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Arrange to recycle old XLOG log segment files as new segment files,

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rather than deleting them only to have to create more.  Steady state
is 2*CHECKPOINT_SEGMENTS + WAL_FILES + 1 segment files, which will
simply be renamed rather than constantly deleted and recreated.
To make this safe, added current XLOG file/offset number to page
header of XLOG pages, so that an un-overwritten page from an old
incarnation of a logfile can be reliably told from a valid page.
This change means that if you try to restart postmaster in a CVS-tip
database after installing the change, you'll get a complaint about
bad XLOG page magic number.  If you don't want to initdb, run
contrib/pg_resetxlog (and be sure you shut down the old postmaster
cleanly).
This commit is contained in:
Tom Lane
2001-07-19 02:12:35 +00:00
parent 8b77efdded
commit 7d4d5c00f0
3 changed files with 209 additions and 84 deletions
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5
src/include/access/xlog.h
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@@ -6,7 +6,7 @@
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $Id: xlog.h,v 1.23 2001/03/22 04:00:32 momjian Exp $
* $Id: xlog.h,v 1.24 2001/07/19 02:12:35 tgl Exp $
*/
#ifndef XLOG_H
#define XLOG_H
@@ -109,13 +109,14 @@ typedef struct XLogContRecord
/*
* Each page of XLOG file has a header like this:
*/
#define XLOG_PAGE_MAGIC 0xD058 /* can be used as WAL version indicator */
#define XLOG_PAGE_MAGIC 0xD059 /* can be used as WAL version indicator */
typedef struct XLogPageHeaderData
{
uint16 xlp_magic; /* magic value for correctness checks */
uint16 xlp_info; /* flag bits, see below */
StartUpID xlp_sui; /* StartUpID of first record on page */
XLogRecPtr xlp_pageaddr; /* XLOG address of this page */
} XLogPageHeaderData;
#define SizeOfXLogPHD MAXALIGN(sizeof(XLogPageHeaderData))