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author | Bruce Momjian <bruce@momjian.us> | 2002-04-11 23:20:04 +0000 |
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committer | Bruce Momjian <bruce@momjian.us> | 2002-04-11 23:20:04 +0000 |
commit | 50b5d4bf76f1b9b62d1127dca1f28d09f9657afa (patch) | |
tree | 828c7696ab408a625da8ad267ff421a7d17f0130 /doc/src | |
parent | 0c9790e616429a1af444b9839ba6dc967d7f4292 (diff) | |
download | postgresql-50b5d4bf76f1b9b62d1127dca1f28d09f9657afa.tar.gz postgresql-50b5d4bf76f1b9b62d1127dca1f28d09f9657afa.zip |
Add mention of function CREATE INDEX usage.
Diffstat (limited to 'doc/src')
-rw-r--r-- | doc/src/sgml/ref/create_index.sgml | 62 |
1 files changed, 32 insertions, 30 deletions
diff --git a/doc/src/sgml/ref/create_index.sgml b/doc/src/sgml/ref/create_index.sgml index ed4bb66aadc..5e660527781 100644 --- a/doc/src/sgml/ref/create_index.sgml +++ b/doc/src/sgml/ref/create_index.sgml @@ -1,5 +1,5 @@ <!-- -$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_index.sgml,v 1.27 2002/03/22 19:20:38 petere Exp $ +$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_index.sgml,v 1.28 2002/04/11 23:20:04 momjian Exp $ PostgreSQL documentation --> @@ -76,9 +76,10 @@ CREATE [ UNIQUE ] INDEX <replaceable class="parameter">index_name</replaceable> <term><replaceable class="parameter">acc_method</replaceable></term> <listitem> <para> - The name of the access method to be used for - the index. The default access method is <literal>BTREE</literal>. - <application>PostgreSQL</application> provides four access methods for indexes: + The name of the access method to be used for the index. The + default access method is <literal>BTREE</literal>. + <application>PostgreSQL</application> provides four access + methods for indexes: <variablelist> <varlistentry> @@ -225,26 +226,27 @@ ERROR: Cannot create index: 'index_name' already exists. </para> <para> - In the second syntax shown above, an index is defined - on the result of a user-specified function - <replaceable class="parameter">func_name</replaceable> applied - to one or more columns of a single table. - These <firstterm>functional indexes</firstterm> - can be used to obtain fast access to data - based on operators that would normally require some - transformation to apply them to the base data. + In the second syntax shown above, an index is defined on the result + of a user-specified function <replaceable + class="parameter">func_name</replaceable> applied to one or more + columns of a single table. These <firstterm>functional + indexes</firstterm> can be used to obtain fast access to data based + on operators that would normally require some transformation to apply + them to the base data. For example, a functional index on + <literal>upper(col)</> would allow the clause + <literal>WHERE upper(col) = 'JIM'</> to use an index. </para> <para> - <application>PostgreSQL</application> provides B-tree, R-tree, hash, and GiST access methods for - indexes. The B-tree access method is an implementation of - Lehman-Yao high-concurrency B-trees. The R-tree access method - implements standard R-trees using Guttman's quadratic split algorithm. - The hash access method is an implementation of Litwin's linear - hashing. We mention the algorithms used solely to indicate that all - of these access methods are fully dynamic and do not have to be - optimized periodically (as is the case with, for example, static hash - access methods). + <application>PostgreSQL</application> provides B-tree, R-tree, hash, + and GiST access methods for indexes. The B-tree access method is an + implementation of Lehman-Yao high-concurrency B-trees. The R-tree + access method implements standard R-trees using Guttman's quadratic + split algorithm. The hash access method is an implementation of + Litwin's linear hashing. We mention the algorithms used solely to + indicate that all of these access methods are fully dynamic and do + not have to be optimized periodically (as is the case with, for + example, static hash access methods). </para> <para> @@ -338,18 +340,18 @@ ERROR: Cannot create index: 'index_name' already exists. <para> An <firstterm>operator class</firstterm> can be specified for each - column of an index. The operator class identifies the operators to - be used by the index for that column. For example, a B-tree index on + column of an index. The operator class identifies the operators to be + used by the index for that column. For example, a B-tree index on four-byte integers would use the <literal>int4_ops</literal> class; this operator class includes comparison functions for four-byte - integers. In practice the default operator class for the field's - data type is usually sufficient. The main point of having operator classes + integers. In practice the default operator class for the field's data + type is usually sufficient. The main point of having operator classes is that for some data types, there could be more than one meaningful - ordering. For example, we might want to sort a complex-number data type - either by absolute value or by real part. We could do this by defining - two operator classes for the data type and then selecting the proper - class when making an index. There are also some operator classes with - special purposes: + ordering. For example, we might want to sort a complex-number data + type either by absolute value or by real part. We could do this by + defining two operator classes for the data type and then selecting + the proper class when making an index. There are also some operator + classes with special purposes: <itemizedlist> <listitem> |