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Add a couple of notes pointing out that GIN index build time is very

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sensitive to maintenance_work_mem (something I just learned the hard
way).
This commit is contained in:
Tom Lane 2007-11-16 03:23:07 +00:00
parent f639df0d61
commit fb8b38e4bf
2 changed files with 22 additions and 4 deletions
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17
doc/src/sgml/gin.sgml
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@ -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"> <chapter id="GIN">
<title>GIN Indexes</title> <title>GIN Indexes</title>
@ -161,6 +161,17 @@
</listitem> </listitem>
</varlistentry> </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> <varlistentry>
<term><xref linkend="guc-gin-fuzzy-search-limit"></term> <term><xref linkend="guc-gin-fuzzy-search-limit"></term>
<listitem> <listitem>
@ -177,8 +188,8 @@
</para> </para>
<para> <para>
To facilitate controlled execution of such queries To facilitate controlled execution of such queries
<acronym>GIN</acronym> has a configurable soft upper limit on the size <acronym>GIN</acronym> has a configurable soft upper limit on the
of the returned set, the number of rows returned, the
<varname>gin_fuzzy_search_limit</varname> configuration parameter. <varname>gin_fuzzy_search_limit</varname> configuration parameter.
It is set to 0 (meaning no limit) by default. 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 If a non-zero limit is set, then the returned set is a subset of

9
doc/src/sgml/textsearch.sgml
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@ -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"> <chapter id="textsearch">
<title id="textsearch-title">Full Text Search</title> <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. lexemes better but are slower to update.
</para> </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> <para>
Partitioning of big collections and the proper use of GiST and GIN indexes Partitioning of big collections and the proper use of GiST and GIN indexes
allows the implementation of very fast searches with online update. allows the implementation of very fast searches with online update.