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Add mention of function CREATE INDEX usage.

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This commit is contained in:
Bruce Momjian 2002-04-11 23:20:04 +00:00
parent 0c9790e616
commit 50b5d4bf76
2 changed files with 41 additions and 39 deletions
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62
doc/src/sgml/ref/create_index.sgml
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@ -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 PostgreSQL documentation
--> -->
@ -76,9 +76,10 @@ CREATE [ UNIQUE ] INDEX <replaceable class="parameter">index_name</replaceable>
<term><replaceable class="parameter">acc_method</replaceable></term> <term><replaceable class="parameter">acc_method</replaceable></term>
<listitem> <listitem>
<para> <para>
The name of the access method to be used for The name of the access method to be used for the index. The
the index. The default access method is <literal>BTREE</literal>. default access method is <literal>BTREE</literal>.
<application>PostgreSQL</application> provides four access methods for indexes: <application>PostgreSQL</application> provides four access
methods for indexes:
<variablelist> <variablelist>
<varlistentry> <varlistentry>
@ -225,26 +226,27 @@ ERROR: Cannot create index: 'index_name' already exists.
</para> </para>
<para> <para>
In the second syntax shown above, an index is defined In the second syntax shown above, an index is defined on the result
on the result of a user-specified function of a user-specified function <replaceable
<replaceable class="parameter">func_name</replaceable> applied class="parameter">func_name</replaceable> applied to one or more
to one or more columns of a single table. columns of a single table. These <firstterm>functional
These <firstterm>functional indexes</firstterm> indexes</firstterm> can be used to obtain fast access to data based
can be used to obtain fast access to data on operators that would normally require some transformation to apply
based on operators that would normally require some them to the base data. For example, a functional index on
transformation to apply them to the base data. <literal>upper(col)</> would allow the clause
<literal>WHERE upper(col) = 'JIM'</> to use an index.
</para> </para>
<para> <para>
<application>PostgreSQL</application> provides B-tree, R-tree, hash, and GiST access methods for <application>PostgreSQL</application> provides B-tree, R-tree, hash,
indexes. The B-tree access method is an implementation of and GiST access methods for indexes. The B-tree access method is an
Lehman-Yao high-concurrency B-trees. The R-tree access method implementation of Lehman-Yao high-concurrency B-trees. The R-tree
implements standard R-trees using Guttman's quadratic split algorithm. access method implements standard R-trees using Guttman's quadratic
The hash access method is an implementation of Litwin's linear split algorithm. The hash access method is an implementation of
hashing. We mention the algorithms used solely to indicate that all Litwin's linear hashing. We mention the algorithms used solely to
of these access methods are fully dynamic and do not have to be indicate that all of these access methods are fully dynamic and do
optimized periodically (as is the case with, for example, static hash not have to be optimized periodically (as is the case with, for
access methods). example, static hash access methods).
</para> </para>
<para> <para>
@ -338,18 +340,18 @@ ERROR: Cannot create index: 'index_name' already exists.
<para> <para>
An <firstterm>operator class</firstterm> can be specified for each An <firstterm>operator class</firstterm> can be specified for each
column of an index. The operator class identifies the operators to column of an index. The operator class identifies the operators to be
be used by the index for that column. For example, a B-tree index on 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; four-byte integers would use the <literal>int4_ops</literal> class;
this operator class includes comparison functions for four-byte this operator class includes comparison functions for four-byte
integers. In practice the default operator class for the field's integers. In practice the default operator class for the field's data
data type is usually sufficient. The main point of having operator classes type is usually sufficient. The main point of having operator classes
is that for some data types, there could be more than one meaningful 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 ordering. For example, we might want to sort a complex-number data
either by absolute value or by real part. We could do this by defining type either by absolute value or by real part. We could do this by
two operator classes for the data type and then selecting the proper defining two operator classes for the data type and then selecting
class when making an index. There are also some operator classes with the proper class when making an index. There are also some operator
special purposes: classes with special purposes:
<itemizedlist> <itemizedlist>
<listitem> <listitem>

2
src/backend/commands/command.c
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@ -8,7 +8,7 @@
* *
* *
* IDENTIFICATION * IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.172 2002/04/02 08:51:50 inoue Exp $ * $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.173 2002/04/11 23:20:04 momjian Exp $
* *
* NOTES * NOTES
* The PerformAddAttribute() code, like most of the relation * The PerformAddAttribute() code, like most of the relation