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Mention hash opclasses in 'System Dependencies on Operator Classes',

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which previously only talked about btree opclasses.
This commit is contained in:
Tom Lane 2007-12-02 04:36:40 +00:00
parent 7cac32534f
commit 8ee076325f
1 changed files with 9 additions and 2 deletions
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11
doc/src/sgml/xindex.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/xindex.sgml,v 1.60 2007/04/25 19:48:27 neilc Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/xindex.sgml,v 1.61 2007/12/02 04:36:40 tgl Exp $ -->
<sect1 id="xindex">
<title>Interfacing Extensions To Indexes</title>
@ -893,6 +893,13 @@ ALTER OPERATOR FAMILY integer_ops USING btree ADD
any assumption about the behavior of operators with particular names.
</para>
</note>
<para>
Another important point is that an operator that
appears in a hash operator family is a candidate for hash joins,
hash aggregation, and related optimizations. The hash operator family
is essential here since it identifies the hash function(s) to use.
</para>
</sect2>
<sect2 id="xindex-opclass-features">
@ -950,7 +957,7 @@ CREATE OPERATOR CLASS polygon_ops
is used. In GIN, the <literal>STORAGE</> type identifies the type of
the <quote>key</> values, which normally is different from the type
of the indexed column &mdash; for example, an operator class for
integer array columns might have keys that are just integers. The
integer-array columns might have keys that are just integers. The
GIN <function>extractValue</> and <function>extractQuery</> support
routines are responsible for extracting keys from indexed values.
</para>