From fb8b38e4bf324787d090f77261441bf13b02a69c Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Fri, 16 Nov 2007 03:23:07 +0000
Subject: [PATCH] Add a couple of notes pointing out that GIN index build time
is very sensitive to maintenance_work_mem (something I just learned the hard
way).
---
doc/src/sgml/gin.sgml | 17 ++++++++++++++---
doc/src/sgml/textsearch.sgml | 9 ++++++++-
2 files changed, 22 insertions(+), 4 deletions(-)
diff --git a/doc/src/sgml/gin.sgml b/doc/src/sgml/gin.sgml
index 61a3f0f4ec1..1b7f105ac56 100644
--- a/doc/src/sgml/gin.sgml
+++ b/doc/src/sgml/gin.sgml
@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/gin.sgml,v 2.12 2007/11/13 23:36:26 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/gin.sgml,v 2.13 2007/11/16 03:23:07 tgl Exp $ -->
<chapter id="GIN">
<title>GIN Indexes</title>
@@ -161,6 +161,17 @@
</listitem>
</varlistentry>
+ <varlistentry>
+ <term><xref linkend="guc-maintenance-work-mem"></term>
+ <listitem>
+ <para>
+ Build time for a <acronym>GIN</acronym> index is very sensitive to
+ the <varname>maintenance_work_mem</> setting; it doesn't pay to
+ skimp on work memory during index creation.
+ </para>
+ </listitem>
+ </varlistentry>
+
<varlistentry>
<term><xref linkend="guc-gin-fuzzy-search-limit"></term>
<listitem>
@@ -177,8 +188,8 @@
</para>
<para>
To facilitate controlled execution of such queries
- <acronym>GIN</acronym> has a configurable soft upper limit on the size
- of the returned set, the
+ <acronym>GIN</acronym> has a configurable soft upper limit on the
+ number of rows returned, the
<varname>gin_fuzzy_search_limit</varname> configuration parameter.
It is set to 0 (meaning no limit) by default.
If a non-zero limit is set, then the returned set is a subset of
diff --git a/doc/src/sgml/textsearch.sgml b/doc/src/sgml/textsearch.sgml
index 0a153c465cd..b43872cca5c 100644
--- a/doc/src/sgml/textsearch.sgml
+++ b/doc/src/sgml/textsearch.sgml
@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/textsearch.sgml,v 1.35 2007/11/14 23:48:55 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/textsearch.sgml,v 1.36 2007/11/16 03:23:07 tgl Exp $ -->
<chapter id="textsearch">
<title id="textsearch-title">Full Text Search</title>
@@ -3256,6 +3256,13 @@ EXPLAIN SELECT * FROM apod WHERE textsearch @@ to_tsquery('supernovae');
lexemes better but are slower to update.
</para>
+ <para>
+ Note that <acronym>GIN</acronym> index build time can often be improved
+ by increasing <xref linkend="guc-maintenance-work-mem">, while
+ <acronym>GiST</acronym> index build time is not sensitive to that
+ parameter.
+ </para>
+
<para>
Partitioning of big collections and the proper use of GiST and GIN indexes
allows the implementation of very fast searches with online update.
--
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