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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
-->
@ -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>

2
src/backend/commands/command.c
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@ -8,7 +8,7 @@
*
*
* 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
* The PerformAddAttribute() code, like most of the relation