[postgresql] / src / backend / optimizer / util / clauses.c

/*-------------------------------------------------------------------------
 *
 * clauses.c
 *        routines to manipulate qualification clauses
 *
 * Portions Copyright (c) 1996-2010, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *        src/backend/optimizer/util/clauses.c
 *
 * HISTORY
 *        AUTHOR                        DATE                    MAJOR EVENT
 *        Andrew Yu                     Nov 3, 1994             clause.c and clauses.c combined
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "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 "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 Node *simplify_boolean_equality(Oid opno, List *args);
static Expr *simplify_function(Oid funcid,
                                  Oid result_type, int32 result_typmod, List **args,
                                  bool has_named_args,
                                  bool allow_inline,
                                  eval_const_expressions_context *context);
static List *reorder_function_arguments(List *args, Oid result_type,
                                                   HeapTuple func_tuple,
                                                   eval_const_expressions_context *context);
static List *add_function_defaults(List *args, Oid result_type,
                                          HeapTuple func_tuple,
                                          eval_const_expressions_context *context);
static List *fetch_function_defaults(HeapTuple func_tuple);
static void recheck_cast_function_args(List *args, Oid result_type,
                                                   HeapTuple func_tuple);
static Expr *evaluate_function(Oid funcid,
                                  Oid result_type, int32 result_typmod, 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;
                ListCell   *l;

                Assert(aggref->agglevelsup == 0);
                counts->numAggs++;
                if (aggref->aggorder != NIL || aggref->aggdistinct != NIL)
                        counts->numOrderedAggs++;

                /* extract argument types (ignoring any ORDER BY expressions) */
                inputTypes = (Oid *) palloc(sizeof(Oid) * list_length(aggref->args));
                numArguments = 0;
                foreach(l, aggref->args)
                {
                        TargetEntry *tle = (TargetEntry *) lfirst(l);

                        if (!tle->resjunk)
                                inputTypes[numArguments++] = exprType((Node *) tle->expr);
                }

                /* fetch aggregate transition datatype from pg_aggregate */
                aggTuple = SearchSysCache1(AGGFNOID,
                                                                   ObjectIdGetDatum(aggref->aggfnoid));
                if (!HeapTupleIsValid(aggTuple))
                        elog(ERROR, "cache lookup failed for aggregate %u",
                                 aggref->aggfnoid);
                aggform = (Form_pg_aggregate) GETSTRUCT(aggTuple);
                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.
 *
 * XXX we do not examine sub-selects to see if they contain uses of
 * mutable functions.  It's not real clear if that is correct or not...
 */
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 */
        }
        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 invalid conversions
 * of volatile expressions into indexscan quals.
 *
 * XXX we do not examine sub-selects to see if they contain uses of
 * volatile functions.  It's not real clear if that is correct or not...
 */
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 */
        }
        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 && !expr->argisrow)
                        result = find_nonnullable_rels_walker((Node *) expr->arg, false);
        }
        else if (IsA(node, BooleanTest))
        {
                /* Boolean tests that reject NULL are strict at top level */
                BooleanTest *expr = (BooleanTest *) node;

                if (top_level &&
                        (expr->booltesttype == IS_TRUE ||
                         expr->booltesttype == IS_FALSE ||
                         expr->booltesttype == IS_NOT_UNKNOWN))
                        result = find_nonnullable_rels_walker((Node *) expr->arg, false);
        }
        else if (IsA(node, PlaceHolderVar))
        {
                PlaceHolderVar *phv = (PlaceHolderVar *) node;

                result = find_nonnullable_rels_walker((Node *) phv->phexpr, top_level);
        }
        return result;
}

/*
 * find_nonnullable_vars
 *              Determine which Vars are forced nonnullable by given clause.
 *
 * Returns a list of all level-zero Vars that are referenced in the clause in
 * such a way that the clause cannot possibly return TRUE if any of these Vars
 * is NULL.  (It is OK to err on the side of conservatism; hence the analysis
 * here is simplistic.)
 *
 * The semantics here are subtly different from contain_nonstrict_functions:
 * that function is concerned with NULL results from arbitrary expressions,
 * but here we assume that the input is a Boolean expression, and wish to
 * see if NULL inputs will provably cause a FALSE-or-NULL result.  We expect
 * the expression to have been AND/OR flattened and converted to implicit-AND
 * format.
 *
 * The result is a palloc'd List, but we have not copied the member Var nodes.
 * Also, we don't bother trying to eliminate duplicate entries.
 *
 * top_level is TRUE while scanning top-level AND/OR structure; here, showing
 * the result is either FALSE or NULL is good enough.  top_level is FALSE when
 * we have descended below a NOT or a strict function: now we must be able to
 * prove that the subexpression goes to NULL.
 *
 * We don't use expression_tree_walker here because we don't want to descend
 * through very many kinds of nodes; only the ones we can be sure are strict.
 */
List *
find_nonnullable_vars(Node *clause)
{
        return find_nonnullable_vars_walker(clause, true);
}

static List *
find_nonnullable_vars_walker(Node *node, bool top_level)
{
        List       *result = NIL;
        ListCell   *l;

        if (node == NULL)
                return NIL;
        if (IsA(node, Var))
        {
                Var                *var = (Var *) node;

                if (var->varlevelsup == 0)
                        result = list_make1(var);
        }
        else if (IsA(node, List))
        {
                /*
                 * At top level, we are examining an implicit-AND list: if any of the
                 * arms produces FALSE-or-NULL then the result is FALSE-or-NULL. If
                 * not at top level, we are examining the arguments of a strict
                 * function: if any of them produce NULL then the result of the
                 * function must be NULL.  So in both cases, the set of nonnullable
                 * vars is the union of those found in the arms, and we pass down the
                 * top_level flag unmodified.
                 */
                foreach(l, (List *) node)
                {
                        result = list_concat(result,
                                                                 find_nonnullable_vars_walker(lfirst(l),
                                                                                                                          top_level));
                }
        }
        else if (IsA(node, FuncExpr))
        {
                FuncExpr   *expr = (FuncExpr *) node;

                if (func_strict(expr->funcid))
                        result = find_nonnullable_vars_walker((Node *) expr->args, false);
        }
        else if (IsA(node, OpExpr))
        {
                OpExpr     *expr = (OpExpr *) node;

                set_opfuncid(expr);
                if (func_strict(expr->opfuncid))
                        result = find_nonnullable_vars_walker((Node *) expr->args, false);
        }
        else if (IsA(node, ScalarArrayOpExpr))
        {
                ScalarArrayOpExpr *expr = (ScalarArrayOpExpr *) node;

                if (is_strict_saop(expr, true))
                        result = find_nonnullable_vars_walker((Node *) expr->args, false);
        }
        else if (IsA(node, BoolExpr))
        {
                BoolExpr   *expr = (BoolExpr *) node;

                switch (expr->boolop)
                {
                        case AND_EXPR:
                                /* At top level we can just recurse (to the List case) */
                                if (top_level)
                                {
                                        result = find_nonnullable_vars_walker((Node *) expr->args,
                                                                                                                  top_level);
                                        break;
                                }

                                /*
                                 * Below top level, even if one arm produces NULL, the result
                                 * could be FALSE (hence not NULL).  However, if *all* the
                                 * arms produce NULL then the result is NULL, so we can take
                                 * the intersection of the sets of nonnullable vars, just as
                                 * for OR.      Fall through to share code.
                                 */
                                /* FALL THRU */
                        case OR_EXPR:

                                /*
                                 * OR is strict if all of its arms are, so we can take the
                                 * intersection of the sets of nonnullable vars for each arm.
                                 * This works for both values of top_level.
                                 */
                                foreach(l, expr->args)
                                {
                                        List       *subresult;

                                        subresult = find_nonnullable_vars_walker(lfirst(l),
                                                                                                                         top_level);
                                        if (result == NIL)      /* first subresult? */
                                                result = subresult;
                                        else
                                                result = list_intersection(result, subresult);

                                        /*
                                         * If the intersection is empty, we can stop looking. This
                                         * also justifies the test for first-subresult above.
                                         */
                                        if (result == NIL)
                                                break;
                                }
                                break;
                        case NOT_EXPR:
                                /* NOT will return null if its arg is null */
                                result = find_nonnullable_vars_walker((Node *) expr->args,
                                                                                                          false);
                                break;
                        default:
                                elog(ERROR, "unrecognized boolop: %d", (int) expr->boolop);
                                break;
                }
        }
        else if (IsA(node, RelabelType))
        {
                RelabelType *expr = (RelabelType *) node;

                result = find_nonnullable_vars_walker((Node *) expr->arg, top_level);
        }
        else if (IsA(node, CoerceViaIO))
        {
                /* not clear this is useful, but it can't hurt */
                CoerceViaIO *expr = (CoerceViaIO *) node;

                result = find_nonnullable_vars_walker((Node *) expr->arg, false);
        }
        else if (IsA(node, ArrayCoerceExpr))
        {
                /* ArrayCoerceExpr is strict at the array level */
                ArrayCoerceExpr *expr = (ArrayCoerceExpr *) node;

                result = find_nonnullable_vars_walker((Node *) expr->arg, top_level);
        }
        else if (IsA(node, ConvertRowtypeExpr))
        {
                /* not clear this is useful, but it can't hurt */
                ConvertRowtypeExpr *expr = (ConvertRowtypeExpr *) node;

                result = find_nonnullable_vars_walker((Node *) expr->arg, top_level);
        }
        else if (IsA(node, NullTest))
        {
                /* IS NOT NULL can be considered strict, but only at top level */
                NullTest   *expr = (NullTest *) node;

                if (top_level && expr->nulltesttype == IS_NOT_NULL && !expr->argisrow)
                        result = find_nonnullable_vars_walker((Node *) expr->arg, false);
        }
        else if (IsA(node, BooleanTest))
        {
                /* Boolean tests that reject NULL are strict at top level */
                BooleanTest *expr = (BooleanTest *) node;

                if (top_level &&
                        (expr->booltesttype == IS_TRUE ||
                         expr->booltesttype == IS_FALSE ||
                         expr->booltesttype == IS_NOT_UNKNOWN))
                        result = find_nonnullable_vars_walker((Node *) expr->arg, false);
        }
        else if (IsA(node, PlaceHolderVar))
        {
                PlaceHolderVar *phv = (PlaceHolderVar *) node;

                result = find_nonnullable_vars_walker((Node *) phv->phexpr, top_level);
        }
        return result;
}

/*
 * find_forced_null_vars
 *              Determine which Vars must be NULL for the given clause to return TRUE.
 *
 * This is the complement of find_nonnullable_vars: find the level-zero Vars
 * that must be NULL for the clause to return TRUE.  (It is OK to err on the
 * side of conservatism; hence the analysis here is simplistic.  In fact,
 * we only detect simple "var IS NULL" tests at the top level.)
 *
 * The result is a palloc'd List, but we have not copied the member Var nodes.
 * Also, we don't bother trying to eliminate duplicate entries.
 */
List *
find_forced_null_vars(Node *node)
{
        List       *result = NIL;
        Var                *var;
        ListCell   *l;

        if (node == NULL)
                return NIL;
        /* Check single-clause cases using subroutine */
        var = find_forced_null_var(node);
        if (var)
        {
                result = list_make1(var);
        }
        /* Otherwise, handle AND-conditions */
        else if (IsA(node, List))
        {
                /*
                 * At top level, we are examining an implicit-AND list: if any of the
                 * arms produces FALSE-or-NULL then the result is FALSE-or-NULL.
                 */
                foreach(l, (List *) node)
                {
                        result = list_concat(result,
                                                                 find_forced_null_vars(lfirst(l)));
                }
        }
        else if (IsA(node, BoolExpr))
        {
                BoolExpr   *expr = (BoolExpr *) node;

                /*
                 * We don't bother considering the OR case, because it's fairly
                 * unlikely anyone would write "v1 IS NULL OR v1 IS NULL". Likewise,
                 * the NOT case isn't worth expending code on.
                 */
                if (expr->boolop == AND_EXPR)
                {
                        /* At top level we can just recurse (to the List case) */
                        result = find_forced_null_vars((Node *) expr->args);
                }
        }
        return result;
}

/*
 * find_forced_null_var
 *              Return the Var forced null by the given clause, or NULL if it's
 *              not an IS NULL-type clause.  For success, the clause must enforce
 *              *only* nullness of the particular Var, not any other conditions.
 *
 * This is just the single-clause case of find_forced_null_vars(), without
 * any allowance for AND conditions.  It's used by initsplan.c on individual
 * qual clauses.  The reason for not just applying find_forced_null_vars()
 * is that if an AND of an IS NULL clause with something else were to somehow
 * survive AND/OR flattening, initsplan.c might get fooled into discarding
 * the whole clause when only the IS NULL part of it had been proved redundant.
 */
Var *
find_forced_null_var(Node *node)
{
        if (node == NULL)
                return NULL;
        if (IsA(node, NullTest))
        {
                /* check for var IS NULL */
                NullTest   *expr = (NullTest *) node;

                if (expr->nulltesttype == IS_NULL && !expr->argisrow)
                {
                        Var                *var = (Var *) expr->arg;

                        if (var && IsA(var, Var) &&
                                var->varlevelsup == 0)
                                return var;
                }
        }
        else if (IsA(node, BooleanTest))
        {
                /* var IS UNKNOWN is equivalent to var IS NULL */
                BooleanTest *expr = (BooleanTest *) node;

                if (expr->booltesttype == IS_UNKNOWN)
                {
                        Var                *var = (Var *) expr->arg;

                        if (var && IsA(var, Var) &&
                                var->varlevelsup == 0)
                                return var;
                }
        }
        return NULL;
}

/*
 * Can we treat a ScalarArrayOpExpr as strict?
 *
 * If "falseOK" is true, then a "false" result can be considered strict,
 * else we need to guarantee an actual NULL result for NULL input.
 *
 * "foo op ALL array" is strict if the op is strict *and* we can prove
 * that the array input isn't an empty array.  We can check that
 * for the cases of an array constant and an ARRAY[] construct.
 *
 * "foo op ANY array" is strict in the falseOK sense if the op is strict.
 * If not falseOK, the test is the same as for "foo op ALL array".
 */
static bool
is_strict_saop(ScalarArrayOpExpr *expr, bool falseOK)
{
        Node       *rightop;

        /* The contained operator must be strict. */
        set_sa_opfuncid(expr);
        if (!func_strict(expr->opfuncid))
                return false;
        /* If ANY and falseOK, that's all we need to check. */
        if (expr->useOr && falseOK)
                return true;
        /* Else, we have to see if the array is provably non-empty. */
        Assert(list_length(expr->args) == 2);
        rightop = (Node *) lsecond(expr->args);
        if (rightop && IsA(rightop, Const))
        {
                Datum           arraydatum = ((Const *) rightop)->constvalue;
                bool            arrayisnull = ((Const *) rightop)->constisnull;
                ArrayType  *arrayval;
                int                     nitems;

                if (arrayisnull)
                        return false;
                arrayval = DatumGetArrayTypeP(arraydatum);
                nitems = ArrayGetNItems(ARR_NDIM(arrayval), ARR_DIMS(arrayval));
                if (nitems > 0)
                        return true;
        }
        else if (rightop && IsA(rightop, ArrayExpr))
        {
                ArrayExpr  *arrayexpr = (ArrayExpr *) rightop;

                if (arrayexpr->elements != NIL && !arrayexpr->multidims)
                        return true;
        }
        return false;
}


/*****************************************************************************
 *              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.
 *
 * Whenever a function is eliminated from the expression by means of
 * constant-expression evaluation or inlining, we add the function to
 * root->glob->invalItems.  This ensures the plan is known to depend on
 * such functions, even though they aren't referenced anymore.
 *
 * We assume that the tree has already been type-checked and contains
 * only operators and functions that are reasonable to try to execute.
 *
 * NOTE: "root" can be passed as NULL if the caller never wants to do any
 * Param substitutions nor receive info about inlined functions.
 *
 * NOTE: the planner assumes that this will always flatten nested AND and
 * OR clauses into N-argument form.  See comments in prepqual.c.
 *
 * NOTE: another critical effect is that any function calls that require
 * default arguments will be expanded, and named-argument calls will be
 * converted to positional notation.  The executor won't handle either.
 *--------------------
 */
Node *
eval_const_expressions(PlannerInfo *root, Node *node)
{
        eval_const_expressions_context context;

        if (root)
        {
                context.boundParams = root->glob->boundParams;  /* bound Params */
                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;
                bool            has_named_args;
                Expr       *simple;
                FuncExpr   *newexpr;
                ListCell   *lc;

                /*
                 * Reduce constants in the FuncExpr's arguments, and check to see if
                 * there are any named args.
                 */
                args = NIL;
                has_named_args = false;
                foreach(lc, expr->args)
                {
                        Node       *arg = (Node *) lfirst(lc);

                        arg = eval_const_expressions_mutator(arg, context);
                        if (IsA(arg, NamedArgExpr))
                                has_named_args = true;
                        args = lappend(args, arg);
                }

                /*
                 * 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,
                                                                   has_named_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.  Note that we have also converted the argument list to
                 * positional notation.
                 */
                newexpr = makeNode(FuncExpr);
                newexpr->funcid = expr->funcid;
                newexpr->funcresulttype = expr->funcresulttype;
                newexpr->funcretset = expr->funcretset;
                newexpr->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,
                                                                   false, true, context);
                if (simple)                             /* successfully simplified it */
                        return (Node *) simple;

                /*
                 * If the operator is boolean equality or inequality, we know how to
                 * simplify cases involving one constant and one non-constant
                 * argument.
                 */
                if (expr->opno == BooleanEqualOperator ||
                        expr->opno == BooleanNotEqualOperator)
                {
                        simple = (Expr *) simplify_boolean_equality(expr->opno, args);
                        if (simple)                     /* successfully simplified it */
                                return (Node *) simple;
                }

                /*
                 * The expression cannot be simplified any further, so build and
                 * return a replacement OpExpr node using the possibly-simplified
                 * arguments.
                 */
                newexpr = makeNode(OpExpr);
                newexpr->opno = expr->opno;
                newexpr->opfuncid = expr->opfuncid;
                newexpr->opresulttype = expr->opresulttype;
                newexpr->opretset = expr->opretset;
                newexpr->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, 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);

                                        /*
                                         * Use negate_clause() to see if we can simplify away
                                         * the NOT.
                                         */
                                        return negate_clause(arg);
                                }
                        default:
                                elog(ERROR, "unrecognized boolop: %d",
                                         (int) expr->boolop);
                                break;
                }
        }
        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,
                                                                   false, 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,
                                                                           false, true, context);
                        if (simple)                     /* successfully simplified input fn */
                                return (Node *) simple;
                }

                /*
                 * The expression cannot be simplified any further, so build and
                 * return a replacement CoerceViaIO node using the possibly-simplified
                 * argument.
                 */
                newexpr = makeNode(CoerceViaIO);
                newexpr->arg = 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.
                 *----------
                 */
                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;
                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))
                {
                        /*
                         * We break ROW(...) IS [NOT] NULL into separate tests on its
                         * component fields.  This form is usually more efficient to
                         * evaluate, as well as being more amenable to optimization.
                         */
                        RowExpr    *rarg = (RowExpr *) arg;
                        List       *newargs = NIL;
                        ListCell   *l;

                        Assert(ntest->argisrow);

                        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;
                                newntest->argisrow = type_is_rowtype(exprType(relem));
                                newargs = lappend(newargs, newntest);
                        }
                        /* If all the inputs were constants, result is TRUE */
                        if (newargs == NIL)
                                return makeBoolConst(true, false);
                        /* If only one nonconst input, it's the result */
                        if (list_length(newargs) == 1)
                                return (Node *) linitial(newargs);
                        /* Else we need an AND node */
                        return (Node *) make_andclause(newargs);
                }
                if (!ntest->argisrow && arg && IsA(arg, Const))
                {
                        Const      *carg = (Const *) arg;
                        bool            result;

                        switch (ntest->nulltesttype)
                        {
                                case IS_NULL:
                                        result = carg->constisnull;
                                        break;
                                case IS_NOT_NULL:
                                        result = !carg->constisnull;
                                        break;
                                default:
                                        elog(ERROR, "unrecognized nulltesttype: %d",
                                                 (int) ntest->nulltesttype);
                                        result = false;         /* keep compiler quiet */
                                        break;
                        }

                        return makeBoolConst(result, false);
                }

                newntest = makeNode(NullTest);
                newntest->arg = (Expr *) arg;
                newntest->nulltesttype = ntest->nulltesttype;
                newntest->argisrow = ntest->argisrow;
                return (Node *) newntest;
        }
        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
 * or inequality condition
 *
 * Inputs are the operator OID and the simplified arguments to the operator.
 * Returns a simplified expression if successful, or NULL if cannot
 * simplify the expression.
 *
 * The idea here is to reduce "x = true" to "x" and "x = false" to "NOT x",
 * or similarly "x <> true" to "NOT x" and "x <> false" to "x".
 * This is only marginally useful in itself, but doing it in constant folding
 * ensures that we will recognize these forms as being equivalent in, for
 * example, partial index matching.
 *
 * We come here only if simplify_function has failed; therefore we cannot
 * see two constant inputs, nor a constant-NULL input.
 */
static Node *
simplify_boolean_equality(Oid opno, List *args)
{
        Node       *leftop;
        Node       *rightop;

        Assert(list_length(args) == 2);
        leftop = linitial(args);
        rightop = lsecond(args);
        if (leftop && IsA(leftop, Const))
        {
                Assert(!((Const *) leftop)->constisnull);
                if (opno == BooleanEqualOperator)
                {
                        if (DatumGetBool(((Const *) leftop)->constvalue))
                                return rightop; /* true = foo */
                        else
                                return negate_clause(rightop); /* false = foo */
                }
                else
                {
                        if (DatumGetBool(((Const *) leftop)->constvalue))
                                return negate_clause(rightop); /* true <> foo */
                        else
                                return rightop; /* false <> foo */
                }
        }
        if (rightop && IsA(rightop, Const))
        {
                Assert(!((Const *) rightop)->constisnull);
                if (opno == BooleanEqualOperator)
                {
                        if (DatumGetBool(((Const *) rightop)->constvalue))
                                return leftop;  /* foo = true */
                        else
                                return negate_clause(leftop);   /* foo = false */
                }
                else
                {
                        if (DatumGetBool(((Const *) rightop)->constvalue))
                                return negate_clause(leftop);   /* foo <> true */
                        else
                                return leftop;  /* foo <> false */
                }
        }
        return NULL;
}

/*
 * Subroutine for eval_const_expressions: try to simplify a function call
 * (which might originally have been an operator; we don't care)
 *
 * Inputs are the function OID, actual result type OID (which is needed for
 * polymorphic functions) 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 converting named-notation argument
 * lists into positional notation and/or adding any needed default argument
 * expressions; 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 has_named_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 = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcid));
        if (!HeapTupleIsValid(func_tuple))
                elog(ERROR, "cache lookup failed for function %u", funcid);

        /*
         * While we have the tuple, reorder named arguments and add default
         * arguments if needed.
         */
        if (has_named_args)
                *args = reorder_function_arguments(*args, result_type, func_tuple,
                                                                                   context);
        else 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;
}

/*
 * reorder_function_arguments: convert named-notation args to positional args
 *
 * This function also inserts default argument values as needed, since it's
 * impossible to form a truly valid positional call without that.
 */
static List *
reorder_function_arguments(List *args, Oid result_type, HeapTuple func_tuple,
                                                   eval_const_expressions_context *context)
{
        Form_pg_proc funcform = (Form_pg_proc) GETSTRUCT(func_tuple);
        int                     pronargs = funcform->pronargs;
        int                     nargsprovided = list_length(args);
        Node       *argarray[FUNC_MAX_ARGS];
        Bitmapset  *defargnumbers;
        ListCell   *lc;
        int                     i;

        Assert(nargsprovided <= pronargs);
        if (pronargs > FUNC_MAX_ARGS)
                elog(ERROR, "too many function arguments");
        MemSet(argarray, 0, pronargs * sizeof(Node *));

        /* Deconstruct the argument list into an array indexed by argnumber */
        i = 0;
        foreach(lc, args)
        {
                Node       *arg = (Node *) lfirst(lc);

                if (!IsA(arg, NamedArgExpr))
                {
                        /* positional argument, assumed to precede all named args */
                        Assert(argarray[i] == NULL);
                        argarray[i++] = arg;
                }
                else
                {
                        NamedArgExpr *na = (NamedArgExpr *) arg;

                        Assert(argarray[na->argnumber] == NULL);
                        argarray[na->argnumber] = (Node *) na->arg;
                }
        }

        /*
         * Fetch default expressions, if needed, and insert into array at proper
         * locations (they aren't necessarily consecutive or all used)
         */
        defargnumbers = NULL;
        if (nargsprovided < pronargs)
        {
                List       *defaults = fetch_function_defaults(func_tuple);

                i = pronargs - funcform->pronargdefaults;
                foreach(lc, defaults)
                {
                        if (argarray[i] == NULL)
                        {
                                argarray[i] = (Node *) lfirst(lc);
                                defargnumbers = bms_add_member(defargnumbers, i);
                        }
                        i++;
                }
        }

        /* Now reconstruct the args list in proper order */
        args = NIL;
        for (i = 0; i < pronargs; i++)
        {
                Assert(argarray[i] != NULL);
                args = lappend(args, argarray[i]);
        }

        /* Recheck argument types and add casts if needed */
        recheck_cast_function_args(args, result_type, func_tuple);

        /*
         * Lastly, we have to recursively simplify the defaults we just added (but
         * don't recurse on the args passed in, as we already did those). This
         * isn't merely an optimization, it's *necessary* since there could be
         * functions with named or defaulted arguments down in there.
         *
         * Note that we do this last in hopes of simplifying any typecasts that
         * were added by recheck_cast_function_args --- there shouldn't be any new
         * casts added to the explicit arguments, but casts on the defaults are
         * possible.
         */
        if (defargnumbers != NULL)
        {
                i = 0;
                foreach(lc, args)
                {
                        if (bms_is_member(i, defargnumbers))
                                lfirst(lc) = eval_const_expressions_mutator((Node *) lfirst(lc),
                                                                                                                        context);
                        i++;
                }
        }

        return args;
}

/*
 * add_function_defaults: add missing function arguments from its defaults
 *
 * This is used only when the argument list was positional to begin with,
 * and so we know we just need to add defaults at the end.
 */
static List *
add_function_defaults(List *args, 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);
        List       *defaults;
        int                     ndelete;
        ListCell   *lc;

        /* Get all the default expressions from the pg_proc tuple */
        defaults = fetch_function_defaults(func_tuple);

        /* Delete any unused defaults from the list */
        ndelete = nargsprovided + list_length(defaults) - funcform->pronargs;
        if (ndelete < 0)
                elog(ERROR, "not enough default arguments");
        while (ndelete-- > 0)
                defaults = list_delete_first(defaults);

        /* And form the combined argument list */
        args = list_concat(args, defaults);

        /* Recheck argument types and add casts if needed */
        recheck_cast_function_args(args, result_type, func_tuple);

        /*
         * Lastly, we have to recursively simplify the defaults we just added (but
         * don't recurse on the args passed in, as we already did those). This
         * isn't merely an optimization, it's *necessary* since there could be
         * functions with named or defaulted arguments down in there.
         *
         * Note that we do this last in hopes of simplifying any typecasts that
         * were added by recheck_cast_function_args --- there shouldn't be any new
         * casts added to the explicit arguments, but casts on the defaults are
         * possible.
         */
        foreach(lc, args)
        {
                if (nargsprovided-- > 0)
                        continue;                       /* skip original arg positions */
                lfirst(lc) = eval_const_expressions_mutator((Node *) lfirst(lc),
                                                                                                        context);
        }

        return args;
}

/*
 * fetch_function_defaults: get function's default arguments as expression list
 */
static List *
fetch_function_defaults(HeapTuple func_tuple)
{
        List       *defaults;
        Datum           proargdefaults;
        bool            isnull;
        char       *str;

        /* The error cases here shouldn't happen, but check anyway */
        proargdefaults = SysCacheGetAttr(PROCOID, func_tuple,
                                                                         Anum_pg_proc_proargdefaults,
                                                                         &isnull);
        if (isnull)
                elog(ERROR, "not enough default arguments");
        str = TextDatumGetCString(proargdefaults);
        defaults = (List *) stringToNode(str);
        Assert(IsA(defaults, List));
        pfree(str);
        return defaults;
}

/*
 * recheck_cast_function_args: recheck function args and typecast as needed
 * after adding defaults.
 *
 * It is possible for some of the defaulted arguments to be polymorphic;
 * therefore we can't assume that the default expressions have the correct
 * data types already.  We have to re-resolve polymorphics and do coercion
 * just like the parser did.
 *
 * This should be a no-op if there are no polymorphic arguments,
 * but we do it anyway to be sure.
 *
 * Note: if any casts are needed, the args list is modified in-place.
 */
static void
recheck_cast_function_args(List *args, Oid result_type, HeapTuple func_tuple)
{
        Form_pg_proc funcform = (Form_pg_proc) GETSTRUCT(func_tuple);
        int                     nargs;
        Oid                     actual_arg_types[FUNC_MAX_ARGS];
        Oid                     declared_arg_types[FUNC_MAX_ARGS];
        Oid                     rettype;
        ListCell   *lc;

        if (list_length(args) > FUNC_MAX_ARGS)
                elog(ERROR, "too many function arguments");
        nargs = 0;
        foreach(lc, args)
        {
                actual_arg_types[nargs++] = exprType((Node *) lfirst(lc));
        }
        Assert(nargs == funcform->pronargs);
        memcpy(declared_arg_types, funcform->proargtypes.values,
                   funcform->pronargs * sizeof(Oid));
        rettype = enforce_generic_type_consistency(actual_arg_types,
                                                                                           declared_arg_types,
                                                                                           nargs,
                                                                                           funcform->prorettype,
                                                                                           false);
        /* let's just check we got the same answer as the parser did ... */
        if (rettype != result_type)
                elog(ERROR, "function's resolved result type changed during planning");

        /* perform any necessary typecasting of arguments */
        make_fn_arguments(NULL, args, actual_arg_types, declared_arg_types);
}

/*
 * 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.
 *
 * 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 ||
                !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;
        Oid                     func_oid;
        HeapTuple       func_tuple;
        Form_pg_proc funcform;
        Oid                *argtypes;
        char       *src;
        Datum           tmp;
        bool            isNull;
        bool            modifyTargetList;
        MemoryContext oldcxt;
        MemoryContext mycxt;
        List       *saveInvalItems;
        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;
        func_oid = fexpr->funcid;

        /*
         * The function must be declared to return a set, else inlining would
         * change the results if the contained SELECT didn't return exactly one
         * row.
         */
        if (!fexpr->funcretset)
                return NULL;

        /*
         * Refuse to inline if the arguments contain any volatile functions or
         * sub-selects.  Volatile functions are rejected because inlining may
         * result in the arguments being evaluated multiple times, risking a
         * change in behavior.  Sub-selects are rejected partly for implementation
         * reasons (pushing them down another level might change their behavior)
         * and partly because they're likely to be expensive and so multiple
         * evaluation would be bad.
         */
        if (contain_volatile_functions((Node *) fexpr->args) ||
                contain_subplans((Node *) fexpr->args))
                return NULL;

        /* Check permission to call function (fail later, if not) */
        if (pg_proc_aclcheck(func_oid, GetUserId(), ACL_EXECUTE) != ACLCHECK_OK)
                return NULL;

        /*
         * OK, let's take a look at the function's pg_proc entry.
         */
        func_tuple = SearchSysCache1(PROCOID, ObjectIdGetDatum(func_oid));
        if (!HeapTupleIsValid(func_tuple))
                elog(ERROR, "cache lookup failed for function %u", func_oid);
        funcform = (Form_pg_proc) GETSTRUCT(func_tuple);

        /*
         * Forget it if the function is not SQL-language or has other showstopper
         * properties.  In particular it mustn't be declared STRICT, since we
         * couldn't enforce that.  It also mustn't be VOLATILE, because that is
         * supposed to cause it to be executed with its own snapshot, rather than
         * sharing the snapshot of the calling query.  (Rechecking proretset is
         * just paranoia.)
         */
        if (funcform->prolang != SQLlanguageId ||
                funcform->proisstrict ||
                funcform->provolatile == PROVOLATILE_VOLATILE ||
                funcform->prosecdef ||
                !funcform->proretset ||
                !heap_attisnull(func_tuple, Anum_pg_proc_proconfig))
        {
                ReleaseSysCache(func_tuple);
                return NULL;
        }

        /*
         * Make a temporary memory context, so that we don't leak all the stuff
         * that parsing might create.
         */
        mycxt = AllocSetContextCreate(CurrentMemoryContext,
                                                                  "inline_set_returning_function",
                                                                  ALLOCSET_DEFAULT_MINSIZE,
                                                                  ALLOCSET_DEFAULT_INITSIZE,
                                                                  ALLOCSET_DEFAULT_MAXSIZE);
        oldcxt = MemoryContextSwitchTo(mycxt);

        /*
         * When we call eval_const_expressions below, it might try to add items
         * to root->glob->invalItems.  Since it is running in the temp context,
         * those items will be in that context, and will need to be copied out
         * if we're successful.  Temporarily reset the list so that we can keep
         * those items separate from the pre-existing list contents.
         */
        saveInvalItems = root->glob->invalItems;
        root->glob->invalItems = NIL;

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

        /*
         * Setup error traceback support for ereport().  This is so that we can
         * finger the function that bad information came from.
         */
        callback_arg.proname = NameStr(funcform->proname);
        callback_arg.prosrc = src;

        sqlerrcontext.callback = sql_inline_error_callback;
        sqlerrcontext.arg = (void *) &callback_arg;
        sqlerrcontext.previous = error_context_stack;
        error_context_stack = &sqlerrcontext;

        /*
         * Run eval_const_expressions on the function call.  This is necessary to
         * ensure that named-argument notation is converted to positional notation
         * and any default arguments are inserted.      It's a bit of overkill for the
         * arguments, since they'll get processed again later, but no harm will be
         * done.
         */
        fexpr = (FuncExpr *) eval_const_expressions(root, (Node *) fexpr);

        /* It should still be a call of the same function, but let's check */
        if (!IsA(fexpr, FuncExpr) ||
                fexpr->funcid != func_oid)
                goto fail;

        /* Arg list length should now match the function */
        if (list_length(fexpr->args) != funcform->pronargs)
                goto fail;

        /* 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(func_oid, fexpr->funcresulttype,
                                                         querytree_list,
                                                         &modifyTargetList, NULL) &&
                (get_typtype(fexpr->funcresulttype) == TYPTYPE_COMPOSITE ||
                 fexpr->funcresulttype == RECORDOID))
                goto fail;                              /* reject not-whole-tuple-result cases */

        /*
         * If we had to modify the tlist to make it match, and the statement is
         * one in which changing the tlist contents could change semantics, we
         * have to punt and not inline.
         */
        if (modifyTargetList)
                goto fail;

        /*
         * If it returns RECORD, we have to check against the column type list
         * provided in the RTE; check_sql_fn_retval can't do that.  (If no match,
         * we just fail to inline, rather than complaining; see notes for
         * tlist_matches_coltypelist.)
         */
        if (fexpr->funcresulttype == RECORDOID &&
                !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);

        /* copy up any new invalItems, too */
        root->glob->invalItems = list_concat(saveInvalItems,
                                                                                 copyObject(root->glob->invalItems));

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

        /*
         * 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, func_oid);

        return querytree;

        /* Here if func is not inlinable: release temp memory and return NULL */
fail:
        MemoryContextSwitchTo(oldcxt);
        root->glob->invalItems = saveInvalItems;
        MemoryContextDelete(mycxt);
        error_context_stack = sqlerrcontext.previous;
        ReleaseSysCache(func_tuple);

        return NULL;
}

/*
 * Replace Param nodes by appropriate actual parameters
 *
 * This is just enough different from substitute_actual_parameters()
 * that it needs its own code.
 */
static Query *
substitute_actual_srf_parameters(Query *expr, int nargs, List *args)
{
        substitute_actual_srf_parameters_context context;

        context.nargs = nargs;
        context.args = args;
        context.sublevels_up = 1;

        return query_tree_mutator(expr,
                                                          substitute_actual_srf_parameters_mutator,
                                                          &context,
                                                          0);
}

static Node *
substitute_actual_srf_parameters_mutator(Node *node,
                                                   substitute_actual_srf_parameters_context *context)
{
        Node       *result;

        if (node == NULL)
                return NULL;
        if (IsA(node, Query))
        {
                context->sublevels_up++;
                result = (Node *) query_tree_mutator((Query *) node,
                                                                        substitute_actual_srf_parameters_mutator,
                                                                                         (void *) context,
                                                                                         0);
                context->sublevels_up--;
                return result;
        }
        if (IsA(node, Param))
        {
                Param      *param = (Param *) node;

                if (param->paramkind == PARAM_EXTERN)
                {
                        if (param->paramid <= 0 || param->paramid > context->nargs)
                                elog(ERROR, "invalid paramid: %d", param->paramid);

                        /*
                         * Since the parameter is being inserted into a subquery, we must
                         * adjust levels.
                         */
                        result = copyObject(list_nth(context->args, param->paramid - 1));
                        IncrementVarSublevelsUp(result, context->sublevels_up, 0);
                        return result;
                }
        }
        return expression_tree_mutator(node,
                                                                   substitute_actual_srf_parameters_mutator,
                                                                   (void *) context);
}

/*
 * 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;
}