prepqual.c File Reference

#include "postgres.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/optimizer.h"
#include "utils/lsyscache.h"

Include dependency graph for prepqual.c:

Go to the source code of this file.

Functions
static List *	pull_ands (List *andlist)
static List *	pull_ors (List *orlist)
static Expr *	find_duplicate_ors (Expr *qual, bool is_check)
static Expr *	process_duplicate_ors (List *orlist)
Node *	negate_clause (Node *node)
Expr *	canonicalize_qual (Expr *qual, bool is_check)

Function Documentation

canonicalize_qual()

Expr * canonicalize_qual	(	Expr *	qual,
		bool	is_check
	)

Definition at line 293 of file prepqual.c.

{
    Expr       *newqual;
 
    /* Quick exit for empty qual */
    if (qual == NULL)
        return NULL;
 
    /* This should not be invoked on quals in implicit-AND format */
    Assert(!IsA(qual, List));
 
    /*
     * Pull up redundant subclauses in OR-of-AND trees.  We do this only
     * within the top-level AND/OR structure; there's no point in looking
     * deeper.  Also remove any NULL constants in the top-level structure.
     */
    newqual = find_duplicate_ors(qual, is_check);
 
    return newqual;
}

References Assert(), find_duplicate_ors(), and IsA.

Referenced by ConstraintImpliedByRelConstraint(), convert_EXISTS_to_ANY(), DoCopy(), get_proposed_default_constraint(), get_relation_constraints(), preprocess_expression(), and RelationGetIndexPredicate().

find_duplicate_ors()

static Expr * find_duplicate_ors ( Expr *  qual, bool  is_check  )

static

Definition at line 406 of file prepqual.c.

{
    if (is_orclause(qual))
    {
        List       *orlist = NIL;
        ListCell   *temp;
 
        /* Recurse */
        foreach(temp, ((BoolExpr *) qual)->args)
        {
            Expr       *arg = (Expr *) lfirst(temp);
 
            arg = find_duplicate_ors(arg, is_check);
 
            /* Get rid of any constant inputs */
            if (arg && IsA(arg, Const))
            {
                Const      *carg = (Const *) arg;
 
                if (is_check)
                {
                    /* Within OR in CHECK, drop constant FALSE */
                    if (!carg->constisnull && !DatumGetBool(carg->constvalue))
                        continue;
                    /* Constant TRUE or NULL, so OR reduces to TRUE */
                    return (Expr *) makeBoolConst(true, false);
                }
                else
                {
                    /* Within OR in WHERE, drop constant FALSE or NULL */
                    if (carg->constisnull || !DatumGetBool(carg->constvalue))
                        continue;
                    /* Constant TRUE, so OR reduces to TRUE */
                    return arg;
                }
            }
 
            orlist = lappend(orlist, arg);
        }
 
        /* Flatten any ORs pulled up to just below here */
        orlist = pull_ors(orlist);
 
        /* Now we can look for duplicate ORs */
        return process_duplicate_ors(orlist);
    }
    else if (is_andclause(qual))
    {
        List       *andlist = NIL;
        ListCell   *temp;
 
        /* Recurse */
        foreach(temp, ((BoolExpr *) qual)->args)
        {
            Expr       *arg = (Expr *) lfirst(temp);
 
            arg = find_duplicate_ors(arg, is_check);
 
            /* Get rid of any constant inputs */
            if (arg && IsA(arg, Const))
            {
                Const      *carg = (Const *) arg;
 
                if (is_check)
                {
                    /* Within AND in CHECK, drop constant TRUE or NULL */
                    if (carg->constisnull || DatumGetBool(carg->constvalue))
                        continue;
                    /* Constant FALSE, so AND reduces to FALSE */
                    return arg;
                }
                else
                {
                    /* Within AND in WHERE, drop constant TRUE */
                    if (!carg->constisnull && DatumGetBool(carg->constvalue))
                        continue;
                    /* Constant FALSE or NULL, so AND reduces to FALSE */
                    return (Expr *) makeBoolConst(false, false);
                }
            }
 
            andlist = lappend(andlist, arg);
        }
 
        /* Flatten any ANDs introduced just below here */
        andlist = pull_ands(andlist);
 
        /* AND of no inputs reduces to TRUE */
        if (andlist == NIL)
            return (Expr *) makeBoolConst(true, false);
 
        /* Single-expression AND just reduces to that expression */
        if (list_length(andlist) == 1)
            return (Expr *) linitial(andlist);
 
        /* Else we still need an AND node */
        return make_andclause(andlist);
    }
    else
        return qual;
}

References arg, generate_unaccent_rules::args, DatumGetBool(), find_duplicate_ors(), is_andclause(), is_orclause(), IsA, lappend(), lfirst, linitial, list_length(), make_andclause(), makeBoolConst(), NIL, process_duplicate_ors(), pull_ands(), and pull_ors().

Referenced by canonicalize_qual(), and find_duplicate_ors().

negate_clause()

Node * negate_clause

(

Node *

node

)

Definition at line 73 of file prepqual.c.

{
    if (node == NULL)           /* should not happen */
        elog(ERROR, "can't negate an empty subexpression");
    switch (nodeTag(node))
    {
        case T_Const:
            {
                Const      *c = (Const *) node;
 
                /* NOT NULL is still NULL */
                if (c->constisnull)
                    return makeBoolConst(false, true);
                /* otherwise pretty easy */
                return makeBoolConst(!DatumGetBool(c->constvalue), false);
            }
            break;
        case T_OpExpr:
            {
                /*
                 * Negate operator if possible: (NOT (< A B)) => (>= A B)
                 */
                OpExpr     *opexpr = (OpExpr *) node;
                Oid         negator = get_negator(opexpr->opno);
 
                if (negator)
                {
                    OpExpr     *newopexpr = makeNode(OpExpr);
 
                    newopexpr->opno = negator;
                    newopexpr->opfuncid = InvalidOid;
                    newopexpr->opresulttype = opexpr->opresulttype;
                    newopexpr->opretset = opexpr->opretset;
                    newopexpr->opcollid = opexpr->opcollid;
                    newopexpr->inputcollid = opexpr->inputcollid;
                    newopexpr->args = opexpr->args;
                    newopexpr->location = opexpr->location;
                    return (Node *) newopexpr;
                }
            }
            break;
        case T_ScalarArrayOpExpr:
            {
                /*
                 * Negate a ScalarArrayOpExpr if its operator has a negator;
                 * for example x = ANY (list) becomes x <> ALL (list)
                 */
                ScalarArrayOpExpr *saopexpr = (ScalarArrayOpExpr *) node;
                Oid         negator = get_negator(saopexpr->opno);
 
                if (negator)
                {
                    ScalarArrayOpExpr *newopexpr = makeNode(ScalarArrayOpExpr);
 
                    newopexpr->opno = negator;
                    newopexpr->opfuncid = InvalidOid;
                    newopexpr->hashfuncid = InvalidOid;
                    newopexpr->negfuncid = InvalidOid;
                    newopexpr->useOr = !saopexpr->useOr;
                    newopexpr->inputcollid = saopexpr->inputcollid;
                    newopexpr->args = saopexpr->args;
                    newopexpr->location = saopexpr->location;
                    return (Node *) newopexpr;
                }
            }
            break;
        case T_BoolExpr:
            {
                BoolExpr   *expr = (BoolExpr *) node;
 
                switch (expr->boolop)
                {
                        /*--------------------
                         * Apply DeMorgan's Laws:
                         *      (NOT (AND A B)) => (OR (NOT A) (NOT B))
                         *      (NOT (OR A B))  => (AND (NOT A) (NOT B))
                         * i.e., swap AND for OR and negate each subclause.
                         *
                         * If the input is already AND/OR flat and has no NOT
                         * directly above AND or OR, this transformation preserves
                         * those properties.  For example, if no direct child of
                         * the given AND clause is an AND or a NOT-above-OR, then
                         * the recursive calls of negate_clause() can't return any
                         * OR clauses.  So we needn't call pull_ors() before
                         * building a new OR clause.  Similarly for the OR case.
                         *--------------------
                         */
                    case AND_EXPR:
                        {
                            List       *nargs = NIL;
                            ListCell   *lc;
 
                            foreach(lc, expr->args)
                            {
                                nargs = lappend(nargs,
                                                negate_clause(lfirst(lc)));
                            }
                            return (Node *) make_orclause(nargs);
                        }
                        break;
                    case OR_EXPR:
                        {
                            List       *nargs = NIL;
                            ListCell   *lc;
 
                            foreach(lc, expr->args)
                            {
                                nargs = lappend(nargs,
                                                negate_clause(lfirst(lc)));
                            }
                            return (Node *) make_andclause(nargs);
                        }
                        break;
                    case NOT_EXPR:
 
                        /*
                         * NOT underneath NOT: they cancel.  We assume the
                         * input is already simplified, so no need to recurse.
                         */
                        return (Node *) linitial(expr->args);
                    default:
                        elog(ERROR, "unrecognized boolop: %d",
                             (int) expr->boolop);
                        break;
                }
            }
            break;
        case T_NullTest:
            {
                NullTest   *expr = (NullTest *) node;
 
                /*
                 * In the rowtype case, the two flavors of NullTest are *not*
                 * logical inverses, so we can't simplify.  But it does work
                 * for scalar datatypes.
                 */
                if (!expr->argisrow)
                {
                    NullTest   *newexpr = makeNode(NullTest);
 
                    newexpr->arg = expr->arg;
                    newexpr->nulltesttype = (expr->nulltesttype == IS_NULL ?
                                             IS_NOT_NULL : IS_NULL);
                    newexpr->argisrow = expr->argisrow;
                    newexpr->location = expr->location;
                    return (Node *) newexpr;
                }
            }
            break;
        case T_BooleanTest:
            {
                BooleanTest *expr = (BooleanTest *) node;
                BooleanTest *newexpr = makeNode(BooleanTest);
 
                newexpr->arg = expr->arg;
                switch (expr->booltesttype)
                {
                    case IS_TRUE:
                        newexpr->booltesttype = IS_NOT_TRUE;
                        break;
                    case IS_NOT_TRUE:
                        newexpr->booltesttype = IS_TRUE;
                        break;
                    case IS_FALSE:
                        newexpr->booltesttype = IS_NOT_FALSE;
                        break;
                    case IS_NOT_FALSE:
                        newexpr->booltesttype = IS_FALSE;
                        break;
                    case IS_UNKNOWN:
                        newexpr->booltesttype = IS_NOT_UNKNOWN;
                        break;
                    case IS_NOT_UNKNOWN:
                        newexpr->booltesttype = IS_UNKNOWN;
                        break;
                    default:
                        elog(ERROR, "unrecognized booltesttype: %d",
                             (int) expr->booltesttype);
                        break;
                }
                newexpr->location = expr->location;
                return (Node *) newexpr;
            }
            break;
        default:
            /* else fall through */
            break;
    }
 
    /*
     * Otherwise we don't know how to simplify this, so just tack on an
     * explicit NOT node.
     */
    return (Node *) make_notclause((Expr *) node);
}

References AND_EXPR, NullTest::arg, BooleanTest::arg, OpExpr::args, ScalarArrayOpExpr::args, BoolExpr::args, BoolExpr::boolop, BooleanTest::booltesttype, DatumGetBool(), elog, ERROR, get_negator(), InvalidOid, IS_FALSE, IS_NOT_FALSE, IS_NOT_NULL, IS_NOT_TRUE, IS_NOT_UNKNOWN, IS_NULL, IS_TRUE, IS_UNKNOWN, lappend(), lfirst, linitial, OpExpr::location, ScalarArrayOpExpr::location, NullTest::location, BooleanTest::location, make_andclause(), make_notclause(), make_orclause(), makeBoolConst(), makeNode, negate_clause(), NIL, nodeTag, NOT_EXPR, NullTest::nulltesttype, OpExpr::opno, ScalarArrayOpExpr::opno, OR_EXPR, and ScalarArrayOpExpr::useOr.

Referenced by eval_const_expressions_mutator(), match_boolean_partition_clause(), negate_clause(), and simplify_boolean_equality().

process_duplicate_ors()

static Expr * process_duplicate_ors ( List *  orlist )

static

Definition at line 517 of file prepqual.c.

{
    List       *reference = NIL;
    int         num_subclauses = 0;
    List       *winners;
    List       *neworlist;
    ListCell   *temp;
 
    /* OR of no inputs reduces to FALSE */
    if (orlist == NIL)
        return (Expr *) makeBoolConst(false, false);
 
    /* Single-expression OR just reduces to that expression */
    if (list_length(orlist) == 1)
        return (Expr *) linitial(orlist);
 
    /*
     * Choose the shortest AND clause as the reference list --- obviously, any
     * subclause not in this clause isn't in all the clauses. If we find a
     * clause that's not an AND, we can treat it as a one-element AND clause,
     * which necessarily wins as shortest.
     */
    foreach(temp, orlist)
    {
        Expr       *clause = (Expr *) lfirst(temp);
 
        if (is_andclause(clause))
        {
            List       *subclauses = ((BoolExpr *) clause)->args;
            int         nclauses = list_length(subclauses);
 
            if (reference == NIL || nclauses < num_subclauses)
            {
                reference = subclauses;
                num_subclauses = nclauses;
            }
        }
        else
        {
            reference = list_make1(clause);
            break;
        }
    }
 
    /*
     * Just in case, eliminate any duplicates in the reference list.
     */
    reference = list_union(NIL, reference);
 
    /*
     * Check each element of the reference list to see if it's in all the OR
     * clauses.  Build a new list of winning clauses.
     */
    winners = NIL;
    foreach(temp, reference)
    {
        Expr       *refclause = (Expr *) lfirst(temp);
        bool        win = true;
        ListCell   *temp2;
 
        foreach(temp2, orlist)
        {
            Expr       *clause = (Expr *) lfirst(temp2);
 
            if (is_andclause(clause))
            {
                if (!list_member(((BoolExpr *) clause)->args, refclause))
                {
                    win = false;
                    break;
                }
            }
            else
            {
                if (!equal(refclause, clause))
                {
                    win = false;
                    break;
                }
            }
        }
 
        if (win)
            winners = lappend(winners, refclause);
    }
 
    /*
     * If no winners, we can't transform the OR
     */
    if (winners == NIL)
        return make_orclause(orlist);
 
    /*
     * Generate new OR list consisting of the remaining sub-clauses.
     *
     * If any clause degenerates to empty, then we have a situation like (A
     * AND B) OR (A), which can be reduced to just A --- that is, the
     * additional conditions in other arms of the OR are irrelevant.
     *
     * Note that because we use list_difference, any multiple occurrences of a
     * winning clause in an AND sub-clause will be removed automatically.
     */
    neworlist = NIL;
    foreach(temp, orlist)
    {
        Expr       *clause = (Expr *) lfirst(temp);
 
        if (is_andclause(clause))
        {
            List       *subclauses = ((BoolExpr *) clause)->args;
 
            subclauses = list_difference(subclauses, winners);
            if (subclauses != NIL)
            {
                if (list_length(subclauses) == 1)
                    neworlist = lappend(neworlist, linitial(subclauses));
                else
                    neworlist = lappend(neworlist, make_andclause(subclauses));
            }
            else
            {
                neworlist = NIL;    /* degenerate case, see above */
                break;
            }
        }
        else
        {
            if (!list_member(winners, clause))
                neworlist = lappend(neworlist, clause);
            else
            {
                neworlist = NIL;    /* degenerate case, see above */
                break;
            }
        }
    }
 
    /*
     * Append reduced OR to the winners list, if it's not degenerate, handling
     * the special case of one element correctly (can that really happen?).
     * Also be careful to maintain AND/OR flatness in case we pulled up a
     * sub-sub-OR-clause.
     */
    if (neworlist != NIL)
    {
        if (list_length(neworlist) == 1)
            winners = lappend(winners, linitial(neworlist));
        else
            winners = lappend(winners, make_orclause(pull_ors(neworlist)));
    }
 
    /*
     * And return the constructed AND clause, again being wary of a single
     * element and AND/OR flatness.
     */
    if (list_length(winners) == 1)
        return (Expr *) linitial(winners);
    else
        return make_andclause(pull_ands(winners));
}

References equal(), is_andclause(), lappend(), lfirst, linitial, list_difference(), list_length(), list_make1, list_member(), list_union(), make_andclause(), make_orclause(), makeBoolConst(), NIL, pull_ands(), and pull_ors().

Referenced by find_duplicate_ors().

pull_ands()

static List * pull_ands ( List *  andlist )

static

Definition at line 323 of file prepqual.c.

{
    List       *out_list = NIL;
    ListCell   *arg;
 
    foreach(arg, andlist)
    {
        Node       *subexpr = (Node *) lfirst(arg);
 
        if (is_andclause(subexpr))
            out_list = list_concat(out_list,
                                   pull_ands(((BoolExpr *) subexpr)->args));
        else
            out_list = lappend(out_list, subexpr);
    }
    return out_list;
}

References arg, generate_unaccent_rules::args, is_andclause(), lappend(), lfirst, list_concat(), NIL, and pull_ands().

Referenced by find_duplicate_ors(), process_duplicate_ors(), and pull_ands().

pull_ors()

static List * pull_ors ( List *  orlist )

static

Definition at line 349 of file prepqual.c.

{
    List       *out_list = NIL;
    ListCell   *arg;
 
    foreach(arg, orlist)
    {
        Node       *subexpr = (Node *) lfirst(arg);
 
        if (is_orclause(subexpr))
            out_list = list_concat(out_list,
                                   pull_ors(((BoolExpr *) subexpr)->args));
        else
            out_list = lappend(out_list, subexpr);
    }
    return out_list;
}

References arg, generate_unaccent_rules::args, is_orclause(), lappend(), lfirst, list_concat(), NIL, and pull_ors().

Referenced by find_duplicate_ors(), process_duplicate_ors(), and pull_ors().