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1 | | -<!-- $PostgreSQL: pgsql/doc/src/sgml/xindex.sgml,v 1.60 2007/04/25 19:48:27 neilc Exp $ --> |
| 1 | +<!-- $PostgreSQL: pgsql/doc/src/sgml/xindex.sgml,v 1.61 2007/12/02 04:36:40 tgl Exp $ --> |
2 | 2 |
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3 | 3 | <sect1 id="xindex"> |
4 | 4 | <title>Interfacing Extensions To Indexes</title> |
@@ -893,6 +893,13 @@ ALTER OPERATOR FAMILY integer_ops USING btree ADD |
893 | 893 | any assumption about the behavior of operators with particular names. |
894 | 894 | </para> |
895 | 895 | </note> |
| 896 | + |
| 897 | + <para> |
| 898 | + Another important point is that an operator that |
| 899 | + appears in a hash operator family is a candidate for hash joins, |
| 900 | + hash aggregation, and related optimizations. The hash operator family |
| 901 | + is essential here since it identifies the hash function(s) to use. |
| 902 | + </para> |
896 | 903 | </sect2> |
897 | 904 |
|
898 | 905 | <sect2 id="xindex-opclass-features"> |
@@ -950,7 +957,7 @@ CREATE OPERATOR CLASS polygon_ops |
950 | 957 | is used. In GIN, the <literal>STORAGE</> type identifies the type of |
951 | 958 | the <quote>key</> values, which normally is different from the type |
952 | 959 | of the indexed column — for example, an operator class for |
953 | | - integerarray columns might have keys that are just integers. The |
| 960 | + integer-array columns might have keys that are just integers. The |
954 | 961 | GIN <function>extractValue</> and <function>extractQuery</> support |
955 | 962 | routines are responsible for extracting keys from indexed values. |
956 | 963 | </para> |
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