From 70d756970b7b2e93e6f807f5c55e2ad7727e212a Mon Sep 17 00:00:00 2001
From: Magnus Hagander
Date: Tue, 5 Aug 2008 12:09:30 +0000
Subject: 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.
---
 doc/src/sgml/monitoring.sgml | 13 ++++++++++++-
 doc/src/sgml/storage.sgml    |  8 +++++++-
 2 files changed, 19 insertions(+), 2 deletions(-)

(limited to 'doc/src')

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 0d56e39d6f4..29a3e107030 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/monitoring.sgml,v 1.60 2008/06/18 17:44:12 neilc Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/monitoring.sgml,v 1.61 2008/08/05 12:09:30 mha Exp $ -->
 
 <chapter id="monitoring">
  <title>Monitoring Database Activity</title>
@@ -164,6 +164,17 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
    only superusers are allowed to change these parameters with
    <command>SET</>.)
   </para>
+
+  <para>
+   The statistics collector communicates with the backends needing 
+   information (including autovacuum) through temporary files.
+   These files are stored in the <filename>pg_stat_tmp</filename> subdirectory.
+   When the postmaster shuts down, a permanent copy of the statistics
+   data is stored in the <filename>global</filename> subdirectory. For increased
+   performance, it is possible to mount or symlink a RAM based
+   filesystem to the <filename>pg_stat_tmp</filename> directory.
+  </para>
+
  </sect2>
 
  <sect2 id="monitoring-stats-views">
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml
index 0303a2b3d4e..e564fd2be9a 100644
--- a/doc/src/sgml/storage.sgml
+++ b/doc/src/sgml/storage.sgml
@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/storage.sgml,v 1.23 2008/05/02 01:08:26 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/storage.sgml,v 1.24 2008/08/05 12:09:30 mha Exp $ -->
 
 <chapter id="storage">
 
@@ -77,6 +77,12 @@ Item
   (used for shared row locks)</entry> 
 </row>
 
+<row>
+ <entry><filename>pg_stat_tmp</></entry>
+ <entry>Subdirectory containing temporary files for the statistics
+  subsystem</entry>
+</row>
+
 <row>
  <entry><filename>pg_subtrans</></entry>
  <entry>Subdirectory containing subtransaction status data</entry>
-- 
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