/*-------------------------------------------------------------------------
 *
 * clauses.c
 *	  routines to manipulate qualification clauses
 *
 * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *	  $PostgreSQL: pgsql/src/backend/optimizer/util/clauses.c,v 1.277.2.3 2010/08/14 15:47:30 tgl Exp $
 *
 * HISTORY
 *	  AUTHOR			DATE			MAJOR EVENT
 *	  Andrew Yu			Nov 3, 1994		clause.c and clauses.c combined
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.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_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/lsyscache.h"
#include "utils/memutils.h"
#include "utils/syscache.h"
#include "utils/typcache.h"


typedef struct
{
	ParamListInfo boundParams;
	PlannerGlobal *glob;
	List	   *active_fns;
	Node	   *case_val;
	bool		estimate;
} 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 pull_agg_clause_walker(Node *node, List **context);
static bool count_agg_clauses_walker(Node *node, AggClauseCounts *counts);
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_nonstrict_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 bool set_coercionform_dontcare_walker(Node *node, void *context);
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 Expr *simplify_boolean_equality(List *args);
static Expr *simplify_function(Oid funcid,
				  Oid result_type, int32 result_typmod, List **args,
				  bool allow_inline,
				  eval_const_expressions_context *context);
static List *add_function_defaults(List *args, Oid result_type,
					  HeapTuple func_tuple,
					  eval_const_expressions_context *context);
static Expr *evaluate_function(Oid funcid,
				  Oid result_type, int32 result_typmod, List *args,
				  HeapTuple func_tuple,
				  eval_const_expressions_context *context);
static Expr *inline_function(Oid funcid, Oid result_type, List *args,
				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 Expr *evaluate_expr(Expr *expr, Oid result_type, int32 result_typmod);
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);


/*****************************************************************************
 *		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).
 */
Expr *
make_opclause(Oid opno, Oid opresulttype, bool opretset,
			  Expr *leftop, Expr *rightop)
{
	OpExpr	   *expr = makeNode(OpExpr);

	expr->opno = opno;
	expr->opfuncid = InvalidOid;
	expr->opresulttype = opresulttype;
	expr->opretset = opretset;
	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(Expr *clause)
{
	OpExpr	   *expr = (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(Expr *clause)
{
	OpExpr	   *expr = (OpExpr *) 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
		return list_make1(clause);
}


/*****************************************************************************
 *		Aggregate-function clause manipulation
 *****************************************************************************/

/*
 * contain_agg_clause
 *	  Recursively search for Aggref nodes 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 */
	}
	Assert(!IsA(node, SubLink));
	return expression_tree_walker(node, contain_agg_clause_walker, context);
}

/*
 * pull_agg_clause
 *	  Recursively search for Aggref nodes within a clause.
 *
 *	  Returns a List of all Aggrefs 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.
 */
List *
pull_agg_clause(Node *clause)
{
	List	   *result = NIL;

	(void) pull_agg_clause_walker(clause, &result);
	return result;
}

static bool
pull_agg_clause_walker(Node *node, List **context)
{
	if (node == NULL)
		return false;
	if (IsA(node, Aggref))
	{
		Assert(((Aggref *) node)->agglevelsup == 0);
		*context = lappend(*context, node);
		return false;			/* no need to descend into arguments */
	}
	Assert(!IsA(node, SubLink));
	return expression_tree_walker(node, pull_agg_clause_walker,
								  (void *) context);
}

/*
 * count_agg_clauses
 *	  Recursively count the Aggref nodes in an expression tree.
 *
 *	  Note: this also checks for nested aggregates, which are an error.
 *
 * We not only count the nodes, but 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 AggClauseCounts for the exact
 * set of statistics returned.
 *
 * NOTE that the counts are ADDED to those already in *counts ... 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(Node *clause, AggClauseCounts *counts)
{
	/* no setup needed */
	count_agg_clauses_walker(clause, counts);
}

static bool
count_agg_clauses_walker(Node *node, AggClauseCounts *counts)
{
	if (node == NULL)
		return false;
	if (IsA(node, Aggref))
	{
		Aggref	   *aggref = (Aggref *) node;
		Oid		   *inputTypes;
		int			numArguments;
		HeapTuple	aggTuple;
		Form_pg_aggregate aggform;
		Oid			aggtranstype;
		int			i;
		ListCell   *l;

		Assert(aggref->agglevelsup == 0);
		counts->numAggs++;
		if (aggref->aggdistinct)
			counts->numDistinctAggs++;

		/* extract argument types */
		numArguments = list_length(aggref->args);
		inputTypes = (Oid *) palloc(sizeof(Oid) * numArguments);
		i = 0;
		foreach(l, aggref->args)
		{
			inputTypes[i++] = exprType((Node *) lfirst(l));
		}

		/* fetch aggregate transition datatype from pg_aggregate */
		aggTuple = SearchSysCache(AGGFNOID,
								  ObjectIdGetDatum(aggref->aggfnoid),
								  0, 0, 0);
		if (!HeapTupleIsValid(aggTuple))
			elog(ERROR, "cache lookup failed for aggregate %u",
				 aggref->aggfnoid);
		aggform = (Form_pg_aggregate) GETSTRUCT(aggTuple);
		aggtranstype = aggform->aggtranstype;
		ReleaseSysCache(aggTuple);

		/* resolve actual type of transition state, if polymorphic */
		if (IsPolymorphicType(aggtranstype))
		{
			/* have to fetch the agg's declared input types... */
			Oid		   *declaredArgTypes;
			int			agg_nargs;

			(void) get_func_signature(aggref->aggfnoid,
									  &declaredArgTypes, &agg_nargs);
			Assert(agg_nargs == numArguments);
			aggtranstype = enforce_generic_type_consistency(inputTypes,
															declaredArgTypes,
															agg_nargs,
															aggtranstype,
															false);
			pfree(declaredArgTypes);
		}

		/*
		 * 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		aggtranstypmod;
			int32		avgwidth;

			/*
			 * If transition state is of same type as first input, assume it's
			 * the same typmod (same width) as well.  This works for cases
			 * like MAX/MIN and is probably somewhat reasonable otherwise.
			 */
			if (numArguments > 0 && aggtranstype == inputTypes[0])
				aggtranstypmod = exprTypmod((Node *) linitial(aggref->args));
			else
				aggtranstypmod = -1;

			avgwidth = get_typavgwidth(aggtranstype, aggtranstypmod);
			avgwidth = MAXALIGN(avgwidth);

			counts->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.  We assume usage of
			 * 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.
			 */
			counts->transitionSpace += ALLOCSET_DEFAULT_INITSIZE;
		}

		/*
		 * Complain if the aggregate's arguments contain any aggregates;
		 * nested agg functions are semantically nonsensical.
		 */
		if (contain_agg_clause((Node *) aggref->args))
			ereport(ERROR,
					(errcode(ERRCODE_GROUPING_ERROR),
					 errmsg("aggregate function calls cannot be nested")));

		/*
		 * Having checked that, we need not recurse into the argument.
		 */
		return false;
	}
	Assert(!IsA(node, SubLink));
	return expression_tree_walker(node, count_agg_clauses_walker,
								  (void *) counts);
}


/*****************************************************************************
 *		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 checkExprHasWindowFuncs(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++;

		/*
		 * Complain if the window function's arguments contain window
		 * functions
		 */
		if (contain_window_function((Node *) wfunc->args))
			ereport(ERROR,
					(errcode(ERRCODE_WINDOWING_ERROR),
					 errmsg("window function calls cannot be nested")));

		/*
		 * Having checked that, we need not recurse into the argument.
		 */
		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 in a set result.
 *
 * We use the product of the rowcount estimates of all the functions in
 * the given tree.  The result is 1 if there are no 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 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, 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;
	if (IsA(node, NullIfExpr))
		return false;

	return expression_tree_walker(node, expression_returns_set_rows_walker,
								  (void *) count);
}


/*****************************************************************************
 *		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;
	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, 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, 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, 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);
}

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, 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, 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, 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);
	}
	return expression_tree_walker(node, contain_volatile_functions_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, 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, NullIfExpr))
		return true;
	if (IsA(node, NullTest))
		return true;
	if (IsA(node, BooleanTest))
		return true;
	return expression_tree_walker(node, contain_nonstrict_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))
	{
		ScalarArrayOpExpr *expr = (ScalarArrayOpExpr *) node;

		if (is_strict_saop(expr, true))
			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, 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)
			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, 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)
			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)
		{
			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;
}


/*****************************************************************************
 *		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 and opretset are assumed not to 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.
	 */

	temp = clause->largs;
	clause->largs = clause->rargs;
	clause->rargs = temp;
}

/*
 * strip_implicit_coercions: remove implicit coercions at top level of tree
 *
 * Note: there isn't any useful thing we can do with a RowExpr here, so
 * just return it unchanged, even if it's marked as an implicit coercion.
 */
Node *
strip_implicit_coercions(Node *node)
{
	if (node == NULL)
		return NULL;
	if (IsA(node, FuncExpr))
	{
		FuncExpr   *f = (FuncExpr *) node;

		if (f->funcformat == COERCE_IMPLICIT_CAST)
			return strip_implicit_coercions(linitial(f->args));
	}
	else if (IsA(node, RelabelType))
	{
		RelabelType *r = (RelabelType *) node;

		if (r->relabelformat == COERCE_IMPLICIT_CAST)
			return strip_implicit_coercions((Node *) r->arg);
	}
	else if (IsA(node, CoerceViaIO))
	{
		CoerceViaIO *c = (CoerceViaIO *) node;

		if (c->coerceformat == COERCE_IMPLICIT_CAST)
			return strip_implicit_coercions((Node *) c->arg);
	}
	else if (IsA(node, ArrayCoerceExpr))
	{
		ArrayCoerceExpr *c = (ArrayCoerceExpr *) node;

		if (c->coerceformat == COERCE_IMPLICIT_CAST)
			return strip_implicit_coercions((Node *) c->arg);
	}
	else if (IsA(node, ConvertRowtypeExpr))
	{
		ConvertRowtypeExpr *c = (ConvertRowtypeExpr *) node;

		if (c->convertformat == COERCE_IMPLICIT_CAST)
			return strip_implicit_coercions((Node *) c->arg);
	}
	else if (IsA(node, CoerceToDomain))
	{
		CoerceToDomain *c = (CoerceToDomain *) node;

		if (c->coercionformat == COERCE_IMPLICIT_CAST)
			return strip_implicit_coercions((Node *) c->arg);
	}
	return node;
}

/*
 * set_coercionform_dontcare: set all CoercionForm fields to COERCE_DONTCARE
 *
 * This is used to make index expressions and index predicates more easily
 * comparable to clauses of queries.  CoercionForm is not semantically
 * significant (for cases where it does matter, the significant info is
 * coded into the coercion function arguments) so we can ignore it during
 * comparisons.  Thus, for example, an index on "foo::int4" can match an
 * implicit coercion to int4.
 *
 * Caution: the passed expression tree is modified in-place.
 */
void
set_coercionform_dontcare(Node *node)
{
	(void) set_coercionform_dontcare_walker(node, NULL);
}

static bool
set_coercionform_dontcare_walker(Node *node, void *context)
{
	if (node == NULL)
		return false;
	if (IsA(node, FuncExpr))
		((FuncExpr *) node)->funcformat = COERCE_DONTCARE;
	else if (IsA(node, RelabelType))
		((RelabelType *) node)->relabelformat = COERCE_DONTCARE;
	else if (IsA(node, CoerceViaIO))
		((CoerceViaIO *) node)->coerceformat = COERCE_DONTCARE;
	else if (IsA(node, ArrayCoerceExpr))
		((ArrayCoerceExpr *) node)->coerceformat = COERCE_DONTCARE;
	else if (IsA(node, ConvertRowtypeExpr))
		((ConvertRowtypeExpr *) node)->convertformat = COERCE_DONTCARE;
	else if (IsA(node, RowExpr))
		((RowExpr *) node)->row_format = COERCE_DONTCARE;
	else if (IsA(node, CoerceToDomain))
		((CoerceToDomain *) node)->coercionformat = COERCE_DONTCARE;
	return expression_tree_walker(node, set_coercionform_dontcare_walker,
								  context);
}

/*
 * 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)
{
	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)
	{
		ReleaseTupleDesc(tupdesc);
		return false;
	}
	ReleaseTupleDesc(tupdesc);
	return true;
}


/*--------------------
 * 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.
 *
 * 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.
 *
 * 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.
 *--------------------
 */
Node *
eval_const_expressions(PlannerInfo *root, Node *node)
{
	eval_const_expressions_context context;

	if (root)
	{
		context.boundParams = root->glob->boundParams;	/* bound Params */
		context.glob = root->glob;		/* for inlined-function dependencies */
	}
	else
	{
		context.boundParams = NULL;
		context.glob = NULL;
	}
	context.active_fns = NIL;	/* nothing being recursively simplified */
	context.case_val = NULL;	/* no CASE being examined */
	context.estimate = false;	/* safe transformations only */
	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.glob = NULL;
	context.active_fns = NIL;	/* nothing being recursively simplified */
	context.case_val = NULL;	/* no CASE being examined */
	context.estimate = true;	/* unsafe transformations OK */
	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;
	if (IsA(node, 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,
											  (int) typLen,
											  pval,
											  prm->isnull,
											  typByVal);
				}
			}
		}
		/* Not replaceable, so just copy the Param (no need to recurse) */
		return (Node *) copyObject(param);
	}
	if (IsA(node, FuncExpr))
	{
		FuncExpr   *expr = (FuncExpr *) node;
		List	   *args;
		Expr	   *simple;
		FuncExpr   *newexpr;

		/*
		 * Reduce constants in the FuncExpr'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);

		/*
		 * 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),
								   &args,
								   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.
		 */
		newexpr = makeNode(FuncExpr);
		newexpr->funcid = expr->funcid;
		newexpr->funcresulttype = expr->funcresulttype;
		newexpr->funcretset = expr->funcretset;
		newexpr->funcformat = expr->funcformat;
		newexpr->args = args;
		newexpr->location = expr->location;
		return (Node *) newexpr;
	}
	if (IsA(node, OpExpr))
	{
		OpExpr	   *expr = (OpExpr *) node;
		List	   *args;
		Expr	   *simple;
		OpExpr	   *newexpr;

		/*
		 * Reduce constants in the OpExpr'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);

		/*
		 * 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,
								   &args,
								   true, context);
		if (simple)				/* successfully simplified it */
			return (Node *) simple;

		/*
		 * If the operator is boolean equality, we know how to simplify cases
		 * involving one constant and one non-constant argument.
		 */
		if (expr->opno == BooleanEqualOperator)
		{
			simple = simplify_boolean_equality(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->args = args;
		newexpr->location = expr->location;
		return (Node *) newexpr;
	}
	if (IsA(node, 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,
									   &args,
									   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->args = args;
		newexpr->location = expr->location;
		return (Node *) newexpr;
	}
	if (IsA(node, 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);
					if (IsA(arg, Const))
					{
						Const	   *const_input = (Const *) arg;

						/* NOT NULL => NULL */
						if (const_input->constisnull)
							return makeBoolConst(false, true);
						/* otherwise pretty easy */
						return makeBoolConst(!DatumGetBool(const_input->constvalue),
											 false);
					}
					else if (not_clause(arg))
					{
						/* Cancel NOT/NOT */
						return (Node *) get_notclausearg((Expr *) arg);
					}
					/* Else we still need a NOT node */
					return (Node *) make_notclause((Expr *) arg);
				}
			default:
				elog(ERROR, "unrecognized boolop: %d",
					 (int) expr->boolop);
				break;
		}
	}
	if (IsA(node, SubPlan) ||
		IsA(node, 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;
	}
	if (IsA(node, 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;
			return (Node *) con;
		}
		else
		{
			RelabelType *newrelabel = makeNode(RelabelType);

			newrelabel->arg = (Expr *) arg;
			newrelabel->resulttype = relabel->resulttype;
			newrelabel->resulttypmod = relabel->resulttypmod;
			newrelabel->relabelformat = relabel->relabelformat;
			newrelabel->location = relabel->location;
			return (Node *) newrelabel;
		}
	}
	if (IsA(node, CoerceViaIO))
	{
		CoerceViaIO *expr = (CoerceViaIO *) node;
		Expr	   *arg;
		List	   *args;
		Oid			outfunc;
		bool		outtypisvarlena;
		Oid			infunc;
		Oid			intypioparam;
		Expr	   *simple;
		CoerceViaIO *newexpr;

		/*
		 * Reduce constants in the CoerceViaIO's argument.
		 */
		arg = (Expr *) eval_const_expressions_mutator((Node *) expr->arg,
													  context);
		args = list_make1(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.
		 */
		getTypeOutputInfo(exprType((Node *) arg), &outfunc, &outtypisvarlena);
		getTypeInputInfo(expr->resulttype, &infunc, &intypioparam);

		simple = simplify_function(outfunc,
								   CSTRINGOID, -1,
								   &args,
								   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, sizeof(Oid),
										ObjectIdGetDatum(intypioparam),
										false, true),
							  makeConst(INT4OID, -1, sizeof(int32),
										Int32GetDatum(-1),
										false, true));

			simple = simplify_function(infunc,
									   expr->resulttype, -1,
									   &args,
									   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 = arg;
		newexpr->resulttype = expr->resulttype;
		newexpr->coerceformat = expr->coerceformat;
		newexpr->location = expr->location;
		return (Node *) newexpr;
	}
	if (IsA(node, 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->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);

		/* Else we must return the partially-simplified node */
		return (Node *) newexpr;
	}
	if (IsA(node, 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 result).
		 *
		 * 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 comment 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 condition */
				/* 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->arg = (Expr *) newarg;
		newcase->args = newargs;
		newcase->defresult = (Expr *) defresult;
		newcase->location = caseexpr->location;
		return (Node *) newcase;
	}
	if (IsA(node, 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);
	}
	if (IsA(node, 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->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));

		return (Node *) newarray;
	}
	if (IsA(node, 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);

		newcoalesce = makeNode(CoalesceExpr);
		newcoalesce->coalescetype = coalesceexpr->coalescetype;
		newcoalesce->args = newargs;
		newcoalesce->location = coalesceexpr->location;
		return (Node *) newcoalesce;
	}
	if (IsA(node, 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.
		 *
		 * We must however 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)
		{
			if (rowtype_field_matches(((Var *) arg)->vartype,
									  fselect->fieldnum,
									  fselect->resulttype,
									  fselect->resulttypmod))
				return (Node *) makeVar(((Var *) arg)->varno,
										fselect->fieldnum,
										fselect->resulttype,
										fselect->resulttypmod,
										((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->resulttype == exprType(fld) &&
					fselect->resulttypmod == exprTypmod(fld))
					return fld;
			}
		}
		newfselect = makeNode(FieldSelect);
		newfselect->arg = (Expr *) arg;
		newfselect->fieldnum = fselect->fieldnum;
		newfselect->resulttype = fselect->resulttype;
		newfselect->resulttypmod = fselect->resulttypmod;
		return (Node *) newfselect;
	}
	if (IsA(node, NullTest))
	{
		NullTest   *ntest = (NullTest *) node;
		NullTest   *newntest;
		Node	   *arg;

		arg = eval_const_expressions_mutator((Node *) ntest->arg,
											 context);
		if (arg && IsA(arg, RowExpr))
		{
			RowExpr    *rarg = (RowExpr *) arg;
			List	   *newargs = NIL;
			ListCell   *l;

			/*
			 * 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.
			 */
			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;
				}
				newntest = makeNode(NullTest);
				newntest->arg = (Expr *) relem;
				newntest->nulltesttype = ntest->nulltesttype;
				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 (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;
		return (Node *) newntest;
	}
	if (IsA(node, 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;
	}
	if (IsA(node, PlaceHolderVar) &&context->estimate)
	{
		/*
		 * 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).
		 */
		PlaceHolderVar *phv = (PlaceHolderVar *) node;

		return eval_const_expressions_mutator((Node *) phv->phexpr,
											  context);
	}

	/*
	 * 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
 *
 * Input is the list of 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".
 * This is only marginally useful in itself, but doing it in constant folding
 * ensures that we will recognize the two 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 Expr *
simplify_boolean_equality(List *args)
{
	Expr	   *leftop;
	Expr	   *rightop;

	Assert(list_length(args) == 2);
	leftop = linitial(args);
	rightop = lsecond(args);
	if (leftop && IsA(leftop, Const))
	{
		Assert(!((Const *) leftop)->constisnull);
		if (DatumGetBool(((Const *) leftop)->constvalue))
			return rightop;		/* true = foo */
		else
			return make_notclause(rightop);		/* false = foo */
	}
	if (rightop && IsA(rightop, Const))
	{
		Assert(!((Const *) rightop)->constisnull);
		if (DatumGetBool(((Const *) rightop)->constvalue))
			return leftop;		/* foo = true */
		else
			return make_notclause(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) and typmod, and the pre-simplified argument list;
 * 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 adding any default argument
 * expressions onto the function argument list; which is a bit grotty,
 * but it avoids an extra fetch of the function's pg_proc tuple.  For this
 * reason, the args list is pass-by-reference, and it may get modified
 * even if simplification fails.
 */
static Expr *
simplify_function(Oid funcid, Oid result_type, int32 result_typmod,
				  List **args,
				  bool allow_inline,
				  eval_const_expressions_context *context)
{
	HeapTuple	func_tuple;
	Expr	   *newexpr;

	/*
	 * We have two strategies for simplification: either execute the function
	 * to deliver a constant result, or expand in-line the body of the
	 * function definition (which only works for simple SQL-language
	 * functions, but that is a common case).  In either case we need access
	 * to the function's pg_proc tuple, so fetch it just once to use in both
	 * attempts.
	 */
	func_tuple = SearchSysCache(PROCOID,
								ObjectIdGetDatum(funcid),
								0, 0, 0);
	if (!HeapTupleIsValid(func_tuple))
		elog(ERROR, "cache lookup failed for function %u", funcid);

	/* While we have the tuple, check if we need to add defaults */
	if (((Form_pg_proc) GETSTRUCT(func_tuple))->pronargs > list_length(*args))
		*args = add_function_defaults(*args, result_type, func_tuple, context);

	newexpr = evaluate_function(funcid, result_type, result_typmod, *args,
								func_tuple, context);

	if (!newexpr && allow_inline)
		newexpr = inline_function(funcid, result_type, *args,
								  func_tuple, context);

	ReleaseSysCache(func_tuple);

	return newexpr;
}

/*
 * add_function_defaults: add missing function arguments from its 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.
 */
static List *
add_function_defaults(List *args, Oid result_type, HeapTuple func_tuple,
					  eval_const_expressions_context *context)
{
	Form_pg_proc funcform = (Form_pg_proc) GETSTRUCT(func_tuple);
	int			nargsprovided = list_length(args);
	Datum		proargdefaults;
	bool		isnull;
	char	   *str;
	List	   *defaults;
	int			ndelete;
	int			nargs;
	Oid			actual_arg_types[FUNC_MAX_ARGS];
	Oid			declared_arg_types[FUNC_MAX_ARGS];
	Oid			rettype;
	ListCell   *lc;

	/* 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);
	/* 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 */
	args = list_concat(args, defaults);
	Assert(list_length(args) == funcform->pronargs);

	/*
	 * The next part should be a no-op if there are no polymorphic arguments,
	 * but we do it anyway to be sure.
	 */
	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));
	}
	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);

	/*
	 * Lastly, we have to recursively simplify the arguments we just added
	 * (but don't recurse on the ones passed in, as we already did those).
	 * This isn't merely an optimization, it's *necessary* since there could
	 * be functions with defaulted arguments down in there.
	 */
	foreach(lc, args)
	{
		if (nargsprovided-- > 0)
			continue;			/* skip original arg positions */
		lfirst(lc) = eval_const_expressions_mutator((Node *) lfirst(lc),
													context);
	}

	return args;
}

/*
 * 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, List *args,
				  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);

	/*
	 * 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
		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->funcformat = COERCE_DONTCARE;		/* doesn't matter */
	newexpr->args = args;
	newexpr->location = -1;

	return evaluate_expr((Expr *) newexpr, result_type, result_typmod);
}

/*
 * 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.
 *
 * Returns a simplified expression if successful, or NULL if cannot
 * simplify the function.
 */
static Expr *
inline_function(Oid funcid, Oid result_type, List *args,
				HeapTuple func_tuple,
				eval_const_expressions_context *context)
{
	Form_pg_proc funcform = (Form_pg_proc) GETSTRUCT(func_tuple);
	Oid		   *argtypes;
	char	   *src;
	Datum		tmp;
	bool		isNull;
	bool		modifyTargetList;
	MemoryContext oldcxt;
	MemoryContext mycxt;
	inline_error_callback_arg callback_arg;
	ErrorContextCallback sqlerrcontext;
	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;

	/*
	 * 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;

	/* Check for polymorphic arguments, and substitute actual arg types */
	argtypes = (Oid *) palloc(funcform->pronargs * sizeof(Oid));
	memcpy(argtypes, funcform->proargtypes.values,
		   funcform->pronargs * sizeof(Oid));
	for (i = 0; i < funcform->pronargs; i++)
	{
		if (IsPolymorphicType(argtypes[i]))
		{
			argtypes[i] = exprType((Node *) list_nth(args, i));
		}
	}

	/*
	 * 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;

	querytree = parse_analyze(linitial(raw_parsetree_list), src,
							  argtypes, funcform->pronargs);

	/*
	 * The single command must be a simple "SELECT expression".
	 */
	if (!IsA(querytree, Query) ||
		querytree->commandType != CMD_SELECT ||
		querytree->utilityStmt ||
		querytree->intoClause ||
		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;

	/*
	 * 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);

	/*
	 * 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->glob)
		record_plan_function_dependency(context->glob, 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.
 */
static Expr *
evaluate_expr(Expr *expr, Oid result_type, int32 result_typmod)
{
	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, 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)
{
	FuncExpr   *fexpr;
	HeapTuple	func_tuple;
	Form_pg_proc funcform;
	Oid		   *argtypes;
	char	   *src;
	Datum		tmp;
	bool		isNull;
	bool		modifyTargetList;
	MemoryContext oldcxt;
	MemoryContext mycxt;
	inline_error_callback_arg callback_arg;
	ErrorContextCallback sqlerrcontext;
	List	   *raw_parsetree_list;
	List	   *querytree_list;
	Query	   *querytree;
	int			i;

	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 FROM item isn't a simple FuncExpr */
	fexpr = (FuncExpr *) rte->funcexpr;
	if (fexpr == NULL || !IsA(fexpr, FuncExpr))
		return NULL;

	/*
	 * 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(fexpr->funcid, GetUserId(), ACL_EXECUTE) != ACLCHECK_OK)
		return NULL;

	/*
	 * OK, let's take a look at the function's pg_proc entry.
	 */
	func_tuple = SearchSysCache(PROCOID,
								ObjectIdGetDatum(fexpr->funcid),
								0, 0, 0);
	if (!HeapTupleIsValid(func_tuple))
		elog(ERROR, "cache lookup failed for function %u", fexpr->funcid);
	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.  (The nargs check is just
	 * paranoia, ditto rechecking proretset.)
	 */
	if (funcform->prolang != SQLlanguageId ||
		funcform->proisstrict ||
		funcform->provolatile == PROVOLATILE_VOLATILE ||
		funcform->prosecdef ||
		!funcform->proretset ||
		!heap_attisnull(func_tuple, Anum_pg_proc_proconfig) ||
		funcform->pronargs != list_length(fexpr->args))
	{
		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);

	/* Fetch the function body */
	tmp = SysCacheGetAttr(PROCOID,
						  func_tuple,
						  Anum_pg_proc_prosrc,
						  &isNull);
	if (isNull)
		elog(ERROR, "null prosrc for function %u", fexpr->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;

	/* Check for polymorphic arguments, and substitute actual arg types */
	argtypes = (Oid *) palloc(funcform->pronargs * sizeof(Oid));
	memcpy(argtypes, funcform->proargtypes.values,
		   funcform->pronargs * sizeof(Oid));
	for (i = 0; i < funcform->pronargs; i++)
	{
		if (IsPolymorphicType(argtypes[i]))
		{
			argtypes[i] = exprType((Node *) list_nth(fexpr->args, i));
		}
	}

	/*
	 * 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(linitial(raw_parsetree_list), src,
											argtypes, funcform->pronargs);
	if (list_length(querytree_list) != 1)
		goto fail;
	querytree = linitial(querytree_list);

	/*
	 * The single command must be a regular results-returning SELECT.
	 */
	if (!IsA(querytree, Query) ||
		querytree->commandType != CMD_SELECT ||
		querytree->utilityStmt ||
		querytree->intoClause)
		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(fexpr->funcid, 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(fexpr->funcid, NULL, NULL) == TYPEFUNC_RECORD &&
		!tlist_matches_coltypelist(querytree->targetList, rte->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);

	MemoryContextDelete(mycxt);
	error_context_stack = sqlerrcontext.previous;
	ReleaseSysCache(func_tuple);

	/*
	 * 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->glob, fexpr->funcid);

	return querytree;

	/* Here if func is not inlinable: release temp memory and return NULL */
fail:
	MemoryContextSwitchTo(oldcxt);
	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);
}

/*
 * 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;
}
