinkType = EXPR_SUBLINK;
        get_first_col_type(plan, &node->firstColType, &node->firstColTypmod);
        node->plan_id = list_length(root->glob->subplans);

        root->init_plans = lappend(root->init_plans, node);

        /*
         * The node can't have any inputs (since it's an initplan), so the
         * parParam and args lists remain empty.
         */

        cost_subplan(root, node, plan);

        /*
         * Make a Param that will be the subplan's output.
         */
        prm = generate_new_param(root, resulttype, resulttypmod);
        node->setParam = list_make1_int(prm->paramid);

        /* Label the subplan for EXPLAIN purposes */
        node->plan_name = palloc(64);
        sprintf(node->plan_name, "InitPlan %d (returns $%d)",
                        node->plan_id, prm->paramid);

        return prm;
}