text: /*-------------------------------------------------------------------------
   *
   * subselect.c
   *	  Planning routines for subselects and parameters.
   *
   * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   * IDENTIFICATION
   *	  src/backend/optimizer/plan/subselect.c
   *
   *-------------------------------------------------------------------------
   */
  #include "postgres.h"
  
  #include "access/htup_details.h"
  #include "catalog/pg_operator.h"
  #include "catalog/pg_type.h"
  #include "executor/executor.h"
  #include "miscadmin.h"
  #include "nodes/graphnodes.h"
  #include "nodes/makefuncs.h"
  #include "nodes/nodeFuncs.h"
  #include "optimizer/clauses.h"
  #include "optimizer/cost.h"
  #include "optimizer/pathnode.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 "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, PlannerInfo *subroot,
  			  List *plan_params,
  			  SubLinkType subLinkType, int subLinkId,
  			  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(PlannerInfo *root, 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,
  			  int gather_param,
  			  Bitmapset *valid_params,
  			  Bitmapset *scan_params);
  static bool finalize_primnode(Node *node, finalize_primnode_context *context);
  static bool finalize_agg_primnode(Node *node, finalize_primnode_context *context);
  
  
  /*
   * Select a PARAM_EXEC number to identify the given Var as a parameter for
   * the current subquery, or for a nestloop's inner scan.
   * If the Var already has a param in the current context, return that one.
   */
  static int
  assign_param_for_var(PlannerInfo *root, Var *var)
  {
  	ListCell   *ppl;
  	PlannerParamItem *pitem;
  	Index		levelsup;
  
  	/* Find the query level the Var belongs to */
  	for (levelsup = var->varlevelsup; levelsup > 0; levelsup--)
  		root = root->parent_root;
  
  	/* If there's already a matching PlannerParamItem there, just use it */
  	foreach(ppl, root->plan_params)
  	{
  		pitem = (PlannerParamItem *) lfirst(ppl);
  		if (IsA(pitem->item, Var))
  		{
  			Var		   *pvar = (Var *) pitem->item;
  
  			/*
  			 * This comparison must match _equalVar(), except for ignoring
  			 * varlevelsup.  Note that _equalVar() ignores the location.
  			 */
  			if (pvar->varno == var->varno &&
  				pvar->varattno == var->varattno &&
  				pvar->vartype == var->vartype &&
  				pvar->vartypmod == var->vartypmod &&
  				pvar->varcollid == var->varcollid &&
  				pvar->varnoold == var->varnoold &&
  				pvar->varoattno == var->varoattno)
  				return pitem->paramId;
  		}
  	}
  
  	/* Nope, so make a new one */
  	var = copyObject(var);
  	var->varlevelsup = 0;
  
  	pitem = makeNode(PlannerParamItem);
  	pitem->item = (Node *) var;
  	pitem->paramId = root->glob->nParamExec++;
  
  	root->plan_params = lappend(root->plan_params, pitem);
  
  	return pitem->paramId;
  }
  
  /*
   * 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;
  	int			i;
  
  	Assert(var->varlevelsup > 0 && var->varlevelsup < root->query_level);
  
  	/* Find the Var in the appropriate plan_params, or add it if not present */
  	i = assign_param_for_var(root, var);
  
  	retval = makeNode(Param);
  	retval->paramkind = PARAM_EXEC;
  	retval->paramid = i;
  	retval->paramtype = var->vartype;
  	retval->paramtypmod = var->vartypmod;
  	retval->paramcollid = var->varcollid;
  	retval->location = var->location;
  
  	return retval;
  }
  
  /*
   * Generate a Param node to replace the given Var, which will be supplied
   * from an upper NestLoop join node.
   *
   * This is effectively the same as replace_outer_var, except that we expect
   * the Var to be local to the current query level.
   */
  Param *
  assign_nestloop_param_var(PlannerInfo *root, Var *var)
  {
  	Param	   *retval;
  	int			i;
  
  	Assert(var->varlevelsup == 0);
  
  	i = assign_param_for_var(root, var);
  
  	retval = makeNode(Param);
  	retval->paramkind = PARAM_EXEC;
  	retval->paramid = i;
  	retval->paramtype = var->vartype;
  	retval->paramtypmod = var->vartypmod;
  	retval->paramcollid = var->varcollid;
  	retval->location = var->location;
  
  	return retval;
  }
  
  /*
   * Select a PARAM_EXEC number to identify the given PlaceHolderVar as a
   * parameter for the current subquery, or for a nestloop's inner scan.
   * If the PHV already has a param in the current context, return that one.
   *
   * This is just like assign_param_for_var, except for PlaceHolderVars.
   */
  static int
  assign_param_for_placeholdervar(PlannerInfo *root, PlaceHolderVar *phv)
  {
  	ListCell   *ppl;
  	PlannerParamItem *pitem;
  	Index		levelsup;
  
  	/* Find the query level the PHV belongs to */
  	for (levelsup = phv->phlevelsup; levelsup > 0; levelsup--)
  		root = root->parent_root;
  
  	/* If there's already a matching PlannerParamItem there, just use it */
  	foreach(ppl, root->plan_params)
  	{
  		pitem = (PlannerParamItem *) lfirst(ppl);
  		if (IsA(pitem->item, PlaceHolderVar))
  		{
  			PlaceHolderVar *pphv = (PlaceHolderVar *) pitem->item;
  
  			/* We assume comparing the PHIDs is sufficient */
  			if (pphv->phid == phv->phid)
  				return pitem->paramId;
  		}
  	}
  
  	/* Nope, so make a new one */
  	phv = copyObject(phv);
  	if (phv->phlevelsup != 0)
  	{
  		IncrementVarSublevelsUp((Node *) phv, -((int) phv->phlevelsup), 0);
  		Assert(phv->phlevelsup == 0);
  	}
  
  	pitem = makeNode(PlannerParamItem);
  	pitem->item = (Node *) phv;
  	pitem->paramId = root->glob->nParamExec++;
  
  	root->plan_params = lappend(root->plan_params, pitem);
  
  	return pitem->paramId;
  }
  
  /*
   * Generate a Param node to replace the given PlaceHolderVar,
   * which is expected to have phlevelsup > 0 (ie, it is not local).
   *
   * This is just like replace_outer_var, except for PlaceHolderVars.
   */
  static Param *
  replace_outer_placeholdervar(PlannerInfo *root, PlaceHolderVar *phv)
  {
  	Param	   *retval;
  	int			i;
  
  	Assert(phv->phlevelsup > 0 && phv->phlevelsup < root->query_level);
  
  	/* Find the PHV in the appropriate plan_params, or add it if not present */
  	i = assign_param_for_placeholdervar(root, phv);
  
  	retval = makeNode(Param);
  	retval->paramkind = PARAM_EXEC;
  	retval->paramid = i;
  	retval->paramtype = exprType((Node *) phv->phexpr);
  	retval->paramtypmod = exprTypmod((Node *) phv->phexpr);
  	retval->paramcollid = exprCollation((Node *) phv->phexpr);
  	retval->location = -1;
  
  	return retval;
  }
  
  /*
   * Generate a Param node to replace the given PlaceHolderVar, which will be
   * supplied from an upper NestLoop join node.
   *
   * This is just like assign_nestloop_param_var, except for PlaceHolderVars.
   */
  Param *
  assign_nestloop_param_placeholdervar(PlannerInfo *root, PlaceHolderVar *phv)
  {
  	Param	   *retval;
  	int			i;
  
  	Assert(phv->phlevelsup == 0);
  
  	i = assign_param_for_placeholdervar(root, phv);
  
  	retval = makeNode(Param);
  	retval->paramkind = PARAM_EXEC;
  	retval->paramid = i;
  	retval->paramtype = exprType((Node *) phv->phexpr);
  	retval->paramtypmod = exprTypmod((Node *) phv->phexpr);
  	retval->paramcollid = exprCollation((Node *) phv->phexpr);
  	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		levelsup;
  
  	Assert(agg->agglevelsup > 0 && agg->agglevelsup < root->query_level);
  
  	/* Find the query level the Aggref belongs to */
  	for (levelsup = agg->agglevelsup; levelsup > 0; levelsup--)
  		root = root->parent_root;
  
  	/*
  	 * It does not seem worthwhile to try to match duplicate outer aggs. Just
  	 * make a new slot every time.
  	 */
  	agg = copyObject(agg);
  	IncrementVarSublevelsUp((Node *) agg, -((int) agg->agglevelsup), 0);
  	Assert(agg->agglevelsup == 0);
  
  	pitem = makeNode(PlannerParamItem);
  	pitem->item = (Node *) agg;
  	pitem->paramId = root->glob->nParamExec++;
  
  	root->plan_params = lappend(root->plan_params, pitem);
  
  	retval = makeNode(Param);
  	retval->paramkind = PARAM_EXEC;
  	retval->paramid = pitem->paramId;
  	retval->paramtype = agg->aggtype;
  	retval->paramtypmod = -1;
  	retval->paramcollid = agg->aggcollid;
  	retval->location = agg->location;
  
  	return retval;
  }
  
  /*
   * Generate a Param node to replace the given GroupingFunc expression which is
   * expected to have agglevelsup > 0 (ie, it is not local).
   */
  static Param *
  replace_outer_grouping(PlannerInfo *root, GroupingFunc *grp)
  {
  	Param	   *retval;
  	PlannerParamItem *pitem;
  	Index		levelsup;
  
  	Assert(grp->agglevelsup > 0 && grp->agglevelsup < root->query_level);
  
  	/* Find the query level the GroupingFunc belongs to */
  	for (levelsup = grp->agglevelsup; levelsup > 0; levelsup--)
  		root = root->parent_root;
  
  	/*
  	 * It does not seem worthwhile to try to match duplicate outer aggs. Just
  	 * make a new slot every time.
  	 */
  	grp = copyObject(grp);
  	IncrementVarSublevelsUp((Node *) grp, -((int) grp->agglevelsup), 0);
  	Assert(grp->agglevelsup == 0);
  
  	pitem = makeNode(PlannerParamItem);
  	pitem->item = (Node *) grp;
  	pitem->paramId = root->glob->nParamExec++;
  
  	root->plan_params = lappend(root->plan_params, pitem);
  
  	retval = makeNode(Param);
  	retval->paramkind = PARAM_EXEC;
  	retval->paramid = pitem->paramId;
  	retval->paramtype = exprType((Node *) grp);
  	retval->paramtypmod = -1;
  	retval->paramcollid = InvalidOid;
  	retval->location = grp->location;
  
  	return retval;
  }
  
  /*
   * Generate a new Param node that will not conflict with any other.
   *
   * This is used to create Params representing subplan outputs.
   * We don't need to build a PlannerParamItem for such a Param, but we do
   * need to record the PARAM_EXEC slot number as being allocated.
   */
  static Param *
  generate_new_param(PlannerInfo *root, Oid paramtype, int32 paramtypmod,
  				   Oid paramcollation)
  {
  	Param	   *retval;
  
  	retval = makeNode(Param);
  	retval->paramkind = PARAM_EXEC;
  	retval->paramid = root->glob->nParamExec++;
  	retval->paramtype = paramtype;
  	retval->paramtypmod = paramtypmod;
  	retval->paramcollid = paramcollation;
  	retval->location = -1;
  
  	return retval;
  }
  
  /*
   * Assign a (nonnegative) PARAM_EXEC ID for a special parameter (one that
   * is not actually used to carry a value at runtime).  Such parameters are
   * used for special runtime signaling purposes, such as connecting a
   * recursive union node to its worktable scan node or forcing plan
   * re-evaluation within the EvalPlanQual mechanism.  No actual Param node
   * exists with this ID, however.
   */
  int
  SS_assign_special_param(PlannerInfo *root)
  {
  	return root->glob->nParamExec++;
  }
  
  /*
   * Get the datatype/typmod/collation of the first column of the plan's output.
   *
   * This information is stored for ARRAY_SUBLINK execution and for
   * exprType()/exprTypmod()/exprCollation(), 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,
  				   Oid *colcollation)
  {
  	/* In cases such as EXISTS, tlist might be empty; arbitrarily use VOID */
  	if (plan->targetlist)
  	{
  		TargetEntry *tent = linitial_node(TargetEntry, plan->targetlist);
  
  		if (!tent->resjunk)
  		{
  			*coltype = exprType((Node *) tent->expr);
  			*coltypmod = exprTypmod((Node *) tent->expr);
  			*colcollation = exprCollation((Node *) tent->expr);
  			return;
  		}
  	}
  	*coltype = VOIDOID;
  	*coltypmod = -1;
  	*colcollation = InvalidOid;
  }
  
  /*
   * Convert a SubLink (as created by the parser) into a SubPlan.
   *
   * We are given the SubLink's contained query, type, ID, 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.  If we're going to do the subplan as a
   * regular subplan, this will be the constructed SubPlan node.  If we're going
   * to do the subplan as an InitPlan, the SubPlan node instead goes into
   * root->init_plans, and what we return here is an expression tree
   * representing the InitPlan's result: usually just a Param node representing
   * a single scalar result, but possibly a row comparison tree containing
   * multiple Param nodes, or for a MULTIEXPR subquery a simple NULL constant
   * (since the real output Params are elsewhere in the tree, and the MULTIEXPR
   * subquery itself is in a resjunk tlist entry whose value is uninteresting).
   */
  static Node *
  make_subplan(PlannerInfo *root, Query *orig_subquery,
  			 SubLinkType subLinkType, int subLinkId,
  			 Node *testexpr, bool isTopQual)
  {
  	Query	   *subquery;
  	bool		simple_exists = false;
  	double		tuple_fraction;
  	PlannerInfo *subroot;
  	RelOptInfo *final_rel;
  	Path	   *best_path;
  	Plan	   *plan;
  	List	   *plan_params;
  	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 = 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(root, 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, MULTIEXPR, 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 */
  
  	/* plan_params should not be in use in current query level */
  	Assert(root->plan_params == NIL);
  
  	/* Generate Paths for the subquery */
  	subroot = subquery_planner(root->glob, subquery,
  							   root,
  							   false, tuple_fraction);
  
  	/* Isolate the params needed by this specific subplan */
  	plan_params = root->plan_params;
  	root->plan_params = NIL;
  
  	/*
  	 * Select best Path and turn it into a Plan.  At least for now, there
  	 * seems no reason to postpone doing that.
  	 */
  	final_rel = fetch_upper_rel(subroot, UPPERREL_FINAL, NULL);
  	best_path = get_cheapest_fractional_path(final_rel, tuple_fraction);
  
  	plan = create_plan(subroot, best_path);
  
  	/* And convert to SubPlan or InitPlan format. */
  	result = build_subplan(root, plan, subroot, plan_params,
  						   subLinkType, subLinkId,
  						   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 = copyObject(orig_subquery);
  		/* and re-simplify */
  		simple_exists = simplify_EXISTS_query(root, 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 Paths for the ANY subquery; we'll need all rows */
  			subroot = subquery_planner(root->glob, subquery,
  									   root,
  									   false, 0.0);
  
  			/* Isolate the params needed by this specific subplan */
  			plan_params = root->plan_params;
  			root->plan_params = NIL;
  
  			/* Select best Path and turn it into a Plan */
  			final_rel = fetch_upper_rel(subroot, UPPERREL_FINAL, NULL);
  			best_path = final_rel->cheapest_total_path;
  
  			plan = create_plan(subroot, best_path);
  
  			/* Now we can check if it'll fit in work_mem */
  			/* XXX can we check this at the Path stage? */
  			if (subplan_is_hashable(plan))
  			{
  				SubPlan    *hashplan;
  				AlternativeSubPlan *asplan;
  
  				/* OK, convert to SubPlan format. */
  				hashplan = castNode(SubPlan,
  									build_subplan(root, plan, subroot,
  												  plan_params,
  												  ANY_SUBLINK, 0,
  												  newtestexpr,
  												  false, true));
  				/* Check we got what we expected */
  				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 a replacement expression if we decide to
   * make it an InitPlan, as explained in the comments for make_subplan.
   */
  static Node *
  build_subplan(PlannerInfo *root, Plan *plan, PlannerInfo *subroot,
  			  List *plan_params,
  			  SubLinkType subLinkType, int subLinkId,
  			  Node *testexpr, bool adjust_testexpr,
  			  bool unknownEqFalse)
  {
  	Node	   *result;
  	SubPlan    *splan;
  	bool		isInitPlan;
  	ListCell   *lc;
  
  	/*
  	 * 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->firstColCollation);
  	splan->useHashTable = false;
  	splan->unknownEqFalse = unknownEqFalse;
  	splan->parallel_safe = plan->parallel_safe;
  	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.
  	 */
  	foreach(lc, plan_params)
  	{
  		PlannerParamItem *pitem = (PlannerParamItem *) lfirst(lc);
  		Node	   *arg = pitem->item;
  
  		/*
  		 * The Var, PlaceHolderVar, or Aggref has already been adjusted to
  		 * have the correct varlevelsup, phlevelsup, or agglevelsup.
  		 *
  		 * If it's a PlaceHolderVar or Aggref, its arguments might contain
  		 * SubLinks, which have not yet been processed (see the comments for
  		 * SS_replace_correlation_vars).  Do that now.
  		 */
  		if (IsA(arg, PlaceHolderVar) ||
  			IsA(arg, Aggref))
  			arg = SS_process_sublinks(root, arg, false);
  
  		splan->parParam = lappend_int(splan->parParam, pitem->paramId);
  		splan->args = lappend(splan->args, arg);
  	}
  
  	/*
  	 * Un-correlated or undirect correlated plans of EXISTS, EXPR, ARRAY,
  	 * ROWCOMPARE, or MULTIEXPR types can be used as initPlans.  For EXISTS,
  	 * EXPR, or ARRAY, we return 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, and then return that tree.  For MULTIEXPR, we return a
  	 * null constant: the resjunk targetlist item containing the SubLink does
  	 * not need to return anything useful, since the referencing Params are
  	 * elsewhere.
  	 */
  	if (splan->parParam == NIL && subLinkType == EXISTS_SUBLINK)
  	{
  		Param	   *prm;
  
  		Assert(testexpr == NULL);
  		prm = generate_new_param(root, BOOLOID, -1, InvalidOid);
  		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),
  								 exprCollation((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_promoted_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),
  								 exprCollation((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 if (subLinkType == MULTIEXPR_SUBLINK)
  	{
  		/*
  		 * Whether it's an initplan or not, it needs to set a PARAM_EXEC Param
  		 * for each output column.
  		 */
  		List	   *params;
  
  		Assert(testexpr == NULL);
  		params = generate_subquery_params(root,
  										  plan->targetlist,
  										  &splan->setParam);
  
  		/*
  		 * Save the list of replacement Params in the n'th cell of
  		 * root->multiexpr_params; setrefs.c will use it to replace
  		 * PARAM_MULTIEXPR Params.
  		 */
  		while (list_length(root->multiexpr_params) < subLinkId)
  			root->multiexpr_params = lappend(root->multiexpr_params, NIL);
  		lc = list_nth_cell(root->multiexpr_params, subLinkId - 1);
  		Assert(lfirst(lc) == NIL);
  		lfirst(lc) = params;
  
  		/* It can be an initplan if there are no parParams. */
  		if (splan->parParam == NIL)
  		{
  			isInitPlan = true;
  			result = (Node *) makeNullConst(RECORDOID, -1, InvalidOid);
  		}
  		else
  		{
  			isInitPlan = false;
  			result = (Node *) splan;
  		}
  	}
  	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.  Also, if enable_material
  		 * is false, then the user does not want us to materialize anything
  		 * unnecessarily, so we don't.
  		 */
  		else if (splan->parParam == NIL && enable_material &&
  				 !ExecMaterializesOutput(nodeTag(plan)))
  			plan = materialize_finished_plan(plan);
  
  		result = (Node *) splan;
  		isInitPlan = false;
  	}
  
  	/*
  	 * Add the subplan and its PlannerInfo to the global lists.
  	 */
  	root->glob->subplans = lappend(root->glob->subplans, plan);
  	root->glob->subroots = lappend(root->glob->subroots, subroot);
  	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 */
  	splan->plan_name = palloc(32 + 12 * list_length(splan->setParam));
  	sprintf(splan->plan_name, "%s %d",
  			isInitPlan ? "InitPlan" : "SubPlan",
  			splan->plan_id);
  	if (splan->setParam)
  	{
  		char	   *ptr = splan->plan_name + strlen(splan->plan_name);
  
  		ptr += sprintf(ptr, " (returns ");
  		foreach(lc, splan->setParam)
  		{
  			ptr += sprintf(ptr, "$%d%s",
  						   lfirst_int(lc),
  						   lnext(lc) ? "," : ")");
  		}
  	}
  
  	/* 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),
  								   exprCollation((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 = makeVarFromTargetEntry(varno, tent);
  		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.
   */
  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));
  		}
  	}
  	if (IsA(node, SubLink))
  	{
  		/*
  		 * If we come across a nested SubLink, it is neither necessary nor
  		 * correct to recurse into it: any PARAM_SUBLINKs we might find inside
  		 * belong to the inner SubLink not the outer. So just return it as-is.
  		 *
  		 * This reasoning depends on the assumption that nothing will pull
  		 * subexpressions into or out of the testexpr field of a SubLink, at
  		 * least not without replacing PARAM_SUBLINKs first.  If we did want
  		 * to do that we'd need to rethink the parser-output representation
  		 * altogether, since currently PARAM_SUBLINKs are only unique per
  		 * SubLink not globally across the query.  The whole point of
  		 * replacing them with Vars or PARAM_EXEC nodes is to make them
  		 * globally unique before they escape from the SubLink's testexpr.
  		 *
  		 * Note: this can't happen when called during SS_process_sublinks,
  		 * because that recursively processes inner SubLinks first.  It can
  		 * happen when called from convert_ANY_sublink_to_join, though.
  		 */
  		return node;
  	}
  	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 heap tuple overhead 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(SizeofHeapTupleHeader));
  	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;
  }
  
  /*
   * Check expression is hashable + strict
   *
   * We could use op_hashjoinable() and op_strict(), but do it like this to
   * avoid a redundant cache lookup.
   */
  static bool
  hash_ok_operator(OpExpr *expr)
  {
  	Oid			opid = expr->opno;
  
  	/* quick out if not a binary operator */
  	if (list_length(expr->args) != 2)
  		return false;
  	if (opid == ARRAY_EQ_OP)
  	{
  		/* array_eq is strict, but must check input type to ensure hashable */
  		/* XXX record_eq will need same treatment when it becomes hashable */
  		Node	   *leftarg = linitial(expr->args);
  
  		return op_hashjoinable(opid, exprType(leftarg));
  	}
  	else
  	{
  		/* else must look up the operator properties */
  		HeapTuple	tup;
  		Form_pg_operator optup;
  
  		tup = SearchSysCache1(OPEROID, ObjectIdGetDatum(opid));
  		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);
  		CmdType		cmdType = ((Query *) cte->ctequery)->commandType;
  		Query	   *subquery;
  		PlannerInfo *subroot;
  		RelOptInfo *final_rel;
  		Path	   *best_path;
  		Plan	   *plan;
  		SubPlan    *splan;
  		int			paramid;
  
  		/*
  		 * Ignore SELECT CTEs that are not actually referenced anywhere.
  		 */
  		if (cte->cterefcount == 0 && cmdType == CMD_SELECT)
  		{
  			/* 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);
  
  		/* plan_params should not be in use in current query level */
  		Assert(root->plan_params == NIL);
  
  		/*
  		 * Generate Paths for the CTE query.  Always plan for full retrieval
  		 * --- we don't have enough info to predict otherwise.
  		 */
  		subroot = subquery_planner(root->glob, subquery,
  								   root,
  								   cte->cterecursive, 0.0);
  
  		/*
  		 * Since the current query level doesn't yet contain any RTEs, it
  		 * should not be possible for the CTE to have requested parameters of
  		 * this level.
  		 */
  		if (root->plan_params)
  			elog(ERROR, "unexpected outer reference in CTE query");
  
  		/*
  		 * Select best Path and turn it into a Plan.  At least for now, there
  		 * seems no reason to postpone doing that.
  		 */
  		final_rel = fetch_upper_rel(subroot, UPPERREL_FINAL, NULL);
  		best_path = final_rel->cheapest_total_path;
  
  		plan = create_plan(subroot, best_path);
  
  		/*
  		 * 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->firstColCollation);
  		splan->useHashTable = false;
  		splan->unknownEqFalse = false;
  
  		/*
  		 * CTE scans are not considered for parallelism (cf
  		 * set_rel_consider_parallel), and even if they were, initPlans aren't
  		 * parallel-safe.
  		 */
  		splan->parallel_safe = false;
  		splan->setParam = NIL;
  		splan->parParam = NIL;
  		splan->args = NIL;
  
  		/*
  		 * The node can't have any inputs (since it's an initplan), so the
  		 * parParam and args lists remain empty.  (It could contain references
  		 * to earlier CTEs' output param IDs, but CTE outputs are not
  		 * propagated via the args list.)
  		 */
  
  		/*
  		 * Assign a param ID to represent the CTE's output.  No ordinary
  		 * "evaluation" of this param slot ever happens, but we use the param
  		 * ID for setParam/chgParam signaling just as if the CTE plan were
  		 * returning a simple scalar output.  (Also, the executor abuses the
  		 * ParamExecData slot for this param ID for communication among
  		 * multiple CteScan nodes that might be scanning this CTE.)
  		 */
  		paramid = SS_assign_special_param(root);
  		splan->setParam = list_make1_int(paramid);
  
  		/*
  		 * Add the subplan and its PlannerInfo to the global lists.
  		 */
  		root->glob->subplans = lappend(root->glob->subplans, plan);
  		root->glob->subroots = lappend(root->glob->subroots, subroot);
  		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 = psprintf("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.)
   *
   * On success, the caller is also responsible for recursively applying
   * pull_up_sublinks processing to the rarg and quals of the returned JoinExpr.
   * (On failure, there is no need to do anything, since pull_up_sublinks will
   * be applied when we recursively plan the sub-select.)
   *
   * 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;
  	ParseState *pstate;
  
  	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;
  
  	/* Create a dummy ParseState for addRangeTableEntryForSubquery */
  	pstate = make_parsestate(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(pstate,
  										subselect,
  										makeAlias("ANY_subquery", NIL),
  										false,
  										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);
  
  	/*
  	 * Can't flatten if it contains WITH.  (We could arrange to pull up the
  	 * WITH into the parent query's cteList, but that risks changing the
  	 * semantics, since a WITH ought to be executed once per associated query
  	 * call.)  Note that convert_ANY_sublink_to_join doesn't have to reject
  	 * this case, since it just produces a subquery RTE that doesn't have to
  	 * get flattened into the parent query.
  	 */
  	if (subselect->cteList)
  		return NULL;
  
  	/*
  	 * Copy the subquery so we can modify it safely (see comments in
  	 * make_subplan).
  	 */
  	subselect = 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(root, 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(PlannerInfo *root, Query *query)
  {
  	/*
  	 * We don't try to simplify at all if the query uses set operations,
  	 * aggregates, grouping sets, SRFs, modifying CTEs, HAVING, OFFSET, or FOR
  	 * UPDATE/SHARE; none of these seem likely in normal usage and their
  	 * possible effects are complex.  (Note: we could ignore an "OFFSET 0"
  	 * clause, but that traditionally is used as an optimization fence, so we
  	 * don't.)
  	 */
  	if (query->commandType != CMD_SELECT ||
  		query->setOperations ||
  		query->hasAggs ||
  		query->groupingSets ||
  		query->hasWindowFuncs ||
  		query->hasTargetSRFs ||
  		query->hasModifyingCTE ||
  		query->havingQual ||
  		query->limitOffset ||
  		query->rowMarks)
  		return false;
  
  	/*
  	 * LIMIT with a constant positive (or NULL) value doesn't affect the
  	 * semantics of EXISTS, so let's ignore such clauses.  This is worth doing
  	 * because people accustomed to certain other DBMSes may be in the habit
  	 * of writing EXISTS(SELECT ... LIMIT 1) as an optimization.  If there's a
  	 * LIMIT with anything else as argument, though, we can't simplify.
  	 */
  	if (query->limitCount)
  	{
  		/*
  		 * The LIMIT clause has not yet been through eval_const_expressions,
  		 * so we have to apply that here.  It might seem like this is a waste
  		 * of cycles, since the only case plausibly worth worrying about is
  		 * "LIMIT 1" ... but what we'll actually see is "LIMIT int8(1::int4)",
  		 * so we have to fold constants or we're not going to recognize it.
  		 */
  		Node	   *node = eval_const_expressions(root, query->limitCount);
  		Const	   *limit;
  
  		/* Might as well update the query if we simplified the clause. */
  		query->limitCount = node;
  
  		if (!IsA(node, Const))
  			return false;
  
  		limit = (Const *) node;
  		Assert(limit->consttype == INT8OID);
  		if (!limit->constisnull && DatumGetInt64(limit->constvalue) <= 0)
  			return false;
  
  		/* Whether or not the targetlist is safe, we can drop the LIMIT. */
  		query->limitCount = NULL;
  	}
  
  	/*
  	 * 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,
  			   *opcollations,
  			   *newWhere,
  			   *tlist,
  			   *testlist,
  			   *paramids;
  	ListCell   *lc,
  			   *rc,
  			   *oc,
  			   *cc;
  	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_ext((Expr *) whereClause, false);
  	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 = opcollations = 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);
  				opcollations = lappend_oid(opcollations, expr->inputcollid);
  				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);
  					opcollations = lappend_oid(opcollations, expr->inputcollid);
  					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 "forfour" so we have to chase one of the lists manually */
  	cc = list_head(opcollations);
  	forthree(lc, leftargs, rc, rightargs, oc, opids)
  	{
  		Node	   *leftarg = (Node *) lfirst(lc);
  		Node	   *rightarg = (Node *) lfirst(rc);
  		Oid			opid = lfirst_oid(oc);
  		Oid			opcollation = lfirst_oid(cc);
  		Param	   *param;
  
  		cc = lnext(cc);
  		param = generate_new_param(root,
  								   exprType(rightarg),
  								   exprTypmod(rightarg),
  								   exprCollation(rightarg));
  		tlist = lappend(tlist,
  						makeTargetEntry((Expr *) rightarg,
  										resno++,
  										NULL,
  										false));
  		testlist = lappend(testlist,
  						   make_opclause(opid, BOOLOID, false,
  										 (Expr *) leftarg, (Expr *) param,
  										 InvalidOid, opcollation));
  		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 PlaceHolderVars and 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 PHVs and 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_placeholdervar and replace_outer_agg).  That's exactly
   * what we want for the vars of the parent level --- but if a PHV's or
   * 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 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 PHVs/aggregates.  Those are not touched inside the
   * intermediate query level, either.  Instead, SS_process_sublinks recurses on
   * them after copying the PHV or 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, PlaceHolderVar))
  	{
  		if (((PlaceHolderVar *) node)->phlevelsup > 0)
  			return (Node *) replace_outer_placeholdervar(root,
  														 (PlaceHolderVar *) node);
  	}
  	if (IsA(node, Aggref))
  	{
  		if (((Aggref *) node)->agglevelsup > 0)
  			return (Node *) replace_outer_agg(root, (Aggref *) node);
  	}
  	if (IsA(node, GroupingFunc))
  	{
  		if (((GroupingFunc *) node)->agglevelsup > 0)
  			return (Node *) replace_outer_grouping(root, (GroupingFunc *) 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,
  							sublink->subLinkId,
  							testexpr,
  							context->isTopQual);
  	}
  
  	/*
  	 * Don't recurse into the arguments of an outer PHV or 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 PHV or Aggref
  	 * into the arguments to be passed down to the current subplan.
  	 */
  	if (IsA(node, PlaceHolderVar))
  	{
  		if (((PlaceHolderVar *) node)->phlevelsup > 0)
  			return node;
  	}
  	else 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_identify_outer_params - identify the Params available from outer levels
   *
   * This must be run after SS_replace_correlation_vars and SS_process_sublinks
   * processing is complete in a given query level as well as all of its
   * descendant levels (which means it's most practical to do it at the end of
   * processing the query level).  We compute the set of paramIds that outer
   * levels will make available to this level+descendants, and record it in
   * root->outer_params for use while computing extParam/allParam sets in final
   * plan cleanup.  (We can't just compute it then, because the upper levels'
   * plan_params lists are transient and will be gone by then.)
   */
  void
  SS_identify_outer_params(PlannerInfo *root)
  {
  	Bitmapset  *outer_params;
  	PlannerInfo *proot;
  	ListCell   *l;
  
  	/*
  	 * If no parameters have been assigned anywhere in the tree, we certainly
  	 * don't need to do anything here.
  	 */
  	if (root->glob->nParamExec == 0)
  		return;
  
  	/*
  	 * Scan all query levels above this one to see which parameters are due to
  	 * be available from them, either because lower query levels have
  	 * requested them (via plan_params) or because they will be available from
  	 * initPlans of those levels.
  	 */
  	outer_params = NULL;
  	for (proot = root->parent_root; proot != NULL; proot = proot->parent_root)
  	{
  		/* Include ordinary Var/PHV/Aggref params */
  		foreach(l, proot->plan_params)
  		{
  			PlannerParamItem *pitem = (PlannerParamItem *) lfirst(l);
  
  			outer_params = bms_add_member(outer_params, pitem->paramId);
  		}
  		/* Include any outputs of outer-level initPlans */
  		foreach(l, proot->init_plans)
  		{
  			SubPlan    *initsubplan = (SubPlan *) lfirst(l);
  			ListCell   *l2;
  
  			foreach(l2, initsubplan->setParam)
  			{
  				outer_params = bms_add_member(outer_params, lfirst_int(l2));
  			}
  		}
  		/* Include worktable ID, if a recursive query is being planned */
  		if (proot->wt_param_id >= 0)
  			outer_params = bms_add_member(outer_params, proot->wt_param_id);
  	}
  	root->outer_params = outer_params;
  }
  
  /*
   * SS_charge_for_initplans - account for initplans in Path costs & parallelism
   *
   * If any initPlans have been created in the current query level, they will
   * get attached to the Plan tree created from whichever Path we select from
   * the given rel.  Increment all that rel's Paths' costs to account for them,
   * and make sure the paths get marked as parallel-unsafe, since we can't
   * currently transmit initPlans to parallel workers.
   *
   * This is separate from SS_attach_initplans because we might conditionally
   * create more initPlans during create_plan(), depending on which Path we
   * select.  However, Paths that would generate such initPlans are expected
   * to have included their cost already.
   */
  void
  SS_charge_for_initplans(PlannerInfo *root, RelOptInfo *final_rel)
  {
  	Cost		initplan_cost;
  	ListCell   *lc;
  
  	/* Nothing to do if no initPlans */
  	if (root->init_plans == NIL)
  		return;
  
  	/*
  	 * Compute the cost increment just once, since it will be the same for all
  	 * Paths.  We assume each initPlan gets run once during top plan startup.
  	 * This is a conservative overestimate, since in fact an initPlan might be
  	 * executed later than plan startup, or even not at all.
  	 */
  	initplan_cost = 0;
  	foreach(lc, root->init_plans)
  	{
  		SubPlan    *initsubplan = (SubPlan *) lfirst(lc);
  
  		initplan_cost += initsubplan->startup_cost + initsubplan->per_call_cost;
  	}
  
  	/*
  	 * Now adjust the costs and parallel_safe flags.
  	 */
  	foreach(lc, final_rel->pathlist)
  	{
  		Path	   *path = (Path *) lfirst(lc);
  
  		path->startup_cost += initplan_cost;
  		path->total_cost += initplan_cost;
  		path->parallel_safe = false;
  	}
  
  	/* We needn't do set_cheapest() here, caller will do it */
  }
  
  /*
   * SS_attach_initplans - attach initplans to topmost plan node
   *
   * Attach any initplans created in the current query level to the specified
   * plan node, which should normally be the topmost node for the query level.
   * (In principle the initPlans could go in any node at or above where they're
   * referenced; but there seems no reason to put them any lower than the
   * topmost node, so we don't bother to track exactly where they came from.)
   * We do not touch the plan node's cost; the initplans should have been
   * accounted for in path costing.
   */
  void
  SS_attach_initplans(PlannerInfo *root, Plan *plan)
  {
  	plan->initPlan = root->init_plans;
  }
  
  /*
   * SS_finalize_plan - do final parameter processing for a completed Plan.
   *
   * This recursively computes the extParam and allParam sets for every Plan
   * node in the given plan tree.  (Oh, and RangeTblFunction.funcparams too.)
   *
   * We assume that SS_finalize_plan has already been run on any initplans or
   * subplans the plan tree could reference.
   */
  void
  SS_finalize_plan(PlannerInfo *root, Plan *plan)
  {
  	/* No setup needed, just recurse through plan tree. */
  	(void) finalize_plan(root, plan, -1, root->outer_params, NULL);
  }
  
  /*
   * Recursive processing of all nodes in the plan tree
   *
   * gather_param is the rescan_param of an ancestral Gather/GatherMerge,
   * or -1 if there is none.
   *
   * valid_params is the set of param IDs supplied by outer plan levels
   * that are valid to reference in this plan node or its children.
   *
   * scan_params is a set of param IDs to force scan plan nodes to reference.
   * This is for EvalPlanQual support, and is always NULL at the top of the
   * recursion.
   *
   * The return value is the computed allParam set for the given Plan node.
   * This is just an internal notational convenience: we can add a child
   * plan's allParams to the set of param IDs of interest to this level
   * in the same statement that recurses to that child.
   *
   * Do not scribble on caller's values of valid_params or scan_params!
   *
   * Note: although we attempt to deal with initPlans anywhere in the tree, the
   * logic is not really right.  The problem is that a plan node might return an
   * output Param of its initPlan as a targetlist item, in which case it's valid
   * for the parent plan level to reference that same Param; the parent's usage
   * will be converted into a Var referencing the child plan node by setrefs.c.
   * But this function would see the parent's reference as out of scope and
   * complain about it.  For now, this does not matter because the planner only
   * attaches initPlans to the topmost plan node in a query level, so the case
   * doesn't arise.  If we ever merge this processing into setrefs.c, maybe it
   * can be handled more cleanly.
   */
  static Bitmapset *
  finalize_plan(PlannerInfo *root, Plan *plan,
  			  int gather_param,
  			  Bitmapset *valid_params,
  			  Bitmapset *scan_params)
  {
  	finalize_primnode_context context;
  	int			locally_added_param;
  	Bitmapset  *nestloop_params;
  	Bitmapset  *initExtParam;
  	Bitmapset  *initSetParam;
  	Bitmapset  *child_params;
  	ListCell   *l;
  
  	if (plan == NULL)
  		return NULL;
  
  	context.root = root;
  	context.paramids = NULL;	/* initialize set to empty */
  	locally_added_param = -1;	/* there isn't one */
  	nestloop_params = NULL;		/* there aren't any */
  
  	/*
  	 * Examine any initPlans to determine the set of external params they
  	 * reference and the set of output params they supply.  (We assume
  	 * SS_finalize_plan was run on them already.)
  	 */
  	initExtParam = initSetParam = NULL;
  	foreach(l, plan->initPlan)
  	{
  		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));
  		}
  	}
  
  	/* Any setParams are validly referenceable in this node and children */
  	if (initSetParam)
  		valid_params = bms_union(valid_params, initSetParam);
  
  	/*
  	 * 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);
  
  	/*
  	 * If it's a parallel-aware scan node, mark it as dependent on the parent
  	 * Gather/GatherMerge's rescan Param.
  	 */
  	if (plan->parallel_aware)
  	{
  		if (gather_param < 0)
  			elog(ERROR, "parallel-aware plan node is not below a Gather");
  		context.paramids =
  			bms_add_member(context.paramids, gather_param);
  	}
  
  	/* Check additional node-type-specific fields */
  	switch (nodeTag(plan))
  	{
  		case T_Result:
  			finalize_primnode(((Result *) plan)->resconstantqual,
  							  &context);
  			break;
  
  		case T_SeqScan:
  			context.paramids = bms_add_members(context.paramids, scan_params);
  			break;
  
  		case T_SampleScan:
  			finalize_primnode((Node *) ((SampleScan *) plan)->tablesample,
  							  &context);
  			context.paramids = bms_add_members(context.paramids, scan_params);
  			break;
  
  		case T_IndexScan:
  			finalize_primnode((Node *) ((IndexScan *) plan)->indexqual,
  							  &context);
  			finalize_primnode((Node *) ((IndexScan *) plan)->indexorderby,
  							  &context);
  
  			/*
  			 * we need not look at indexqualorig, since it will have the same
  			 * param references as indexqual.  Likewise, we can ignore
  			 * indexorderbyorig.
  			 */
  			context.paramids = bms_add_members(context.paramids, scan_params);
  			break;
  
  		case T_IndexOnlyScan:
  			finalize_primnode((Node *) ((IndexOnlyScan *) plan)->indexqual,
  							  &context);
  			finalize_primnode((Node *) ((IndexOnlyScan *) plan)->indexorderby,
  							  &context);
  
  			/*
  			 * we need not look at indextlist, since it cannot contain Params.
  			 */
  			context.paramids = bms_add_members(context.paramids, scan_params);
  			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);
  			context.paramids = bms_add_members(context.paramids, scan_params);
  			break;
  
  		case T_TidScan:
  			finalize_primnode((Node *) ((TidScan *) plan)->tidquals,
  							  &context);
  			context.paramids = bms_add_members(context.paramids, scan_params);
  			break;
  
  		case T_SubqueryScan:
  			{
  				SubqueryScan *sscan = (SubqueryScan *) plan;
  				RelOptInfo *rel;
  
  				/* We must run SS_finalize_plan on the subquery */
  				rel = find_base_rel(root, sscan->scan.scanrelid);
  				SS_finalize_plan(rel->subroot, sscan->subplan);
  
  				/* Now we can add its extParams to the parent's params */
  				context.paramids = bms_add_members(context.paramids,
  												   sscan->subplan->extParam);
  				/* We need scan_params too, though */
  				context.paramids = bms_add_members(context.paramids,
  												   scan_params);
  			}
  			break;
  
  		case T_FunctionScan:
  			{
  				FunctionScan *fscan = (FunctionScan *) plan;
  				ListCell   *lc;
  
  				/*
  				 * Call finalize_primnode independently on each function
  				 * expression, so that we can record which params are
  				 * referenced in each, in order to decide which need
  				 * re-evaluating during rescan.
  				 */
  				foreach(lc, fscan->functions)
  				{
  					RangeTblFunction *rtfunc = (RangeTblFunction *) lfirst(lc);
  					finalize_primnode_context funccontext;
  
  					funccontext = context;
  					funccontext.paramids = NULL;
  
  					finalize_primnode(rtfunc->funcexpr, &funccontext);
  
  					/* remember results for execution */
  					rtfunc->funcparams = funccontext.paramids;
  
  					/* add the function's params to the overall set */
  					context.paramids = bms_add_members(context.paramids,
  													   funccontext.paramids);
  				}
  
  				context.paramids = bms_add_members(context.paramids,
  												   scan_params);
  			}
  			break;
  
  		case T_TableFuncScan:
  			finalize_primnode((Node *) ((TableFuncScan *) plan)->tablefunc,
  							  &context);
  			context.paramids = bms_add_members(context.paramids, scan_params);
  			break;
  
  		case T_ValuesScan:
  			finalize_primnode((Node *) ((ValuesScan *) plan)->values_lists,
  							  &context);
  			context.paramids = bms_add_members(context.paramids, scan_params);
  			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.  (We assume
  				 * SS_finalize_plan was run on the CTE plan already.)
  				 */
  				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
  
  				context.paramids = bms_add_members(context.paramids,
  												   scan_params);
  			}
  			break;
  
  		case T_WorkTableScan:
  			context.paramids =
  				bms_add_member(context.paramids,
  							   ((WorkTableScan *) plan)->wtParam);
  			context.paramids = bms_add_members(context.paramids, scan_params);
  			break;
  
  		case T_NamedTuplestoreScan:
  			context.paramids = bms_add_members(context.paramids, scan_params);
  			break;
  
  		case T_ForeignScan:
  			{
  				ForeignScan *fscan = (ForeignScan *) plan;
  
  				finalize_primnode((Node *) fscan->fdw_exprs,
  								  &context);
  				finalize_primnode((Node *) fscan->fdw_recheck_quals,
  								  &context);
  
  				/* We assume fdw_scan_tlist cannot contain Params */
  				context.paramids = bms_add_members(context.paramids,
  												   scan_params);
  			}
  			break;
  
  		case T_CustomScan:
  			{
  				CustomScan *cscan = (CustomScan *) plan;
  				ListCell   *lc;
  
  				finalize_primnode((Node *) cscan->custom_exprs,
  								  &context);
  				/* We assume custom_scan_tlist cannot contain Params */
  				context.paramids =
  					bms_add_members(context.paramids, scan_params);
  
  				/* child nodes if any */
  				foreach(lc, cscan->custom_plans)
  				{
  					context.paramids =
  						bms_add_members(context.paramids,
  										finalize_plan(root,
  													  (Plan *) lfirst(lc),
  													  gather_param,
  													  valid_params,
  													  scan_params));
  				}
  			}
  			break;
  
  		case T_ModifyTable:
  			{
  				ModifyTable *mtplan = (ModifyTable *) plan;
  				ListCell   *l;
  
  				/* Force descendant scan nodes to reference epqParam */
  				locally_added_param = mtplan->epqParam;
  				valid_params = bms_add_member(bms_copy(valid_params),
  											  locally_added_param);
  				scan_params = bms_add_member(bms_copy(scan_params),
  											 locally_added_param);
  				finalize_primnode((Node *) mtplan->returningLists,
  								  &context);
  				finalize_primnode((Node *) mtplan->onConflictSet,
  								  &context);
  				finalize_primnode((Node *) mtplan->onConflictWhere,
  								  &context);
  				/* exclRelTlist contains only Vars, doesn't need examination */
  				foreach(l, mtplan->plans)
  				{
  					context.paramids =
  						bms_add_members(context.paramids,
  										finalize_plan(root,
  													  (Plan *) lfirst(l),
  													  gather_param,
  													  valid_params,
  													  scan_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),
  													  gather_param,
  													  valid_params,
  													  scan_params));
  				}
  			}
  			break;
  
  		case T_MergeAppend:
  			{
  				ListCell   *l;
  
  				foreach(l, ((MergeAppend *) plan)->mergeplans)
  				{
  					context.paramids =
  						bms_add_members(context.paramids,
  										finalize_plan(root,
  													  (Plan *) lfirst(l),
  													  gather_param,
  													  valid_params,
  													  scan_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),
  													  gather_param,
  													  valid_params,
  													  scan_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),
  													  gather_param,
  													  valid_params,
  													  scan_params));
  				}
  			}
  			break;
  
  		case T_NestLoop:
  		case T_NestLoopVLE:
  			{
  				ListCell   *l;
  
  				finalize_primnode((Node *) ((Join *) plan)->joinqual,
  								  &context);
  				/* collect set of params that will be passed to right child */
  				foreach(l, ((NestLoop *) plan)->nestParams)
  				{
  					NestLoopParam *nlp = (NestLoopParam *) lfirst(l);
  
  					nestloop_params = bms_add_member(nestloop_params,
  													 nlp->paramno);
  				}
  			}
  			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:
  			/* child nodes are allowed to reference wtParam */
  			locally_added_param = ((RecursiveUnion *) plan)->wtParam;
  			valid_params = bms_add_member(bms_copy(valid_params),
  										  locally_added_param);
  			/* wtParam does *not* get added to scan_params */
  			break;
  
  		case T_LockRows:
  			/* Force descendant scan nodes to reference epqParam */
  			locally_added_param = ((LockRows *) plan)->epqParam;
  			valid_params = bms_add_member(bms_copy(valid_params),
  										  locally_added_param);
  			scan_params = bms_add_member(bms_copy(scan_params),
  										 locally_added_param);
  			break;
  
  		case T_Agg:
  			{
  				Agg		   *agg = (Agg *) plan;
  
  				/*
  				 * AGG_HASHED plans need to know which Params are referenced
  				 * in aggregate calls.  Do a separate scan to identify them.
  				 */
  				if (agg->aggstrategy == AGG_HASHED)
  				{
  					finalize_primnode_context aggcontext;
  
  					aggcontext.root = root;
  					aggcontext.paramids = NULL;
  					finalize_agg_primnode((Node *) agg->plan.targetlist,
  										  &aggcontext);
  					finalize_agg_primnode((Node *) agg->plan.qual,
  										  &aggcontext);
  					agg->aggParams = aggcontext.paramids;
  				}
  			}
  			break;
  
  		case T_WindowAgg:
  			finalize_primnode(((WindowAgg *) plan)->startOffset,
  							  &context);
  			finalize_primnode(((WindowAgg *) plan)->endOffset,
  							  &context);
  			break;
  
  		case T_Gather:
  			/* child nodes are allowed to reference rescan_param, if any */
  			locally_added_param = ((Gather *) plan)->rescan_param;
  			if (locally_added_param >= 0)
  			{
  				valid_params = bms_add_member(bms_copy(valid_params),
  											  locally_added_param);
  
  				/*
  				 * We currently don't support nested Gathers.  The issue so
  				 * far as this function is concerned would be how to identify
  				 * which child nodes depend on which Gather.
  				 */
  				Assert(gather_param < 0);
  				/* Pass down rescan_param to child parallel-aware nodes */
  				gather_param = locally_added_param;
  			}
  			/* rescan_param does *not* get added to scan_params */
  			break;
  
  		case T_GatherMerge:
  			/* child nodes are allowed to reference rescan_param, if any */
  			locally_added_param = ((GatherMerge *) plan)->rescan_param;
  			if (locally_added_param >= 0)
  			{
  				valid_params = bms_add_member(bms_copy(valid_params),
  											  locally_added_param);
  
  				/*
  				 * We currently don't support nested Gathers.  The issue so
  				 * far as this function is concerned would be how to identify
  				 * which child nodes depend on which Gather.
  				 */
  				Assert(gather_param < 0);
  				/* Pass down rescan_param to child parallel-aware nodes */
  				gather_param = locally_added_param;
  			}
  			/* rescan_param does *not* get added to scan_params */
  			break;
  
  		case T_ProjectSet:
  		case T_Hash:
  		case T_Material:
  		case T_Sort:
  		case T_Unique:
  		case T_SetOp:
  		case T_Group:
  		case T_Hash2Side:
  			/* no node-type-specific fields need fixing */
  			break;
  
  		case T_ModifyGraph:
  			{
  				ModifyGraph *mgplan = (ModifyGraph *) plan;
  				ListCell   *lc;
  
  				foreach(lc, mgplan->pattern)
  				{
  					GraphPath  *gpath = lfirst(lc);
  					ListCell   *le;
  
  					foreach(le, gpath->chain)
  					{
  						Node	   *elem = lfirst(le);
  						Node	   *expr;
  
  						if (IsA(elem, GraphVertex))
  						{
  							expr = ((GraphVertex *) elem)->expr;
  						}
  						else
  						{
  							Assert(IsA(elem, GraphEdge));
  							expr = ((GraphEdge *) elem)->expr;
  						}
  
  						finalize_primnode(expr, &context);
  					}
  				}
  
  				foreach(lc, mgplan->exprs)
  				{
  					GraphDelElem *gde = lfirst(lc);
  
  					finalize_primnode(gde->elem, &context);
  				}
  
  				foreach(lc, mgplan->sets)
  				{
  					GraphSetProp *gsp = lfirst(lc);
  
  					finalize_primnode(gsp->elem, &context);
  					finalize_primnode(gsp->expr, &context);
  				}
  
  				context.paramids =
  						bms_add_members(context.paramids,
  										finalize_plan(root,
  													  mgplan->subplan,
  													  gather_param,
  													  valid_params,
  													  scan_params));
  			}
  			break;
  
  		case T_Shortestpath:
  			finalize_primnode(((Shortestpath *) plan)->source, &context);
  			finalize_primnode(((Shortestpath *) plan)->target, &context);
  			break;
  
  		case T_Dijkstra:
  			finalize_primnode(((Dijkstra *) plan)->source, &context);
  			finalize_primnode(((Dijkstra *) plan)->target, &context);
  			finalize_primnode(((Dijkstra *) plan)->limit, &context);
  			break;
  
  		default:
  			elog(ERROR, "unrecognized node type: %d",
  				 (int) nodeTag(plan));
  	}
  
  	/* Process left and right child plans, if any */
  	child_params = finalize_plan(root,
  								 plan->lefttree,
  								 gather_param,
  								 valid_params,
  								 scan_params);
  	context.paramids = bms_add_members(context.paramids, child_params);
  
  	if (nestloop_params)
  	{
  		/* right child can reference nestloop_params as well as valid_params */
  		child_params = finalize_plan(root,
  									 plan->righttree,
  									 gather_param,
  									 bms_union(nestloop_params, valid_params),
  									 scan_params);
  		/* ... and they don't count as parameters used at my level */
  		child_params = bms_difference(child_params, nestloop_params);
  		bms_free(nestloop_params);
  	}
  	else
  	{
  		/* easy case */
  		child_params = finalize_plan(root,
  									 plan->righttree,
  									 gather_param,
  									 valid_params,
  									 scan_params);
  	}
  	context.paramids = bms_add_members(context.paramids, child_params);
  
  	/*
  	 * Any locally generated parameter doesn't count towards its generating
  	 * plan node's external dependencies.  (Note: if we changed valid_params
  	 * and/or scan_params, we leak those bitmapsets; not worth the notational
  	 * trouble to clean them up.)
  	 */
  	if (locally_added_param >= 0)
  	{
  		context.paramids = bms_del_member(context.paramids,
  										  locally_added_param);
  	}
  
  	/* Now we have all the paramids referenced in this node and children */
  
  	if (!bms_is_subset(context.paramids, valid_params))
  		elog(ERROR, "plan should not reference subplan's variable");
  
  	/*
  	 * The plan node's allParam and extParam fields should include all its
  	 * referenced paramids, plus contributions from any child initPlans.
  	 * However, any setParams of the initPlans should not be present in the
  	 * parent node's extParams, only in its allParams.  (It's possible that
  	 * some initPlans have extParams that are setParams of other initPlans.)
  	 */
  
  	/* allParam must include initplans' extParams and setParams */
  	plan->allParam = bms_union(context.paramids, initExtParam);
  	plan->allParam = bms_add_members(plan->allParam, initSetParam);
  	/* extParam must include any initplan extParams */
  	plan->extParam = bms_union(context.paramids, initExtParam);
  	/* but not any initplan setParams */
  	plan->extParam = bms_del_members(plan->extParam, initSetParam);
  
  	/*
  	 * For speed at execution time, make sure extParam/allParam are actually
  	 * NULL if they are empty sets.
  	 */
  	if (bms_is_empty(plan->extParam))
  		plan->extParam = NULL;
  	if (bms_is_empty(plan->allParam))
  		plan->allParam = NULL;
  
  	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.  (We assume SS_finalize_plan was run on
  		 * the subplan already.)
  		 */
  		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);
  }
  
  /*
   * finalize_agg_primnode: find all Aggref nodes in the given expression tree,
   * and add IDs of all PARAM_EXEC params appearing within their aggregated
   * arguments to the result set.
   */
  static bool
  finalize_agg_primnode(Node *node, finalize_primnode_context *context)
  {
  	if (node == NULL)
  		return false;
  	if (IsA(node, Aggref))
  	{
  		Aggref	   *agg = (Aggref *) node;
  
  		/* we should not consider the direct arguments, if any */
  		finalize_primnode((Node *) agg->args, context);
  		finalize_primnode((Node *) agg->aggfilter, context);
  		return false;			/* there can't be any Aggrefs below here */
  	}
  	return expression_tree_walker(node, finalize_agg_primnode,
  								  (void *) context);
  }
  
  /*
   * SS_make_initplan_output_param - make a Param for an initPlan's output
   *
   * The plan is expected to return a scalar value of the given type/collation.
   *
   * Note that in some cases the initplan may not ever appear in the finished
   * plan tree.  If that happens, we'll have wasted a PARAM_EXEC slot, which
   * is no big deal.
   */
  Param *
  SS_make_initplan_output_param(PlannerInfo *root,
  							  Oid resulttype, int32 resulttypmod,
  							  Oid resultcollation)
  {
  	return generate_new_param(root, resulttype, resulttypmod, resultcollation);
  }
  
  /*
   * SS_make_initplan_from_plan - given a plan tree, make it an InitPlan
   *
   * We build an EXPR_SUBLINK SubPlan node and put it into the initplan
   * list for the outer query level.  A Param that represents the initplan's
   * output has already been assigned using SS_make_initplan_output_param.
   */
  void
  SS_make_initplan_from_plan(PlannerInfo *root,
  						   PlannerInfo *subroot, Plan *plan,
  						   Param *prm)
  {
  	SubPlan    *node;
  
  	/*
  	 * Add the subplan and its PlannerInfo to the global lists.
  	 */
  	root->glob->subplans = lappend(root->glob->subplans, plan);
  	root->glob->subroots = lappend(root->glob->subroots, subroot);
  
  	/*
  	 * 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;
  	node->plan_id = list_length(root->glob->subplans);
  	node->plan_name = psprintf("InitPlan %d (returns $%d)",
  							   node->plan_id, prm->paramid);
  	get_first_col_type(plan, &node->firstColType, &node->firstColTypmod,
  					   &node->firstColCollation);
  	node->setParam = list_make1_int(prm->paramid);
  
  	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.
  	 */
  
  	/* Set costs of SubPlan using info from the plan tree */
  	cost_subplan(subroot, node, plan);
  }
  