diff options
Diffstat (limited to 'doc/src/sgml/indices.sgml')
| -rw-r--r-- | doc/src/sgml/indices.sgml | 14 |
1 files changed, 9 insertions, 5 deletions
diff --git a/doc/src/sgml/indices.sgml b/doc/src/sgml/indices.sgml index 0a6defbf62..2c238d3429 100644 --- a/doc/src/sgml/indices.sgml +++ b/doc/src/sgml/indices.sgml @@ -1,4 +1,4 @@ -<!-- $PostgreSQL: pgsql/doc/src/sgml/indices.sgml,v 1.70 2007/02/14 20:47:15 tgl Exp $ --> +<!-- $PostgreSQL: pgsql/doc/src/sgml/indices.sgml,v 1.71 2007/04/06 22:33:41 tgl Exp $ --> <chapter id="indexes"> <title id="indexes-title">Indexes</title> @@ -147,8 +147,8 @@ CREATE INDEX test1_id_index ON test1 (id); Constructs equivalent to combinations of these operators, such as <literal>BETWEEN</> and <literal>IN</>, can also be implemented with - a B-tree index search. (But note that <literal>IS NULL</> is not - equivalent to <literal>=</> and is not indexable.) + a B-tree index search. Also, an <literal>IS NULL</> condition on + an index column can be used with a B-tree index. </para> <para> @@ -180,8 +180,9 @@ CREATE INDEX test1_id_index ON test1 (id); Hash indexes can only handle simple equality comparisons. The query planner will consider using a hash index whenever an indexed column is involved in a comparison using the - <literal>=</literal> operator. The following command is used to - create a hash index: + <literal>=</literal> operator. (But hash indexes do not support + <literal>IS NULL</> searches.) + The following command is used to create a hash index: <synopsis> CREATE INDEX <replaceable>name</replaceable> ON <replaceable>table</replaceable> USING hash (<replaceable>column</replaceable>); </synopsis> @@ -234,6 +235,8 @@ CREATE INDEX <replaceable>name</replaceable> ON <replaceable>table</replaceable> (See <xref linkend="functions-geometry"> for the meaning of these operators.) + Also, an <literal>IS NULL</> condition on + an index column can be used with a GiST index. Many other GiST operator classes are available in the <literal>contrib</> collection or as separate projects. For more information see <xref linkend="GiST">. @@ -266,6 +269,7 @@ CREATE INDEX <replaceable>name</replaceable> ON <replaceable>table</replaceable> (See <xref linkend="functions-array"> for the meaning of these operators.) + GIN indexes cannot use <literal>IS NULL</> as a search condition. Other GIN operator classes are available in the <literal>contrib</> <literal>tsearch2</literal> and <literal>intarray</literal> modules. For more information see <xref linkend="GIN">. |