From 87d95ca04d0b794c2ba49f40f6a2ee1d94835cac Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sat, 1 May 1999 19:09:46 +0000
Subject: [PATCH] Arrange for VACUUM to delete the init file that relcache.c
uses to save a little bit of backend startup time. This way, the first
backend started after a VACUUM will rebuild the init file with up-to-date
statistics for the critical system indexes.
---
src/backend/commands/vacuum.c | 18 +++++++++++++--
src/backend/utils/cache/relcache.c | 35 +++++++++++++++---------------
src/include/utils/relcache.h | 8 ++++++-
3 files changed, 41 insertions(+), 20 deletions(-)
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index dcb3365a7ba..757580ccbe8 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.99 1999/04/12 16:56:36 vadim Exp $
+ * $Header: /cvsroot/pgsql/src/backend/commands/vacuum.c,v 1.100 1999/05/01 19:09:46 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -46,6 +46,7 @@
#include "utils/inval.h"
#include "utils/mcxt.h"
#include "utils/portal.h"
+#include "utils/relcache.h"
#include "utils/syscache.h"
#ifndef HAVE_GETRUSAGE
@@ -219,7 +220,20 @@ vc_init()
static void
vc_shutdown()
{
- /* on entry, not in a transaction */
+ /* on entry, we are not in a transaction */
+
+ /* Flush the init file that relcache.c uses to save startup time.
+ * The next backend startup will rebuild the init file with up-to-date
+ * information from pg_class. This lets the optimizer see the stats that
+ * we've collected for certain critical system indexes. See relcache.c
+ * for more details.
+ *
+ * Ignore any failure to unlink the file, since it might not be there
+ * if no backend has been started since the last vacuum...
+ */
+ unlink(RELCACHE_INIT_FILENAME);
+
+ /* remove the vacuum cleaner lock file */
if (unlink("pg_vlock") < 0)
elog(ERROR, "vacuum: can't destroy lock file!");
diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c
index 464d94021a6..38edc3a790a 100644
--- a/src/backend/utils/cache/relcache.c
+++ b/src/backend/utils/cache/relcache.c
@@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/utils/cache/relcache.c,v 1.59 1999/02/21 03:49:36 scrappy Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/cache/relcache.c,v 1.60 1999/05/01 19:09:44 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -77,7 +77,6 @@
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/relcache.h"
-#include "utils/relcache.h"
#include "utils/syscache.h"
@@ -87,13 +86,6 @@ static Relation RelationNameCacheGetRelation(char *relationName);
static void init_irels(void);
static void write_irels(void);
-/* ----------------
- * defines
- * ----------------
- */
-#define private static
-#define INIT_FILENAME "pg_internal.init"
-
/* ----------------
* externs
* ----------------
@@ -1826,11 +1818,20 @@ RelCheckFetch(Relation relation)
* from an initialization file in the data/base/... directory.
*
* + If the initialization file isn't there, then we create the
- * relation descriptor using sequential scans and write it to
+ * relation descriptors using sequential scans and write 'em to
* the initialization file for use by subsequent backends.
*
- * This is complicated and interferes with system changes, but
- * performance is so bad that we're willing to pay the tax.
+ * We could dispense with the initialization file and just build the
+ * critical reldescs the hard way on every backend startup, but that
+ * slows down backend startup noticeably if pg_class is large.
+ *
+ * As of v6.5, vacuum.c deletes the initialization file at completion
+ * of a VACUUM, so that it will be rebuilt at the next backend startup.
+ * This ensures that vacuum-collected stats for the system indexes
+ * will eventually get used by the optimizer --- otherwise the relcache
+ * entries for these indexes will show zero sizes forever, since the
+ * relcache entries are pinned in memory and will never be reloaded
+ * from pg_class.
*/
/* pg_attnumind, pg_classnameind, pg_classoidind */
@@ -1852,9 +1853,9 @@ init_irels(void)
int relno;
#ifndef __CYGWIN32__
- if ((fd = FileNameOpenFile(INIT_FILENAME, O_RDONLY, 0600)) < 0)
+ if ((fd = FileNameOpenFile(RELCACHE_INIT_FILENAME, O_RDONLY, 0600)) < 0)
#else
- if ((fd = FileNameOpenFile(INIT_FILENAME, O_RDONLY | O_BINARY, 0600)) < 0)
+ if ((fd = FileNameOpenFile(RELCACHE_INIT_FILENAME, O_RDONLY | O_BINARY, 0600)) < 0)
#endif
{
write_irels();
@@ -2017,12 +2018,12 @@ write_irels(void)
RelationBuildDescInfo bi;
#ifndef __CYGWIN32__
- fd = FileNameOpenFile(INIT_FILENAME, O_WRONLY | O_CREAT | O_TRUNC, 0600);
+ fd = FileNameOpenFile(RELCACHE_INIT_FILENAME, O_WRONLY | O_CREAT | O_TRUNC, 0600);
#else
- fd = FileNameOpenFile(INIT_FILENAME, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, 0600);
+ fd = FileNameOpenFile(RELCACHE_INIT_FILENAME, O_WRONLY | O_CREAT | O_TRUNC | O_BINARY, 0600);
#endif
if (fd < 0)
- elog(FATAL, "cannot create init file %s", INIT_FILENAME);
+ elog(FATAL, "cannot create init file %s", RELCACHE_INIT_FILENAME);
FileSeek(fd, 0L, SEEK_SET);
diff --git a/src/include/utils/relcache.h b/src/include/utils/relcache.h
index d5f63f3af31..d95a9a27fe3 100644
--- a/src/include/utils/relcache.h
+++ b/src/include/utils/relcache.h
@@ -6,7 +6,7 @@
*
* Copyright (c) 1994, Regents of the University of California
*
- * $Id: relcache.h,v 1.11 1999/02/13 23:22:31 momjian Exp $
+ * $Id: relcache.h,v 1.12 1999/05/01 19:09:43 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -34,4 +34,10 @@ extern void RelationRegisterRelation(Relation relation);
extern void RelationPurgeLocalRelation(bool xactComitted);
extern void RelationInitialize(void);
+/*
+ * both vacuum.c and relcache.c need to know the name of the relcache init file
+ */
+
+#define RELCACHE_INIT_FILENAME "pg_internal.init"
+
#endif /* RELCACHE_H */
--
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