text: /*-------------------------------------------------------------------------
   *
   * clauses.c
   *	  routines to manipulate qualification clauses
   *
   * Portions Copyright (c) 2005-2008, Greenplum inc
   * Portions Copyright (c) 2012-Present Pivotal Software, Inc.
   * Portions Copyright (c) 1996-2014, PostgreSQL Global Development Group
   * Portions Copyright (c) 1994, Regents of the University of California
   *
   *
   * IDENTIFICATION
   *	  src/backend/optimizer/util/clauses.c
   *
   * HISTORY
   *	  AUTHOR			DATE			MAJOR EVENT
   *	  Andrew Yu			Nov 3, 1994		clause.c and clauses.c combined
   *
   *-------------------------------------------------------------------------
   */
  
  #include "postgres.h"
  
  #include "access/htup_details.h"
  #include "catalog/pg_aggregate.h"
  #include "catalog/pg_language.h"
  #include "catalog/pg_operator.h"
  #include "catalog/pg_proc.h"
  #include "catalog/pg_type.h"
  #include "executor/executor.h"
  #include "executor/functions.h"
  #include "funcapi.h"
  #include "miscadmin.h"
  #include "nodes/makefuncs.h"
  #include "nodes/nodeFuncs.h"
  #include "optimizer/clauses.h"
  #include "optimizer/cost.h"
  #include "optimizer/planmain.h"
  #include "optimizer/prep.h"
  #include "optimizer/var.h"
  #include "parser/analyze.h"
  #include "parser/parse_agg.h"
  #include "parser/parse_coerce.h"
  #include "parser/parse_func.h"
  #include "rewrite/rewriteManip.h"
  #include "tcop/tcopprot.h"
  #include "utils/acl.h"
  #include "utils/builtins.h"
  #include "utils/datum.h"
  #include "utils/fmgroids.h"
  #include "utils/lsyscache.h"
  #include "utils/memutils.h"
  #include "utils/syscache.h"
  #include "utils/typcache.h"
  
  
  typedef struct
  {
  	PlannerInfo *root;
  	AggClauseCosts *costs;
  } count_agg_clauses_context;
  
  typedef struct
  {
  	ParamListInfo boundParams;
  	PlannerInfo *root;
  	List	   *active_fns;
  	Node	   *case_val;
  	bool		estimate;
  	bool		eval_stable_functions;
  	bool		recurse_queries; /* recurse into query structures */
  	bool		recurse_sublink_testexpr; /* recurse into sublink test expressions */
  	Size        max_size; /* max constant binary size in bytes, 0: no restrictions */
  } eval_const_expressions_context;
  
  typedef struct
  {
  	int			nargs;
  	List	   *args;
  	int		   *usecounts;
  } substitute_actual_parameters_context;
  
  typedef struct
  {
  	int			nargs;
  	List	   *args;
  	int			sublevels_up;
  } substitute_actual_srf_parameters_context;
  
  typedef struct
  {
  	char	   *proname;
  	char	   *prosrc;
  } inline_error_callback_arg;
  
  static bool contain_agg_clause_walker(Node *node, void *context);
  static bool count_agg_clauses_walker(Node *node,
  						 count_agg_clauses_context *context);
  static bool find_window_functions_walker(Node *node, WindowFuncLists *lists);
  static bool expression_returns_set_rows_walker(Node *node, double *count);
  static bool contain_subplans_walker(Node *node, void *context);
  static bool contain_mutable_functions_walker(Node *node, void *context);
  static bool contain_volatile_functions_walker(Node *node, void *context);
  static bool contain_volatile_functions_not_nextval_walker(Node *node, void *context);
  static bool contain_nonstrict_functions_walker(Node *node, void *context);
  static bool contain_context_dependent_node(Node *clause);
  static bool contain_context_dependent_node_walker(Node *node, int *flags);
  static bool contain_leaky_functions_walker(Node *node, void *context);
  static Relids find_nonnullable_rels_walker(Node *node, bool top_level);
  static List *find_nonnullable_vars_walker(Node *node, bool top_level);
  static bool is_strict_saop(ScalarArrayOpExpr *expr, bool falseOK);
  static Node *eval_const_expressions_mutator(Node *node,
  							   eval_const_expressions_context *context);
  static List *simplify_or_arguments(List *args,
  					  eval_const_expressions_context *context,
  					  bool *haveNull, bool *forceTrue);
  static List *simplify_and_arguments(List *args,
  					   eval_const_expressions_context *context,
  					   bool *haveNull, bool *forceFalse);
  static Node *simplify_boolean_equality(Oid opno, List *args);
  static Expr *simplify_function(Oid funcid,
  				  Oid result_type, int32 result_typmod,
  				  Oid result_collid, Oid input_collid, List **args_p,
  				  bool funcvariadic, bool process_args, bool allow_non_const,
  				  eval_const_expressions_context *context);
  static bool large_const(Expr *expr, Size max_size);
  static List *expand_function_arguments(List *args, Oid result_type,
  						  HeapTuple func_tuple);
  static List *reorder_function_arguments(List *args, HeapTuple func_tuple);
  static List *add_function_defaults(List *args, HeapTuple func_tuple);
  static List *fetch_function_defaults(HeapTuple func_tuple);
  static void recheck_cast_function_args(List *args, Oid result_type,
  						   HeapTuple func_tuple);
  static Expr *evaluate_function(Oid funcid, Oid result_type, int32 result_typmod,
  				  Oid result_collid, Oid input_collid, List *args,
  				  bool funcvariadic,
  				  HeapTuple func_tuple,
  				  eval_const_expressions_context *context);
  static Expr *inline_function(Oid funcid, Oid result_type, Oid result_collid,
  				Oid input_collid, List *args,
  				bool funcvariadic,
  				HeapTuple func_tuple,
  				eval_const_expressions_context *context);
  static Node *substitute_actual_parameters(Node *expr, int nargs, List *args,
  							 int *usecounts);
  static Node *substitute_actual_parameters_mutator(Node *node,
  							  substitute_actual_parameters_context *context);
  static void sql_inline_error_callback(void *arg);
  static Query *substitute_actual_srf_parameters(Query *expr,
  								 int nargs, List *args);
  static Node *substitute_actual_srf_parameters_mutator(Node *node,
  						  substitute_actual_srf_parameters_context *context);
  static bool tlist_matches_coltypelist(List *tlist, List *coltypelist);
  static bool contain_grouping_clause_walker(Node *node, void *context);
  
  /*
   * Greenplum specific functions
   */
  static bool should_eval_stable_functions(PlannerInfo *root);
  
  /*****************************************************************************
   *		OPERATOR clause functions
   *****************************************************************************/
  
  /*
   * make_opclause
   *	  Creates an operator clause given its operator info, left operand
   *	  and right operand (pass NULL to create single-operand clause),
   *	  and collation info.
   */
  Expr *
  make_opclause(Oid opno, Oid opresulttype, bool opretset,
  			  Expr *leftop, Expr *rightop,
  			  Oid opcollid, Oid inputcollid)
  {
  	OpExpr	   *expr = makeNode(OpExpr);
  
  	expr->opno = opno;
  	expr->opfuncid = InvalidOid;
  	expr->opresulttype = opresulttype;
  	expr->opretset = opretset;
  	expr->opcollid = opcollid;
  	expr->inputcollid = inputcollid;
  	if (rightop)
  		expr->args = list_make2(leftop, rightop);
  	else
  		expr->args = list_make1(leftop);
  	expr->location = -1;
  	return (Expr *) expr;
  }
  
  /*
   * get_leftop
   *
   * Returns the left operand of a clause of the form (op expr expr)
   *		or (op expr)
   */
  Node *
  get_leftop(const Expr *clause)
  {
  	const OpExpr *expr = (const OpExpr *) clause;
  
  	if (expr->args != NIL)
  		return linitial(expr->args);
  	else
  		return NULL;
  }
  
  /*
   * get_rightop
   *
   * Returns the right operand in a clause of the form (op expr expr).
   * NB: result will be NULL if applied to a unary op clause.
   */
  Node *
  get_rightop(const Expr *clause)
  {
  	const OpExpr *expr = (const OpExpr *) clause;
  
  	if (list_length(expr->args) >= 2)
  		return lsecond(expr->args);
  	else
  		return NULL;
  }
  
  /*
   * get_leftscalararrayop
   *
   * Returns the left operand of a clause of the form (scalar op ANY/ALL (array))
   */
  Node *
  get_leftscalararrayop(const Expr *clause)
  {
  	const ScalarArrayOpExpr *expr = (const ScalarArrayOpExpr *) clause;
  
  	if (expr->args != NIL)
  		return linitial(expr->args);
  	else
  		return NULL;
  }
  
  /*
   * get_rightscalararrayop
   *
   * Returns the right operand in a clause of the form (scalar op ANY/ALL (array)).
   */
  Node *
  get_rightscalararrayop(const Expr *clause)
  {
  	const ScalarArrayOpExpr *expr = (const ScalarArrayOpExpr *) clause;
  
  	if (list_length(expr->args) >= 2)
  		return lsecond(expr->args);
  	else
  		return NULL;
  }
  
  /*****************************************************************************
   *		NOT clause functions
   *****************************************************************************/
  
  /*
   * not_clause
   *
   * Returns t iff this is a 'not' clause: (NOT expr).
   */
  bool
  not_clause(Node *clause)
  {
  	return (clause != NULL &&
  			IsA(clause, BoolExpr) &&
  			((BoolExpr *) clause)->boolop == NOT_EXPR);
  }
  
  /*
   * make_notclause
   *
   * Create a 'not' clause given the expression to be negated.
   */
  Expr *
  make_notclause(Expr *notclause)
  {
  	BoolExpr   *expr = makeNode(BoolExpr);
  
  	expr->boolop = NOT_EXPR;
  	expr->args = list_make1(notclause);
  	expr->location = -1;
  	return (Expr *) expr;
  }
  
  /*
   * get_notclausearg
   *
   * Retrieve the clause within a 'not' clause
   */
  Expr *
  get_notclausearg(Expr *notclause)
  {
  	return linitial(((BoolExpr *) notclause)->args);
  }
  
  /*****************************************************************************
   *		OR clause functions
   *****************************************************************************/
  
  /*
   * or_clause
   *
   * Returns t iff the clause is an 'or' clause: (OR { expr }).
   */
  bool
  or_clause(Node *clause)
  {
  	return (clause != NULL &&
  			IsA(clause, BoolExpr) &&
  			((BoolExpr *) clause)->boolop == OR_EXPR);
  }
  
  /*
   * make_orclause
   *
   * Creates an 'or' clause given a list of its subclauses.
   */
  Expr *
  make_orclause(List *orclauses)
  {
  	BoolExpr   *expr = makeNode(BoolExpr);
  
  	expr->boolop = OR_EXPR;
  	expr->args = orclauses;
  	expr->location = -1;
  	return (Expr *) expr;
  }
  
  /*****************************************************************************
   *		AND clause functions
   *****************************************************************************/
  
  
  /*
   * and_clause
   *
   * Returns t iff its argument is an 'and' clause: (AND { expr }).
   */
  bool
  and_clause(Node *clause)
  {
  	return (clause != NULL &&
  			IsA(clause, BoolExpr) &&
  			((BoolExpr *) clause)->boolop == AND_EXPR);
  }
  
  /*
   * make_andclause
   *
   * Creates an 'and' clause given a list of its subclauses.
   */
  Expr *
  make_andclause(List *andclauses)
  {
  	BoolExpr   *expr = makeNode(BoolExpr);
  
  	expr->boolop = AND_EXPR;
  	expr->args = andclauses;
  	expr->location = -1;
  	return (Expr *) expr;
  }
  
  /*
   * make_and_qual
   *
   * Variant of make_andclause for ANDing two qual conditions together.
   * Qual conditions have the property that a NULL nodetree is interpreted
   * as 'true'.
   *
   * NB: this makes no attempt to preserve AND/OR flatness; so it should not
   * be used on a qual that has already been run through prepqual.c.
   */
  Node *
  make_and_qual(Node *qual1, Node *qual2)
  {
  	if (qual1 == NULL)
  		return qual2;
  	if (qual2 == NULL)
  		return qual1;
  	return (Node *) make_andclause(list_make2(qual1, qual2));
  }
  
  /*
   * Sometimes (such as in the input of ExecQual), we use lists of expression
   * nodes with implicit AND semantics.
   *
   * These functions convert between an AND-semantics expression list and the
   * ordinary representation of a boolean expression.
   *
   * Note that an empty list is considered equivalent to TRUE.
   */
  Expr *
  make_ands_explicit(List *andclauses)
  {
  	if (andclauses == NIL)
  		return (Expr *) makeBoolConst(true, false);
  	else if (list_length(andclauses) == 1)
  		return (Expr *) linitial(andclauses);
  	else
  		return make_andclause(andclauses);
  }
  
  List *
  make_ands_implicit(Expr *clause)
  {
  	/*
  	 * NB: because the parser sets the qual field to NULL in a query that has
  	 * no WHERE clause, we must consider a NULL input clause as TRUE, even
  	 * though one might more reasonably think it FALSE.  Grumble. If this
  	 * causes trouble, consider changing the parser's behavior.
  	 */
  	if (clause == NULL)
  		return NIL;				/* NULL -> NIL list == TRUE */
  	else if (and_clause((Node *) clause))
  		return ((BoolExpr *) clause)->args;
  	else if (IsA(clause, Const) &&
  			 !((Const *) clause)->constisnull &&
  			 DatumGetBool(((Const *) clause)->constvalue))
  		return NIL;				/* constant TRUE input -> NIL list */
  	else if (IsA(clause, List))
  	{
  		/* already a list */
  		Assert(list_length((List *) clause) == 0 || !IsA(list_nth((List *) clause, 0), List));
  		return (List *) clause;
  	}
  	else
  		return list_make1(clause);
  }
  
  
  /*****************************************************************************
   *		Aggregate-function clause manipulation
   *****************************************************************************/
  
  /*
   * contain_agg_clause
   *	  Recursively search for Aggref nodes, GroupId, GroupingFunc within a clause.
   *
   *	  Returns true if any aggregate found.
   *
   * This does not descend into subqueries, and so should be used only after
   * reduction of sublinks to subplans, or in contexts where it's known there
   * are no subqueries.  There mustn't be outer-aggregate references either.
   *
   * (If you want something like this but able to deal with subqueries,
   * see rewriteManip.c's contain_aggs_of_level().)
   */
  bool
  contain_agg_clause(Node *clause)
  {
  	return contain_agg_clause_walker(clause, NULL);
  }
  
  static bool
  contain_agg_clause_walker(Node *node, void *context)
  {
  	if (node == NULL)
  		return false;
  	if (IsA(node, Aggref))
  	{
  		Assert(((Aggref *) node)->agglevelsup == 0);
  		return true;			/* abort the tree traversal and return true */
  	}
  
  	if (IsA(node, GroupId) || IsA(node, GroupingFunc))
  		return true;
  
  	Assert(!IsA(node, SubLink));
  	return expression_tree_walker(node, contain_agg_clause_walker, context);
  }
  
  /*
   * count_agg_clauses
   *	  Recursively count the Aggref nodes in an expression tree, and
   *	  accumulate other cost information about them too.
   *
   *	  Note: this also checks for nested aggregates, which are an error.
   *
   * We not only count the nodes, but estimate their execution costs, and
   * attempt to estimate the total space needed for their transition state
   * values if all are evaluated in parallel (as would be done in a HashAgg
   * plan).  See AggClauseCosts for the exact set of statistics collected.
   *
   * NOTE that the counts/costs are ADDED to those already in *costs ... so
   * the caller is responsible for zeroing the struct initially.
   *
   * This does not descend into subqueries, and so should be used only after
   * reduction of sublinks to subplans, or in contexts where it's known there
   * are no subqueries.  There mustn't be outer-aggregate references either.
   */
  void
  count_agg_clauses(PlannerInfo *root, Node *clause, AggClauseCosts *costs)
  {
  	count_agg_clauses_context context;
  
  	context.root = root;
  	context.costs = costs;
  	(void) count_agg_clauses_walker(clause, &context);
  }
  
  static bool
  count_agg_clauses_walker(Node *node, count_agg_clauses_context *context)
  {
  	if (node == NULL)
  		return false;
  	if (IsA(node, Aggref))
  	{
  		Aggref	   *aggref = (Aggref *) node;
  		AggClauseCosts *costs = context->costs;
  		HeapTuple	aggTuple;
  		Form_pg_aggregate aggform;
  		Oid			aggtransfn;
  		Oid			aggfinalfn;
  		Oid			aggcombinefn;
  		Oid			aggserialfn;
  		Oid			aggdeserialfn;
  		Oid			aggtranstype;
  		int32		aggtransspace;
  		QualCost	argcosts;
  		Oid			inputTypes[FUNC_MAX_ARGS];
  		int			numArguments;
  
  		Assert(aggref->agglevelsup == 0);
  
  		/*
  		 * Fetch info about aggregate from pg_aggregate.  Note it's correct to
  		 * ignore the moving-aggregate variant, since what we're concerned
  		 * with here is aggregates not window functions.
  		 */
  		aggTuple = SearchSysCache1(AGGFNOID,
  								   ObjectIdGetDatum(aggref->aggfnoid));
  		if (!HeapTupleIsValid(aggTuple))
  			elog(ERROR, "cache lookup failed for aggregate %u",
  				 aggref->aggfnoid);
  		aggform = (Form_pg_aggregate) GETSTRUCT(aggTuple);
  		aggtransfn = aggform->aggtransfn;
  		aggfinalfn = aggform->aggfinalfn;
  		aggcombinefn = aggform->aggcombinefn;
  		aggserialfn = aggform->aggserialfn;
  		aggdeserialfn = aggform->aggdeserialfn;
  		aggtranstype = aggform->aggtranstype;
  		aggtransspace = aggform->aggtransspace;
  		ReleaseSysCache(aggTuple);
  
  		/* count it; note ordered-set aggs always have nonempty aggorder */
  		costs->numAggs++;
  		if (aggref->aggorder != NIL || aggref->aggdistinct != NIL)
  			costs->numOrderedAggs++;
  
  		/*
  		 * The PostgreSQL 'numOrderedAggs' field includes DISTINCT aggregates,
  		 * too, but cdbgroup.c handles DISTINCT aggregates differently, and
  		 * needs to know if there are any purely ordered aggs, not counting
  		 * DISTINCT aggs.
  		 */
  		if (aggref->aggorder != NIL)
  			costs->numPureOrderedAggs++;
  
  		if (aggref->aggdistinct != NIL)
  		{
  			ListCell *lc;
  
  			foreach(lc, aggref->args)
  			{
  				TargetEntry *tle = (TargetEntry *) lfirst(lc);
  
  				if ( !list_member(costs->dqaArgs, tle->expr) )
  					costs->dqaArgs = lappend(costs->dqaArgs, tle->expr);
  			}
  		}
  
  		/*
  		 * If there is no combine function, then partial aggregation is
  		 * not possible. (Note: This is slightly different from the hasNonPartial
  		 * flag in upstream: hasNonPartial is set to 'false', also when there are
  		 * any distinct aggregates, but hasNonCombine is strictly about whether
  		 * every aggregate has a combine function.
  		 */
  		if (!OidIsValid(aggcombinefn))
  			costs->hasNonCombine = true; /* Nope! */
  
  		/*
  		 * If we have any aggs with transtype INTERNAL then we must check
  		 * whether they have serialization/deserialization functions; if
  		 * not, we can't serialize partial-aggregation results.
  		 */
  		if (aggtranstype == INTERNALOID &&
  				 (!OidIsValid(aggserialfn) || !OidIsValid(aggdeserialfn)))
  			costs->hasNonSerial = true;
  
  		/* add component function execution costs to appropriate totals */
  		costs->transCost.per_tuple += get_func_cost(aggtransfn) * cpu_operator_cost;
  		if (OidIsValid(aggfinalfn))
  			costs->finalCost += get_func_cost(aggfinalfn) * cpu_operator_cost;
  
  		/* also add the input expressions' cost to per-input-row costs */
  		cost_qual_eval_node(&argcosts, (Node *) aggref->args, context->root);
  		costs->transCost.startup += argcosts.startup;
  		costs->transCost.per_tuple += argcosts.per_tuple;
  
  		/*
  		 * Add any filter's cost to per-input-row costs.
  		 *
  		 * XXX Ideally we should reduce input expression costs according to
  		 * filter selectivity, but it's not clear it's worth the trouble.
  		 */
  		if (aggref->aggfilter)
  		{
  			cost_qual_eval_node(&argcosts, (Node *) aggref->aggfilter,
  								context->root);
  			costs->transCost.startup += argcosts.startup;
  			costs->transCost.per_tuple += argcosts.per_tuple;
  		}
  
  		/*
  		 * If there are direct arguments, treat their evaluation cost like the
  		 * cost of the finalfn.
  		 */
  		if (aggref->aggdirectargs)
  		{
  			cost_qual_eval_node(&argcosts, (Node *) aggref->aggdirectargs,
  								context->root);
  			costs->transCost.startup += argcosts.startup;
  			costs->finalCost += argcosts.per_tuple;
  		}
  
  		/* extract argument types (ignoring any ORDER BY expressions) */
  		numArguments = get_aggregate_argtypes(aggref, inputTypes);
  
  		/* resolve actual type of transition state, if polymorphic */
  		aggtranstype = resolve_aggregate_transtype(aggref->aggfnoid,
  												   aggtranstype,
  												   inputTypes,
  												   numArguments);
  
  		/*
  		 * If the transition type is pass-by-value then it doesn't add
  		 * anything to the required size of the hashtable.  If it is
  		 * pass-by-reference then we have to add the estimated size of the
  		 * value itself, plus palloc overhead.
  		 */
  		if (!get_typbyval(aggtranstype))
  		{
  			int32		avgwidth;
  
  			/* Use average width if aggregate definition gave one */
  			if (aggtransspace > 0)
  				avgwidth = aggtransspace;
  			else
  			{
  				/*
  				 * If transition state is of same type as first aggregated
  				 * input, assume it's the same typmod (same width) as well.
  				 * This works for cases like MAX/MIN and is probably somewhat
  				 * reasonable otherwise.
  				 */
  				int			numdirectargs = list_length(aggref->aggdirectargs);
  				int32		aggtranstypmod;
  
  				if (numArguments > numdirectargs &&
  					aggtranstype == inputTypes[numdirectargs])
  					aggtranstypmod = exprTypmod((Node *) linitial(aggref->args));
  				else
  					aggtranstypmod = -1;
  
  				avgwidth = get_typavgwidth(aggtranstype, aggtranstypmod);
  			}
  
  			avgwidth = MAXALIGN(avgwidth);
  			costs->transitionSpace += avgwidth + 2 * sizeof(void *);
  		}
  		else if (aggtranstype == INTERNALOID)
  		{
  			/*
  			 * INTERNAL transition type is a special case: although INTERNAL
  			 * is pass-by-value, it's almost certainly being used as a pointer
  			 * to some large data structure.  The aggregate definition can
  			 * provide an estimate of the size.  If it doesn't, then we assume
  			 * ALLOCSET_DEFAULT_INITSIZE, which is a good guess if the data is
  			 * being kept in a private memory context, as is done by
  			 * array_agg() for instance.
  			 */
  			if (aggtransspace > 0)
  				costs->transitionSpace += aggtransspace;
  			else
  				costs->transitionSpace += ALLOCSET_DEFAULT_INITSIZE;
  		}
  
  		/*
  		 * Complain if the aggregate's arguments contain any aggregates;
  		 * nested agg functions are semantically nonsensical.  Aggregates in
  		 * the FILTER clause are detected in transformAggregateCall().
  		 */
  		if (contain_agg_clause((Node *) aggref->args) ||
  			contain_agg_clause((Node *) aggref->aggorder))
  			ereport(ERROR,
  					(errcode(ERRCODE_GROUPING_ERROR),
  					 errmsg("aggregate function calls cannot be nested")));
  
  		/*
  		 * We assume that the parser checked that there are no aggregates (of
  		 * this level anyway) in the aggregated arguments, direct arguments,
  		 * or filter clause.  Hence, we need not recurse into any of them. (If
  		 * either the parser or the planner screws up on this point, the
  		 * executor will still catch it; see ExecInitExpr.)
  		 */
  		return false;
  	}
  	Assert(!IsA(node, SubLink));
  	return expression_tree_walker(node, count_agg_clauses_walker,
  								  (void *) context);
  }
  
  
  /*****************************************************************************
   *		Window-function clause manipulation
   *****************************************************************************/
  
  /*
   * contain_window_function
   *	  Recursively search for WindowFunc nodes within a clause.
   *
   * Since window functions don't have level fields, but are hard-wired to
   * be associated with the current query level, this is just the same as
   * rewriteManip.c's function.
   */
  bool
  contain_window_function(Node *clause)
  {
  	return contain_windowfuncs(clause);
  }
  
  /*
   * find_window_functions
   *	  Locate all the WindowFunc nodes in an expression tree, and organize
   *	  them by winref ID number.
   *
   * Caller must provide an upper bound on the winref IDs expected in the tree.
   */
  WindowFuncLists *
  find_window_functions(Node *clause, Index maxWinRef)
  {
  	WindowFuncLists *lists = palloc(sizeof(WindowFuncLists));
  
  	lists->numWindowFuncs = 0;
  	lists->maxWinRef = maxWinRef;
  	lists->windowFuncs = (List **) palloc0((maxWinRef + 1) * sizeof(List *));
  	(void) find_window_functions_walker(clause, lists);
  	return lists;
  }
  
  static bool
  find_window_functions_walker(Node *node, WindowFuncLists *lists)
  {
  	if (node == NULL)
  		return false;
  	if (IsA(node, WindowFunc))
  	{
  		WindowFunc *wfunc = (WindowFunc *) node;
  
  		/* winref is unsigned, so one-sided test is OK */
  		if (wfunc->winref > lists->maxWinRef)
  			elog(ERROR, "WindowFunc contains out-of-range winref %u",
  				 wfunc->winref);
  		lists->windowFuncs[wfunc->winref] =
  			lappend(lists->windowFuncs[wfunc->winref], wfunc);
  		lists->numWindowFuncs++;
  
  		/*
  		 * We assume that the parser checked that there are no window
  		 * functions in the arguments or filter clause.  Hence, we need not
  		 * recurse into them.  (If either the parser or the planner screws up
  		 * on this point, the executor will still catch it; see ExecInitExpr.)
  		 */
  		return false;
  	}
  	Assert(!IsA(node, SubLink));
  	return expression_tree_walker(node, find_window_functions_walker,
  								  (void *) lists);
  }
  
  
  /*****************************************************************************
   *		Support for expressions returning sets
   *****************************************************************************/
  
  /*
   * expression_returns_set_rows
   *	  Estimate the number of rows returned by a set-returning expression.
   *	  The result is 1 if there are no set-returning functions.
   *
   * We use the product of the rowcount estimates of all the functions in
   * the given tree (this corresponds to the behavior of ExecMakeFunctionResult
   * for nested set-returning functions).
   *
   * Note: keep this in sync with expression_returns_set() in nodes/nodeFuncs.c.
   */
  double
  expression_returns_set_rows(Node *clause)
  {
  	double		result = 1;
  
  	(void) expression_returns_set_rows_walker(clause, &result);
  	return clamp_row_est(result);
  }
  
  static bool
  expression_returns_set_rows_walker(Node *node, double *count)
  {
  	if (node == NULL)
  		return false;
  	if (IsA(node, FuncExpr))
  	{
  		FuncExpr   *expr = (FuncExpr *) node;
  
  		if (expr->funcretset)
  			*count *= get_func_rows(expr->funcid);
  	}
  	if (IsA(node, OpExpr))
  	{
  		OpExpr	   *expr = (OpExpr *) node;
  
  		if (expr->opretset)
  		{
  			set_opfuncid(expr);
  			*count *= get_func_rows(expr->opfuncid);
  		}
  	}
  
  	/* Avoid recursion for some cases that can't return a set */
  	if (IsA(node, Aggref))
  		return false;
  	if (IsA(node, WindowFunc))
  		return false;
  	if (IsA(node, DistinctExpr))
  		return false;
  	if (IsA(node, NullIfExpr))
  		return false;
  	if (IsA(node, ScalarArrayOpExpr))
  		return false;
  	if (IsA(node, BoolExpr))
  		return false;
  	if (IsA(node, SubLink))
  		return false;
  	if (IsA(node, SubPlan))
  		return false;
  	if (IsA(node, AlternativeSubPlan))
  		return false;
  	if (IsA(node, ArrayExpr))
  		return false;
  	if (IsA(node, RowExpr))
  		return false;
  	if (IsA(node, RowCompareExpr))
  		return false;
  	if (IsA(node, CoalesceExpr))
  		return false;
  	if (IsA(node, MinMaxExpr))
  		return false;
  	if (IsA(node, XmlExpr))
  		return false;
  
  	return expression_tree_walker(node, expression_returns_set_rows_walker,
  								  (void *) count);
  }
  
  /*
   * tlist_returns_set_rows
   *	  Estimate the number of rows returned by a set-returning targetlist.
   *	  The result is 1 if there are no set-returning functions.
   *
   * Here, the result is the largest rowcount estimate of any of the tlist's
   * expressions, not the product as you would get from naively applying
   * expression_returns_set_rows() to the whole tlist.  The behavior actually
   * implemented by ExecTargetList produces a number of rows equal to the least
   * common multiple of the expression rowcounts, so that the product would be
   * a worst-case estimate that is typically not realistic.  Taking the max as
   * we do here is a best-case estimate that might not be realistic either,
   * but it's probably closer for typical usages.  We don't try to compute the
   * actual LCM because we're working with very approximate estimates, so their
   * LCM would be unduly noisy.
   */
  double
  tlist_returns_set_rows(List *tlist)
  {
  	double		result = 1;
  	ListCell   *lc;
  
  	foreach(lc, tlist)
  	{
  		TargetEntry *tle = (TargetEntry *) lfirst(lc);
  		double		colresult;
  
  		colresult = expression_returns_set_rows((Node *) tle->expr);
  		if (result < colresult)
  			result = colresult;
  	}
  	return result;
  }
  
  
  /*****************************************************************************
   *		Subplan clause manipulation
   *****************************************************************************/
  
  /*
   * contain_subplans
   *	  Recursively search for subplan nodes within a clause.
   *
   * If we see a SubLink node, we will return TRUE.  This is only possible if
   * the expression tree hasn't yet been transformed by subselect.c.  We do not
   * know whether the node will produce a true subplan or just an initplan,
   * but we make the conservative assumption that it will be a subplan.
   *
   * Returns true if any subplan found.
   */
  bool
  contain_subplans(Node *clause)
  {
  	return contain_subplans_walker(clause, NULL);
  }
  
  static bool
  contain_subplans_walker(Node *node, void *context)
  {
  	if (node == NULL)
  		return false;
  	if (IsA(node, SubPlan) ||
  		IsA(node, AlternativeSubPlan) ||
  		IsA(node, SubLink))
  		return true;			/* abort the tree traversal and return true */
  	return expression_tree_walker(node, contain_subplans_walker, context);
  }
  
  
  /*****************************************************************************
   *		Check clauses for mutable functions
   *****************************************************************************/
  
  /*
   * contain_mutable_functions
   *	  Recursively search for mutable functions within a clause.
   *
   * Returns true if any mutable function (or operator implemented by a
   * mutable function) is found.  This test is needed so that we don't
   * mistakenly think that something like "WHERE random() < 0.5" can be treated
   * as a constant qualification.
   *
   * We will recursively look into Query nodes (i.e., SubLink sub-selects)
   * but not into SubPlans.  See comments for contain_volatile_functions().
   */
  bool
  contain_mutable_functions(Node *clause)
  {
  	return contain_mutable_functions_walker(clause, NULL);
  }
  
  static bool
  contain_mutable_functions_walker(Node *node, void *context)
  {
  	if (node == NULL)
  		return false;
  
      /* the functions in predtest.c handle expressions and
       * RestrictInfo objects -- so make this function handle
       * them too for convenience */
      if (IsA(node, RestrictInfo))
      {
          RestrictInfo * info = (RestrictInfo *) node;
          return contain_mutable_functions_walker((Node*)info->clause, context);
      }
  
  	if (IsA(node, FuncExpr))
  	{
  		FuncExpr   *expr = (FuncExpr *) node;
  
  		if (func_volatile(expr->funcid) != PROVOLATILE_IMMUTABLE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, OpExpr))
  	{
  		OpExpr	   *expr = (OpExpr *) node;
  
  		set_opfuncid(expr);
  		if (func_volatile(expr->opfuncid) != PROVOLATILE_IMMUTABLE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, DistinctExpr))
  	{
  		DistinctExpr *expr = (DistinctExpr *) node;
  
  		set_opfuncid((OpExpr *) expr);	/* rely on struct equivalence */
  		if (func_volatile(expr->opfuncid) != PROVOLATILE_IMMUTABLE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, NullIfExpr))
  	{
  		NullIfExpr *expr = (NullIfExpr *) node;
  
  		set_opfuncid((OpExpr *) expr);	/* rely on struct equivalence */
  		if (func_volatile(expr->opfuncid) != PROVOLATILE_IMMUTABLE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, ScalarArrayOpExpr))
  	{
  		ScalarArrayOpExpr *expr = (ScalarArrayOpExpr *) node;
  
  		set_sa_opfuncid(expr);
  		if (func_volatile(expr->opfuncid) != PROVOLATILE_IMMUTABLE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, CoerceViaIO))
  	{
  		CoerceViaIO *expr = (CoerceViaIO *) node;
  		Oid			iofunc;
  		Oid			typioparam;
  		bool		typisvarlena;
  
  		/* check the result type's input function */
  		getTypeInputInfo(expr->resulttype,
  						 &iofunc, &typioparam);
  		if (func_volatile(iofunc) != PROVOLATILE_IMMUTABLE)
  			return true;
  		/* check the input type's output function */
  		getTypeOutputInfo(exprType((Node *) expr->arg),
  						  &iofunc, &typisvarlena);
  		if (func_volatile(iofunc) != PROVOLATILE_IMMUTABLE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, ArrayCoerceExpr))
  	{
  		ArrayCoerceExpr *expr = (ArrayCoerceExpr *) node;
  
  		if (OidIsValid(expr->elemfuncid) &&
  			func_volatile(expr->elemfuncid) != PROVOLATILE_IMMUTABLE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, RowCompareExpr))
  	{
  		RowCompareExpr *rcexpr = (RowCompareExpr *) node;
  		ListCell   *opid;
  
  		foreach(opid, rcexpr->opnos)
  		{
  			if (op_volatile(lfirst_oid(opid)) != PROVOLATILE_IMMUTABLE)
  				return true;
  		}
  		/* else fall through to check args */
  	}
  	else if (IsA(node, Query))
  	{
  		/* Recurse into subselects */
  		return query_tree_walker((Query *) node,
  								 contain_mutable_functions_walker,
  								 context, 0);
  	}
  	return expression_tree_walker(node, contain_mutable_functions_walker,
  								  context);
  }
  
  
  /*****************************************************************************
   *		Check clauses for volatile functions
   *****************************************************************************/
  
  /*
   * contain_volatile_functions
   *	  Recursively search for volatile functions within a clause.
   *
   * Returns true if any volatile function (or operator implemented by a
   * volatile function) is found. This test prevents, for example,
   * invalid conversions of volatile expressions into indexscan quals.
   *
   * We will recursively look into Query nodes (i.e., SubLink sub-selects)
   * but not into SubPlans.  This is a bit odd, but intentional.  If we are
   * looking at a SubLink, we are probably deciding whether a query tree
   * transformation is safe, and a contained sub-select should affect that;
   * for example, duplicating a sub-select containing a volatile function
   * would be bad.  However, once we've got to the stage of having SubPlans,
   * subsequent planning need not consider volatility within those, since
   * the executor won't change its evaluation rules for a SubPlan based on
   * volatility.
   */
  bool
  contain_volatile_functions(Node *clause)
  {
  	return contain_volatile_functions_walker(clause, NULL);
  }
  
  bool
  contain_volatile_functions_not_nextval(Node *clause)
  {
  	return contain_volatile_functions_not_nextval_walker(clause, NULL);
  }
  
  /*
   * General purpose code for checking expression volatility.
   *
   * Special purpose code for use in COPY is almost identical to this,
   * so any changes here may also be needed in other contain_volatile...
   * functions.
   */
  static bool
  contain_volatile_functions_walker(Node *node, void *context)
  {
  	if (node == NULL)
  		return false;
  	if (IsA(node, FuncExpr))
  	{
  		FuncExpr   *expr = (FuncExpr *) node;
  
  		if (func_volatile(expr->funcid) == PROVOLATILE_VOLATILE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, OpExpr))
  	{
  		OpExpr	   *expr = (OpExpr *) node;
  
  		set_opfuncid(expr);
  		if (func_volatile(expr->opfuncid) == PROVOLATILE_VOLATILE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, DistinctExpr))
  	{
  		DistinctExpr *expr = (DistinctExpr *) node;
  
  		set_opfuncid((OpExpr *) expr);	/* rely on struct equivalence */
  		if (func_volatile(expr->opfuncid) == PROVOLATILE_VOLATILE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, NullIfExpr))
  	{
  		NullIfExpr *expr = (NullIfExpr *) node;
  
  		set_opfuncid((OpExpr *) expr);	/* rely on struct equivalence */
  		if (func_volatile(expr->opfuncid) == PROVOLATILE_VOLATILE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, ScalarArrayOpExpr))
  	{
  		ScalarArrayOpExpr *expr = (ScalarArrayOpExpr *) node;
  
  		set_sa_opfuncid(expr);
  		if (func_volatile(expr->opfuncid) == PROVOLATILE_VOLATILE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, CoerceViaIO))
  	{
  		CoerceViaIO *expr = (CoerceViaIO *) node;
  		Oid			iofunc;
  		Oid			typioparam;
  		bool		typisvarlena;
  
  		/* check the result type's input function */
  		getTypeInputInfo(expr->resulttype,
  						 &iofunc, &typioparam);
  		if (func_volatile(iofunc) == PROVOLATILE_VOLATILE)
  			return true;
  		/* check the input type's output function */
  		getTypeOutputInfo(exprType((Node *) expr->arg),
  						  &iofunc, &typisvarlena);
  		if (func_volatile(iofunc) == PROVOLATILE_VOLATILE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, ArrayCoerceExpr))
  	{
  		ArrayCoerceExpr *expr = (ArrayCoerceExpr *) node;
  
  		if (OidIsValid(expr->elemfuncid) &&
  			func_volatile(expr->elemfuncid) == PROVOLATILE_VOLATILE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, RowCompareExpr))
  	{
  		/* RowCompare probably can't have volatile ops, but check anyway */
  		RowCompareExpr *rcexpr = (RowCompareExpr *) node;
  		ListCell   *opid;
  
  		foreach(opid, rcexpr->opnos)
  		{
  			if (op_volatile(lfirst_oid(opid)) == PROVOLATILE_VOLATILE)
  				return true;
  		}
  		/* else fall through to check args */
  	}
  	else if (IsA(node, Query))
  	{
  		/* Recurse into subselects */
  		return query_tree_walker((Query *) node,
  								 contain_volatile_functions_walker,
  								 context, 0);
  	}
  	else if (IsA(node, ReshuffleExpr))
  		return true;
  
  	return expression_tree_walker(node, contain_volatile_functions_walker,
  								  context);
  }
  
  /*
   * Special purpose version of contain_volatile_functions for use in COPY
   */
  static bool
  contain_volatile_functions_not_nextval_walker(Node *node, void *context)
  {
  	if (node == NULL)
  		return false;
  	if (IsA(node, FuncExpr))
  	{
  		FuncExpr   *expr = (FuncExpr *) node;
  
  		/*
  		 * For this case only, we want to ignore the volatility of the
  		 * nextval() function, since some callers want this.
  		 */
  		if (expr->funcid != F_NEXTVAL_OID &&
  			func_volatile(expr->funcid) == PROVOLATILE_VOLATILE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, OpExpr))
  	{
  		OpExpr	   *expr = (OpExpr *) node;
  
  		set_opfuncid(expr);
  		if (func_volatile(expr->opfuncid) == PROVOLATILE_VOLATILE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, DistinctExpr))
  	{
  		DistinctExpr *expr = (DistinctExpr *) node;
  
  		set_opfuncid((OpExpr *) expr);	/* rely on struct equivalence */
  		if (func_volatile(expr->opfuncid) == PROVOLATILE_VOLATILE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, NullIfExpr))
  	{
  		NullIfExpr *expr = (NullIfExpr *) node;
  
  		set_opfuncid((OpExpr *) expr);	/* rely on struct equivalence */
  		if (func_volatile(expr->opfuncid) == PROVOLATILE_VOLATILE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, ScalarArrayOpExpr))
  	{
  		ScalarArrayOpExpr *expr = (ScalarArrayOpExpr *) node;
  
  		set_sa_opfuncid(expr);
  		if (func_volatile(expr->opfuncid) == PROVOLATILE_VOLATILE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, CoerceViaIO))
  	{
  		CoerceViaIO *expr = (CoerceViaIO *) node;
  		Oid			iofunc;
  		Oid			typioparam;
  		bool		typisvarlena;
  
  		/* check the result type's input function */
  		getTypeInputInfo(expr->resulttype,
  						 &iofunc, &typioparam);
  		if (func_volatile(iofunc) == PROVOLATILE_VOLATILE)
  			return true;
  		/* check the input type's output function */
  		getTypeOutputInfo(exprType((Node *) expr->arg),
  						  &iofunc, &typisvarlena);
  		if (func_volatile(iofunc) == PROVOLATILE_VOLATILE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, ArrayCoerceExpr))
  	{
  		ArrayCoerceExpr *expr = (ArrayCoerceExpr *) node;
  
  		if (OidIsValid(expr->elemfuncid) &&
  			func_volatile(expr->elemfuncid) == PROVOLATILE_VOLATILE)
  			return true;
  		/* else fall through to check args */
  	}
  	else if (IsA(node, RowCompareExpr))
  	{
  		/* RowCompare probably can't have volatile ops, but check anyway */
  		RowCompareExpr *rcexpr = (RowCompareExpr *) node;
  		ListCell   *opid;
  
  		foreach(opid, rcexpr->opnos)
  		{
  			if (op_volatile(lfirst_oid(opid)) == PROVOLATILE_VOLATILE)
  				return true;
  		}
  		/* else fall through to check args */
  	}
  	return expression_tree_walker(node, contain_volatile_functions_not_nextval_walker,
  								  context);
  }
  
  /*****************************************************************************
   *		Check clauses for nonstrict functions
   *****************************************************************************/
  
  /*
   * contain_nonstrict_functions
   *	  Recursively search for nonstrict functions within a clause.
   *
   * Returns true if any nonstrict construct is found --- ie, anything that
   * could produce non-NULL output with a NULL input.
   *
   * The idea here is that the caller has verified that the expression contains
   * one or more Var or Param nodes (as appropriate for the caller's need), and
   * now wishes to prove that the expression result will be NULL if any of these
   * inputs is NULL.  If we return false, then the proof succeeded.
   */
  bool
  contain_nonstrict_functions(Node *clause)
  {
  	return contain_nonstrict_functions_walker(clause, NULL);
  }
  
  static bool
  contain_nonstrict_functions_walker(Node *node, void *context)
  {
  	if (node == NULL)
  		return false;
  	if (IsA(node, Aggref))
  	{
  		/* an aggregate could return non-null with null input */
  		return true;
  	}
  	if (IsA(node, WindowFunc))
  	{
  		/* a window function could return non-null with null input */
  		return true;
  	}
  	if (IsA(node, ArrayRef))
  	{
  		/* array assignment is nonstrict, but subscripting is strict */
  		if (((ArrayRef *) node)->refassgnexpr != NULL)
  			return true;
  		/* else fall through to check args */
  	}
  	if (IsA(node, FuncExpr))
  	{
  		FuncExpr   *expr = (FuncExpr *) node;
  
  		if (!func_strict(expr->funcid))
  			return true;
  		/* else fall through to check args */
  	}
  	if (IsA(node, OpExpr))
  	{
  		OpExpr	   *expr = (OpExpr *) node;
  
  		set_opfuncid(expr);
  		if (!func_strict(expr->opfuncid))
  			return true;
  		/* else fall through to check args */
  	}
  	if (IsA(node, DistinctExpr))
  	{
  		/* IS DISTINCT FROM is inherently non-strict */
  		return true;
  	}
  	if (IsA(node, NullIfExpr))
  		return true;
  	if (IsA(node, ScalarArrayOpExpr))
  	{
  		ScalarArrayOpExpr *expr = (ScalarArrayOpExpr *) node;
  
  		if (!is_strict_saop(expr, false))
  			return true;
  		/* else fall through to check args */
  	}
  	if (IsA(node, BoolExpr))
  	{
  		BoolExpr   *expr = (BoolExpr *) node;
  
  		switch (expr->boolop)
  		{
  			case AND_EXPR:
  			case OR_EXPR:
  				/* AND, OR are inherently non-strict */
  				return true;
  			default:
  				break;
  		}
  	}
  	if (IsA(node, SubLink))
  	{
  		/* In some cases a sublink might be strict, but in general not */
  		return true;
  	}
  	if (IsA(node, SubPlan))
  		return true;
  	if (IsA(node, AlternativeSubPlan))
  		return true;
  	/* ArrayCoerceExpr is strict at the array level, regardless of elemfunc */
  	if (IsA(node, FieldStore))
  		return true;
  	if (IsA(node, CaseExpr))
  		return true;
  	if (IsA(node, ArrayExpr))
  		return true;
  	if (IsA(node, RowExpr))
  		return true;
  	if (IsA(node, RowCompareExpr))
  		return true;
  	if (IsA(node, CoalesceExpr))
  		return true;
  	if (IsA(node, MinMaxExpr))
  		return true;
  	if (IsA(node, XmlExpr))
  		return true;
  	if (IsA(node, NullTest))
  		return true;
  	if (IsA(node, BooleanTest))
  		return true;
  	return expression_tree_walker(node, contain_nonstrict_functions_walker,
  								  context);
  }
  
  /*****************************************************************************
   *		Check clauses for context-dependent nodes
   *****************************************************************************/
  
  /*
   * contain_context_dependent_node
   *	  Recursively search for context-dependent nodes within a clause.
   *
   * CaseTestExpr nodes must appear directly within the corresponding CaseExpr,
   * not nested within another one, or they'll see the wrong test value.  If one
   * appears "bare" in the arguments of a SQL function, then we can't inline the
   * SQL function for fear of creating such a situation.
   *
   * CoerceToDomainValue would have the same issue if domain CHECK expressions
   * could get inlined into larger expressions, but presently that's impossible.
   * Still, it might be allowed in future, or other node types with similar
   * issues might get invented.  So give this function a generic name, and set
   * up the recursion state to allow multiple flag bits.
   */
  static bool
  contain_context_dependent_node(Node *clause)
  {
  	int			flags = 0;
  
  	return contain_context_dependent_node_walker(clause, &flags);
  }
  
  #define CCDN_IN_CASEEXPR	0x0001		/* CaseTestExpr okay here? */
  
  static bool
  contain_context_dependent_node_walker(Node *node, int *flags)
  {
  	if (node == NULL)
  		return false;
  	if (IsA(node, CaseTestExpr))
  		return !(*flags & CCDN_IN_CASEEXPR);
  	if (IsA(node, CaseExpr))
  	{
  		CaseExpr   *caseexpr = (CaseExpr *) node;
  
  		/*
  		 * If this CASE doesn't have a test expression, then it doesn't create
  		 * a context in which CaseTestExprs should appear, so just fall
  		 * through and treat it as a generic expression node.
  		 */
  		if (caseexpr->arg)
  		{
  			int			save_flags = *flags;
  			bool		res;
  
  			/*
  			 * Note: in principle, we could distinguish the various sub-parts
  			 * of a CASE construct and set the flag bit only for some of them,
  			 * since we are only expecting CaseTestExprs to appear in the
  			 * "expr" subtree of the CaseWhen nodes.  But it doesn't really
  			 * seem worth any extra code.  If there are any bare CaseTestExprs
  			 * elsewhere in the CASE, something's wrong already.
  			 */
  			*flags |= CCDN_IN_CASEEXPR;
  			res = expression_tree_walker(node,
  									   contain_context_dependent_node_walker,
  										 (void *) flags);
  			*flags = save_flags;
  			return res;
  		}
  	}
  	return expression_tree_walker(node, contain_context_dependent_node_walker,
  								  (void *) flags);
  }
  
  /*****************************************************************************
   *		  Check clauses for non-leakproof functions
   *****************************************************************************/
  
  /*
   * contain_leaky_functions
   *		Recursively search for leaky functions within a clause.
   *
   * Returns true if any function call with side-effect may be present in the
   * clause.  Qualifiers from outside the a security_barrier view should not
   * be pushed down into the view, lest the contents of tuples intended to be
   * filtered out be revealed via side effects.
   */
  bool
  contain_leaky_functions(Node *clause)
  {
  	return contain_leaky_functions_walker(clause, NULL);
  }
  
  static bool
  contain_leaky_functions_walker(Node *node, void *context)
  {
  	if (node == NULL)
  		return false;
  
  	switch (nodeTag(node))
  	{
  		case T_Var:
  		case T_Const:
  		case T_Param:
  		case T_ArrayExpr:
  		case T_NamedArgExpr:
  		case T_BoolExpr:
  		case T_RelabelType:
  		case T_CaseExpr:
  		case T_CaseTestExpr:
  		case T_RowExpr:
  		case T_MinMaxExpr:
  		case T_NullTest:
  		case T_BooleanTest:
  		case T_List:
  
  			/*
  			 * We know these node types don't contain function calls; but
  			 * something further down in the node tree might.
  			 */
  			break;
  
  		case T_FuncExpr:
  			{
  				FuncExpr   *expr = (FuncExpr *) node;
  
  				if (!get_func_leakproof(expr->funcid))
  					return true;
  			}
  			break;
  
  		case T_OpExpr:
  		case T_DistinctExpr:	/* struct-equivalent to OpExpr */
  		case T_NullIfExpr:		/* struct-equivalent to OpExpr */
  			{
  				OpExpr	   *expr = (OpExpr *) node;
  
  				set_opfuncid(expr);
  				if (!get_func_leakproof(expr->opfuncid))
  					return true;
  			}
  			break;
  
  		case T_ScalarArrayOpExpr:
  			{
  				ScalarArrayOpExpr *expr = (ScalarArrayOpExpr *) node;
  
  				set_sa_opfuncid(expr);
  				if (!get_func_leakproof(expr->opfuncid))
  					return true;
  			}
  			break;
  
  		case T_CoerceViaIO:
  			{
  				CoerceViaIO *expr = (CoerceViaIO *) node;
  				Oid			funcid;
  				Oid			ioparam;
  				bool		varlena;
  
  				getTypeInputInfo(exprType((Node *) expr->arg),
  								 &funcid, &ioparam);
  				if (!get_func_leakproof(funcid))
  					return true;
  
  				getTypeOutputInfo(expr->resulttype, &funcid, &varlena);
  				if (!get_func_leakproof(funcid))
  					return true;
  			}
  			break;
  
  		case T_ArrayCoerceExpr:
  			{
  				ArrayCoerceExpr *expr = (ArrayCoerceExpr *) node;
  				Oid			funcid;
  				Oid			ioparam;
  				bool		varlena;
  
  				getTypeInputInfo(exprType((Node *) expr->arg),
  								 &funcid, &ioparam);
  				if (!get_func_leakproof(funcid))
  					return true;
  				getTypeOutputInfo(expr->resulttype, &funcid, &varlena);
  				if (!get_func_leakproof(funcid))
  					return true;
  			}
  			break;
  
  		case T_RowCompareExpr:
  			{
  				RowCompareExpr *rcexpr = (RowCompareExpr *) node;
  				ListCell   *opid;
  
  				foreach(opid, rcexpr->opnos)
  				{
  					Oid			funcid = get_opcode(lfirst_oid(opid));
  
  					if (!get_func_leakproof(funcid))
  						return true;
  				}
  			}
  			break;
  
  		default:
  
  			/*
  			 * If we don't recognize the node tag, assume it might be leaky.
  			 * This prevents an unexpected security hole if someone adds a new
  			 * node type that can call a function.
  			 */
  			return true;
  	}
  	return expression_tree_walker(node, contain_leaky_functions_walker,
  								  context);
  }
  
  /*
   * find_nonnullable_rels
   *		Determine which base rels are forced nonnullable by given clause.
   *
   * Returns the set of all Relids that are referenced in the clause in such
   * a way that the clause cannot possibly return TRUE if any of these Relids
   * is an all-NULL row.  (It is OK to err on the side of conservatism; hence
   * the analysis here is simplistic.)
   *
   * The semantics here are subtly different from contain_nonstrict_functions:
   * that function is concerned with NULL results from arbitrary expressions,
   * but here we assume that the input is a Boolean expression, and wish to
   * see if NULL inputs will provably cause a FALSE-or-NULL result.  We expect
   * the expression to have been AND/OR flattened and converted to implicit-AND
   * format.
   *
   * Note: this function is largely duplicative of find_nonnullable_vars().
   * The reason not to simplify this function into a thin wrapper around
   * find_nonnullable_vars() is that the tested conditions really are different:
   * a clause like "t1.v1 IS NOT NULL OR t1.v2 IS NOT NULL" does not prove
   * that either v1 or v2 can't be NULL, but it does prove that the t1 row
   * as a whole can't be all-NULL.
   *
   * top_level is TRUE while scanning top-level AND/OR structure; here, showing
   * the result is either FALSE or NULL is good enough.  top_level is FALSE when
   * we have descended below a NOT or a strict function: now we must be able to
   * prove that the subexpression goes to NULL.
   *
   * We don't use expression_tree_walker here because we don't want to descend
   * through very many kinds of nodes; only the ones we can be sure are strict.
   */
  Relids
  find_nonnullable_rels(Node *clause)
  {
  	return find_nonnullable_rels_walker(clause, true);
  }
  
  static Relids
  find_nonnullable_rels_walker(Node *node, bool top_level)
  {
  	Relids		result = NULL;
  	ListCell   *l;
  
  	if (node == NULL)
  		return NULL;
  	if (IsA(node, Var))
  	{
  		Var		   *var = (Var *) node;
  
  		if (var->varlevelsup == 0)
  			result = bms_make_singleton(var->varno);
  	}
  	else if (IsA(node, List))
  	{
  		/*
  		 * At top level, we are examining an implicit-AND list: if any of the
  		 * arms produces FALSE-or-NULL then the result is FALSE-or-NULL. If
  		 * not at top level, we are examining the arguments of a strict
  		 * function: if any of them produce NULL then the result of the
  		 * function must be NULL.  So in both cases, the set of nonnullable
  		 * rels is the union of those found in the arms, and we pass down the
  		 * top_level flag unmodified.
  		 */
  		foreach(l, (List *) node)
  		{
  			result = bms_join(result,
  							  find_nonnullable_rels_walker(lfirst(l),
  														   top_level));
  		}
  	}
  	else if (IsA(node, FuncExpr))
  	{
  		FuncExpr   *expr = (FuncExpr *) node;
  
  		if (func_strict(expr->funcid))
  			result = find_nonnullable_rels_walker((Node *) expr->args, false);
  	}
  	else if (IsA(node, OpExpr))
  	{
  		OpExpr	   *expr = (OpExpr *) node;
  
  		set_opfuncid(expr);
  		if (func_strict(expr->opfuncid))
  			result = find_nonnullable_rels_walker((Node *) expr->args, false);
  	}
  	else if (IsA(node, ScalarArrayOpExpr))
  	{
  		/* Strict if it's "foo op ANY array" and op is strict */
  		ScalarArrayOpExpr *expr = (ScalarArrayOpExpr *) node;
  
  		if (expr->useOr && op_strict(expr->opno))
  			result = find_nonnullable_rels_walker((Node *) expr->args, false);
  	}
  	else if (IsA(node, BoolExpr))
  	{
  		BoolExpr   *expr = (BoolExpr *) node;
  
  		switch (expr->boolop)
  		{
  			case AND_EXPR:
  				/* At top level we can just recurse (to the List case) */
  				if (top_level)
  				{
  					result = find_nonnullable_rels_walker((Node *) expr->args,
  														  top_level);
  					break;
  				}
  
  				/*
  				 * Below top level, even if one arm produces NULL, the result
  				 * could be FALSE (hence not NULL).  However, if *all* the
  				 * arms produce NULL then the result is NULL, so we can take
  				 * the intersection of the sets of nonnullable rels, just as
  				 * for OR.  Fall through to share code.
  				 */
  				/* FALL THRU */
  			case OR_EXPR:
  
  				/*
  				 * OR is strict if all of its arms are, so we can take the
  				 * intersection of the sets of nonnullable rels for each arm.
  				 * This works for both values of top_level.
  				 */
  				foreach(l, expr->args)
  				{
  					Relids		subresult;
  
  					subresult = find_nonnullable_rels_walker(lfirst(l),
  															 top_level);
  					if (result == NULL) /* first subresult? */
  						result = subresult;
  					else
  						result = bms_int_members(result, subresult);
  
  					/*
  					 * If the intersection is empty, we can stop looking. This
  					 * also justifies the test for first-subresult above.
  					 */
  					if (bms_is_empty(result))
  						break;
  				}
  				break;
  			case NOT_EXPR:
  				/* NOT will return null if its arg is null */
  				result = find_nonnullable_rels_walker((Node *) expr->args,
  													  false);
  				break;
  			default:
  				elog(ERROR, "unrecognized boolop: %d", (int) expr->boolop);
  				break;
  		}
  	}
  	else if (IsA(node, RelabelType))
  	{
  		RelabelType *expr = (RelabelType *) node;
  
  		result = find_nonnullable_rels_walker((Node *) expr->arg, top_level);
  	}
  	else if (IsA(node, CoerceViaIO))
  	{
  		/* not clear this is useful, but it can't hurt */
  		CoerceViaIO *expr = (CoerceViaIO *) node;
  
  		result = find_nonnullable_rels_walker((Node *) expr->arg, top_level);
  	}
  	else if (IsA(node, ArrayCoerceExpr))
  	{
  		/* ArrayCoerceExpr is strict at the array level */
  		ArrayCoerceExpr *expr = (ArrayCoerceExpr *) node;
  
  		result = find_nonnullable_rels_walker((Node *) expr->arg, top_level);
  	}
  	else if (IsA(node, ConvertRowtypeExpr))
  	{
  		/* not clear this is useful, but it can't hurt */
  		ConvertRowtypeExpr *expr = (ConvertRowtypeExpr *) node;
  
  		result = find_nonnullable_rels_walker((Node *) expr->arg, top_level);
  	}
  	else if (IsA(node, CollateExpr))
  	{
  		CollateExpr *expr = (CollateExpr *) node;
  
  		result = find_nonnullable_rels_walker((Node *) expr->arg, top_level);
  	}
  	else if (IsA(node, NullTest))
  	{
  		/* IS NOT NULL can be considered strict, but only at top level */
  		NullTest   *expr = (NullTest *) node;
  
  		if (top_level && expr->nulltesttype == IS_NOT_NULL && !expr->argisrow)
  			result = find_nonnullable_rels_walker((Node *) expr->arg, false);
  	}
  	else if (IsA(node, BooleanTest))
  	{
  		/* Boolean tests that reject NULL are strict at top level */
  		BooleanTest *expr = (BooleanTest *) node;
  
  		if (top_level &&
  			(expr->booltesttype == IS_TRUE ||
  			 expr->booltesttype == IS_FALSE ||
  			 expr->booltesttype == IS_NOT_UNKNOWN))
  			result = find_nonnullable_rels_walker((Node *) expr->arg, false);
  	}
  	else if (IsA(node, PlaceHolderVar))
  	{
  		PlaceHolderVar *phv = (PlaceHolderVar *) node;
  
  		result = find_nonnullable_rels_walker((Node *) phv->phexpr, top_level);
  	}
  	return result;
  }
  
  /*
   * find_nonnullable_vars
   *		Determine which Vars are forced nonnullable by given clause.
   *
   * Returns a list of all level-zero Vars that are referenced in the clause in
   * such a way that the clause cannot possibly return TRUE if any of these Vars
   * is NULL.  (It is OK to err on the side of conservatism; hence the analysis
   * here is simplistic.)
   *
   * The semantics here are subtly different from contain_nonstrict_functions:
   * that function is concerned with NULL results from arbitrary expressions,
   * but here we assume that the input is a Boolean expression, and wish to
   * see if NULL inputs will provably cause a FALSE-or-NULL result.  We expect
   * the expression to have been AND/OR flattened and converted to implicit-AND
   * format.
   *
   * The result is a palloc'd List, but we have not copied the member Var nodes.
   * Also, we don't bother trying to eliminate duplicate entries.
   *
   * top_level is TRUE while scanning top-level AND/OR structure; here, showing
   * the result is either FALSE or NULL is good enough.  top_level is FALSE when
   * we have descended below a NOT or a strict function: now we must be able to
   * prove that the subexpression goes to NULL.
   *
   * We don't use expression_tree_walker here because we don't want to descend
   * through very many kinds of nodes; only the ones we can be sure are strict.
   */
  List *
  find_nonnullable_vars(Node *clause)
  {
  	return find_nonnullable_vars_walker(clause, true);
  }
  
  static List *
  find_nonnullable_vars_walker(Node *node, bool top_level)
  {
  	List	   *result = NIL;
  	ListCell   *l;
  
  	if (node == NULL)
  		return NIL;
  	if (IsA(node, Var))
  	{
  		Var		   *var = (Var *) node;
  
  		if (var->varlevelsup == 0)
  			result = list_make1(var);
  	}
  	else if (IsA(node, List))
  	{
  		/*
  		 * At top level, we are examining an implicit-AND list: if any of the
  		 * arms produces FALSE-or-NULL then the result is FALSE-or-NULL. If
  		 * not at top level, we are examining the arguments of a strict
  		 * function: if any of them produce NULL then the result of the
  		 * function must be NULL.  So in both cases, the set of nonnullable
  		 * vars is the union of those found in the arms, and we pass down the
  		 * top_level flag unmodified.
  		 */
  		foreach(l, (List *) node)
  		{
  			result = list_concat(result,
  								 find_nonnullable_vars_walker(lfirst(l),
  															  top_level));
  		}
  	}
  	else if (IsA(node, FuncExpr))
  	{
  		FuncExpr   *expr = (FuncExpr *) node;
  
  		if (func_strict(expr->funcid))
  			result = find_nonnullable_vars_walker((Node *) expr->args, false);
  	}
  	else if (IsA(node, OpExpr))
  	{
  		OpExpr	   *expr = (OpExpr *) node;
  
  		set_opfuncid(expr);
  		if (func_strict(expr->opfuncid))
  			result = find_nonnullable_vars_walker((Node *) expr->args, false);
  	}
  	else if (IsA(node, ScalarArrayOpExpr))
  	{
  		ScalarArrayOpExpr *expr = (ScalarArrayOpExpr *) node;
  
  		if (is_strict_saop(expr, true))
  			result = find_nonnullable_vars_walker((Node *) expr->args, false);
  	}
  	else if (IsA(node, BoolExpr))
  	{
  		BoolExpr   *expr = (BoolExpr *) node;
  
  		switch (expr->boolop)
  		{
  			case AND_EXPR:
  				/* At top level we can just recurse (to the List case) */
  				if (top_level)
  				{
  					result = find_nonnullable_vars_walker((Node *) expr->args,
  														  top_level);
  					break;
  				}
  
  				/*
  				 * Below top level, even if one arm produces NULL, the result
  				 * could be FALSE (hence not NULL).  However, if *all* the
  				 * arms produce NULL then the result is NULL, so we can take
  				 * the intersection of the sets of nonnullable vars, just as
  				 * for OR.  Fall through to share code.
  				 */
  				/* FALL THRU */
  			case OR_EXPR:
  
  				/*
  				 * OR is strict if all of its arms are, so we can take the
  				 * intersection of the sets of nonnullable vars for each arm.
  				 * This works for both values of top_level.
  				 */
  				foreach(l, expr->args)
  				{
  					List	   *subresult;
  
  					subresult = find_nonnullable_vars_walker(lfirst(l),
  															 top_level);
  					if (result == NIL)	/* first subresult? */
  						result = subresult;
  					else
  						result = list_intersection(result, subresult);
  
  					/*
  					 * If the intersection is empty, we can stop looking. This
  					 * also justifies the test for first-subresult above.
  					 */
  					if (result == NIL)
  						break;
  				}
  				break;
  			case NOT_EXPR:
  				/* NOT will return null if its arg is null */
  				result = find_nonnullable_vars_walker((Node *) expr->args,
  													  false);
  				break;
  			default:
  				elog(ERROR, "unrecognized boolop: %d", (int) expr->boolop);
  				break;
  		}
  	}
  	else if (IsA(node, RelabelType))
  	{
  		RelabelType *expr = (RelabelType *) node;
  
  		result = find_nonnullable_vars_walker((Node *) expr->arg, top_level);
  	}
  	else if (IsA(node, CoerceViaIO))
  	{
  		/* not clear this is useful, but it can't hurt */
  		CoerceViaIO *expr = (CoerceViaIO *) node;
  
  		result = find_nonnullable_vars_walker((Node *) expr->arg, false);
  	}
  	else if (IsA(node, ArrayCoerceExpr))
  	{
  		/* ArrayCoerceExpr is strict at the array level */
  		ArrayCoerceExpr *expr = (ArrayCoerceExpr *) node;
  
  		result = find_nonnullable_vars_walker((Node *) expr->arg, top_level);
  	}
  	else if (IsA(node, ConvertRowtypeExpr))
  	{
  		/* not clear this is useful, but it can't hurt */
  		ConvertRowtypeExpr *expr = (ConvertRowtypeExpr *) node;
  
  		result = find_nonnullable_vars_walker((Node *) expr->arg, top_level);
  	}
  	else if (IsA(node, CollateExpr))
  	{
  		CollateExpr *expr = (CollateExpr *) node;
  
  		result = find_nonnullable_vars_walker((Node *) expr->arg, top_level);
  	}
  	else if (IsA(node, NullTest))
  	{
  		/* IS NOT NULL can be considered strict, but only at top level */
  		NullTest   *expr = (NullTest *) node;
  
  		if (top_level && expr->nulltesttype == IS_NOT_NULL && !expr->argisrow)
  			result = find_nonnullable_vars_walker((Node *) expr->arg, false);
  	}
  	else if (IsA(node, BooleanTest))
  	{
  		/* Boolean tests that reject NULL are strict at top level */
  		BooleanTest *expr = (BooleanTest *) node;
  
  		if (top_level &&
  			(expr->booltesttype == IS_TRUE ||
  			 expr->booltesttype == IS_FALSE ||
  			 expr->booltesttype == IS_NOT_UNKNOWN))
  			result = find_nonnullable_vars_walker((Node *) expr->arg, false);
  	}
  	else if (IsA(node, PlaceHolderVar))
  	{
  		PlaceHolderVar *phv = (PlaceHolderVar *) node;
  
  		result = find_nonnullable_vars_walker((Node *) phv->phexpr, top_level);
  	}
  	return result;
  }
  
  /*
   * find_forced_null_vars
   *		Determine which Vars must be NULL for the given clause to return TRUE.
   *
   * This is the complement of find_nonnullable_vars: find the level-zero Vars
   * that must be NULL for the clause to return TRUE.  (It is OK to err on the
   * side of conservatism; hence the analysis here is simplistic.  In fact,
   * we only detect simple "var IS NULL" tests at the top level.)
   *
   * The result is a palloc'd List, but we have not copied the member Var nodes.
   * Also, we don't bother trying to eliminate duplicate entries.
   */
  List *
  find_forced_null_vars(Node *node)
  {
  	List	   *result = NIL;
  	Var		   *var;
  	ListCell   *l;
  
  	if (node == NULL)
  		return NIL;
  	/* Check single-clause cases using subroutine */
  	var = find_forced_null_var(node);
  	if (var)
  	{
  		result = list_make1(var);
  	}
  	/* Otherwise, handle AND-conditions */
  	else if (IsA(node, List))
  	{
  		/*
  		 * At top level, we are examining an implicit-AND list: if any of the
  		 * arms produces FALSE-or-NULL then the result is FALSE-or-NULL.
  		 */
  		foreach(l, (List *) node)
  		{
  			result = list_concat(result,
  								 find_forced_null_vars(lfirst(l)));
  		}
  	}
  	else if (IsA(node, BoolExpr))
  	{
  		BoolExpr   *expr = (BoolExpr *) node;
  
  		/*
  		 * We don't bother considering the OR case, because it's fairly
  		 * unlikely anyone would write "v1 IS NULL OR v1 IS NULL". Likewise,
  		 * the NOT case isn't worth expending code on.
  		 */
  		if (expr->boolop == AND_EXPR)
  		{
  			/* At top level we can just recurse (to the List case) */
  			result = find_forced_null_vars((Node *) expr->args);
  		}
  	}
  	return result;
  }
  
  /*
   * find_forced_null_var
   *		Return the Var forced null by the given clause, or NULL if it's
   *		not an IS NULL-type clause.  For success, the clause must enforce
   *		*only* nullness of the particular Var, not any other conditions.
   *
   * This is just the single-clause case of find_forced_null_vars(), without
   * any allowance for AND conditions.  It's used by initsplan.c on individual
   * qual clauses.  The reason for not just applying find_forced_null_vars()
   * is that if an AND of an IS NULL clause with something else were to somehow
   * survive AND/OR flattening, initsplan.c might get fooled into discarding
   * the whole clause when only the IS NULL part of it had been proved redundant.
   */
  Var *
  find_forced_null_var(Node *node)
  {
  	if (node == NULL)
  		return NULL;
  	if (IsA(node, NullTest))
  	{
  		/* check for var IS NULL */
  		NullTest   *expr = (NullTest *) node;
  
  		if (expr->nulltesttype == IS_NULL && !expr->argisrow)
  		{
  			Var		   *var = (Var *) expr->arg;
  
  			if (var && IsA(var, Var) &&
  				var->varlevelsup == 0)
  				return var;
  		}
  	}
  	else if (IsA(node, BooleanTest))
  	{
  		/* var IS UNKNOWN is equivalent to var IS NULL */
  		BooleanTest *expr = (BooleanTest *) node;
  
  		if (expr->booltesttype == IS_UNKNOWN)
  		{
  			Var		   *var = (Var *) expr->arg;
  
  			if (var && IsA(var, Var) &&
  				var->varlevelsup == 0)
  				return var;
  		}
  	}
  	return NULL;
  }
  
  /*
   * Can we treat a ScalarArrayOpExpr as strict?
   *
   * If "falseOK" is true, then a "false" result can be considered strict,
   * else we need to guarantee an actual NULL result for NULL input.
   *
   * "foo op ALL array" is strict if the op is strict *and* we can prove
   * that the array input isn't an empty array.  We can check that
   * for the cases of an array constant and an ARRAY[] construct.
   *
   * "foo op ANY array" is strict in the falseOK sense if the op is strict.
   * If not falseOK, the test is the same as for "foo op ALL array".
   */
  static bool
  is_strict_saop(ScalarArrayOpExpr *expr, bool falseOK)
  {
  	Node	   *rightop;
  
  	/* The contained operator must be strict. */
  	set_sa_opfuncid(expr);
  	if (!func_strict(expr->opfuncid))
  		return false;
  	/* If ANY and falseOK, that's all we need to check. */
  	if (expr->useOr && falseOK)
  		return true;
  	/* Else, we have to see if the array is provably non-empty. */
  	Assert(list_length(expr->args) == 2);
  	rightop = (Node *) lsecond(expr->args);
  	if (rightop && IsA(rightop, Const))
  	{
  		Datum		arraydatum = ((Const *) rightop)->constvalue;
  		bool		arrayisnull = ((Const *) rightop)->constisnull;
  		ArrayType  *arrayval;
  		int			nitems;
  
  		if (arrayisnull)
  			return false;
  		arrayval = DatumGetArrayTypeP(arraydatum);
  		nitems = ArrayGetNItems(ARR_NDIM(arrayval), ARR_DIMS(arrayval));
  		if (nitems > 0)
  			return true;
  	}
  	else if (rightop && IsA(rightop, ArrayExpr))
  	{
  		ArrayExpr  *arrayexpr = (ArrayExpr *) rightop;
  
  		if (arrayexpr->elements != NIL && !arrayexpr->multidims)
  			return true;
  	}
  	return false;
  }
  
  
  
  typedef struct
  {
  	char		exec_location;
  } check_execute_on_functions_context;
  
  static bool
  check_execute_on_functions_walker(Node *node,
  								  check_execute_on_functions_context *context)
  {
  	if (node == NULL)
  		return false;
  
  	if (IsA(node, FuncExpr))
  	{
  		FuncExpr   *expr = (FuncExpr *) node;
  		char		exec_location;
  
  		exec_location = func_exec_location(expr->funcid);
  		if (exec_location != PROEXECLOCATION_ANY && exec_location != context->exec_location)
  		{
  			if (context->exec_location != PROEXECLOCATION_ANY)
  				ereport(ERROR,
  						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
  						 errmsg("cannot mix EXECUTE ON MASTER and EXECUTE ON ALL SEGMENTS functions in same query level")));
  			context->exec_location = exec_location;
  		}
  		/* fall through to check args */
  	}
  	return expression_tree_walker(node, check_execute_on_functions_walker, context);
  }
  
  
  char
  check_execute_on_functions(Node *clause)
  {
  	check_execute_on_functions_context context;
  
  	context.exec_location = PROEXECLOCATION_ANY;
  
  	check_execute_on_functions_walker(clause, &context);
  
  	return context.exec_location;
  }
  
  /*****************************************************************************
   *		Check for "pseudo-constant" clauses
   *****************************************************************************/
  
  /*
   * is_pseudo_constant_clause
   *	  Detect whether an expression is "pseudo constant", ie, it contains no
   *	  variables of the current query level and no uses of volatile functions.
   *	  Such an expr is not necessarily a true constant: it can still contain
   *	  Params and outer-level Vars, not to mention functions whose results
   *	  may vary from one statement to the next.  However, the expr's value
   *	  will be constant over any one scan of the current query, so it can be
   *	  used as, eg, an indexscan key.
   *
   * CAUTION: this function omits to test for one very important class of
   * not-constant expressions, namely aggregates (Aggrefs).  In current usage
   * this is only applied to WHERE clauses and so a check for Aggrefs would be
   * a waste of cycles; but be sure to also check contain_agg_clause() if you
   * want to know about pseudo-constness in other contexts.  The same goes
   * for window functions (WindowFuncs).
   */
  bool
  is_pseudo_constant_clause(Node *clause)
  {
  	/*
  	 * We could implement this check in one recursive scan.  But since the
  	 * check for volatile functions is both moderately expensive and unlikely
  	 * to fail, it seems better to look for Vars first and only check for
  	 * volatile functions if we find no Vars.
  	 */
  	if (!contain_var_clause(clause) &&
  		!contain_volatile_functions(clause))
  		return true;
  	return false;
  }
  
  /*
   * is_pseudo_constant_clause_relids
   *	  Same as above, except caller already has available the var membership
   *	  of the expression; this lets us avoid the contain_var_clause() scan.
   */
  bool
  is_pseudo_constant_clause_relids(Node *clause, Relids relids)
  {
  	if (bms_is_empty(relids) &&
  		!contain_volatile_functions(clause))
  		return true;
  	return false;
  }
  
  
  /*****************************************************************************
   *																			 *
   *		General clause-manipulating routines								 *
   *																			 *
   *****************************************************************************/
  
  /*
   * NumRelids
   *		(formerly clause_relids)
   *
   * Returns the number of different relations referenced in 'clause'.
   */
  int
  NumRelids(Node *clause)
  {
  	Relids		varnos = pull_varnos(clause);
  	int			result = bms_num_members(varnos);
  
  	bms_free(varnos);
  	return result;
  }
  
  /*
   * CommuteOpExpr: commute a binary operator clause
   *
   * XXX the clause is destructively modified!
   */
  void
  CommuteOpExpr(OpExpr *clause)
  {
  	Oid			opoid;
  	Node	   *temp;
  
  	/* Sanity checks: caller is at fault if these fail */
  	if (!is_opclause(clause) ||
  		list_length(clause->args) != 2)
  		elog(ERROR, "cannot commute non-binary-operator clause");
  
  	opoid = get_commutator(clause->opno);
  
  	if (!OidIsValid(opoid))
  		elog(ERROR, "could not find commutator for operator %u",
  			 clause->opno);
  
  	/*
  	 * modify the clause in-place!
  	 */
  	clause->opno = opoid;
  	clause->opfuncid = InvalidOid;
  	/* opresulttype, opretset, opcollid, inputcollid need not change */
  
  	temp = linitial(clause->args);
  	linitial(clause->args) = lsecond(clause->args);
  	lsecond(clause->args) = temp;
  }
  
  /*
   * CommuteRowCompareExpr: commute a RowCompareExpr clause
   *
   * XXX the clause is destructively modified!
   */
  void
  CommuteRowCompareExpr(RowCompareExpr *clause)
  {
  	List	   *newops;
  	List	   *temp;
  	ListCell   *l;
  
  	/* Sanity checks: caller is at fault if these fail */
  	if (!IsA(clause, RowCompareExpr))
  		elog(ERROR, "expected a RowCompareExpr");
  
  	/* Build list of commuted operators */
  	newops = NIL;
  	foreach(l, clause->opnos)
  	{
  		Oid			opoid = lfirst_oid(l);
  
  		opoid = get_commutator(opoid);
  		if (!OidIsValid(opoid))
  			elog(ERROR, "could not find commutator for operator %u",
  				 lfirst_oid(l));
  		newops = lappend_oid(newops, opoid);
  	}
  
  	/*
  	 * modify the clause in-place!
  	 */
  	switch (clause->rctype)
  	{
  		case ROWCOMPARE_LT:
  			clause->rctype = ROWCOMPARE_GT;
  			break;
  		case ROWCOMPARE_LE:
  			clause->rctype = ROWCOMPARE_GE;
  			break;
  		case ROWCOMPARE_GE:
  			clause->rctype = ROWCOMPARE_LE;
  			break;
  		case ROWCOMPARE_GT:
  			clause->rctype = ROWCOMPARE_LT;
  			break;
  		default:
  			elog(ERROR, "unexpected RowCompare type: %d",
  				 (int) clause->rctype);
  			break;
  	}
  
  	clause->opnos = newops;
  
  	/*
  	 * Note: we need not change the opfamilies list; we assume any btree
  	 * opfamily containing an operator will also contain its commutator.
  	 * Collations don't change either.
  	 */
  
  	temp = clause->largs;
  	clause->largs = clause->rargs;
  	clause->rargs = temp;
  }
  
  /*
   * Helper for eval_const_expressions: check that datatype of an attribute
   * is still what it was when the expression was parsed.  This is needed to
   * guard against improper simplification after ALTER COLUMN TYPE.  (XXX we
   * may well need to make similar checks elsewhere?)
   */
  static bool
  rowtype_field_matches(Oid rowtypeid, int fieldnum,
  					  Oid expectedtype, int32 expectedtypmod,
  					  Oid expectedcollation)
  {
  	TupleDesc	tupdesc;
  	Form_pg_attribute attr;
  
  	/* No issue for RECORD, since there is no way to ALTER such a type */
  	if (rowtypeid == RECORDOID)
  		return true;
  	tupdesc = lookup_rowtype_tupdesc(rowtypeid, -1);
  	if (fieldnum <= 0 || fieldnum > tupdesc->natts)
  	{
  		ReleaseTupleDesc(tupdesc);
  		return false;
  	}
  	attr = tupdesc->attrs[fieldnum - 1];
  	if (attr->attisdropped ||
  		attr->atttypid != expectedtype ||
  		attr->atttypmod != expectedtypmod ||
  		attr->attcollation != expectedcollation)
  	{
  		ReleaseTupleDesc(tupdesc);
  		return false;
  	}
  	ReleaseTupleDesc(tupdesc);
  	return true;
  }
  
  
  /**
   * fold_constants
   *
   * Recurses into query tree and folds all constant expressions.
   */
  
  Query *
  fold_constants(PlannerInfo *root, Query *q, ParamListInfo boundParams, Size max_size)
  {
  	eval_const_expressions_context context;
  
  	context.root = root;
  	context.boundParams = boundParams;
  	context.active_fns = NIL;	/* nothing being recursively simplified */
  	context.case_val = NULL;	/* no CASE being examined */
  	context.estimate = false;	/* safe transformations only */
  	context.recurse_queries = true; /* recurse into query structures */
  	context.recurse_sublink_testexpr = false; /* do not recurse into sublink test expressions */
  
  	context.max_size = max_size;
  	
  	context.eval_stable_functions = should_eval_stable_functions(root);
  
  	return (Query *) query_or_expression_tree_mutator
  						(
  						(Node *) q,
  						eval_const_expressions_mutator,
  						&context,
  						0
  						);
  }
  
  /*
   * Transform a small array constant to an ArrayExpr.
   *
   * This is used by ORCA, to transform the array argument of a ScalarArrayExpr
   * into an ArrayExpr. If a ScalarArrayExpr has an ArrayExpr argument, ORCA can
   * perform some optimizations - partition pruning at least - by first expanding
   * the ArrayExpr into its disjunctive normal form and then deriving constraints
   * based on the elements in the ArrayExpr. It doesn't currently know how to
   * extract elements from an Array const, however, so to enable those
   * optimizations in ORCA, we convert small Array Consts into corresponding
   * ArrayExprs.
   *
   * If the argument is not an array constant or the number of elements in the
   * array is greater than optimizer_array_expansion_threshold, returns the
   * original Const unmodified since it is expensive to derive constraints for
   * large arrays.
   */
  Expr *
  transform_array_Const_to_ArrayExpr(Const *c)
  {
  	Oid			elemtype;
  	int16		elemlen;
  	bool		elembyval;
  	char		elemalign;
  	int			nelems;
  	Datum	   *elems;
  	bool	   *nulls;
  	ArrayType  *ac;
  	ArrayExpr *aexpr;
  	int			i;
  
  	Assert(IsA(c, Const));
  
  	/* Does it look like the right kind of an array Const? */
  	if (c->constisnull)
  		return (Expr *) c;	/* NULL const */
  
  	elemtype = get_element_type(c->consttype);
  	if (elemtype == InvalidOid)
  		return (Expr *) c;	/* not an array */
  
  	ac = DatumGetArrayTypeP(c->constvalue);
  	nelems = ArrayGetNItems(ARR_NDIM(ac), ARR_DIMS(ac));
  
  	/* All set, extract the elements, and an ArrayExpr to hold them. */
  	get_typlenbyvalalign(elemtype, &elemlen, &elembyval, &elemalign);
  	deconstruct_array(ac, elemtype, elemlen, elembyval, elemalign,
  					  &elems, &nulls, &nelems);
  
  	if (nelems > optimizer_array_expansion_threshold)
  		return (Expr *) c;	/* too many elements */
  
  	aexpr = makeNode(ArrayExpr);
  	aexpr->array_typeid = c->consttype;
  	aexpr->element_typeid = elemtype;
  	aexpr->multidims = false;
  	aexpr->location = c->location;
  
  	for (i = 0; i < nelems; i++)
  	{
  		aexpr->elements = lappend(aexpr->elements,
  								  makeConst(elemtype,
  											-1,
  											c->constcollid,
  											elemlen,
  											elems[i],
  											nulls[i],
  											elembyval));
  	}
  
  	return (Expr *) aexpr;
  }
  
  /*--------------------
   * eval_const_expressions
   *
   * Reduce any recognizably constant subexpressions of the given
   * expression tree, for example "2 + 2" => "4".  More interestingly,
   * we can reduce certain boolean expressions even when they contain
   * non-constant subexpressions: "x OR true" => "true" no matter what
   * the subexpression x is.  (XXX We assume that no such subexpression
   * will have important side-effects, which is not necessarily a good
   * assumption in the presence of user-defined functions; do we need a
   * pg_proc flag that prevents discarding the execution of a function?)
   *
   * We do understand that certain functions may deliver non-constant
   * results even with constant inputs, "nextval()" being the classic
   * example.  Functions that are not marked "immutable" in pg_proc
   * will not be pre-evaluated here, although we will reduce their
   * arguments as far as possible.
   *
   * Whenever a function is eliminated from the expression by means of
   * constant-expression evaluation or inlining, we add the function to
   * root->glob->invalItems.  This ensures the plan is known to depend on
   * such functions, even though they aren't referenced anymore.
   *
   * We assume that the tree has already been type-checked and contains
   * only operators and functions that are reasonable to try to execute.
   *
   * NOTE: "root" can be passed as NULL if the caller never wants to do any
   * Param substitutions nor receive info about inlined functions.
   *
   * NOTE: the planner assumes that this will always flatten nested AND and
   * OR clauses into N-argument form.  See comments in prepqual.c.
   *
   * NOTE: another critical effect is that any function calls that require
   * default arguments will be expanded, and named-argument calls will be
   * converted to positional notation.  The executor won't handle either.
   *--------------------
   */
  Node *
  eval_const_expressions(PlannerInfo *root, Node *node)
  {
  	eval_const_expressions_context context;
  
  	if (root)
  		context.boundParams = root->glob->boundParams;	/* bound Params */
  	else
  		context.boundParams = NULL;
  	context.root = root;		/* for inlined-function dependencies */
  	context.active_fns = NIL;	/* nothing being recursively simplified */
  	context.case_val = NULL;	/* no CASE being examined */
  	context.estimate = false;	/* safe transformations only */
  	context.recurse_queries = false; /* do not recurse into query structures */
  	context.recurse_sublink_testexpr = true;
  	context.max_size = 0;
  	context.eval_stable_functions = should_eval_stable_functions(root);
  
  	return eval_const_expressions_mutator(node, &context);
  }
  
  /*--------------------
   * estimate_expression_value
   *
   * This function attempts to estimate the value of an expression for
   * planning purposes.  It is in essence a more aggressive version of
   * eval_const_expressions(): we will perform constant reductions that are
   * not necessarily 100% safe, but are reasonable for estimation purposes.
   *
   * Currently the extra steps that are taken in this mode are:
   * 1. Substitute values for Params, where a bound Param value has been made
   *	  available by the caller of planner(), even if the Param isn't marked
   *	  constant.  This effectively means that we plan using the first supplied
   *	  value of the Param.
   * 2. Fold stable, as well as immutable, functions to constants.
   * 3. Reduce PlaceHolderVar nodes to their contained expressions.
   *--------------------
   */
  Node *
  estimate_expression_value(PlannerInfo *root, Node *node)
  {
  	eval_const_expressions_context context;
  
  	context.boundParams = root->glob->boundParams;		/* bound Params */
  	/* we do not need to mark the plan as depending on inlined functions */
  	context.root = NULL;
  	context.active_fns = NIL;	/* nothing being recursively simplified */
  	context.case_val = NULL;	/* no CASE being examined */
  	context.estimate = true;	/* unsafe transformations OK */
  	context.recurse_queries = false; /* do not recurse into query structures */
  	context.recurse_sublink_testexpr = true;
  	context.max_size = 0;
  
  	return eval_const_expressions_mutator(node, &context);
  }
  
  static Node *
  eval_const_expressions_mutator(Node *node,
  							   eval_const_expressions_context *context)
  {
  	if (node == NULL)
  		return NULL;
  	switch (nodeTag(node))
  	{
  		case T_Param:
  			{
  				Param	   *param = (Param *) node;
  
  				/* Look to see if we've been given a value for this Param */
  				if (param->paramkind == PARAM_EXTERN &&
  					context->boundParams != NULL &&
  					param->paramid > 0 &&
  					param->paramid <= context->boundParams->numParams)
  				{
  					ParamExternData *prm = &context->boundParams->params[param->paramid - 1];
  
  					if (OidIsValid(prm->ptype))
  					{
  						/* OK to substitute parameter value? */
  						if (context->estimate ||
  							(prm->pflags & PARAM_FLAG_CONST))
  						{
  							/*
  							 * Return a Const representing the param value.
  							 * Must copy pass-by-ref datatypes, since the
  							 * Param might be in a memory context
  							 * shorter-lived than our output plan should be.
  							 */
  							int16		typLen;
  							bool		typByVal;
  							Datum		pval;
  
  							Assert(prm->ptype == param->paramtype);
  							get_typlenbyval(param->paramtype,
  											&typLen, &typByVal);
  							if (prm->isnull || typByVal)
  								pval = prm->value;
  							else
  								pval = datumCopy(prm->value, typByVal, typLen);
  							return (Node *) makeConst(param->paramtype,
  													  param->paramtypmod,
  													  param->paramcollid,
  													  (int) typLen,
  													  pval,
  													  prm->isnull,
  													  typByVal);
  						}
  					}
  				}
  
  				/*
  				 * Not replaceable, so just copy the Param (no need to
  				 * recurse)
  				 */
  				return (Node *) copyObject(param);
  			}
  		case T_WindowFunc:
  			{
  				WindowFunc *expr = (WindowFunc *) node;
  				Oid			funcid = expr->winfnoid;
  				List	   *args;
  				Expr	   *aggfilter;
  				HeapTuple	func_tuple;
  				WindowFunc *newexpr;
  
  				/*
  				 * We can't really simplify a WindowFunc node, but we mustn't
  				 * just fall through to the default processing, because we
  				 * have to apply expand_function_arguments to its argument
  				 * list.  That takes care of inserting default arguments and
  				 * expanding named-argument notation.
  				 */
  				func_tuple = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
  				if (!HeapTupleIsValid(func_tuple))
  					elog(ERROR, "cache lookup failed for function %u", funcid);
  
  				args = expand_function_arguments(expr->args, expr->wintype,
  												 func_tuple);
  
  				ReleaseSysCache(func_tuple);
  
  				/* Now, recursively simplify the args (which are a List) */
  				args = (List *)
  					expression_tree_mutator((Node *) args,
  											eval_const_expressions_mutator,
  											(void *) context);
  				/* ... and the filter expression, which isn't */
  				aggfilter = (Expr *)
  					eval_const_expressions_mutator((Node *) expr->aggfilter,
  												   context);
  
  				/* And build the replacement WindowFunc node */
  				newexpr = makeNode(WindowFunc);
  				newexpr->winfnoid = expr->winfnoid;
  				newexpr->wintype = expr->wintype;
  				newexpr->wincollid = expr->wincollid;
  				newexpr->inputcollid = expr->inputcollid;
  				newexpr->args = args;
  				newexpr->aggfilter = aggfilter;
  				newexpr->winref = expr->winref;
  				newexpr->winstar = expr->winstar;
  				newexpr->winagg = expr->winagg;
  				newexpr->windistinct = expr->windistinct;
  				newexpr->location = expr->location;
  
  				return (Node *) newexpr;
  			}
  		case T_FuncExpr:
  			{
  				FuncExpr   *expr = (FuncExpr *) node;
  				List	   *args = expr->args;
  				Expr	   *simple;
  				FuncExpr   *newexpr;
  
  				/*
  				 * Code for op/func reduction is pretty bulky, so split it out
  				 * as a separate function.  Note: exprTypmod normally returns
  				 * -1 for a FuncExpr, but not when the node is recognizably a
  				 * length coercion; we want to preserve the typmod in the
  				 * eventual Const if so.
  				 */
  				simple = simplify_function(expr->funcid,
  										   expr->funcresulttype,
  										   exprTypmod(node),
  										   expr->funccollid,
  										   expr->inputcollid,
  										   &args,
  										   expr->funcvariadic,
  										   true,
  										   true,
  										   context);
  				if (simple)		/* successfully simplified it */
  					return (Node *) simple;
  
  				/*
  				 * The expression cannot be simplified any further, so build
  				 * and return a replacement FuncExpr node using the
  				 * possibly-simplified arguments.  Note that we have also
  				 * converted the argument list to positional notation.
  				 */
  				newexpr = makeNode(FuncExpr);
  				newexpr->funcid = expr->funcid;
  				newexpr->funcresulttype = expr->funcresulttype;
  				newexpr->funcretset = expr->funcretset;
  				newexpr->funcvariadic = expr->funcvariadic;
  				newexpr->funcformat = expr->funcformat;
  				newexpr->funccollid = expr->funccollid;
  				newexpr->inputcollid = expr->inputcollid;
  				newexpr->args = args;
  				newexpr->location = expr->location;
  				return (Node *) newexpr;
  			}
  		case T_OpExpr:
  			{
  				OpExpr	   *expr = (OpExpr *) node;
  				List	   *args = expr->args;
  				Expr	   *simple;
  				OpExpr	   *newexpr;
  
  				/*
  				 * Need to get OID of underlying function.  Okay to scribble
  				 * on input to this extent.
  				 */
  				set_opfuncid(expr);
  
  				/*
  				 * Code for op/func reduction is pretty bulky, so split it out
  				 * as a separate function.
  				 */
  				simple = simplify_function(expr->opfuncid,
  										   expr->opresulttype, -1,
  										   expr->opcollid,
  										   expr->inputcollid,
  										   &args,
  										   false,
  										   true,
  										   true,
  										   context);
  				if (simple)		/* successfully simplified it */
  					return (Node *) simple;
  
  				/*
  				 * If the operator is boolean equality or inequality, we know
  				 * how to simplify cases involving one constant and one
  				 * non-constant argument.
  				 */
  				if (expr->opno == BooleanEqualOperator ||
  					expr->opno == BooleanNotEqualOperator)
  				{
  					simple = (Expr *) simplify_boolean_equality(expr->opno,
  																args);
  					if (simple) /* successfully simplified it */
  						return (Node *) simple;
  				}
  
  				/*
  				 * The expression cannot be simplified any further, so build
  				 * and return a replacement OpExpr node using the
  				 * possibly-simplified arguments.
  				 */
  				newexpr = makeNode(OpExpr);
  				newexpr->opno = expr->opno;
  				newexpr->opfuncid = expr->opfuncid;
  				newexpr->opresulttype = expr->opresulttype;
  				newexpr->opretset = expr->opretset;
  				newexpr->opcollid = expr->opcollid;
  				newexpr->inputcollid = expr->inputcollid;
  				newexpr->args = args;
  				newexpr->location = expr->location;
  				return (Node *) newexpr;
  			}
  		case T_DistinctExpr:
  			{
  				DistinctExpr *expr = (DistinctExpr *) node;
  				List	   *args;
  				ListCell   *arg;
  				bool		has_null_input = false;
  				bool		all_null_input = true;
  				bool		has_nonconst_input = false;
  				Expr	   *simple;
  				DistinctExpr *newexpr;
  
  				/*
  				 * Reduce constants in the DistinctExpr's arguments.  We know
  				 * args is either NIL or a List node, so we can call
  				 * expression_tree_mutator directly rather than recursing to
  				 * self.
  				 */
  				args = (List *) expression_tree_mutator((Node *) expr->args,
  											  eval_const_expressions_mutator,
  														(void *) context);
  
  				/*
  				 * We must do our own check for NULLs because DistinctExpr has
  				 * different results for NULL input than the underlying
  				 * operator does.
  				 */
  				foreach(arg, args)
  				{
  					if (IsA(lfirst(arg), Const))
  					{
  						has_null_input |= ((Const *) lfirst(arg))->constisnull;
  						all_null_input &= ((Const *) lfirst(arg))->constisnull;
  					}
  					else
  						has_nonconst_input = true;
  				}
  
  				/* all constants? then can optimize this out */
  				if (!has_nonconst_input)
  				{
  					/* all nulls? then not distinct */
  					if (all_null_input)
  						return makeBoolConst(false, false);
  
  					/* one null? then distinct */
  					if (has_null_input)
  						return makeBoolConst(true, false);
  
  					/* otherwise try to evaluate the '=' operator */
  					/* (NOT okay to try to inline it, though!) */
  
  					/*
  					 * Need to get OID of underlying function.  Okay to
  					 * scribble on input to this extent.
  					 */
  					set_opfuncid((OpExpr *) expr);		/* rely on struct
  														 * equivalence */
  
  					/*
  					 * Code for op/func reduction is pretty bulky, so split it
  					 * out as a separate function.
  					 */
  					simple = simplify_function(expr->opfuncid,
  											   expr->opresulttype, -1,
  											   expr->opcollid,
  											   expr->inputcollid,
  											   &args,
  											   false,
  											   false,
  											   false,
  											   context);
  					if (simple) /* successfully simplified it */
  					{
  						/*
  						 * Since the underlying operator is "=", must negate
  						 * its result
  						 */
  						Const	   *csimple = (Const *) simple;
  
  						Assert(IsA(csimple, Const));
  						csimple->constvalue =
  							BoolGetDatum(!DatumGetBool(csimple->constvalue));
  						return (Node *) csimple;
  					}
  				}
  
  				/*
  				 * The expression cannot be simplified any further, so build
  				 * and return a replacement DistinctExpr node using the
  				 * possibly-simplified arguments.
  				 */
  				newexpr = makeNode(DistinctExpr);
  				newexpr->opno = expr->opno;
  				newexpr->opfuncid = expr->opfuncid;
  				newexpr->opresulttype = expr->opresulttype;
  				newexpr->opretset = expr->opretset;
  				newexpr->opcollid = expr->opcollid;
  				newexpr->inputcollid = expr->inputcollid;
  				newexpr->args = args;
  				newexpr->location = expr->location;
  				return (Node *) newexpr;
  			}
  		case T_BoolExpr:
  			{
  				BoolExpr   *expr = (BoolExpr *) node;
  
  				switch (expr->boolop)
  				{
  					case OR_EXPR:
  						{
  							List	   *newargs;
  							bool		haveNull = false;
  							bool		forceTrue = false;
  
  							newargs = simplify_or_arguments(expr->args,
  															context,
  															&haveNull,
  															&forceTrue);
  							if (forceTrue)
  								return makeBoolConst(true, false);
  							if (haveNull)
  								newargs = lappend(newargs,
  												  makeBoolConst(false, true));
  							/* If all the inputs are FALSE, result is FALSE */
  							if (newargs == NIL)
  								return makeBoolConst(false, false);
  
  							/*
  							 * If only one nonconst-or-NULL input, it's the
  							 * result
  							 */
  							if (list_length(newargs) == 1)
  								return (Node *) linitial(newargs);
  							/* Else we still need an OR node */
  							return (Node *) make_orclause(newargs);
  						}
  					case AND_EXPR:
  						{
  							List	   *newargs;
  							bool		haveNull = false;
  							bool		forceFalse = false;
  
  							newargs = simplify_and_arguments(expr->args,
  															 context,
  															 &haveNull,
  															 &forceFalse);
  							if (forceFalse)
  								return makeBoolConst(false, false);
  							if (haveNull)
  								newargs = lappend(newargs,
  												  makeBoolConst(false, true));
  							/* If all the inputs are TRUE, result is TRUE */
  							if (newargs == NIL)
  								return makeBoolConst(true, false);
  
  							/*
  							 * If only one nonconst-or-NULL input, it's the
  							 * result
  							 */
  							if (list_length(newargs) == 1)
  								return (Node *) linitial(newargs);
  							/* Else we still need an AND node */
  							return (Node *) make_andclause(newargs);
  						}
  					case NOT_EXPR:
  						{
  							Node	   *arg;
  
  							Assert(list_length(expr->args) == 1);
  							arg = eval_const_expressions_mutator(linitial(expr->args),
  																 context);
  
  							/*
  							 * Use negate_clause() to see if we can simplify
  							 * away the NOT.
  							 */
  							return negate_clause(arg);
  						}
  					default:
  						elog(ERROR, "unrecognized boolop: %d",
  							 (int) expr->boolop);
  						break;
  				}
  				break;
  			}
  		case T_SubPlan:
  		case T_AlternativeSubPlan:
  
  			/*
  			 * Return a SubPlan unchanged --- too late to do anything with it.
  			 *
  			 * XXX should we ereport() here instead?  Probably this routine
  			 * should never be invoked after SubPlan creation.
  			 */
  			return node;
  		case T_RelabelType:
  			{
  				/*
  				 * If we can simplify the input to a constant, then we don't
  				 * need the RelabelType node anymore: just change the type
  				 * field of the Const node.  Otherwise, must copy the
  				 * RelabelType node.
  				 */
  				RelabelType *relabel = (RelabelType *) node;
  				Node	   *arg;
  
  				arg = eval_const_expressions_mutator((Node *) relabel->arg,
  													 context);
  
  				/*
  				 * If we find stacked RelabelTypes (eg, from foo :: int ::
  				 * oid) we can discard all but the top one.
  				 */
  				while (arg && IsA(arg, RelabelType))
  					arg = (Node *) ((RelabelType *) arg)->arg;
  
  				if (arg && IsA(arg, Const))
  				{
  					Const	   *con = (Const *) arg;
  
  					con->consttype = relabel->resulttype;
  					con->consttypmod = relabel->resulttypmod;
  					con->constcollid = relabel->resultcollid;
  					return (Node *) con;
  				}
  				else
  				{
  					RelabelType *newrelabel = makeNode(RelabelType);
  
  					newrelabel->arg = (Expr *) arg;
  					newrelabel->resulttype = relabel->resulttype;
  					newrelabel->resulttypmod = relabel->resulttypmod;
  					newrelabel->resultcollid = relabel->resultcollid;
  					newrelabel->relabelformat = relabel->relabelformat;
  					newrelabel->location = relabel->location;
  					return (Node *) newrelabel;
  				}
  			}
  		case T_CoerceViaIO:
  			{
  				CoerceViaIO *expr = (CoerceViaIO *) node;
  				List	   *args;
  				Oid			outfunc;
  				bool		outtypisvarlena;
  				Oid			infunc;
  				Oid			intypioparam;
  				Expr	   *simple;
  				CoerceViaIO *newexpr;
  
  				/* Make a List so we can use simplify_function */
  				args = list_make1(expr->arg);
  
  				/*
  				 * CoerceViaIO represents calling the source type's output
  				 * function then the result type's input function.  So, try to
  				 * simplify it as though it were a stack of two such function
  				 * calls.  First we need to know what the functions are.
  				 *
  				 * Note that the coercion functions are assumed not to care
  				 * about input collation, so we just pass InvalidOid for that.
  				 */
  				getTypeOutputInfo(exprType((Node *) expr->arg),
  								  &outfunc, &outtypisvarlena);
  				getTypeInputInfo(expr->resulttype,
  								 &infunc, &intypioparam);
  
  				simple = simplify_function(outfunc,
  										   CSTRINGOID, -1,
  										   InvalidOid,
  										   InvalidOid,
  										   &args,
  										   false,
  										   true,
  										   true,
  										   context);
  				if (simple)		/* successfully simplified output fn */
  				{
  					/*
  					 * Input functions may want 1 to 3 arguments.  We always
  					 * supply all three, trusting that nothing downstream will
  					 * complain.
  					 */
  					args = list_make3(simple,
  									  makeConst(OIDOID,
  												-1,
  												InvalidOid,
  												sizeof(Oid),
  											  ObjectIdGetDatum(intypioparam),
  												false,
  												true),
  									  makeConst(INT4OID,
  												-1,
  												InvalidOid,
  												sizeof(int32),
  												Int32GetDatum(-1),
  												false,
  												true));
  
  					simple = simplify_function(infunc,
  											   expr->resulttype, -1,
  											   expr->resultcollid,
  											   InvalidOid,
  											   &args,
  											   false,
  											   false,
  											   true,
  											   context);
  					if (simple) /* successfully simplified input fn */
  						return (Node *) simple;
  				}
  
  				/*
  				 * The expression cannot be simplified any further, so build
  				 * and return a replacement CoerceViaIO node using the
  				 * possibly-simplified argument.
  				 */
  				newexpr = makeNode(CoerceViaIO);
  				newexpr->arg = (Expr *) linitial(args);
  				newexpr->resulttype = expr->resulttype;
  				newexpr->resultcollid = expr->resultcollid;
  				newexpr->coerceformat = expr->coerceformat;
  				newexpr->location = expr->location;
  				return (Node *) newexpr;
  			}
  		case T_ArrayCoerceExpr:
  			{
  				ArrayCoerceExpr *expr = (ArrayCoerceExpr *) node;
  				Expr	   *arg;
  				ArrayCoerceExpr *newexpr;
  
  				/*
  				 * Reduce constants in the ArrayCoerceExpr's argument, then
  				 * build a new ArrayCoerceExpr.
  				 */
  				arg = (Expr *) eval_const_expressions_mutator((Node *) expr->arg,
  															  context);
  
  				newexpr = makeNode(ArrayCoerceExpr);
  				newexpr->arg = arg;
  				newexpr->elemfuncid = expr->elemfuncid;
  				newexpr->resulttype = expr->resulttype;
  				newexpr->resulttypmod = expr->resulttypmod;
  				newexpr->resultcollid = expr->resultcollid;
  				newexpr->isExplicit = expr->isExplicit;
  				newexpr->coerceformat = expr->coerceformat;
  				newexpr->location = expr->location;
  
  				/*
  				 * If constant argument and it's a binary-coercible or
  				 * immutable conversion, we can simplify it to a constant.
  				 */
  				if (arg && IsA(arg, Const) &&
  					(!OidIsValid(newexpr->elemfuncid) ||
  				func_volatile(newexpr->elemfuncid) == PROVOLATILE_IMMUTABLE))
  					return (Node *) evaluate_expr((Expr *) newexpr,
  												  newexpr->resulttype,
  												  newexpr->resulttypmod,
  												  newexpr->resultcollid);
  
  				/* Else we must return the partially-simplified node */
  				return (Node *) newexpr;
  			}
  		case T_CollateExpr:
  			{
  				/*
  				 * If we can simplify the input to a constant, then we don't
  				 * need the CollateExpr node at all: just change the
  				 * constcollid field of the Const node.  Otherwise, replace
  				 * the CollateExpr with a RelabelType. (We do that so as to
  				 * improve uniformity of expression representation and thus
  				 * simplify comparison of expressions.)
  				 */
  				CollateExpr *collate = (CollateExpr *) node;
  				Node	   *arg;
  
  				arg = eval_const_expressions_mutator((Node *) collate->arg,
  													 context);
  
  				if (arg && IsA(arg, Const))
  				{
  					Const	   *con = (Const *) arg;
  
  					con->constcollid = collate->collOid;
  					return (Node *) con;
  				}
  				else if (collate->collOid == exprCollation(arg))
  				{
  					/* Don't need a RelabelType either... */
  					return arg;
  				}
  				else
  				{
  					RelabelType *relabel = makeNode(RelabelType);
  
  					relabel->resulttype = exprType(arg);
  					relabel->resulttypmod = exprTypmod(arg);
  					relabel->resultcollid = collate->collOid;
  					relabel->relabelformat = COERCE_IMPLICIT_CAST;
  					relabel->location = collate->location;
  
  					/* Don't create stacked RelabelTypes */
  					while (arg && IsA(arg, RelabelType))
  						arg = (Node *) ((RelabelType *) arg)->arg;
  					relabel->arg = (Expr *) arg;
  
  					return (Node *) relabel;
  				}
  			}
  		case T_CaseExpr:
  			{
  				/*----------
  				 * CASE expressions can be simplified if there are constant
  				 * condition clauses:
  				 *		FALSE (or NULL): drop the alternative
  				 *		TRUE: drop all remaining alternatives
  				 * If the first non-FALSE alternative is a constant TRUE,
  				 * we can simplify the entire CASE to that alternative's
  				 * expression.  If there are no non-FALSE alternatives,
  				 * we simplify the entire CASE to the default result (ELSE).
  				 *
  				 * If we have a simple-form CASE with constant test
  				 * expression, we substitute the constant value for contained
  				 * CaseTestExpr placeholder nodes, so that we have the
  				 * opportunity to reduce constant test conditions.  For
  				 * example this allows
  				 *		CASE 0 WHEN 0 THEN 1 ELSE 1/0 END
  				 * to reduce to 1 rather than drawing a divide-by-0 error.
  				 * Note that when the test expression is constant, we don't
  				 * have to include it in the resulting CASE; for example
  				 *		CASE 0 WHEN x THEN y ELSE z END
  				 * is transformed by the parser to
  				 *		CASE 0 WHEN CaseTestExpr = x THEN y ELSE z END
  				 * which we can simplify to
  				 *		CASE WHEN 0 = x THEN y ELSE z END
  				 * It is not necessary for the executor to evaluate the "arg"
  				 * expression when executing the CASE, since any contained
  				 * CaseTestExprs that might have referred to it will have been
  				 * replaced by the constant.
  				 *----------
  				 */
  				CaseExpr   *caseexpr = (CaseExpr *) node;
  				CaseExpr   *newcase;
  				Node	   *save_case_val;
  				Node	   *newarg;
  				List	   *newargs;
  				bool		const_true_cond;
  				Node	   *defresult = NULL;
  				ListCell   *arg;
  
  				/* Simplify the test expression, if any */
  				newarg = eval_const_expressions_mutator((Node *) caseexpr->arg,
  														context);
  
  				/* Set up for contained CaseTestExpr nodes */
  				save_case_val = context->case_val;
  				if (newarg && IsA(newarg, Const))
  				{
  					context->case_val = newarg;
  					newarg = NULL;		/* not needed anymore, see above */
  				}
  				else
  					context->case_val = NULL;
  
  				/* Simplify the WHEN clauses */
  				newargs = NIL;
  				const_true_cond = false;
  				foreach(arg, caseexpr->args)
  				{
  					CaseWhen   *oldcasewhen = (CaseWhen *) lfirst(arg);
  					Node	   *casecond;
  					Node	   *caseresult;
  
  					Assert(IsA(oldcasewhen, CaseWhen));
  
  					/* Simplify this alternative's test condition */
  					casecond = eval_const_expressions_mutator((Node *) oldcasewhen->expr,
  															  context);
  
  					/*
  					 * If the test condition is constant FALSE (or NULL), then
  					 * drop this WHEN clause completely, without processing
  					 * the result.
  					 */
  					if (casecond && IsA(casecond, Const))
  					{
  						Const	   *const_input = (Const *) casecond;
  
  						if (const_input->constisnull ||
  							!DatumGetBool(const_input->constvalue))
  							continue;	/* drop alternative with FALSE cond */
  						/* Else it's constant TRUE */
  						const_true_cond = true;
  					}
  
  					/* Simplify this alternative's result value */
  					caseresult = eval_const_expressions_mutator((Node *) oldcasewhen->result,
  																context);
  
  					/* If non-constant test condition, emit a new WHEN node */
  					if (!const_true_cond)
  					{
  						CaseWhen   *newcasewhen = makeNode(CaseWhen);
  
  						newcasewhen->expr = (Expr *) casecond;
  						newcasewhen->result = (Expr *) caseresult;
  						newcasewhen->location = oldcasewhen->location;
  						newargs = lappend(newargs, newcasewhen);
  						continue;
  					}
  
  					/*
  					 * Found a TRUE condition, so none of the remaining
  					 * alternatives can be reached.  We treat the result as
  					 * the default result.
  					 */
  					defresult = caseresult;
  					break;
  				}
  
  				/* Simplify the default result, unless we replaced it above */
  				if (!const_true_cond)
  					defresult = eval_const_expressions_mutator((Node *) caseexpr->defresult,
  															   context);
  
  				context->case_val = save_case_val;
  
  				/*
  				 * If no non-FALSE alternatives, CASE reduces to the default
  				 * result
  				 */
  				if (newargs == NIL)
  					return defresult;
  				/* Otherwise we need a new CASE node */
  				newcase = makeNode(CaseExpr);
  				newcase->casetype = caseexpr->casetype;
  				newcase->casecollid = caseexpr->casecollid;
  				newcase->arg = (Expr *) newarg;
  				newcase->args = newargs;
  				newcase->defresult = (Expr *) defresult;
  				newcase->location = caseexpr->location;
  				return (Node *) newcase;
  			}
  		case T_CaseTestExpr:
  			{
  				/*
  				 * If we know a constant test value for the current CASE
  				 * construct, substitute it for the placeholder.  Else just
  				 * return the placeholder as-is.
  				 */
  				if (context->case_val)
  					return copyObject(context->case_val);
  				else
  					return copyObject(node);
  			}
  		case T_ScalarArrayOpExpr:
  			{
  				ScalarArrayOpExpr *saop;
  				Node *scalar;
  				Node *values;
  
  				saop = (ScalarArrayOpExpr *) expression_tree_mutator(node, eval_const_expressions_mutator,
  																	 (void *) context);
  
  				Assert( IsA(saop, ScalarArrayOpExpr));
  				Assert( list_length(saop->args) == 2);
  
  				scalar = (Node *) linitial(saop->args);
  				values = (Node *) lsecond(saop->args);
  
  				if ( IsA(scalar, Const) && IsA(values, Const))
  				{
  					Node *result = (Node *) evaluate_expr( (Expr *) saop, BOOLOID, -1, InvalidOid);
  					Assert(IsA(result, Const));
  					return result;
  				}
  
  				/* note a couple things:
  				 *
  				 * 1) If values is not a constant (it could be an ArrayExpr) then that means
  				 *    the ArrayExpr could not be reduced to a constant ...
  				 * 2) We could further improve this by, for OR scalar array ops, extract only the Const values
  				 *    from the array and make a constant out of those to evaluate.  If it evaluates to true then
  				 *    we can return true, otherwise we can return a new ScalarArrayOpExpr with values being
  				 *    only the non-Const values.  This seems overkill: I think      a in (1,2,3,x,y,z)    is rare
  				 */
  
  				return (Node *) saop; /* this has been walked and is a new one */
  			}
  		case T_ArrayExpr:
  			{
  				ArrayExpr  *arrayexpr = (ArrayExpr *) node;
  				ArrayExpr  *newarray;
  				bool		all_const = true;
  				List	   *newelems;
  				ListCell   *element;
  
  				newelems = NIL;
  				foreach(element, arrayexpr->elements)
  				{
  					Node	   *e;
  
  					e = eval_const_expressions_mutator((Node *) lfirst(element),
  													   context);
  					if (!IsA(e, Const))
  						all_const = false;
  					newelems = lappend(newelems, e);
  				}
  
  				newarray = makeNode(ArrayExpr);
  				newarray->array_typeid = arrayexpr->array_typeid;
  				newarray->array_collid = arrayexpr->array_collid;
  				newarray->element_typeid = arrayexpr->element_typeid;
  				newarray->elements = newelems;
  				newarray->multidims = arrayexpr->multidims;
  				newarray->location = arrayexpr->location;
  
  				if (all_const)
  					return (Node *) evaluate_expr((Expr *) newarray,
  												  newarray->array_typeid,
  												  exprTypmod(node),
  												  newarray->array_collid);
  
  				return (Node *) newarray;
  			}
  		case T_CoalesceExpr:
  			{
  				CoalesceExpr *coalesceexpr = (CoalesceExpr *) node;
  				CoalesceExpr *newcoalesce;
  				List	   *newargs;
  				ListCell   *arg;
  
  				newargs = NIL;
  				foreach(arg, coalesceexpr->args)
  				{
  					Node	   *e;
  
  					e = eval_const_expressions_mutator((Node *) lfirst(arg),
  													   context);
  
  					/*
  					 * We can remove null constants from the list. For a
  					 * non-null constant, if it has not been preceded by any
  					 * other non-null-constant expressions then it is the
  					 * result. Otherwise, it's the next argument, but we can
  					 * drop following arguments since they will never be
  					 * reached.
  					 */
  					if (IsA(e, Const))
  					{
  						if (((Const *) e)->constisnull)
  							continue;	/* drop null constant */
  						if (newargs == NIL)
  							return e;	/* first expr */
  						newargs = lappend(newargs, e);
  						break;
  					}
  					newargs = lappend(newargs, e);
  				}
  
  				/*
  				 * If all the arguments were constant null, the result is just
  				 * null
  				 */
  				if (newargs == NIL)
  					return (Node *) makeNullConst(coalesceexpr->coalescetype,
  												  -1,
  											   coalesceexpr->coalescecollid);
  
  				newcoalesce = makeNode(CoalesceExpr);
  				newcoalesce->coalescetype = coalesceexpr->coalescetype;
  				newcoalesce->coalescecollid = coalesceexpr->coalescecollid;
  				newcoalesce->args = newargs;
  				newcoalesce->location = coalesceexpr->location;
  				return (Node *) newcoalesce;
  			}
  		case T_FieldSelect:
  			{
  				/*
  				 * We can optimize field selection from a whole-row Var into a
  				 * simple Var.  (This case won't be generated directly by the
  				 * parser, because ParseComplexProjection short-circuits it.
  				 * But it can arise while simplifying functions.)  Also, we
  				 * can optimize field selection from a RowExpr construct.
  				 *
  				 * However, replacing a whole-row Var in this way has a
  				 * pitfall: if we've already built the reltargetlist for the
  				 * source relation, then the whole-row Var is scheduled to be
  				 * produced by the relation scan, but the simple Var probably
  				 * isn't, which will lead to a failure in setrefs.c.  This is
  				 * not a problem when handling simple single-level queries, in
  				 * which expression simplification always happens first.  It
  				 * is a risk for lateral references from subqueries, though.
  				 * To avoid such failures, don't optimize uplevel references.
  				 *
  				 * We must also check that the declared type of the field is
  				 * still the same as when the FieldSelect was created --- this
  				 * can change if someone did ALTER COLUMN TYPE on the rowtype.
  				 */
  				FieldSelect *fselect = (FieldSelect *) node;
  				FieldSelect *newfselect;
  				Node	   *arg;
  
  				arg = eval_const_expressions_mutator((Node *) fselect->arg,
  													 context);
  				if (arg && IsA(arg, Var) &&
  					((Var *) arg)->varattno == InvalidAttrNumber &&
  					((Var *) arg)->varlevelsup == 0)
  				{
  					if (rowtype_field_matches(((Var *) arg)->vartype,
  											  fselect->fieldnum,
  											  fselect->resulttype,
  											  fselect->resulttypmod,
  											  fselect->resultcollid))
  						return (Node *) makeVar(((Var *) arg)->varno,
  												fselect->fieldnum,
  												fselect->resulttype,
  												fselect->resulttypmod,
  												fselect->resultcollid,
  												((Var *) arg)->varlevelsup);
  				}
  				if (arg && IsA(arg, RowExpr))
  				{
  					RowExpr    *rowexpr = (RowExpr *) arg;
  
  					if (fselect->fieldnum > 0 &&
  						fselect->fieldnum <= list_length(rowexpr->args))
  					{
  						Node	   *fld = (Node *) list_nth(rowexpr->args,
  													  fselect->fieldnum - 1);
  
  						if (rowtype_field_matches(rowexpr->row_typeid,
  												  fselect->fieldnum,
  												  fselect->resulttype,
  												  fselect->resulttypmod,
  												  fselect->resultcollid) &&
  							fselect->resulttype == exprType(fld) &&
  							fselect->resulttypmod == exprTypmod(fld) &&
  							fselect->resultcollid == exprCollation(fld))
  							return fld;
  					}
  				}
  				newfselect = makeNode(FieldSelect);
  				newfselect->arg = (Expr *) arg;
  				newfselect->fieldnum = fselect->fieldnum;
  				newfselect->resulttype = fselect->resulttype;
  				newfselect->resulttypmod = fselect->resulttypmod;
  				newfselect->resultcollid = fselect->resultcollid;
  				return (Node *) newfselect;
  			}
  		case T_NullTest:
  			{
  				NullTest   *ntest = (NullTest *) node;
  				NullTest   *newntest;
  				Node	   *arg;
  
  				arg = eval_const_expressions_mutator((Node *) ntest->arg,
  													 context);
  				if (ntest->argisrow && arg && IsA(arg, RowExpr))
  				{
  					/*
  					 * We break ROW(...) IS [NOT] NULL into separate tests on
  					 * its component fields.  This form is usually more
  					 * efficient to evaluate, as well as being more amenable
  					 * to optimization.
  					 */
  					RowExpr    *rarg = (RowExpr *) arg;
  					List	   *newargs = NIL;
  					ListCell   *l;
  
  					foreach(l, rarg->args)
  					{
  						Node	   *relem = (Node *) lfirst(l);
  
  						/*
  						 * A constant field refutes the whole NullTest if it's
  						 * of the wrong nullness; else we can discard it.
  						 */
  						if (relem && IsA(relem, Const))
  						{
  							Const	   *carg = (Const *) relem;
  
  							if (carg->constisnull ?
  								(ntest->nulltesttype == IS_NOT_NULL) :
  								(ntest->nulltesttype == IS_NULL))
  								return makeBoolConst(false, false);
  							continue;
  						}
  
  						/*
  						 * Else, make a scalar (argisrow == false) NullTest
  						 * for this field.  Scalar semantics are required
  						 * because IS [NOT] NULL doesn't recurse; see comments
  						 * in ExecEvalNullTest().
  						 */
  						newntest = makeNode(NullTest);
  						newntest->arg = (Expr *) relem;
  						newntest->nulltesttype = ntest->nulltesttype;
  						newntest->argisrow = false;
  						newargs = lappend(newargs, newntest);
  					}
  					/* If all the inputs were constants, result is TRUE */
  					if (newargs == NIL)
  						return makeBoolConst(true, false);
  					/* If only one nonconst input, it's the result */
  					if (list_length(newargs) == 1)
  						return (Node *) linitial(newargs);
  					/* Else we need an AND node */
  					return (Node *) make_andclause(newargs);
  				}
  				if (!ntest->argisrow && arg && IsA(arg, Const))
  				{
  					Const	   *carg = (Const *) arg;
  					bool		result;
  
  					switch (ntest->nulltesttype)
  					{
  						case IS_NULL:
  							result = carg->constisnull;
  							break;
  						case IS_NOT_NULL:
  							result = !carg->constisnull;
  							break;
  						default:
  							elog(ERROR, "unrecognized nulltesttype: %d",
  								 (int) ntest->nulltesttype);
  							result = false;		/* keep compiler quiet */
  							break;
  					}
  
  					return makeBoolConst(result, false);
  				}
  
  				newntest = makeNode(NullTest);
  				newntest->arg = (Expr *) arg;
  				newntest->nulltesttype = ntest->nulltesttype;
  				newntest->argisrow = ntest->argisrow;
  				return (Node *) newntest;
  			}
  		case T_BooleanTest:
  			{
  				BooleanTest *btest = (BooleanTest *) node;
  				BooleanTest *newbtest;
  				Node	   *arg;
  
  				arg = eval_const_expressions_mutator((Node *) btest->arg,
  													 context);
  				if (arg && IsA(arg, Const))
  				{
  					Const	   *carg = (Const *) arg;
  					bool		result;
  
  					switch (btest->booltesttype)
  					{
  						case IS_TRUE:
  							result = (!carg->constisnull &&
  									  DatumGetBool(carg->constvalue));
  							break;
  						case IS_NOT_TRUE:
  							result = (carg->constisnull ||
  									  !DatumGetBool(carg->constvalue));
  							break;
  						case IS_FALSE:
  							result = (!carg->constisnull &&
  									  !DatumGetBool(carg->constvalue));
  							break;
  						case IS_NOT_FALSE:
  							result = (carg->constisnull ||
  									  DatumGetBool(carg->constvalue));
  							break;
  						case IS_UNKNOWN:
  							result = carg->constisnull;
  							break;
  						case IS_NOT_UNKNOWN:
  							result = !carg->constisnull;
  							break;
  						default:
  							elog(ERROR, "unrecognized booltesttype: %d",
  								 (int) btest->booltesttype);
  							result = false;		/* keep compiler quiet */
  							break;
  					}
  
  					return makeBoolConst(result, false);
  				}
  
  				newbtest = makeNode(BooleanTest);
  				newbtest->arg = (Expr *) arg;
  				newbtest->booltesttype = btest->booltesttype;
  				return (Node *) newbtest;
  			}
  		case T_PlaceHolderVar:
  
  			/*
  			 * In estimation mode, just strip the PlaceHolderVar node
  			 * altogether; this amounts to estimating that the contained value
  			 * won't be forced to null by an outer join.  In regular mode we
  			 * just use the default behavior (ie, simplify the expression but
  			 * leave the PlaceHolderVar node intact).
  			 */
  			if (context->estimate)
  			{
  				PlaceHolderVar *phv = (PlaceHolderVar *) node;
  
  				return eval_const_expressions_mutator((Node *) phv->phexpr,
  													  context);
  			}
  			break;
  		default:
  			break;
  	}
  
  	/* prevent recursion into sublinks */
  	if (IsA(node, SubLink) && !context->recurse_sublink_testexpr)
  	{
  		SubLink    *sublink = (SubLink *) node;
  		SubLink    *newnode = copyObject(sublink);
  
  		/*
  		 * Also invoke the mutator on the sublink's Query node, so it
  		 * can recurse into the sub-query if it wants to.
  		 */
  		newnode->subselect = (Node *) query_tree_mutator((Query *) sublink->subselect, eval_const_expressions_mutator, (void*) context, 0);
  		return (Node *) newnode;
  	}
  
  	/* recurse into query structure if requested */
  	if (IsA(node, Query) && context->recurse_queries)
  	{
  		return (Node *)
  					query_tree_mutator
  					(
  					(Query *) node,
  					eval_const_expressions_mutator,
  					(void *) context,
  					0);
  	}
  
  	/*
  	 * For any node type not handled above, we recurse using
  	 * expression_tree_mutator, which will copy the node unchanged but try to
  	 * simplify its arguments (if any) using this routine. For example: we
  	 * cannot eliminate an ArrayRef node, but we might be able to simplify
  	 * constant expressions in its subscripts.
  	 */
  	return expression_tree_mutator(node, eval_const_expressions_mutator,
  								   (void *) context);
  }
  
  /*
   * Subroutine for eval_const_expressions: process arguments of an OR clause
   *
   * This includes flattening of nested ORs as well as recursion to
   * eval_const_expressions to simplify the OR arguments.
   *
   * After simplification, OR arguments are handled as follows:
   *		non constant: keep
   *		FALSE: drop (does not affect result)
   *		TRUE: force result to TRUE
   *		NULL: keep only one
   * We must keep one NULL input because ExecEvalOr returns NULL when no input
   * is TRUE and at least one is NULL.  We don't actually include the NULL
   * here, that's supposed to be done by the caller.
   *
   * The output arguments *haveNull and *forceTrue must be initialized FALSE
   * by the caller.  They will be set TRUE if a null constant or true constant,
   * respectively, is detected anywhere in the argument list.
   */
  static List *
  simplify_or_arguments(List *args,
  					  eval_const_expressions_context *context,
  					  bool *haveNull, bool *forceTrue)
  {
  	List	   *newargs = NIL;
  	List	   *unprocessed_args;
  
  	/*
  	 * Since the parser considers OR to be a binary operator, long OR lists
  	 * become deeply nested expressions.  We must flatten these into long
  	 * argument lists of a single OR operator.  To avoid blowing out the stack
  	 * with recursion of eval_const_expressions, we resort to some tenseness
  	 * here: we keep a list of not-yet-processed inputs, and handle flattening
  	 * of nested ORs by prepending to the to-do list instead of recursing.
  	 */
  	unprocessed_args = list_copy(args);
  	while (unprocessed_args)
  	{
  		Node	   *arg = (Node *) linitial(unprocessed_args);
  
  		unprocessed_args = list_delete_first(unprocessed_args);
  
  		/* flatten nested ORs as per above comment */
  		if (or_clause(arg))
  		{
  			List	   *subargs = list_copy(((BoolExpr *) arg)->args);
  
  			/* overly tense code to avoid leaking unused list header */
  			if (!unprocessed_args)
  				unprocessed_args = subargs;
  			else
  			{
  				List	   *oldhdr = unprocessed_args;
  
  				unprocessed_args = list_concat(subargs, unprocessed_args);
  				pfree(oldhdr);
  			}
  			continue;
  		}
  
  		/* If it's not an OR, simplify it */
  		arg = eval_const_expressions_mutator(arg, context);
  
  		/*
  		 * It is unlikely but not impossible for simplification of a non-OR
  		 * clause to produce an OR.  Recheck, but don't be too tense about it
  		 * since it's not a mainstream case. In particular we don't worry
  		 * about const-simplifying the input twice.
  		 */
  		if (or_clause(arg))
  		{
  			List	   *subargs = list_copy(((BoolExpr *) arg)->args);
  
  			unprocessed_args = list_concat(subargs, unprocessed_args);
  			continue;
  		}
  
  		/*
  		 * OK, we have a const-simplified non-OR argument.  Process it per
  		 * comments above.
  		 */
  		if (IsA(arg, Const))
  		{
  			Const	   *const_input = (Const *) arg;
  
  			if (const_input->constisnull)
  				*haveNull = true;
  			else if (DatumGetBool(const_input->constvalue))
  			{
  				*forceTrue = true;
  
  				/*
  				 * Once we detect a TRUE result we can just exit the loop
  				 * immediately.  However, if we ever add a notion of
  				 * non-removable functions, we'd need to keep scanning.
  				 */
  				return NIL;
  			}
  			/* otherwise, we can drop the constant-false input */
  			continue;
  		}
  
  		/* else emit the simplified arg into the result list */
  		newargs = lappend(newargs, arg);
  	}
  
  	return newargs;
  }
  
  /*
   * Subroutine for eval_const_expressions: process arguments of an AND clause
   *
   * This includes flattening of nested ANDs as well as recursion to
   * eval_const_expressions to simplify the AND arguments.
   *
   * After simplification, AND arguments are handled as follows:
   *		non constant: keep
   *		TRUE: drop (does not affect result)
   *		FALSE: force result to FALSE
   *		NULL: keep only one
   * We must keep one NULL input because ExecEvalAnd returns NULL when no input
   * is FALSE and at least one is NULL.  We don't actually include the NULL
   * here, that's supposed to be done by the caller.
   *
   * The output arguments *haveNull and *forceFalse must be initialized FALSE
   * by the caller.  They will be set TRUE if a null constant or false constant,
   * respectively, is detected anywhere in the argument list.
   */
  static List *
  simplify_and_arguments(List *args,
  					   eval_const_expressions_context *context,
  					   bool *haveNull, bool *forceFalse)
  {
  	List	   *newargs = NIL;
  	List	   *unprocessed_args;
  
  	/* See comments in simplify_or_arguments */
  	unprocessed_args = list_copy(args);
  	while (unprocessed_args)
  	{
  		Node	   *arg = (Node *) linitial(unprocessed_args);
  
  		unprocessed_args = list_delete_first(unprocessed_args);
  
  		/* flatten nested ANDs as per above comment */
  		if (and_clause(arg))
  		{
  			List	   *subargs = list_copy(((BoolExpr *) arg)->args);
  
  			/* overly tense code to avoid leaking unused list header */
  			if (!unprocessed_args)
  				unprocessed_args = subargs;
  			else
  			{
  				List	   *oldhdr = unprocessed_args;
  
  				unprocessed_args = list_concat(subargs, unprocessed_args);
  				pfree(oldhdr);
  			}
  			continue;
  		}
  
  		/* If it's not an AND, simplify it */
  		arg = eval_const_expressions_mutator(arg, context);
  
  		/*
  		 * It is unlikely but not impossible for simplification of a non-AND
  		 * clause to produce an AND.  Recheck, but don't be too tense about it
  		 * since it's not a mainstream case. In particular we don't worry
  		 * about const-simplifying the input twice.
  		 */
  		if (and_clause(arg))
  		{
  			List	   *subargs = list_copy(((BoolExpr *) arg)->args);
  
  			unprocessed_args = list_concat(subargs, unprocessed_args);
  			continue;
  		}
  
  		/*
  		 * OK, we have a const-simplified non-AND argument.  Process it per
  		 * comments above.
  		 */
  		if (IsA(arg, Const))
  		{
  			Const	   *const_input = (Const *) arg;
  
  			if (const_input->constisnull)
  				*haveNull = true;
  			else if (!DatumGetBool(const_input->constvalue))
  			{
  				*forceFalse = true;
  
  				/*
  				 * Once we detect a FALSE result we can just exit the loop
  				 * immediately.  However, if we ever add a notion of
  				 * non-removable functions, we'd need to keep scanning.
  				 */
  				return NIL;
  			}
  			/* otherwise, we can drop the constant-true input */
  			continue;
  		}
  
  		/* else emit the simplified arg into the result list */
  		newargs = lappend(newargs, arg);
  	}
  
  	return newargs;
  }
  
  /*
   * Subroutine for eval_const_expressions: try to simplify boolean equality
   * or inequality condition
   *
   * Inputs are the operator OID and the simplified arguments to the operator.
   * Returns a simplified expression if successful, or NULL if cannot
   * simplify the expression.
   *
   * The idea here is to reduce "x = true" to "x" and "x = false" to "NOT x",
   * or similarly "x <> true" to "NOT x" and "x <> false" to "x".
   * This is only marginally useful in itself, but doing it in constant folding
   * ensures that we will recognize these forms as being equivalent in, for
   * example, partial index matching.
   *
   * We come here only if simplify_function has failed; therefore we cannot
   * see two constant inputs, nor a constant-NULL input.
   */
  static Node *
  simplify_boolean_equality(Oid opno, List *args)
  {
  	Node	   *leftop;
  	Node	   *rightop;
  
  	Assert(list_length(args) == 2);
  	leftop = linitial(args);
  	rightop = lsecond(args);
  	if (leftop && IsA(leftop, Const))
  	{
  		Assert(!((Const *) leftop)->constisnull);
  		if (opno == BooleanEqualOperator)
  		{
  			if (DatumGetBool(((Const *) leftop)->constvalue))
  				return rightop; /* true = foo */
  			else
  				return negate_clause(rightop);	/* false = foo */
  		}
  		else
  		{
  			if (DatumGetBool(((Const *) leftop)->constvalue))
  				return negate_clause(rightop);	/* true <> foo */
  			else
  				return rightop; /* false <> foo */
  		}
  	}
  	if (rightop && IsA(rightop, Const))
  	{
  		Assert(!((Const *) rightop)->constisnull);
  		if (opno == BooleanEqualOperator)
  		{
  			if (DatumGetBool(((Const *) rightop)->constvalue))
  				return leftop;	/* foo = true */
  			else
  				return negate_clause(leftop);	/* foo = false */
  		}
  		else
  		{
  			if (DatumGetBool(((Const *) rightop)->constvalue))
  				return negate_clause(leftop);	/* foo <> true */
  			else
  				return leftop;	/* foo <> false */
  		}
  	}
  	return NULL;
  }
  
  /*
   * Subroutine for eval_const_expressions: try to simplify a function call
   * (which might originally have been an operator; we don't care)
   *
   * Inputs are the function OID, actual result type OID (which is needed for
   * polymorphic functions), result typmod, result collation, the input
   * collation to use for the function, the original argument list (not
   * const-simplified yet, unless process_args is false), and some flags;
   * also the context data for eval_const_expressions.
   *
   * Returns a simplified expression if successful, or NULL if cannot
   * simplify the function call.
   *
   * This function is also responsible for converting named-notation argument
   * lists into positional notation and/or adding any needed default argument
   * expressions; which is a bit grotty, but it avoids extra fetches of the
   * function's pg_proc tuple.  For this reason, the args list is
   * pass-by-reference.  Conversion and const-simplification of the args list
   * will be done even if simplification of the function call itself is not
   * possible.
   */
  /*
   * GPDB_92_MERGE_FIXME: please check if the arguments input by whom is
   * called this function is correct,?
   */
  static Expr *simplify_function(Oid funcid,
  				  Oid result_type, int32 result_typmod,
  				  Oid result_collid, Oid input_collid, List **args_p,
  				  bool funcvariadic, bool process_args, bool allow_non_const,
  				  eval_const_expressions_context *context)
  {
  	List	   *args = *args_p;
  	HeapTuple	func_tuple;
  	Form_pg_proc func_form;
  	Expr	   *newexpr;
  
  	/*
  	 * We have three strategies for simplification: execute the function to
  	 * deliver a constant result, use a transform function to generate a
  	 * substitute node tree, or expand in-line the body of the function
  	 * definition (which only works for simple SQL-language functions, but
  	 * that is a common case).  Each case needs access to the function's
  	 * pg_proc tuple, so fetch it just once.
  	 *
  	 * Note: the allow_non_const flag suppresses both the second and third
  	 * strategies; so if !allow_non_const, simplify_function can only return a
  	 * Const or NULL.  Argument-list rewriting happens anyway, though.
  	 */
  	func_tuple = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
  	if (!HeapTupleIsValid(func_tuple))
  		elog(ERROR, "cache lookup failed for function %u", funcid);
  	func_form = (Form_pg_proc) GETSTRUCT(func_tuple);
  
  	/*
  	 * Process the function arguments, unless the caller did it already.
  	 *
  	 * Here we must deal with named or defaulted arguments, and then
  	 * recursively apply eval_const_expressions to the whole argument list.
  	 */
  	if (process_args)
  	{
  		args = expand_function_arguments(args, result_type, func_tuple);
  		args = (List *) expression_tree_mutator((Node *) args,
  											  eval_const_expressions_mutator,
  												(void *) context);
  		/* Argument processing done, give it back to the caller */
  		*args_p = args;
  	}
  
  	/* Now attempt simplification of the function call proper. */
  
  	newexpr = evaluate_function(funcid, result_type, result_typmod,
  								result_collid, input_collid,
  								args, funcvariadic,
  								func_tuple, context);
  
  	if (large_const(newexpr, context->max_size))
  	{
  		// folded expression prohibitively large
  		newexpr = NULL;
  	}
  
  	if (!newexpr && allow_non_const && OidIsValid(func_form->protransform))
  	{
  		/*
  		 * Build a dummy FuncExpr node containing the simplified arg list.  We
  		 * use this approach to present a uniform interface to the transform
  		 * function regardless of how the function is actually being invoked.
  		 */
  		FuncExpr	fexpr;
  
  		fexpr.xpr.type = T_FuncExpr;
  		fexpr.funcid = funcid;
  		fexpr.funcresulttype = result_type;
  		fexpr.funcretset = func_form->proretset;
  		fexpr.funcvariadic = funcvariadic;
  		fexpr.funcformat = COERCE_EXPLICIT_CALL;
  		fexpr.funccollid = result_collid;
  		fexpr.inputcollid = input_collid;
  		fexpr.args = args;
  		fexpr.location = -1;
  
  		newexpr = (Expr *)
  			DatumGetPointer(OidFunctionCall1(func_form->protransform,
  											 PointerGetDatum(&fexpr)));
  	}
  
  	if (!newexpr && allow_non_const)
  		newexpr = inline_function(funcid, result_type, result_collid,
  								  input_collid, args, funcvariadic,
  								  func_tuple, context);
  
  	ReleaseSysCache(func_tuple);
  
  	return newexpr;
  }
  
  /*
   * expand_function_arguments: convert named-notation args to positional args
   * and/or insert default args, as needed
   *
   * If we need to change anything, the input argument list is copied, not
   * modified.
   *
   * Note: this gets applied to operator argument lists too, even though the
   * cases it handles should never occur there.  This should be OK since it
   * will fall through very quickly if there's nothing to do.
   */
  static List *
  expand_function_arguments(List *args, Oid result_type, HeapTuple func_tuple)
  {
  	Form_pg_proc funcform = (Form_pg_proc) GETSTRUCT(func_tuple);
  	bool		has_named_args = false;
  	ListCell   *lc;
  
  	/* Do we have any named arguments? */
  	foreach(lc, args)
  	{
  		Node	   *arg = (Node *) lfirst(lc);
  
  		if (IsA(arg, NamedArgExpr))
  		{
  			has_named_args = true;
  			break;
  		}
  	}
  
  	/* If so, we must apply reorder_function_arguments */
  	if (has_named_args)
  	{
  		args = reorder_function_arguments(args, func_tuple);
  		/* Recheck argument types and add casts if needed */
  		recheck_cast_function_args(args, result_type, func_tuple);
  	}
  	else if (list_length(args) < funcform->pronargs)
  	{
  		/* No named args, but we seem to be short some defaults */
  		args = add_function_defaults(args, func_tuple);
  		/* Recheck argument types and add casts if needed */
  		recheck_cast_function_args(args, result_type, func_tuple);
  	}
  
  	return args;
  }
  
  /*
   * reorder_function_arguments: convert named-notation args to positional args
   *
   * This function also inserts default argument values as needed, since it's
   * impossible to form a truly valid positional call without that.
   */
  static List *
  reorder_function_arguments(List *args, HeapTuple func_tuple)
  {
  	Form_pg_proc funcform = (Form_pg_proc) GETSTRUCT(func_tuple);
  	int			pronargs = funcform->pronargs;
  	int			nargsprovided = list_length(args);
  	Node	   *argarray[FUNC_MAX_ARGS];
  	ListCell   *lc;
  	int			i;
  
  	Assert(nargsprovided <= pronargs);
  	if (pronargs > FUNC_MAX_ARGS)
  		elog(ERROR, "too many function arguments");
  	MemSet(argarray, 0, pronargs * sizeof(Node *));
  
  	/* Deconstruct the argument list into an array indexed by argnumber */
  	i = 0;
  	foreach(lc, args)
  	{
  		Node	   *arg = (Node *) lfirst(lc);
  
  		if (!IsA(arg, NamedArgExpr))
  		{
  			/* positional argument, assumed to precede all named args */
  			Assert(argarray[i] == NULL);
  			argarray[i++] = arg;
  		}
  		else
  		{
  			NamedArgExpr *na = (NamedArgExpr *) arg;
  
  			Assert(argarray[na->argnumber] == NULL);
  			argarray[na->argnumber] = (Node *) na->arg;
  		}
  	}
  
  	/*
  	 * Fetch default expressions, if needed, and insert into array at proper
  	 * locations (they aren't necessarily consecutive or all used)
  	 */
  	if (nargsprovided < pronargs)
  	{
  		List	   *defaults = fetch_function_defaults(func_tuple);
  
  		i = pronargs - funcform->pronargdefaults;
  		foreach(lc, defaults)
  		{
  			if (argarray[i] == NULL)
  				argarray[i] = (Node *) lfirst(lc);
  			i++;
  		}
  	}
  
  	/* Now reconstruct the args list in proper order */
  	args = NIL;
  	for (i = 0; i < pronargs; i++)
  	{
  		Assert(argarray[i] != NULL);
  		args = lappend(args, argarray[i]);
  	}
  
  	return args;
  }
  
  /*
   * add_function_defaults: add missing function arguments from its defaults
   *
   * This is used only when the argument list was positional to begin with,
   * and so we know we just need to add defaults at the end.
   */
  static List *
  add_function_defaults(List *args, HeapTuple func_tuple)
  {
  	Form_pg_proc funcform = (Form_pg_proc) GETSTRUCT(func_tuple);
  	int			nargsprovided = list_length(args);
  	List	   *defaults;
  	int			ndelete;
  
  	/* Get all the default expressions from the pg_proc tuple */
  	defaults = fetch_function_defaults(func_tuple);
  
  	/* Delete any unused defaults from the list */
  	ndelete = nargsprovided + list_length(defaults) - funcform->pronargs;
  	if (ndelete < 0)
  		elog(ERROR, "not enough default arguments");
  	while (ndelete-- > 0)
  		defaults = list_delete_first(defaults);
  
  	/* And form the combined argument list, not modifying the input list */
  	return list_concat(list_copy(args), defaults);
  }
  
  /*
   * fetch_function_defaults: get function's default arguments as expression list
   */
  static List *
  fetch_function_defaults(HeapTuple func_tuple)
  {
  	List	   *defaults;
  	Datum		proargdefaults;
  	bool		isnull;
  	char	   *str;
  
  	/* The error cases here shouldn't happen, but check anyway */
  	proargdefaults = SysCacheGetAttr(PROCOID, func_tuple,
  									 Anum_pg_proc_proargdefaults,
  									 &isnull);
  	if (isnull)
  		elog(ERROR, "not enough default arguments");
  	str = TextDatumGetCString(proargdefaults);
  	defaults = (List *) stringToNode(str);
  	Assert(IsA(defaults, List));
  	pfree(str);
  	return defaults;
  }
  
  /*
   * recheck_cast_function_args: recheck function args and typecast as needed
   * after adding defaults.
   *
   * It is possible for some of the defaulted arguments to be polymorphic;
   * therefore we can't assume that the default expressions have the correct
   * data types already.  We have to re-resolve polymorphics and do coercion
   * just like the parser did.
   *
   * This should be a no-op if there are no polymorphic arguments,
   * but we do it anyway to be sure.
   *
   * Note: if any casts are needed, the args list is modified in-place;
   * caller should have already copied the list structure.
   */
  static void
  recheck_cast_function_args(List *args, Oid result_type, HeapTuple func_tuple)
  {
  	Form_pg_proc funcform = (Form_pg_proc) GETSTRUCT(func_tuple);
  	int			nargs;
  	Oid			actual_arg_types[FUNC_MAX_ARGS];
  	Oid			declared_arg_types[FUNC_MAX_ARGS];
  	Oid			rettype;
  	ListCell   *lc;
  
  	if (list_length(args) > FUNC_MAX_ARGS)
  		elog(ERROR, "too many function arguments");
  	nargs = 0;
  	foreach(lc, args)
  	{
  		actual_arg_types[nargs++] = exprType((Node *) lfirst(lc));
  	}
  	Assert(nargs == funcform->pronargs);
  	memcpy(declared_arg_types, funcform->proargtypes.values,
  		   funcform->pronargs * sizeof(Oid));
  	rettype = enforce_generic_type_consistency(actual_arg_types,
  											   declared_arg_types,
  											   nargs,
  											   funcform->prorettype,
  											   false);
  	/* let's just check we got the same answer as the parser did ... */
  	if (rettype != result_type)
  		elog(ERROR, "function's resolved result type changed during planning");
  
  	/* perform any necessary typecasting of arguments */
  	make_fn_arguments(NULL, args, actual_arg_types, declared_arg_types);
  }
  
  /*
   * large_const: check if given expression is a Const expression larger than
   * the given size
   *
   */
  static bool
  large_const(Expr *expr, Size max_size)
  {
  	if (NULL == expr || 0 == max_size)
  	{
  		return false;
  	}
  	
  	if (!IsA(expr, Const))
  	{
  		return false;
  	}
  	
  	Const *const_expr = (Const *) expr;
  	
  	if (const_expr->constisnull)
  	{
  		return false;
  	}
  	
  	Size size = datumGetSize(const_expr->constvalue, const_expr->constbyval, const_expr->constlen);
  	return size > max_size;
  }
  
  /*
   * evaluate_function: try to pre-evaluate a function call
   *
   * We can do this if the function is strict and has any constant-null inputs
   * (just return a null constant), or if the function is immutable and has all
   * constant inputs (call it and return the result as a Const node).  In
   * estimation mode we are willing to pre-evaluate stable functions too.
   *
   * Returns a simplified expression if successful, or NULL if cannot
   * simplify the function.
   */
  static Expr *
  evaluate_function(Oid funcid, Oid result_type, int32 result_typmod,
  				  Oid result_collid, Oid input_collid, List *args,
  				  bool funcvariadic,
  				  HeapTuple func_tuple,
  				  eval_const_expressions_context *context)
  {
  	Form_pg_proc funcform = (Form_pg_proc) GETSTRUCT(func_tuple);
  	bool		has_nonconst_input = false;
  	bool		has_null_input = false;
  	ListCell   *arg;
  	FuncExpr   *newexpr;
  
  	/*
  	 * Can't simplify if it returns a set.
  	 */
  	if (funcform->proretset)
  		return NULL;
  
  	/*
  	 * Can't simplify if it returns RECORD.  The immediate problem is that it
  	 * will be needing an expected tupdesc which we can't supply here.
  	 *
  	 * In the case where it has OUT parameters, it could get by without an
  	 * expected tupdesc, but we still have issues: get_expr_result_type()
  	 * doesn't know how to extract type info from a RECORD constant, and in
  	 * the case of a NULL function result there doesn't seem to be any clean
  	 * way to fix that.  In view of the likelihood of there being still other
  	 * gotchas, seems best to leave the function call unreduced.
  	 */
  	if (funcform->prorettype == RECORDOID)
  		return NULL;
  
  	/*
  	 * Check for constant inputs and especially constant-NULL inputs.
  	 */
  	foreach(arg, args)
  	{
  		if (IsA(lfirst(arg), Const))
  			has_null_input |= ((Const *) lfirst(arg))->constisnull;
  		else
  			has_nonconst_input = true;
  	}
  
  	/*
  	 * If the function is strict and has a constant-NULL input, it will never
  	 * be called at all, so we can replace the call by a NULL constant, even
  	 * if there are other inputs that aren't constant, and even if the
  	 * function is not otherwise immutable.
  	 */
  	if (funcform->proisstrict && has_null_input)
  		return (Expr *) makeNullConst(result_type, result_typmod,
  									  result_collid);
  
  	/*
  	 * Otherwise, can simplify only if all inputs are constants. (For a
  	 * non-strict function, constant NULL inputs are treated the same as
  	 * constant non-NULL inputs.)
  	 */
  	if (has_nonconst_input)
  		return NULL;
  
  	/*
  	 * Ordinarily we are only allowed to simplify immutable functions. But for
  	 * purposes of estimation, we consider it okay to simplify functions that
  	 * are merely stable; the risk that the result might change from planning
  	 * time to execution time is worth taking in preference to not being able
  	 * to estimate the value at all.
  	 */
  	if (funcform->provolatile == PROVOLATILE_IMMUTABLE)
  		 /* okay */ ;
  	else if (context->estimate && funcform->provolatile == PROVOLATILE_STABLE)
  		 /* okay */ ;
  	else if (context->eval_stable_functions && funcform->provolatile == PROVOLATILE_STABLE)
  	{
  		/* okay, but we cannot reuse this plan */
  		context->root->glob->oneoffPlan = true;
  	}
  	else
  		return NULL;
  
  	/*
  	 * OK, looks like we can simplify this operator/function.
  	 *
  	 * Build a new FuncExpr node containing the already-simplified arguments.
  	 */
  	newexpr = makeNode(FuncExpr);
  	newexpr->funcid = funcid;
  	newexpr->funcresulttype = result_type;
  	newexpr->funcretset = false;
  	newexpr->funcvariadic = funcvariadic;
  	newexpr->funcformat = COERCE_EXPLICIT_CALL; /* doesn't matter */
  	newexpr->funccollid = result_collid;		/* doesn't matter */
  	newexpr->inputcollid = input_collid;
  	newexpr->args = args;
  	newexpr->location = -1;
  
  	return evaluate_expr((Expr *) newexpr, result_type, result_typmod,
  						 result_collid);
  }
  
  /*
   * inline_function: try to expand a function call inline
   *
   * If the function is a sufficiently simple SQL-language function
   * (just "SELECT expression"), then we can inline it and avoid the rather
   * high per-call overhead of SQL functions.  Furthermore, this can expose
   * opportunities for constant-folding within the function expression.
   *
   * We have to beware of some special cases however.  A directly or
   * indirectly recursive function would cause us to recurse forever,
   * so we keep track of which functions we are already expanding and
   * do not re-expand them.  Also, if a parameter is used more than once
   * in the SQL-function body, we require it not to contain any volatile
   * functions (volatiles might deliver inconsistent answers) nor to be
   * unreasonably expensive to evaluate.  The expensiveness check not only
   * prevents us from doing multiple evaluations of an expensive parameter
   * at runtime, but is a safety value to limit growth of an expression due
   * to repeated inlining.
   *
   * We must also beware of changing the volatility or strictness status of
   * functions by inlining them.
   *
   * Also, at the moment we can't inline functions returning RECORD.  This
   * doesn't work in the general case because it discards information such
   * as OUT-parameter declarations.
   *
   * Also, context-dependent expression nodes in the argument list are trouble.
   *
   * Returns a simplified expression if successful, or NULL if cannot
   * simplify the function.
   */
  static Expr *
  inline_function(Oid funcid, Oid result_type, Oid result_collid,
  				Oid input_collid, List *args,
  				bool funcvariadic,
  				HeapTuple func_tuple,
  				eval_const_expressions_context *context)
  {
  	Form_pg_proc funcform = (Form_pg_proc) GETSTRUCT(func_tuple);
  	char	   *src;
  	Datum		tmp;
  	bool		isNull;
  	bool		modifyTargetList;
  	MemoryContext oldcxt;
  	MemoryContext mycxt;
  	inline_error_callback_arg callback_arg;
  	ErrorContextCallback sqlerrcontext;
  	FuncExpr   *fexpr;
  	SQLFunctionParseInfoPtr pinfo;
  	ParseState *pstate;
  	List	   *raw_parsetree_list;
  	Query	   *querytree;
  	Node	   *newexpr;
  	int		   *usecounts;
  	ListCell   *arg;
  	int			i;
  
  	/*
  	 * Forget it if the function is not SQL-language or has other showstopper
  	 * properties.  (The nargs check is just paranoia.)
  	 */
  	if (funcform->prolang != SQLlanguageId ||
  		funcform->prosecdef ||
  		funcform->proretset ||
  		funcform->prorettype == RECORDOID ||
  		!heap_attisnull(func_tuple, Anum_pg_proc_proconfig) ||
  		funcform->pronargs != list_length(args))
  		return NULL;
  
  	/* Check for recursive function, and give up trying to expand if so */
  	if (list_member_oid(context->active_fns, funcid))
  		return NULL;
  
  	/* Check permission to call function (fail later, if not) */
  	if (pg_proc_aclcheck(funcid, GetUserId(), ACL_EXECUTE) != ACLCHECK_OK)
  		return NULL;
  
  	/* Check whether a plugin wants to hook function entry/exit */
  	if (FmgrHookIsNeeded(funcid))
  		return NULL;
  
  	/*
  	 * Make a temporary memory context, so that we don't leak all the stuff
  	 * that parsing might create.
  	 */
  	mycxt = AllocSetContextCreate(CurrentMemoryContext,
  								  "inline_function",
  								  ALLOCSET_DEFAULT_MINSIZE,
  								  ALLOCSET_DEFAULT_INITSIZE,
  								  ALLOCSET_DEFAULT_MAXSIZE);
  	oldcxt = MemoryContextSwitchTo(mycxt);
  
  	/* Fetch the function body */
  	tmp = SysCacheGetAttr(PROCOID,
  						  func_tuple,
  						  Anum_pg_proc_prosrc,
  						  &isNull);
  	if (isNull)
  		elog(ERROR, "null prosrc for function %u", funcid);
  	src = TextDatumGetCString(tmp);
  
  	/*
  	 * Setup error traceback support for ereport().  This is so that we can
  	 * finger the function that bad information came from.
  	 */
  	callback_arg.proname = NameStr(funcform->proname);
  	callback_arg.prosrc = src;
  
  	sqlerrcontext.callback = sql_inline_error_callback;
  	sqlerrcontext.arg = (void *) &callback_arg;
  	sqlerrcontext.previous = error_context_stack;
  	error_context_stack = &sqlerrcontext;
  
  	/*
  	 * Set up to handle parameters while parsing the function body.  We need a
  	 * dummy FuncExpr node containing the already-simplified arguments to pass
  	 * to prepare_sql_fn_parse_info.  (It is really only needed if there are
  	 * some polymorphic arguments, but for simplicity we always build it.)
  	 */
  	fexpr = makeNode(FuncExpr);
  	fexpr->funcid = funcid;
  	fexpr->funcresulttype = result_type;
  	fexpr->funcretset = false;
  	fexpr->funcvariadic = funcvariadic;
  	fexpr->funcformat = COERCE_EXPLICIT_CALL;	/* doesn't matter */
  	fexpr->funccollid = result_collid;	/* doesn't matter */
  	fexpr->inputcollid = input_collid;
  	fexpr->args = args;
  	fexpr->location = -1;
  
  	pinfo = prepare_sql_fn_parse_info(func_tuple,
  									  (Node *) fexpr,
  									  input_collid);
  
  	/*
  	 * We just do parsing and parse analysis, not rewriting, because rewriting
  	 * will not affect table-free-SELECT-only queries, which is all that we
  	 * care about.  Also, we can punt as soon as we detect more than one
  	 * command in the function body.
  	 */
  	raw_parsetree_list = pg_parse_query(src);
  	if (list_length(raw_parsetree_list) != 1)
  		goto fail;
  
  	pstate = make_parsestate(NULL);
  	pstate->p_sourcetext = src;
  	sql_fn_parser_setup(pstate, pinfo);
  
  	querytree = transformTopLevelStmt(pstate, linitial(raw_parsetree_list));
  
  	free_parsestate(pstate);
  
  	/*
  	 * The single command must be a simple "SELECT expression".
  	 */
  	if (!IsA(querytree, Query) ||
  		querytree->commandType != CMD_SELECT ||
  		querytree->utilityStmt ||
  		querytree->hasAggs ||
  		querytree->hasWindowFuncs ||
  		querytree->hasSubLinks ||
  		querytree->cteList ||
  		querytree->rtable ||
  		querytree->jointree->fromlist ||
  		querytree->jointree->quals ||
  		querytree->groupClause ||
  		querytree->havingQual ||
  		querytree->windowClause ||
  		querytree->distinctClause ||
  		querytree->sortClause ||
  		querytree->limitOffset ||
  		querytree->limitCount ||
  		querytree->setOperations ||
  		list_length(querytree->targetList) != 1)
  		goto fail;
  
  	/*
  	 * Make sure the function (still) returns what it's declared to.  This
  	 * will raise an error if wrong, but that's okay since the function would
  	 * fail at runtime anyway.  Note that check_sql_fn_retval will also insert
  	 * a RelabelType if needed to make the tlist expression match the declared
  	 * type of the function.
  	 *
  	 * Note: we do not try this until we have verified that no rewriting was
  	 * needed; that's probably not important, but let's be careful.
  	 */
  	if (check_sql_fn_retval(funcid, result_type, list_make1(querytree),
  							&modifyTargetList, NULL))
  		goto fail;				/* reject whole-tuple-result cases */
  
  	/* Now we can grab the tlist expression */
  	newexpr = (Node *) ((TargetEntry *) linitial(querytree->targetList))->expr;
  
  	/* Assert that check_sql_fn_retval did the right thing */
  	Assert(exprType(newexpr) == result_type);
  	/* It couldn't have made any dangerous tlist changes, either */
  	Assert(!modifyTargetList);
  
  	/*
  	 * Additional validity checks on the expression.  It mustn't return a set,
  	 * and it mustn't be more volatile than the surrounding function (this is
  	 * to avoid breaking hacks that involve pretending a function is immutable
  	 * when it really ain't).  If the surrounding function is declared strict,
  	 * then the expression must contain only strict constructs and must use
  	 * all of the function parameters (this is overkill, but an exact analysis
  	 * is hard).
  	 */
  	if (expression_returns_set(newexpr))
  		goto fail;
  
  	if (funcform->provolatile == PROVOLATILE_IMMUTABLE &&
  		contain_mutable_functions(newexpr))
  		goto fail;
  	else if (funcform->provolatile == PROVOLATILE_STABLE &&
  			 contain_volatile_functions(newexpr))
  		goto fail;
  
  	if (funcform->proisstrict &&
  		contain_nonstrict_functions(newexpr))
  		goto fail;
  
  	/*
  	 * If any parameter expression contains a context-dependent node, we can't
  	 * inline, for fear of putting such a node into the wrong context.
  	 */
  	if (contain_context_dependent_node((Node *) args))
  		goto fail;
  
  	/*
  	 * We may be able to do it; there are still checks on parameter usage to
  	 * make, but those are most easily done in combination with the actual
  	 * substitution of the inputs.  So start building expression with inputs
  	 * substituted.
  	 */
  	usecounts = (int *) palloc0(funcform->pronargs * sizeof(int));
  	newexpr = substitute_actual_parameters(newexpr, funcform->pronargs,
  										   args, usecounts);
  
  	/* Now check for parameter usage */
  	i = 0;
  	foreach(arg, args)
  	{
  		Node	   *param = lfirst(arg);
  
  		if (usecounts[i] == 0)
  		{
  			/* Param not used at all: uncool if func is strict */
  			if (funcform->proisstrict)
  				goto fail;
  		}
  		else if (usecounts[i] != 1)
  		{
  			/* Param used multiple times: uncool if expensive or volatile */
  			QualCost	eval_cost;
  
  			/*
  			 * We define "expensive" as "contains any subplan or more than 10
  			 * operators".  Note that the subplan search has to be done
  			 * explicitly, since cost_qual_eval() will barf on unplanned
  			 * subselects.
  			 */
  			if (contain_subplans(param))
  				goto fail;
  			cost_qual_eval(&eval_cost, list_make1(param), NULL);
  			if (eval_cost.startup + eval_cost.per_tuple >
  				10 * cpu_operator_cost)
  				goto fail;
  
  			/*
  			 * Check volatility last since this is more expensive than the
  			 * above tests
  			 */
  			if (contain_volatile_functions(param))
  				goto fail;
  		}
  		i++;
  	}
  
  	/*
  	 * Whew --- we can make the substitution.  Copy the modified expression
  	 * out of the temporary memory context, and clean up.
  	 */
  	MemoryContextSwitchTo(oldcxt);
  
  	newexpr = copyObject(newexpr);
  
  	MemoryContextDelete(mycxt);
  
  	/*
  	 * If the result is of a collatable type, force the result to expose the
  	 * correct collation.  In most cases this does not matter, but it's
  	 * possible that the function result is used directly as a sort key or in
  	 * other places where we expect exprCollation() to tell the truth.
  	 */
  	if (OidIsValid(result_collid))
  	{
  		Oid			exprcoll = exprCollation(newexpr);
  
  		if (OidIsValid(exprcoll) && exprcoll != result_collid)
  		{
  			CollateExpr *newnode = makeNode(CollateExpr);
  
  			newnode->arg = (Expr *) newexpr;
  			newnode->collOid = result_collid;
  			newnode->location = -1;
  
  			newexpr = (Node *) newnode;
  		}
  	}
  
  	/*
  	 * Since there is now no trace of the function in the plan tree, we must
  	 * explicitly record the plan's dependency on the function.
  	 */
  	if (context->root)
  		record_plan_function_dependency(context->root, funcid);
  
  	/*
  	 * Recursively try to simplify the modified expression.  Here we must add
  	 * the current function to the context list of active functions.
  	 */
  	context->active_fns = lcons_oid(funcid, context->active_fns);
  	newexpr = eval_const_expressions_mutator(newexpr, context);
  	context->active_fns = list_delete_first(context->active_fns);
  
  	error_context_stack = sqlerrcontext.previous;
  
  	return (Expr *) newexpr;
  
  	/* Here if func is not inlinable: release temp memory and return NULL */
  fail:
  	MemoryContextSwitchTo(oldcxt);
  	MemoryContextDelete(mycxt);
  	error_context_stack = sqlerrcontext.previous;
  
  	return NULL;
  }
  
  /*
   * Replace Param nodes by appropriate actual parameters
   */
  static Node *
  substitute_actual_parameters(Node *expr, int nargs, List *args,
  							 int *usecounts)
  {
  	substitute_actual_parameters_context context;
  
  	context.nargs = nargs;
  	context.args = args;
  	context.usecounts = usecounts;
  
  	return substitute_actual_parameters_mutator(expr, &context);
  }
  
  static Node *
  substitute_actual_parameters_mutator(Node *node,
  							   substitute_actual_parameters_context *context)
  {
  	if (node == NULL)
  		return NULL;
  	if (IsA(node, Param))
  	{
  		Param	   *param = (Param *) node;
  
  		if (param->paramkind != PARAM_EXTERN)
  			elog(ERROR, "unexpected paramkind: %d", (int) param->paramkind);
  		if (param->paramid <= 0 || param->paramid > context->nargs)
  			elog(ERROR, "invalid paramid: %d", param->paramid);
  
  		/* Count usage of parameter */
  		context->usecounts[param->paramid - 1]++;
  
  		/* Select the appropriate actual arg and replace the Param with it */
  		/* We don't need to copy at this time (it'll get done later) */
  		return list_nth(context->args, param->paramid - 1);
  	}
  	return expression_tree_mutator(node, substitute_actual_parameters_mutator,
  								   (void *) context);
  }
  
  /*
   * error context callback to let us supply a call-stack traceback
   */
  static void
  sql_inline_error_callback(void *arg)
  {
  	inline_error_callback_arg *callback_arg = (inline_error_callback_arg *) arg;
  	int			syntaxerrposition;
  
  	/* If it's a syntax error, convert to internal syntax error report */
  	syntaxerrposition = geterrposition();
  	if (syntaxerrposition > 0)
  	{
  		errposition(0);
  		internalerrposition(syntaxerrposition);
  		internalerrquery(callback_arg->prosrc);
  	}
  
  	errcontext("SQL function \"%s\" during inlining", callback_arg->proname);
  }
  
  /*
   * evaluate_expr: pre-evaluate a constant expression
   *
   * We use the executor's routine ExecEvalExpr() to avoid duplication of
   * code and ensure we get the same result as the executor would get.
   */
  Expr *
  evaluate_expr(Expr *expr, Oid result_type, int32 result_typmod,
  			  Oid result_collation)
  {
  	EState	   *estate;
  	ExprState  *exprstate;
  	MemoryContext oldcontext;
  	Datum		const_val;
  	bool		const_is_null;
  	int16		resultTypLen;
  	bool		resultTypByVal;
  
  	/*
  	 * To use the executor, we need an EState.
  	 */
  	estate = CreateExecutorState();
  
  	/* We can use the estate's working context to avoid memory leaks. */
  	oldcontext = MemoryContextSwitchTo(estate->es_query_cxt);
  
  	/* Make sure any opfuncids are filled in. */
  	fix_opfuncids((Node *) expr);
  
  	/*
  	 * Prepare expr for execution.  (Note: we can't use ExecPrepareExpr
  	 * because it'd result in recursively invoking eval_const_expressions.)
  	 */
  	exprstate = ExecInitExpr(expr, NULL);
  
  	/*
  	 * And evaluate it.
  	 *
  	 * It is OK to use a default econtext because none of the ExecEvalExpr()
  	 * code used in this situation will use econtext.  That might seem
  	 * fortuitous, but it's not so unreasonable --- a constant expression does
  	 * not depend on context, by definition, n'est ce pas?
  	 */
  	const_val = ExecEvalExprSwitchContext(exprstate,
  										  GetPerTupleExprContext(estate),
  										  &const_is_null, NULL);
  
  	/* Get info needed about result datatype */
  	get_typlenbyval(result_type, &resultTypLen, &resultTypByVal);
  
  	/* Get back to outer memory context */
  	MemoryContextSwitchTo(oldcontext);
  
  	/*
  	 * Must copy result out of sub-context used by expression eval.
  	 *
  	 * Also, if it's varlena, forcibly detoast it.  This protects us against
  	 * storing TOAST pointers into plans that might outlive the referenced
  	 * data.
  	 */
  	if (!const_is_null)
  	{
  		if (resultTypLen == -1)
  			const_val = PointerGetDatum(PG_DETOAST_DATUM_COPY(const_val));
  		else
  			const_val = datumCopy(const_val, resultTypByVal, resultTypLen);
  	}
  
  	/* Release all the junk we just created */
  	FreeExecutorState(estate);
  
  	/*
  	 * Make the constant result node.
  	 */
  	return (Expr *) makeConst(result_type, result_typmod, result_collation,
  							  resultTypLen,
  							  const_val, const_is_null,
  							  resultTypByVal);
  }
  
  
  /*
   * inline_set_returning_function
   *		Attempt to "inline" a set-returning function in the FROM clause.
   *
   * "rte" is an RTE_FUNCTION rangetable entry.  If it represents a call of a
   * set-returning SQL function that can safely be inlined, expand the function
   * and return the substitute Query structure.  Otherwise, return NULL.
   *
   * This has a good deal of similarity to inline_function(), but that's
   * for the non-set-returning case, and there are enough differences to
   * justify separate functions.
   */
  Query *
  inline_set_returning_function(PlannerInfo *root, RangeTblEntry *rte)
  {
  	RangeTblFunction *rtfunc;
  	FuncExpr   *fexpr;
  	Oid			func_oid;
  	HeapTuple	func_tuple;
  	Form_pg_proc funcform;
  	char	   *src;
  	Datum		tmp;
  	bool		isNull;
  	bool		modifyTargetList;
  	MemoryContext oldcxt;
  	MemoryContext mycxt;
  	List	   *saveInvalItems;
  	inline_error_callback_arg callback_arg;
  	ErrorContextCallback sqlerrcontext;
  	SQLFunctionParseInfoPtr pinfo;
  	List	   *raw_parsetree_list;
  	List	   *querytree_list;
  	Query	   *querytree;
  
  	Assert(rte->rtekind == RTE_FUNCTION);
  
  	/*
  	 * It doesn't make a lot of sense for a SQL SRF to refer to itself in its
  	 * own FROM clause, since that must cause infinite recursion at runtime.
  	 * It will cause this code to recurse too, so check for stack overflow.
  	 * (There's no need to do more.)
  	 */
  	check_stack_depth();
  
  	/* Fail if the RTE has ORDINALITY - we don't implement that here. */
  	if (rte->funcordinality)
  		return NULL;
  
  	/* Fail if RTE isn't a single, simple FuncExpr */
  	if (list_length(rte->functions) != 1)
  		return NULL;
  	rtfunc = (RangeTblFunction *) linitial(rte->functions);
  
  	if (!IsA(rtfunc->funcexpr, FuncExpr))
  		return NULL;
  	fexpr = (FuncExpr *) rtfunc->funcexpr;
  
  	func_oid = fexpr->funcid;
  
  	/*
  	 * The function must be declared to return a set, else inlining would
  	 * change the results if the contained SELECT didn't return exactly one
  	 * row.
  	 */
  	if (!fexpr->funcretset)
  		return NULL;
  
  	/*
  	 * Refuse to inline if the arguments contain any volatile functions or
  	 * sub-selects.  Volatile functions are rejected because inlining may
  	 * result in the arguments being evaluated multiple times, risking a
  	 * change in behavior.  Sub-selects are rejected partly for implementation
  	 * reasons (pushing them down another level might change their behavior)
  	 * and partly because they're likely to be expensive and so multiple
  	 * evaluation would be bad.
  	 */
  	if (contain_volatile_functions((Node *) fexpr->args) ||
  		contain_subplans((Node *) fexpr->args))
  		return NULL;
  
  	/* Check permission to call function (fail later, if not) */
  	if (pg_proc_aclcheck(func_oid, GetUserId(), ACL_EXECUTE) != ACLCHECK_OK)
  		return NULL;
  
  	/* Check whether a plugin wants to hook function entry/exit */
  	if (FmgrHookIsNeeded(func_oid))
  		return NULL;
  
  	/*
  	 * OK, let's take a look at the function's pg_proc entry.
  	 */
  	func_tuple = SearchSysCache1(PROCOID, ObjectIdGetDatum(func_oid));
  	if (!HeapTupleIsValid(func_tuple))
  		elog(ERROR, "cache lookup failed for function %u", func_oid);
  	funcform = (Form_pg_proc) GETSTRUCT(func_tuple);
  
  	/*
  	 * Forget it if the function is not SQL-language or has other showstopper
  	 * properties.  In particular it mustn't be declared STRICT, since we
  	 * couldn't enforce that.  It also mustn't be VOLATILE, because that is
  	 * supposed to cause it to be executed with its own snapshot, rather than
  	 * sharing the snapshot of the calling query.  (Rechecking proretset is
  	 * just paranoia.)
  	 */
  	if (funcform->prolang != SQLlanguageId ||
  		funcform->proisstrict ||
  		funcform->provolatile == PROVOLATILE_VOLATILE ||
  		funcform->prosecdef ||
  		!funcform->proretset ||
  		!heap_attisnull(func_tuple, Anum_pg_proc_proconfig))
  	{
  		ReleaseSysCache(func_tuple);
  		return NULL;
  	}
  
  	/*
  	 * Make a temporary memory context, so that we don't leak all the stuff
  	 * that parsing might create.
  	 */
  	mycxt = AllocSetContextCreate(CurrentMemoryContext,
  								  "inline_set_returning_function",
  								  ALLOCSET_DEFAULT_MINSIZE,
  								  ALLOCSET_DEFAULT_INITSIZE,
  								  ALLOCSET_DEFAULT_MAXSIZE);
  	oldcxt = MemoryContextSwitchTo(mycxt);
  
  	/*
  	 * When we call eval_const_expressions below, it might try to add items to
  	 * root->glob->invalItems.  Since it is running in the temp context, those
  	 * items will be in that context, and will need to be copied out if we're
  	 * successful.  Temporarily reset the list so that we can keep those items
  	 * separate from the pre-existing list contents.
  	 */
  	saveInvalItems = root->glob->invalItems;
  	root->glob->invalItems = NIL;
  
  	/* Fetch the function body */
  	tmp = SysCacheGetAttr(PROCOID,
  						  func_tuple,
  						  Anum_pg_proc_prosrc,
  						  &isNull);
  	if (isNull)
  		elog(ERROR, "null prosrc for function %u", func_oid);
  	src = TextDatumGetCString(tmp);
  
  	/*
  	 * Setup error traceback support for ereport().  This is so that we can
  	 * finger the function that bad information came from.
  	 */
  	callback_arg.proname = NameStr(funcform->proname);
  	callback_arg.prosrc = src;
  
  	sqlerrcontext.callback = sql_inline_error_callback;
  	sqlerrcontext.arg = (void *) &callback_arg;
  	sqlerrcontext.previous = error_context_stack;
  	error_context_stack = &sqlerrcontext;
  
  	/*
  	 * Run eval_const_expressions on the function call.  This is necessary to
  	 * ensure that named-argument notation is converted to positional notation
  	 * and any default arguments are inserted.  It's a bit of overkill for the
  	 * arguments, since they'll get processed again later, but no harm will be
  	 * done.
  	 */
  	fexpr = (FuncExpr *) eval_const_expressions(root, (Node *) fexpr);
  
  	/* It should still be a call of the same function, but let's check */
  	if (!IsA(fexpr, FuncExpr) ||
  		fexpr->funcid != func_oid)
  		goto fail;
  
  	/* Arg list length should now match the function */
  	if (list_length(fexpr->args) != funcform->pronargs)
  		goto fail;
  
  	/*
  	 * Set up to handle parameters while parsing the function body.  We can
  	 * use the FuncExpr just created as the input for
  	 * prepare_sql_fn_parse_info.
  	 */
  	pinfo = prepare_sql_fn_parse_info(func_tuple,
  									  (Node *) fexpr,
  									  fexpr->inputcollid);
  
  	/*
  	 * Parse, analyze, and rewrite (unlike inline_function(), we can't skip
  	 * rewriting here).  We can fail as soon as we find more than one query,
  	 * though.
  	 */
  	raw_parsetree_list = pg_parse_query(src);
  	if (list_length(raw_parsetree_list) != 1)
  		goto fail;
  
  	querytree_list = pg_analyze_and_rewrite_params(linitial(raw_parsetree_list),
  												   src,
  									   (ParserSetupHook) sql_fn_parser_setup,
  												   pinfo);
  	if (list_length(querytree_list) != 1)
  		goto fail;
  	querytree = linitial(querytree_list);
  
  	/*
  	 * The single command must be a plain SELECT.
  	 */
  	if (!IsA(querytree, Query) ||
  		querytree->commandType != CMD_SELECT ||
  		querytree->utilityStmt)
  		goto fail;
  
  	/*
  	 * Make sure the function (still) returns what it's declared to.  This
  	 * will raise an error if wrong, but that's okay since the function would
  	 * fail at runtime anyway.  Note that check_sql_fn_retval will also insert
  	 * RelabelType(s) and/or NULL columns if needed to make the tlist
  	 * expression(s) match the declared type of the function.
  	 *
  	 * If the function returns a composite type, don't inline unless the check
  	 * shows it's returning a whole tuple result; otherwise what it's
  	 * returning is a single composite column which is not what we need.
  	 */
  	if (!check_sql_fn_retval(func_oid, fexpr->funcresulttype,
  							 querytree_list,
  							 &modifyTargetList, NULL) &&
  		(get_typtype(fexpr->funcresulttype) == TYPTYPE_COMPOSITE ||
  		 fexpr->funcresulttype == RECORDOID))
  		goto fail;				/* reject not-whole-tuple-result cases */
  
  	/*
  	 * If we had to modify the tlist to make it match, and the statement is
  	 * one in which changing the tlist contents could change semantics, we
  	 * have to punt and not inline.
  	 */
  	if (modifyTargetList)
  		goto fail;
  
  	/*
  	 * If it returns RECORD, we have to check against the column type list
  	 * provided in the RTE; check_sql_fn_retval can't do that.  (If no match,
  	 * we just fail to inline, rather than complaining; see notes for
  	 * tlist_matches_coltypelist.)	We don't have to do this for functions
  	 * with declared OUT parameters, even though their funcresulttype is
  	 * RECORDOID, so check get_func_result_type too.
  	 */
  	if (fexpr->funcresulttype == RECORDOID &&
  		get_func_result_type(func_oid, NULL, NULL) == TYPEFUNC_RECORD &&
  		!tlist_matches_coltypelist(querytree->targetList,
  								   rtfunc->funccoltypes))
  		goto fail;
  
  	/*
  	 * Looks good --- substitute parameters into the query.
  	 */
  	querytree = substitute_actual_srf_parameters(querytree,
  												 funcform->pronargs,
  												 fexpr->args);
  
  	/*
  	 * Copy the modified query out of the temporary memory context, and clean
  	 * up.
  	 */
  	MemoryContextSwitchTo(oldcxt);
  
  	querytree = copyObject(querytree);
  
  	/* copy up any new invalItems, too */
  	root->glob->invalItems = list_concat(saveInvalItems,
  										 copyObject(root->glob->invalItems));
  
  	MemoryContextDelete(mycxt);
  	error_context_stack = sqlerrcontext.previous;
  	ReleaseSysCache(func_tuple);
  
  	/*
  	 * We don't have to fix collations here because the upper query is already
  	 * parsed, ie, the collations in the RTE are what count.
  	 */
  
  	/*
  	 * Since there is now no trace of the function in the plan tree, we must
  	 * explicitly record the plan's dependency on the function.
  	 */
  	record_plan_function_dependency(root, func_oid);
  
  	return querytree;
  
  	/* Here if func is not inlinable: release temp memory and return NULL */
  fail:
  	MemoryContextSwitchTo(oldcxt);
  	root->glob->invalItems = saveInvalItems;
  	MemoryContextDelete(mycxt);
  	error_context_stack = sqlerrcontext.previous;
  	ReleaseSysCache(func_tuple);
  
  	return NULL;
  }
  
  /*
   * Replace Param nodes by appropriate actual parameters
   *
   * This is just enough different from substitute_actual_parameters()
   * that it needs its own code.
   */
  static Query *
  substitute_actual_srf_parameters(Query *expr, int nargs, List *args)
  {
  	substitute_actual_srf_parameters_context context;
  
  	context.nargs = nargs;
  	context.args = args;
  	context.sublevels_up = 1;
  
  	return query_tree_mutator(expr,
  							  substitute_actual_srf_parameters_mutator,
  							  &context,
  							  0);
  }
  
  static Node *
  substitute_actual_srf_parameters_mutator(Node *node,
  						   substitute_actual_srf_parameters_context *context)
  {
  	Node	   *result;
  
  	if (node == NULL)
  		return NULL;
  	if (IsA(node, Query))
  	{
  		context->sublevels_up++;
  		result = (Node *) query_tree_mutator((Query *) node,
  									substitute_actual_srf_parameters_mutator,
  											 (void *) context,
  											 0);
  		context->sublevels_up--;
  		return result;
  	}
  	if (IsA(node, Param))
  	{
  		Param	   *param = (Param *) node;
  
  		if (param->paramkind == PARAM_EXTERN)
  		{
  			if (param->paramid <= 0 || param->paramid > context->nargs)
  				elog(ERROR, "invalid paramid: %d", param->paramid);
  
  			/*
  			 * Since the parameter is being inserted into a subquery, we must
  			 * adjust levels.
  			 */
  			result = copyObject(list_nth(context->args, param->paramid - 1));
  			IncrementVarSublevelsUp(result, context->sublevels_up, 0);
  			return result;
  		}
  	}
  	return expression_tree_mutator(node,
  								   substitute_actual_srf_parameters_mutator,
  								   (void *) context);
  }
  
  /*
   * flatten_join_alias_var_optimizer
   *	  Replace Vars that reference JOIN outputs with references to the original
   *	  relation variables instead.
   */
  Query *
  flatten_join_alias_var_optimizer(Query *query, int queryLevel)
  {
  	Query *queryNew = (Query *) copyObject(query);
  
  	/* Create a PlannerInfo data structure for this subquery */
  	PlannerInfo *root = makeNode(PlannerInfo);
  	root->parse = queryNew;
  	root->query_level = queryLevel;
  
  	root->glob = makeNode(PlannerGlobal);
  	root->glob->boundParams = NULL;
  	root->glob->subplans = NIL;
  	root->glob->subroots = NIL;
  	root->glob->finalrtable = NIL;
  	root->glob->relationOids = NIL;
  	root->glob->invalItems = NIL;
  	root->glob->transientPlan = false;
  	root->glob->nParamExec = 0;
  
  	root->config = DefaultPlannerConfig();
  
  	root->parent_root = NULL;
  	root->planner_cxt = CurrentMemoryContext;
  	root->init_plans = NIL;
  
  	root->list_cteplaninfo = NIL;
  	root->join_info_list = NIL;
  	root->append_rel_list = NIL;
  
  	root->hasJoinRTEs = false;
  
  	ListCell *plc = NULL;
  	foreach(plc, queryNew->rtable)
  	{
  		RangeTblEntry *rte = (RangeTblEntry *) lfirst(plc);
  
  		if (rte->rtekind == RTE_JOIN)
  		{
  			root->hasJoinRTEs = true;
  			if (IS_OUTER_JOIN(rte->jointype))
  			{
  				break;
  			}
  		}
  	}
  
  	/*
  	 * Flatten join alias for expression in
  	 * 1. targetlist
  	 * 2. returningList
  	 * 3. having qual
  	 * 4. scatterClause
  	 * 5. limit offset
  	 * 6. limit count
  	 * 
  	 * We flatten the above expressions since these entries may be moved during the query 
  	 * normalization step before algebrization. In contrast, the planner flattens alias 
  	 * inside quals to allow predicates involving such vars to be pushed down. 
  	 * 
  	 * Here we ignore the flattening of quals due to the following reasons:
  	 * 1. we assume that the function will be called before Query->DXL translation:
  	 * 2. the quals never gets moved from old query to the new top-level query in the 
  	 * query normalization phase before algebrization. In other words, the quals hang of 
  	 * the same query structure that is now the new derived table.
  	 * 3. the algebrizer can resolve the abiquity of join aliases in quals since we maintain 
  	 * all combinations of <query level, varno, varattno> to DXL-ColId during Query->DXL translation.
  	 * 
  	 */
  
  	List *targetList = queryNew->targetList;
  	if (NIL != targetList)
  	{
  		queryNew->targetList = (List *) flatten_join_alias_vars(root, (Node *) targetList);
  		pfree(targetList);
  	}
  
  	List * returningList = queryNew->returningList;
  	if (NIL != returningList)
  	{
  		queryNew->returningList = (List *) flatten_join_alias_vars(root, (Node *) returningList);
  		pfree(returningList);
  	}
  
  	Node *havingQual = queryNew->havingQual;
  	if (NULL != havingQual)
  	{
  		queryNew->havingQual = flatten_join_alias_vars(root, havingQual);
  		pfree(havingQual);
  	}
  
  	List *scatterClause = queryNew->scatterClause;
  	if (NIL != scatterClause)
  	{
  		queryNew->scatterClause = (List *) flatten_join_alias_vars(root, (Node *) scatterClause);
  		pfree(scatterClause);
  	}
  
  	Node *limitOffset = queryNew->limitOffset;
  	if (NULL != limitOffset)
  	{
  		queryNew->limitOffset = flatten_join_alias_vars(root, limitOffset);
  		pfree(limitOffset);
  	}
  
  	List *windowClause = queryNew->windowClause;
  	if (NIL != queryNew->windowClause)
  	{
  		ListCell *l;
  
  		foreach (l, windowClause)
  		{
  			WindowClause *wc = (WindowClause *) lfirst(l);
  
  			if (wc == NULL)
  				continue;
  
  			if (wc->startOffset)
  				wc->startOffset = flatten_join_alias_vars(root, wc->startOffset);
  
  			if (wc->endOffset)
  				wc->endOffset = flatten_join_alias_vars(root, wc->endOffset);
  		}
  	}
  
  	Node *limitCount = queryNew->limitCount;
  	if (NULL != limitCount)
  	{
  		queryNew->limitCount = flatten_join_alias_vars(root, limitCount);
  		pfree(limitCount);
  	}
  
      return queryNew;
  }
  
  /* 
   * Does grp contain GroupingClause or not? Useful for indentifying use of
   * ROLLUP, CUBE and grouping sets.
   */
  bool
  contain_extended_grouping(List *grp)
  {
  	return contain_grouping_clause_walker((Node *)grp, NULL);
  }
  
  static bool
  contain_grouping_clause_walker(Node *node, void *context)
  {
  	if (node == NULL)
  		return false;
  	else if (IsA(node, GroupingClause))
  		return true;			/* abort the tree traversal and return true */
  	
  	Assert(!IsA(node, SubLink));
  	return expression_tree_walker(node, contain_grouping_clause_walker, 
  								  context);
  }
  
  /*
   * is_grouping_extension -
   *     Return true if a given grpsets contain multiple grouping sets.
   *
   * This function also returns false when a query has a single unique
   * groupig set appearing multiple times.
   */
  bool
  is_grouping_extension(CanonicalGroupingSets *grpsets)
  {
  	if (grpsets == NULL ||
  		grpsets->ngrpsets == 0)
  		return false;
  
  	if (grpsets->ngrpsets == 1)
  		return false;
  
  	return true;
  }
  
  /**
   * Returns true if the equality operator with the given opno
   *   values is a true equality operator (unlike some of the
   *   box/rectangle/etc. types which implement 'goofy' operators).
   *
   * This function currently only knows about built-in types, and is
   *   conservative with regard to which it returns true for (only
   *     ones which have been verified to work the right way).
   */
  bool is_builtin_true_equality_between_same_type(int opno)
  {
  	switch (opno)
  	{
  	case BitEqualOperator:
  	case BooleanEqualOperator:
  	case BPCharEqualOperator:
  	case CashEqualOperator:
  	case CharEqualOperator:
  	case CidEqualOperator:
  	case DateEqualOperator:
  	case Float4EqualOperator:
  	case Float8EqualOperator:
  	case Int2EqualOperator:
  	case Int4EqualOperator:
  	case Int8EqualOperator:
  	case IntervalEqualOperator:
  	case NameEqualOperator:
  	case NumericEqualOperator:
  	case OidEqualOperator:
  	case RelTimeEqualOperator:
  	case TextEqualOperator:
  	case TIDEqualOperator:
  	case TimeEqualOperator:
  	case TimestampEqualOperator:
  	case TimestampTZEqualOperator:
  	case TimeTZEqualOperator:
  	case XidEqualOperator:
  		return true;
  
  	default:
  		return false;
  	}
  }
  
  /**
   * Returns true if the equality operator with the given opno
   *   values is an equality operator, with same type on both sides
   *  (unlike int24 equality) AND the type being compare is greenplum hashable
   *
   *
   * Note that this function is conservative with regard to when it returns true:
   *   it is okay to have some greenplum hashtable types that don't have entries here
   *   (this function may return false even if this is a comparison between
   *        a greenplum hashable type and itself
   *
   * Note also that i think it might be possible for this to return true even
   *   if the operands of the operator are not themselves greenplum hashable,
   *   because of type conversion or something.  I'm not 100% sure on that.
   */
  bool
  is_builtin_greenplum_hashable_equality_between_same_type(int opno)
  {
      switch(opno)
      {
          case BitEqualOperator:
          case BooleanEqualOperator:
          case BPCharEqualOperator:
          case CashEqualOperator:
          case CharEqualOperator:
          case DateEqualOperator:
          case Float4EqualOperator:
          case Float8EqualOperator:
          case Int2EqualOperator:
          case Int4EqualOperator:
          case Int8EqualOperator:
          case IntervalEqualOperator:
          case NameEqualOperator:
          case NumericEqualOperator:
          case OidEqualOperator:
          case RelTimeEqualOperator:
          case TextEqualOperator:
          case TIDEqualOperator:
          case TimeEqualOperator:
          case TimestampEqualOperator:
          case TimestampTZEqualOperator:
          case TimeTZEqualOperator:
  
          /* these new ones were added to list for MPP-7858 */
          case AbsTimeEqualOperator:
          case ByteaEqualOperator:
          case InetEqualOperator: /* for inet and cidr */
          case MacAddrEqualOperator:
          case TIntervalEqualOperator:
          case VarbitEqualOperator:
              return true;
  
  /*
          these types are greenplum hashable but haven't checked the semantics of these types function
          case ACLITEMOID:
          case ANYARRAYOID: 
          case INT2VECTOROID: 
          case OIDVECTOROID: 
          case REGPROCOID: 
          case REGPROCEDUREOID: 
          case REGOPEROID: 
          case REGOPERATOROID: 
          case REGCLASSOID: 
          case REGTYPEOID: 
    */
          default:
  
          return false;
      }
  }
  
  /**
   * Structs and Methods to support searching of matching subexpressions.
   */
  
  typedef struct subexpression_matching_context
  {
  	Expr *needle;	/* This is the expression being searched */
  } subexpression_matching_context;
  
  /**
   * expression_matching_walker checks if the expression 'needle' in context is a sub-expression of hayStack.
   */
  static bool subexpression_matching_walker(Node *hayStack, void *context)
  {
  	Assert(context);
  	subexpression_matching_context *ctx = (subexpression_matching_context *) context;
  	Assert(ctx->needle);
  
  	if (!hayStack)
  	{
  		return false;
  	}
  
  	if (equal(ctx->needle, hayStack))
  	{
  		return true;
  	}
  
  	return expression_tree_walker(hayStack, subexpression_matching_walker, (void *) context);
  }
  
  /**
   * Method checks if expr1 is a subexpression of expr2.
   * For example, expr1 = (x + 2) and expr = (x + 2 ) * 100 + 20 would return true.
   */
  bool subexpression_match(Expr *expr1, Expr *expr2)
  {
  	subexpression_matching_context ctx;
  	ctx.needle = expr1;
  	return subexpression_matching_walker((Node *) expr2, (void *) &ctx);
  }
  
  /*
   * Check whether a SELECT targetlist emits the specified column types,
   * to see if it's safe to inline a function returning record.
   *
   * We insist on exact match here.  The executor allows binary-coercible
   * cases too, but we don't have a way to preserve the correct column types
   * in the correct places if we inline the function in such a case.
   *
   * Note that we only check type OIDs not typmods; this agrees with what the
   * executor would do at runtime, and attributing a specific typmod to a
   * function result is largely wishful thinking anyway.
   */
  static bool
  tlist_matches_coltypelist(List *tlist, List *coltypelist)
  {
  	ListCell   *tlistitem;
  	ListCell   *clistitem;
  
  	clistitem = list_head(coltypelist);
  	foreach(tlistitem, tlist)
  	{
  		TargetEntry *tle = (TargetEntry *) lfirst(tlistitem);
  		Oid			coltype;
  
  		if (tle->resjunk)
  			continue;			/* ignore junk columns */
  
  		if (clistitem == NULL)
  			return false;		/* too many tlist items */
  
  		coltype = lfirst_oid(clistitem);
  		clistitem = lnext(clistitem);
  
  		if (exprType((Node *) tle->expr) != coltype)
  			return false;		/* column type mismatch */
  	}
  
  	if (clistitem != NULL)
  		return false;			/* too few tlist items */
  
  	return true;
  }
  
  /*
   * If this expression is part of a query, and the query isn't a simple
   * "SELECT foo()" style query with no actual tables involved, then we
   * also aggressively evaluate stable functions, in addition to immutable
   * ones. Such plans cannot be reused, and therefore need to be re-planned
   * on every execution, but it can be a big win if it allows partition
   * elimination to happen. That's considered a good tradeoff in GPDB, as
   * typical queries are long-running.
   */
  static bool
  should_eval_stable_functions(PlannerInfo *root)
  {
  	/*
  	 * Without PlannerGlobal, we cannot mark the plan as a `oneoffPlan`
  	 */
  	if (root == NULL) return false;
  	if (root->glob == NULL) return false;
  
  	/*
  	 * If the query has no range table, then there is no reason to need to
  	 * pre-evaluate stable functions, as the output cannot be used as part
  	 * of static partition elimination, unless the query is part of a
  	 * subquery.
  	 */
  	return root->parse->rtable || root->query_level > 1;
  }
  