copyfuncs.c

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/*-------------------------------------------------------------------------
 *
 * copyfuncs.c
 *    Copy functions for Postgres tree nodes.
 *
 *
 * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/nodes/copyfuncs.c
 *
 *-------------------------------------------------------------------------
 */
 
#include "postgres.h"
 
#include "miscadmin.h"
#include "utils/datum.h"
 
 
/*
 * Macros to simplify copying 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 a Copy routine are
 * named 'newnode' and 'from'.
 */
 
/* Copy a simple scalar field (int, float, bool, enum, etc) */
#define COPY_SCALAR_FIELD(fldname) \
    (newnode->fldname = from->fldname)
 
/* Copy a field that is a pointer to some kind of Node or Node tree */
#define COPY_NODE_FIELD(fldname) \
    (newnode->fldname = copyObjectImpl(from->fldname))
 
/* Copy a field that is a pointer to a Bitmapset */
#define COPY_BITMAPSET_FIELD(fldname) \
    (newnode->fldname = bms_copy(from->fldname))
 
/* Copy a field that is a pointer to a C string, or perhaps NULL */
#define COPY_STRING_FIELD(fldname) \
    (newnode->fldname = from->fldname ? pstrdup(from->fldname) : NULL)
 
/* Copy a field that is an inline array */
#define COPY_ARRAY_FIELD(fldname) \
    memcpy(newnode->fldname, from->fldname, sizeof(newnode->fldname))
 
/* Copy a field that is a pointer to a simple palloc'd object of size sz */
#define COPY_POINTER_FIELD(fldname, sz) \
    do { \
        Size    _size = (sz); \
        if (_size > 0) \
        { \
            newnode->fldname = palloc(_size); \
            memcpy(newnode->fldname, from->fldname, _size); \
        } \
    } while (0)
 
/* Copy a parse location field (for Copy, this is same as scalar case) */
#define COPY_LOCATION_FIELD(fldname) \
    (newnode->fldname = from->fldname)
 
 
#include "copyfuncs.funcs.c"
 
 
/*
 * Support functions for nodes with custom_copy_equal attribute
 */
 
static Const *
_copyConst(const Const *from)
{
    Const      *newnode = makeNode(Const);
 
    COPY_SCALAR_FIELD(consttype);
    COPY_SCALAR_FIELD(consttypmod);
    COPY_SCALAR_FIELD(constcollid);
    COPY_SCALAR_FIELD(constlen);
 
    if (from->constbyval || from->constisnull)
    {
        /*
         * passed by value so just copy the datum. Also, don't try to copy
         * struct when value is null!
         */
        newnode->constvalue = from->constvalue;
    }
    else
    {
        /*
         * passed by reference.  We need a palloc'd copy.
         */
        newnode->constvalue = datumCopy(from->constvalue,
                                        from->constbyval,
                                        from->constlen);
    }
 
    COPY_SCALAR_FIELD(constisnull);
    COPY_SCALAR_FIELD(constbyval);
    COPY_LOCATION_FIELD(location);
 
    return newnode;
}
 
static A_Const *
_copyA_Const(const A_Const *from)
{
    A_Const    *newnode = makeNode(A_Const);
 
    COPY_SCALAR_FIELD(isnull);
    if (!from->isnull)
    {
        /* This part must duplicate other _copy*() functions. */
        COPY_SCALAR_FIELD(val.node.type);
        switch (nodeTag(&from->val))
        {
            case T_Integer:
                COPY_SCALAR_FIELD(val.ival.ival);
                break;
            case T_Float:
                COPY_STRING_FIELD(val.fval.fval);
                break;
            case T_Boolean:
                COPY_SCALAR_FIELD(val.boolval.boolval);
                break;
            case T_String:
                COPY_STRING_FIELD(val.sval.sval);
                break;
            case T_BitString:
                COPY_STRING_FIELD(val.bsval.bsval);
                break;
            default:
                elog(ERROR, "unrecognized node type: %d",
                     (int) nodeTag(&from->val));
                break;
        }
    }
 
    COPY_LOCATION_FIELD(location);
 
    return newnode;
}
 
static ExtensibleNode *
_copyExtensibleNode(const ExtensibleNode *from)
{
    ExtensibleNode *newnode;
    const ExtensibleNodeMethods *methods;
 
    methods = GetExtensibleNodeMethods(from->extnodename, false);
    newnode = (ExtensibleNode *) newNode(methods->node_size,
                                         T_ExtensibleNode);
    COPY_STRING_FIELD(extnodename);
 
    /* copy the private fields */
    methods->nodeCopy(newnode, from);
 
    return newnode;
}
 
static Bitmapset *
_copyBitmapset(const Bitmapset *from)
{
    return bms_copy(from);
}
 
 
/*
 * copyObjectImpl -- implementation of copyObject(); see nodes/nodes.h
 *
 * Create a copy of a Node tree or list.  This is a "deep" copy: all
 * substructure is copied too, recursively.
 */
void *
copyObjectImpl(const void *from)
{
    void       *retval;
 
    if (from == NULL)
        return NULL;
 
    /* Guard against stack overflow due to overly complex expressions */
    check_stack_depth();
 
    switch (nodeTag(from))
    {
#include "copyfuncs.switch.c"
 
        case T_List:
            retval = list_copy_deep(from);
            break;
 
            /*
             * Lists of integers, OIDs and XIDs don't need to be deep-copied,
             * so we perform a shallow copy via list_copy()
             */
        case T_IntList:
        case T_OidList:
        case T_XidList:
            retval = list_copy(from);
            break;
 
        default:
            elog(ERROR, "unrecognized node type: %d", (int) nodeTag(from));
            retval = 0;         /* keep compiler quiet */
            break;
    }
 
    return retval;
}