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Remove KSQO from GUC and move file to _deadcode.

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This commit is contained in:
Bruce Momjian
2002-06-16 00:09:12 +00:00
parent b50cbbd66b
commit 0dbfea39f3
8 changed files with 11 additions and 57 deletions
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30
doc/src/sgml/runtime.sgml
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@ -1,5 +1,5 @@
<!--
$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.118 2002/06/15 19:58:53 momjian Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.119 2002/06/16 00:09:11 momjian Exp $
-->
<Chapter Id="runtime">
@ -759,34 +759,6 @@ env PGOPTIONS='-c geqo=off' psql
</listitem>
</varlistentry>
<varlistentry>
<term><varname>KSQO</varname> (<type>boolean</type>)</term>
<listitem>
<para>
The <firstterm>Key Set Query Optimizer</firstterm>
(<acronym>KSQO</acronym>) causes the query planner to convert
queries whose <literal>WHERE</> clause contains many OR'ed AND
clauses (such as <literal>WHERE (a=1 AND b=2) OR (a=2 AND b=3)
...</literal>) into a union query. This method can be faster
than the default implementation, but it doesn't necessarily give
exactly the same results, since <literal>UNION</> implicitly
adds a <literal>SELECT DISTINCT</> clause to eliminate identical
output rows. <acronym>KSQO</acronym> is commonly used when
working with products like <productname>Microsoft
Access</productname>, which tend to generate queries of this
form.
</para>
<para>
The <acronym>KSQO</acronym> algorithm used to be absolutely
essential for queries with many OR'ed AND clauses, but in
<productname>PostgreSQL</productname> 7.0 and later the standard
planner handles these queries fairly successfully; hence the
default is off.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><varname>RANDOM_PAGE_COST</varname> (<type>floating point</type>)</term>
<listitem>