equalfuncs.c

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/*-------------------------------------------------------------------------
 *
 * equalfuncs.c
 *    Equality functions to compare node trees.
 *
 * NOTE: it is intentional that parse location fields (in nodes that have
 * one) are not compared.  This is because we want, for example, a variable
 * "x" to be considered equal() to another reference to "x" in the query.
 *
 *
 * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/nodes/equalfuncs.c
 *
 *-------------------------------------------------------------------------
 */
 
#include "postgres.h"
 
#include "miscadmin.h"
#include "utils/datum.h"
 
 
/*
 * Macros to simplify comparison of different kinds of fields.  Use these
 * wherever possible to reduce the chance for silly typos.  Note that these
 * hard-wire the convention that the local variables in an Equal routine are
 * named 'a' and 'b'.
 */
 
/* Compare a simple scalar field (int, float, bool, enum, etc) */
#define COMPARE_SCALAR_FIELD(fldname) \
    do { \
        if (a->fldname != b->fldname) \
            return false; \
    } while (0)
 
/* Compare a field that is a pointer to some kind of Node or Node tree */
#define COMPARE_NODE_FIELD(fldname) \
    do { \
        if (!equal(a->fldname, b->fldname)) \
            return false; \
    } while (0)
 
/* Compare a field that is a pointer to a Bitmapset */
#define COMPARE_BITMAPSET_FIELD(fldname) \
    do { \
        if (!bms_equal(a->fldname, b->fldname)) \
            return false; \
    } while (0)
 
/* Compare a field that is a pointer to a C string, or perhaps NULL */
#define COMPARE_STRING_FIELD(fldname) \
    do { \
        if (!equalstr(a->fldname, b->fldname)) \
            return false; \
    } while (0)
 
/* Macro for comparing string fields that might be NULL */
#define equalstr(a, b)  \
    (((a) != NULL && (b) != NULL) ? (strcmp(a, b) == 0) : (a) == (b))
 
/* Compare a field that is an inline array */
#define COMPARE_ARRAY_FIELD(fldname) \
    do { \
        if (memcmp(a->fldname, b->fldname, sizeof(a->fldname)) != 0) \
            return false; \
    } while (0)
 
/* Compare a field that is a pointer to a simple palloc'd object of size sz */
#define COMPARE_POINTER_FIELD(fldname, sz) \
    do { \
        if (memcmp(a->fldname, b->fldname, (sz)) != 0) \
            return false; \
    } while (0)
 
/* Compare a parse location field (this is a no-op, per note above) */
#define COMPARE_LOCATION_FIELD(fldname) \
    ((void) 0)
 
/* Compare a CoercionForm field (also a no-op, per comment in primnodes.h) */
#define COMPARE_COERCIONFORM_FIELD(fldname) \
    ((void) 0)
 
 
#include "equalfuncs.funcs.c"
 
 
/*
 * Support functions for nodes with custom_copy_equal attribute
 */
 
static bool
_equalConst(const Const *a, const Const *b)
{
    COMPARE_SCALAR_FIELD(consttype);
    COMPARE_SCALAR_FIELD(consttypmod);
    COMPARE_SCALAR_FIELD(constcollid);
    COMPARE_SCALAR_FIELD(constlen);
    COMPARE_SCALAR_FIELD(constisnull);
    COMPARE_SCALAR_FIELD(constbyval);
    COMPARE_LOCATION_FIELD(location);
 
    /*
     * We treat all NULL constants of the same type as equal. Someday this
     * might need to change?  But datumIsEqual doesn't work on nulls, so...
     */
    if (a->constisnull)
        return true;
    return datumIsEqual(a->constvalue, b->constvalue,
                        a->constbyval, a->constlen);
}
 
static bool
_equalExtensibleNode(const ExtensibleNode *a, const ExtensibleNode *b)
{
    const ExtensibleNodeMethods *methods;
 
    COMPARE_STRING_FIELD(extnodename);
 
    /* At this point, we know extnodename is the same for both nodes. */
    methods = GetExtensibleNodeMethods(a->extnodename, false);
 
    /* compare the private fields */
    if (!methods->nodeEqual(a, b))
        return false;
 
    return true;
}
 
static bool
_equalA_Const(const A_Const *a, const A_Const *b)
{
    /*
     * Hack for in-line val field.  Also val is not valid is isnull is true.
     */
    if (!a->isnull && !b->isnull &&
        !equal(&a->val, &b->val))
        return false;
    COMPARE_SCALAR_FIELD(isnull);
    COMPARE_LOCATION_FIELD(location);
 
    return true;
}
 
/*
 * Lists are handled specially
 */
static bool
_equalList(const List *a, const List *b)
{
    const ListCell *item_a;
    const ListCell *item_b;
 
    /*
     * Try to reject by simple scalar checks before grovelling through all the
     * list elements...
     */
    COMPARE_SCALAR_FIELD(type);
    COMPARE_SCALAR_FIELD(length);
 
    /*
     * We place the switch outside the loop for the sake of efficiency; this
     * may not be worth doing...
     */
    switch (a->type)
    {
        case T_List:
            forboth(item_a, a, item_b, b)
            {
                if (!equal(lfirst(item_a), lfirst(item_b)))
                    return false;
            }
            break;
        case T_IntList:
            forboth(item_a, a, item_b, b)
            {
                if (lfirst_int(item_a) != lfirst_int(item_b))
                    return false;
            }
            break;
        case T_OidList:
            forboth(item_a, a, item_b, b)
            {
                if (lfirst_oid(item_a) != lfirst_oid(item_b))
                    return false;
            }
            break;
        case T_XidList:
            forboth(item_a, a, item_b, b)
            {
                if (lfirst_xid(item_a) != lfirst_xid(item_b))
                    return false;
            }
            break;
        default:
            elog(ERROR, "unrecognized list node type: %d",
                 (int) a->type);
            return false;       /* keep compiler quiet */
    }
 
    /*
     * If we got here, we should have run out of elements of both lists
     */
    Assert(item_a == NULL);
    Assert(item_b == NULL);
 
    return true;
}
 
 
/*
 * equal
 *    returns whether two nodes are equal
 */
bool
equal(const void *a, const void *b)
{
    bool        retval;
 
    if (a == b)
        return true;
 
    /*
     * note that a!=b, so only one of them can be NULL
     */
    if (a == NULL || b == NULL)
        return false;
 
    /*
     * are they the same type of nodes?
     */
    if (nodeTag(a) != nodeTag(b))
        return false;
 
    /* Guard against stack overflow due to overly complex expressions */
    check_stack_depth();
 
    switch (nodeTag(a))
    {
#include "equalfuncs.switch.c"
 
        case T_List:
        case T_IntList:
        case T_OidList:
        case T_XidList:
            retval = _equalList(a, b);
            break;
 
        default:
            elog(ERROR, "unrecognized node type: %d",
                 (int) nodeTag(a));
            retval = false;     /* keep compiler quiet */
            break;
    }
 
    return retval;
}