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Commit8087446

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> That's a fairly useless place to put it, though, since someone would
> only think to look at sort_mem if they already had a clue. It should> be mentioned under bulk data load (in performance tips chapter)Attached is a doc patch that does this. The way I've worded it may notbe the best, though.Neil Conway
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‎doc/src/sgml/perform.sgml

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<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/perform.sgml,v 1.33 2003/09/11 18:30:38 momjian Exp $
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$Header: /cvsroot/pgsql/doc/src/sgml/perform.sgml,v 1.34 2003/10/10 02:08:42 momjian Exp $
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-->
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<chapter id="performance-tips">
@@ -751,11 +751,10 @@ SELECT * FROM x, y, a, b, c WHERE something AND somethingelse;
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<para>
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Use <command>COPY FROM STDIN</command> to load all the rows in one
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command, instead of using
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a series of <command>INSERT</command> commands. This reduces parsing,
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planning, etc.
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overhead a great deal. If you do this then it is not necessary to turn
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off autocommit, since it is only one command anyway.
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command, instead of using a series of <command>INSERT</command>
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commands. This reduces parsing, planning, etc. overhead a great
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deal. If you do this then it is not necessary to turn off
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autocommit, since it is only one command anyway.
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</para>
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</sect2>
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<para>
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If you are loading a freshly created table, the fastest way is to
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create the table, bulk-loadwith <command>COPY</command>, then create any
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indexes needed
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for thetable. Creating an index on pre-existing data is quicker than
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create the table, bulkloadthe table's data using
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<command>COPY</command>, then create anyindexes neededfor the
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table. Creating an index on pre-existing data is quicker than
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updating it incrementally as each row is loaded.
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</para>
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</para>
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</sect2>
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<sect2 id="populate-sort-mem">
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<title>Increase <varname>sort_mem</varname></title>
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<para>
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Temporarily increasing the <varname>sort_mem</varname>
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configuration variable when restoring large amounts of data can
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lead to improved performance. This is because when a B-tree index
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is created from scratch, the existing content of the table needs
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to be sorted. Allowing the merge sort to use more buffer pages
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means that fewer merge passes will be required.
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</para>
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</sect2>
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<sect2 id="populate-analyze">
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<title>Run <command>ANALYZE</command> Afterwards</title>
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‎doc/src/sgml/runtime.sgml

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<!--
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$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.212 2003/10/09 19:05:09 momjian Exp $
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$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.213 2003/10/10 02:08:42 momjian Exp $
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-->
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<Chapter Id="runtime">
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by <literal>ORDER BY</>, merge joins, and <command>CREATE INDEX</>.
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Hash tables are used in hash joins, hash-based aggregation, and
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hash-based processing of <literal>IN</> subqueries. Because
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<command>CREATE INDEX</> is used when restoring a database, it might
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be good to temporarily increase this value during a restore.
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<command>CREATE INDEX</> is used when restoring a database,
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increasing <varname>sort_mem</varname> before doing a large
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restore operation can improve performance.
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</para>
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</listitem>
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</varlistentry>

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