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Diffstat (limited to 'doc/src/sgml/indices.sgml')
| -rw-r--r-- | doc/src/sgml/indices.sgml | 105 |
1 files changed, 41 insertions, 64 deletions
diff --git a/doc/src/sgml/indices.sgml b/doc/src/sgml/indices.sgml index d3bc74da92a..5fa1e79fefb 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 1.54 2005/11/04 23:14:00 petere Exp $ --> +<!-- $PostgreSQL: pgsql/doc/src/sgml/indices.sgml,v 1.55 2005/11/07 17:36:44 tgl Exp $ --> <chapter id="indexes"> <title id="indexes-title">Indexes</title> @@ -104,7 +104,7 @@ CREATE INDEX test1_id_index ON test1 (id); <para> <productname>PostgreSQL</productname> provides several index types: - B-tree, R-tree, Hash, and GiST. Each index type uses a different + B-tree, Hash, and GiST. Each index type uses a different algorithm that is best suited to different types of queries. By default, the <command>CREATE INDEX</command> command will create a B-tree index, which fits the most common situations. @@ -155,43 +155,6 @@ CREATE INDEX test1_id_index ON test1 (id); <para> <indexterm> <primary>index</primary> - <secondary>R-tree</secondary> - </indexterm> - <indexterm> - <primary>R-tree</primary> - <see>index</see> - </indexterm> - R-tree indexes are suited for queries on two-dimensional spatial data. - To create an R-tree index, use a command of the form -<synopsis> -CREATE INDEX <replaceable>name</replaceable> ON <replaceable>table</replaceable> USING rtree (<replaceable>column</replaceable>); -</synopsis> - The <productname>PostgreSQL</productname> query planner will - consider using an R-tree index whenever an indexed column is - involved in a comparison using one of these operators: - - <simplelist> - <member><literal><<</literal></member> - <member><literal>&<</literal></member> - <member><literal>&></literal></member> - <member><literal>>></literal></member> - <member><literal><<|</literal></member> - <member><literal>&<|</literal></member> - <member><literal>|&></literal></member> - <member><literal>|>></literal></member> - <member><literal>~</literal></member> - <member><literal>@</literal></member> - <member><literal>~=</literal></member> - <member><literal>&&</literal></member> - </simplelist> - - (See <xref linkend="functions-geometry"> for the meaning of - these operators.) - </para> - - <para> - <indexterm> - <primary>index</primary> <secondary>hash</secondary> </indexterm> <indexterm> @@ -208,18 +171,6 @@ CREATE INDEX <replaceable>name</replaceable> ON <replaceable>table</replaceable> </synopsis> </para> - <para> - GiST indexes are not a single kind of index, but rather an infrastructure - within which many different indexing strategies can be implemented. - Accordingly, the particular operators with which a GiST index can be - used vary depending on the indexing strategy (the <firstterm>operator - class</>). The standard distribution of - <productname>PostgreSQL</productname> includes GiST operator classes - equivalent to the R-tree operator classes, and many other GiST operator - classes are available in the <literal>contrib</> collection or as separate - projects. For more information see <xref linkend="GiST">. - </para> - <note> <para> Testing has shown <productname>PostgreSQL</productname>'s hash @@ -230,21 +181,47 @@ CREATE INDEX <replaceable>name</replaceable> ON <replaceable>table</replaceable> after a database crash. For these reasons, hash index use is presently discouraged. </para> + </note> - <para> - Similarly, R-tree indexes do not seem to have any performance - advantages compared to the equivalent operations of GiST indexes. - Like hash indexes, they are not WAL-logged and may need - reindexing after a database crash. - </para> + <para> + <indexterm> + <primary>index</primary> + <secondary>GiST</secondary> + </indexterm> + <indexterm> + <primary>GiST</primary> + <see>index</see> + </indexterm> + GiST indexes are not a single kind of index, but rather an infrastructure + within which many different indexing strategies can be implemented. + Accordingly, the particular operators with which a GiST index can be + used vary depending on the indexing strategy (the <firstterm>operator + class</>). As an example, the standard distribution of + <productname>PostgreSQL</productname> includes GiST operator classes + for several two-dimensional geometric data types, which support indexed + queries using these operators: - <para> - While the problems with hash indexes may be fixed eventually, - it is likely that the R-tree index type will be retired in a future - release. Users are encouraged to migrate applications that use R-tree - indexes to GiST indexes. - </para> - </note> + <simplelist> + <member><literal><<</literal></member> + <member><literal>&<</literal></member> + <member><literal>&></literal></member> + <member><literal>>></literal></member> + <member><literal><<|</literal></member> + <member><literal>&<|</literal></member> + <member><literal>|&></literal></member> + <member><literal>|>></literal></member> + <member><literal>~</literal></member> + <member><literal>@</literal></member> + <member><literal>~=</literal></member> + <member><literal>&&</literal></member> + </simplelist> + + (See <xref linkend="functions-geometry"> for the meaning of + these operators.) + Many other GiST operator + classes are available in the <literal>contrib</> collection or as separate + projects. For more information see <xref linkend="GiST">. + </para> </sect1> |