From 9edd720050a2979c684b514f7d5118a8a0d45dff Mon Sep 17 00:00:00 2001
From: Magnus Hagander <magnus@hagander.net>
Date: Mon, 8 Dec 2008 20:30:58 +0000
Subject: [PATCH] Clearify how processes are started by autovacuum, and what
the effect of autovacuum_max_workers parameter is.
Per discussion with Alvaro.
---
doc/src/sgml/maintenance.sgml | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff --git a/doc/src/sgml/maintenance.sgml b/doc/src/sgml/maintenance.sgml
index c2a4ce325c0..09c14782d86 100644
--- a/doc/src/sgml/maintenance.sgml
+++ b/doc/src/sgml/maintenance.sgml
@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/maintenance.sgml,v 1.86 2008/06/16 03:13:14 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/maintenance.sgml,v 1.87 2008/12/08 20:30:58 mha Exp $ -->
<chapter id="maintenance">
<title>Routine Database Maintenance Tasks</title>
@@ -522,10 +522,16 @@ HINT: Stop the postmaster and use a standalone backend to VACUUM in "mydb".
The <quote>autovacuum daemon</> actually consists of multiple processes.
There is a persistent daemon process, called the
<firstterm>autovacuum launcher</firstterm>, which is in charge of starting
- an <firstterm>autovacuum worker</firstterm> process on each database every
- <xref linkend="guc-autovacuum-naptime"> seconds. On each run, the worker
- process checks each table within that database, and executes
- <command>VACUUM</> and/or <command>ANALYZE</> commands as needed.
+ <firstterm>autovacuum worker</firstterm> processes for all databases. The
+ launcher will distribute the work across time, but attempt to start one
+ worker on each database every <xref linkend="guc-autovacuum-naptime">
+ seconds. One worker will be launched for each database, with a maximum
+ of <xref linkend="guc-autovacuum-max-workers"> processes running at the
+ same time. If there are more than
+ <xref linkend="guc-autovacuum-max-workers"> databases to be processed,
+ the next database will be processed as soon as the first worker finishes.
+ The worker processes will check each table within its database and
+ execute <command>VACUUM</> and/or <command>ANALYZE</> as needed.
</para>
<para>
--
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