Move pgstat.tmp into a temporary directory under $PGDATA named pg_stat_tmp.

This allows the use of a ramdrive (either through mount or symlink) for
the temporary file that's written every half second, which should
reduce I/O.

On server shutdown/startup, the file is written to the old location in
the global directory, to preserve data across restarts.

Bump catversion since the $PGDATA directory layout changed.

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 0d56e39d6f470a1dd59003a463676f879696a351..29a3e1070304eebf3cec41993d4d4714b55e7a10 100644 (file)
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -1,4 +1,4 @@
-
+
 
 
  Monitoring Database Activity
@@ -164,6 +164,17 @@ postgres: user database host 
    only superusers are allowed to change these parameters with
    SET.)
   
+
+  
+   The statistics collector communicates with the backends needing 
+   information (including autovacuum) through temporary files.
+   These files are stored in the pg_stat_tmp subdirectory.
+   When the postmaster shuts down, a permanent copy of the statistics
+   data is stored in the global subdirectory. For increased
+   performance, it is possible to mount or symlink a RAM based
+   filesystem to the pg_stat_tmp directory.
+  
+
  
 
  

diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index 0303a2b3d4e5854d82bfb39320c88c5b04aa0271..e564fd2be9a06bf8963adfd86425109c8ca48a76 100644 (file)
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -1,4 +1,4 @@
-
+
 
 
 
@@ -77,6 +77,12 @@ Item
   (used for shared row locks) 
 
 
+
+ pg_stat_tmp
+ Subdirectory containing temporary files for the statistics
+  subsystem
+
+
 
  pg_subtrans
  Subdirectory containing subtransaction status data

diff --git a/src/backend/postmaster/pgstat.c b/src/backend/postmaster/pgstat.c
index d0e190aa44a6c6c8d3ec3fe92e3d2625c073ab77..f78e8840b2f39f9d901ceed94a685cd69e6845dc 100644 (file)
--- a/src/backend/postmaster/pgstat.c
+++ b/src/backend/postmaster/pgstat.c
@@ -13,7 +13,7 @@
  *
  * Copyright (c) 2001-2008, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.177 2008/08/01 13:16:08 alvherre Exp $
+ * $PostgreSQL: pgsql/src/backend/postmaster/pgstat.c,v 1.178 2008/08/05 12:09:30 mha Exp $
  * ----------
  */
 #include "postgres.h"
@@ -68,8 +68,10 @@
  * Paths for the statistics files (relative to installation's $PGDATA).
  * ----------
  */
-#define PGSTAT_STAT_FILENAME   "global/pgstat.stat"
-#define PGSTAT_STAT_TMPFILE        "global/pgstat.tmp"
+#define PGSTAT_STAT_PERMANENT_FILENAME     "global/pgstat.stat"
+#define PGSTAT_STAT_PERMANENT_TMPFILE      "global/pgstat.tmp"
+#define PGSTAT_STAT_FILENAME               "pg_stat_tmp/pgstat.stat"
+#define PGSTAT_STAT_TMPFILE                    "pg_stat_tmp/pgstat.tmp"
 
 /* ----------
  * Timer definitions.
@@ -219,8 +221,8 @@ static void force_statwrite(SIGNAL_ARGS);
 static void pgstat_beshutdown_hook(int code, Datum arg);
 
 static PgStat_StatDBEntry *pgstat_get_db_entry(Oid databaseid, bool create);
-static void pgstat_write_statsfile(void);
-static HTAB *pgstat_read_statsfile(Oid onlydb);
+static void pgstat_write_statsfile(bool permanent);
+static HTAB *pgstat_read_statsfile(Oid onlydb, bool permanent);
 static void backend_read_statsfile(void);
 static void pgstat_read_current_status(void);
 
@@ -510,6 +512,7 @@ void
 pgstat_reset_all(void)
 {
    unlink(PGSTAT_STAT_FILENAME);
+   unlink(PGSTAT_STAT_PERMANENT_FILENAME);
 }
 
 #ifdef EXEC_BACKEND
@@ -2598,7 +2601,7 @@ PgstatCollectorMain(int argc, char *argv[])
     * zero.
     */
    pgStatRunningInCollector = true;
-   pgStatDBHash = pgstat_read_statsfile(InvalidOid);
+   pgStatDBHash = pgstat_read_statsfile(InvalidOid, true);
 
    /*
     * Setup the descriptor set for select(2).  Since only one bit in the set
@@ -2638,7 +2641,7 @@ PgstatCollectorMain(int argc, char *argv[])
            if (!PostmasterIsAlive(true))
                break;
 
-           pgstat_write_statsfile();
+           pgstat_write_statsfile(false);
            need_statwrite = false;
            need_timer = true;
        }
@@ -2806,7 +2809,7 @@ PgstatCollectorMain(int argc, char *argv[])
    /*
     * Save the final stats to reuse at next startup.
     */
-   pgstat_write_statsfile();
+   pgstat_write_statsfile(true);
 
    exit(0);
 }
@@ -2891,10 +2894,14 @@ pgstat_get_db_entry(Oid databaseid, bool create)
  * pgstat_write_statsfile() -
  *
  * Tell the news.
+ * If writing to the permanent file (happens when the collector is
+ * shutting down only), remove the temporary file so that backends
+ * starting up under a new postmaster can't read the old data before
+ * the new collector is ready.
  * ----------
  */
 static void
-pgstat_write_statsfile(void)
+pgstat_write_statsfile(bool permanent)
 {
    HASH_SEQ_STATUS hstat;
    HASH_SEQ_STATUS tstat;
@@ -2904,17 +2911,19 @@ pgstat_write_statsfile(void)
    PgStat_StatFuncEntry *funcentry;
    FILE       *fpout;
    int32       format_id;
+   const char *tmpfile = permanent?PGSTAT_STAT_PERMANENT_TMPFILE:PGSTAT_STAT_TMPFILE;
+   const char *statfile = permanent?PGSTAT_STAT_PERMANENT_FILENAME:PGSTAT_STAT_FILENAME;
 
    /*
     * Open the statistics temp file to write out the current values.
     */
-   fpout = fopen(PGSTAT_STAT_TMPFILE, PG_BINARY_W);
+   fpout = fopen(tmpfile, PG_BINARY_W);
    if (fpout == NULL)
    {
        ereport(LOG,
                (errcode_for_file_access(),
                 errmsg("could not open temporary statistics file \"%s\": %m",
-                       PGSTAT_STAT_TMPFILE)));
+                       tmpfile)));
        return;
    }
 
@@ -2981,26 +2990,29 @@ pgstat_write_statsfile(void)
        ereport(LOG,
                (errcode_for_file_access(),
               errmsg("could not write temporary statistics file \"%s\": %m",
-                     PGSTAT_STAT_TMPFILE)));
+                     tmpfile)));
        fclose(fpout);
-       unlink(PGSTAT_STAT_TMPFILE);
+       unlink(tmpfile);
    }
    else if (fclose(fpout) < 0)
    {
        ereport(LOG,
                (errcode_for_file_access(),
               errmsg("could not close temporary statistics file \"%s\": %m",
-                     PGSTAT_STAT_TMPFILE)));
-       unlink(PGSTAT_STAT_TMPFILE);
+                     tmpfile)));
+       unlink(tmpfile);
    }
-   else if (rename(PGSTAT_STAT_TMPFILE, PGSTAT_STAT_FILENAME) < 0)
+   else if (rename(tmpfile, statfile) < 0)
    {
        ereport(LOG,
                (errcode_for_file_access(),
                 errmsg("could not rename temporary statistics file \"%s\" to \"%s\": %m",
-                       PGSTAT_STAT_TMPFILE, PGSTAT_STAT_FILENAME)));
-       unlink(PGSTAT_STAT_TMPFILE);
+                       tmpfile, statfile)));
+       unlink(tmpfile);
    }
+
+   if (permanent)
+       unlink(PGSTAT_STAT_FILENAME);
 }
 
 
@@ -3012,7 +3024,7 @@ pgstat_write_statsfile(void)
  * ----------
  */
 static HTAB *
-pgstat_read_statsfile(Oid onlydb)
+pgstat_read_statsfile(Oid onlydb, bool permanent)
 {
    PgStat_StatDBEntry *dbentry;
    PgStat_StatDBEntry dbbuf;
@@ -3027,6 +3039,7 @@ pgstat_read_statsfile(Oid onlydb)
    FILE       *fpin;
    int32       format_id;
    bool        found;
+   const char *statfile = permanent?PGSTAT_STAT_PERMANENT_FILENAME:PGSTAT_STAT_FILENAME;
 
    /*
     * The tables will live in pgStatLocalContext.
@@ -3055,7 +3068,7 @@ pgstat_read_statsfile(Oid onlydb)
     * return zero for anything and the collector simply starts from scratch
     * with empty counters.
     */
-   if ((fpin = AllocateFile(PGSTAT_STAT_FILENAME, PG_BINARY_R)) == NULL)
+   if ((fpin = AllocateFile(statfile, PG_BINARY_R)) == NULL)
        return dbhash;
 
    /*
@@ -3244,6 +3257,9 @@ pgstat_read_statsfile(Oid onlydb)
 done:
    FreeFile(fpin);
 
+   if (permanent)
+       unlink(PGSTAT_STAT_PERMANENT_FILENAME);
+
    return dbhash;
 }
 
@@ -3262,9 +3278,9 @@ backend_read_statsfile(void)
 
    /* Autovacuum launcher wants stats about all databases */
    if (IsAutoVacuumLauncherProcess())
-       pgStatDBHash = pgstat_read_statsfile(InvalidOid);
+       pgStatDBHash = pgstat_read_statsfile(InvalidOid, false);
    else
-       pgStatDBHash = pgstat_read_statsfile(MyDatabaseId);
+       pgStatDBHash = pgstat_read_statsfile(MyDatabaseId, false);
 }
 
 

diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index a7ef3c9227dd7dc9b9287e19919c991a2ee37a43..e305c69fa3c47bd01be892c9823561554dece264 100644 (file)
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -42,7 +42,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  * Portions taken from FreeBSD.
  *
- * $PostgreSQL: pgsql/src/bin/initdb/initdb.c,v 1.158 2008/07/19 04:01:29 tgl Exp $
+ * $PostgreSQL: pgsql/src/bin/initdb/initdb.c,v 1.159 2008/08/05 12:09:30 mha Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -2461,7 +2461,8 @@ main(int argc, char *argv[])
        "pg_multixact/offsets",
        "base",
        "base/1",
-       "pg_tblspc"
+       "pg_tblspc",
+       "pg_stat_tmp"
    };
 
    progname = get_progname(argv[0]);

diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
index 49d2a32431db929f0559b24a87f3779dfb41ee76..6be25b05f979444a6e9dcc0f2164630914044d2a 100644 (file)
--- a/src/include/catalog/catversion.h
+++ b/src/include/catalog/catversion.h
@@ -37,7 +37,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.474 2008/08/02 21:32:00 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/catalog/catversion.h,v 1.475 2008/08/05 12:09:30 mha Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -53,6 +53,6 @@
  */
 
 /*                         yyyymmddN */
-#define CATALOG_VERSION_NO 200808011
+#define CATALOG_VERSION_NO 200808051
 
 #endif