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.

diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index dcb3365..757580c 100644 (file)
--- 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 464d940..38edc3a 100644 (file)
--- 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"
 
 
@@ -88,13 +87,6 @@ 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 d5f63f3..d95a9a2 100644 (file)
--- 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 */