1996-07-09 08:22:35 +02:00
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/*-------------------------------------------------------------------------
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*
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1999-02-14 00:22:53 +01:00
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* datum.c
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2000-07-12 04:37:39 +02:00
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* POSTGRES Datum (abstract data type) manipulation routines.
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1996-07-09 08:22:35 +02:00
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*
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2001-01-24 20:43:33 +01:00
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* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
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2000-01-26 06:58:53 +01:00
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* Portions Copyright (c) 1994, Regents of the University of California
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1996-07-09 08:22:35 +02:00
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*
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*
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* IDENTIFICATION
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2001-01-24 20:43:33 +01:00
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* $Header: /cvsroot/pgsql/src/backend/utils/adt/datum.c,v 1.19 2001/01/24 19:43:13 momjian Exp $
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1996-07-09 08:22:35 +02:00
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*
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*-------------------------------------------------------------------------
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*/
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/*
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* In the implementation of the next routines we assume the following:
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*
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* A) if a type is "byVal" then all the information is stored in the
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* Datum itself (i.e. no pointers involved!). In this case the
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2000-07-12 04:37:39 +02:00
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* length of the type is always greater than zero and not more than
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1996-07-09 08:22:35 +02:00
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* "sizeof(Datum)"
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* B) if a type is not "byVal" and it has a fixed length, then
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* the "Datum" always contain a pointer to a stream of bytes.
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* The number of significant bytes are always equal to the length of the
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* type.
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* C) if a type is not "byVal" and is of variable length (i.e. it has
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* length == -1) then "Datum" always points to a "struct varlena".
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* This varlena structure has information about the actual length of this
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* particular instance of the type and about its value.
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*
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2000-07-12 04:37:39 +02:00
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* Note that we do not treat "toasted" datums specially; therefore what
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* will be copied or compared is the compressed data or toast reference.
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1996-07-09 08:22:35 +02:00
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*/
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2000-07-12 04:37:39 +02:00
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1996-07-09 08:22:35 +02:00
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#include "postgres.h"
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2000-07-12 04:37:39 +02:00
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1996-07-09 08:22:35 +02:00
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#include "utils/datum.h"
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/*-------------------------------------------------------------------------
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* datumGetSize
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*
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* Find the "real" size of a datum, given the datum value,
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2000-07-12 04:37:39 +02:00
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* whether it is a "by value", and its length.
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1996-07-09 08:22:35 +02:00
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*
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* To cut a long story short, usually the real size is equal to the
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* type length, with the exception of variable length types which have
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* a length equal to -1. In this case, we have to look at the value of
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* the datum itself (which is a pointer to a 'varlena' struct) to find
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* its size.
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*-------------------------------------------------------------------------
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*/
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Size
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2000-07-12 04:37:39 +02:00
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datumGetSize(Datum value, bool typByVal, int typLen)
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1996-07-09 08:22:35 +02:00
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{
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2000-07-12 04:37:39 +02:00
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Size size;
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1997-09-07 07:04:48 +02:00
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2000-07-12 04:37:39 +02:00
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if (typByVal)
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1997-09-07 07:04:48 +02:00
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{
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2000-07-12 04:37:39 +02:00
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/* Pass-by-value types are always fixed-length */
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Assert(typLen > 0 && typLen <= sizeof(Datum));
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size = (Size) typLen;
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1996-07-09 08:22:35 +02:00
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}
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1997-09-07 07:04:48 +02:00
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else
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2000-07-12 04:37:39 +02:00
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{
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if (typLen == -1)
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1997-09-07 07:04:48 +02:00
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{
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2000-07-12 04:37:39 +02:00
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/* Assume it is a varlena datatype */
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struct varlena *s = (struct varlena *) DatumGetPointer(value);
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1997-09-07 07:04:48 +02:00
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if (!PointerIsValid(s))
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2000-07-12 04:37:39 +02:00
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elog(ERROR, "datumGetSize: Invalid Datum Pointer");
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1997-09-07 07:04:48 +02:00
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size = (Size) VARSIZE(s);
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}
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else
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{
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2000-07-12 04:37:39 +02:00
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/* Fixed-length pass-by-ref type */
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size = (Size) typLen;
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1997-09-07 07:04:48 +02:00
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}
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1996-07-09 08:22:35 +02:00
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}
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1997-09-07 07:04:48 +02:00
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1998-09-01 05:29:17 +02:00
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return size;
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1996-07-09 08:22:35 +02:00
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}
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/*-------------------------------------------------------------------------
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* datumCopy
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*
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* make a copy of a datum
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*
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2000-07-12 04:37:39 +02:00
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* If the datatype is pass-by-reference, memory is obtained with palloc().
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1996-07-09 08:22:35 +02:00
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*-------------------------------------------------------------------------
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*/
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Datum
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2000-07-12 04:37:39 +02:00
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datumCopy(Datum value, bool typByVal, int typLen)
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1996-07-09 08:22:35 +02:00
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{
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1997-09-08 04:41:22 +02:00
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Datum res;
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1997-09-07 07:04:48 +02:00
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2000-07-12 04:37:39 +02:00
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if (typByVal)
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1997-09-07 07:04:48 +02:00
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res = value;
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else
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{
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2000-07-12 04:37:39 +02:00
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Size realSize;
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char *s;
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if (DatumGetPointer(value) == NULL)
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return PointerGetDatum(NULL);
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realSize = datumGetSize(value, typByVal, typLen);
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1997-09-07 07:04:48 +02:00
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s = (char *) palloc(realSize);
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2000-07-12 04:37:39 +02:00
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memcpy(s, DatumGetPointer(value), realSize);
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res = PointerGetDatum(s);
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1997-09-07 07:04:48 +02:00
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}
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1998-09-01 05:29:17 +02:00
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return res;
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1996-07-09 08:22:35 +02:00
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}
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/*-------------------------------------------------------------------------
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* datumFree
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*
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* Free the space occupied by a datum CREATED BY "datumCopy"
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*
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* NOTE: DO NOT USE THIS ROUTINE with datums returned by amgetattr() etc.
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* ONLY datums created by "datumCopy" can be freed!
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*-------------------------------------------------------------------------
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*/
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1997-08-19 23:40:56 +02:00
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#ifdef NOT_USED
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1996-07-09 08:22:35 +02:00
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void
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2000-07-12 04:37:39 +02:00
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datumFree(Datum value, bool typByVal, int typLen)
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1996-07-09 08:22:35 +02:00
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{
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2000-07-12 04:37:39 +02:00
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if (!typByVal)
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1997-09-07 07:04:48 +02:00
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{
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2000-07-12 04:37:39 +02:00
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Pointer s = DatumGetPointer(value);
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1997-09-07 07:04:48 +02:00
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pfree(s);
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}
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1996-07-09 08:22:35 +02:00
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}
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1997-09-07 07:04:48 +02:00
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1997-08-19 23:40:56 +02:00
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#endif
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1996-07-09 08:22:35 +02:00
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/*-------------------------------------------------------------------------
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* datumIsEqual
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*
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* Return true if two datums are equal, false otherwise
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*
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* NOTE: XXX!
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* We just compare the bytes of the two values, one by one.
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* This routine will return false if there are 2 different
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* representations of the same value (something along the lines
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* of say the representation of zero in one's complement arithmetic).
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2000-07-12 04:37:39 +02:00
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* Also, it will probably not give the answer you want if either
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* datum has been "toasted".
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1996-07-09 08:22:35 +02:00
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*-------------------------------------------------------------------------
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*/
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bool
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2000-07-12 04:37:39 +02:00
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datumIsEqual(Datum value1, Datum value2, bool typByVal, int typLen)
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1996-07-09 08:22:35 +02:00
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{
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2000-07-12 04:37:39 +02:00
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bool res;
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1997-09-07 07:04:48 +02:00
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2000-07-12 04:37:39 +02:00
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if (typByVal)
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1997-09-07 07:04:48 +02:00
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{
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/*
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* just compare the two datums. NOTE: just comparing "len" bytes
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* will not do the work, because we do not know how these bytes
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* are aligned inside the "Datum".
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*/
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2000-07-12 04:37:39 +02:00
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res = (value1 == value2);
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1997-09-07 07:04:48 +02:00
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}
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1996-07-09 08:22:35 +02:00
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else
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1997-09-07 07:04:48 +02:00
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{
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2000-07-12 04:37:39 +02:00
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Size size1,
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size2;
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char *s1,
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*s2;
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1996-07-09 08:22:35 +02:00
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1997-09-07 07:04:48 +02:00
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/*
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2000-07-12 04:37:39 +02:00
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* Compare the bytes pointed by the pointers stored in the datums.
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1997-09-07 07:04:48 +02:00
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*/
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2000-07-12 04:37:39 +02:00
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size1 = datumGetSize(value1, typByVal, typLen);
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size2 = datumGetSize(value2, typByVal, typLen);
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1997-09-07 07:04:48 +02:00
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if (size1 != size2)
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1998-09-01 05:29:17 +02:00
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return false;
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1997-09-07 07:04:48 +02:00
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s1 = (char *) DatumGetPointer(value1);
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s2 = (char *) DatumGetPointer(value2);
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2000-07-12 04:37:39 +02:00
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res = (memcmp(s1, s2, size1) == 0);
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1997-09-07 07:04:48 +02:00
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}
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2000-07-12 04:37:39 +02:00
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return res;
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1997-09-07 07:04:48 +02:00
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}
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