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Code

Improve comments for xlog item size #defines.

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This commit is contained in:
Tom Lane 2001-03-25 22:40:58 +00:00
parent 5fb00d424a
commit 571dbe4606
1 changed files with 11 additions and 4 deletions
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15
src/include/access/htup.h
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California * Portions Copyright (c) 1994, Regents of the University of California
* *
* $Id: htup.h,v 1.47 2001/03/22 04:00:27 momjian Exp $ * $Id: htup.h,v 1.48 2001/03/25 22:40:58 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -83,6 +83,11 @@ typedef HeapTupleHeaderData *HeapTupleHeader;
/* /*
* All what we need to find changed tuple (18 bytes) * All what we need to find changed tuple (18 bytes)
*
* NB: on most machines, sizeof(xl_heaptid) will include some trailing pad
* bytes for alignment. We don't want to store the pad space in the XLOG,
* so use SizeOfHeapTid for space calculations. Similar comments apply for
* the other xl_FOO structs.
*/ */
typedef struct xl_heaptid typedef struct xl_heaptid
{ {
@ -90,13 +95,15 @@ typedef struct xl_heaptid
ItemPointerData tid; /* changed tuple id */ ItemPointerData tid; /* changed tuple id */
} xl_heaptid; } xl_heaptid;
#define SizeOfHeapTid (offsetof(xl_heaptid, tid) + SizeOfIptrData)
/* This is what we need to know about delete */ /* This is what we need to know about delete */
typedef struct xl_heap_delete typedef struct xl_heap_delete
{ {
xl_heaptid target; /* deleted tuple id */ xl_heaptid target; /* deleted tuple id */
} xl_heap_delete; } xl_heap_delete;
#define SizeOfHeapDelete (offsetof(xl_heaptid, tid) + SizeOfIptrData) #define SizeOfHeapDelete (offsetof(xl_heap_delete, target) + SizeOfHeapTid)
typedef struct xl_heap_header typedef struct xl_heap_header
{ {
@ -115,14 +122,14 @@ typedef struct xl_heap_insert
/* xl_heap_header & TUPLE DATA FOLLOWS AT END OF STRUCT */ /* xl_heap_header & TUPLE DATA FOLLOWS AT END OF STRUCT */
} xl_heap_insert; } xl_heap_insert;
#define SizeOfHeapInsert (offsetof(xl_heaptid, tid) + SizeOfIptrData) #define SizeOfHeapInsert (offsetof(xl_heap_insert, target) + SizeOfHeapTid)
/* This is what we need to know about update|move */ /* This is what we need to know about update|move */
typedef struct xl_heap_update typedef struct xl_heap_update
{ {
xl_heaptid target; /* deleted tuple id */ xl_heaptid target; /* deleted tuple id */
ItemPointerData newtid; /* new inserted tuple id */ ItemPointerData newtid; /* new inserted tuple id */
/* NEW TUPLE xl_heap_header (XMIN & XMAX FOR MOVE OP) */ /* NEW TUPLE xl_heap_header (PLUS xmax & xmin IF MOVE OP) */
/* and TUPLE DATA FOLLOWS AT END OF STRUCT */ /* and TUPLE DATA FOLLOWS AT END OF STRUCT */
} xl_heap_update; } xl_heap_update;