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Replace functional-index facility with expressional indexes. Any column

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of an index can now be a computed expression instead of a simple variable.
Restrictions on expressions are the same as for predicates (only immutable
functions, no sub-selects).  This fixes problems recently introduced with
inlining SQL functions, because the inlining transformation is applied to
both expression trees so the planner can still match them up.  Along the
way, improve efficiency of handling index predicates (both predicates and
index expressions are now cached by the relcache) and fix 7.3 oversight
that didn't record dependencies of predicate expressions.
This commit is contained in:
Tom Lane
2003-05-28 16:04:02 +00:00
parent e5f19598e0
commit fc8d970cbc
50 changed files with 1351 additions and 1283 deletions
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47
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 1.38 2003/04/22 10:08:08 petere Exp $
$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_index.sgml,v 1.39 2003/05/28 16:03:55 tgl Exp $
PostgreSQL documentation
-->
@@ -16,12 +16,8 @@ PostgreSQL documentation
<refsynopsisdiv>
<synopsis>
CREATE [ UNIQUE ] INDEX <replaceable class="parameter">index_name</replaceable> ON <replaceable class="parameter">table</replaceable>
[ USING <replaceable class="parameter">method</replaceable> ] ( <replaceable class="parameter">column</replaceable> [ <replaceable class="parameter">ops_name</replaceable> ] [, ...] )
[ WHERE <replaceable class="parameter">predicate</replaceable> ]
CREATE [ UNIQUE ] INDEX <replaceable class="parameter">index_name</replaceable> ON <replaceable class="parameter">table</replaceable>
[ USING <replaceable class="parameter">method</replaceable> ] ( <replaceable class="parameter">func_name</replaceable>( <replaceable class="parameter">column</replaceable> [, ... ]) [ <replaceable class="parameter">ops_name</replaceable> ] )
CREATE [ UNIQUE ] INDEX <replaceable class="parameter">index_name</replaceable> ON <replaceable class="parameter">table</replaceable> [ USING <replaceable class="parameter">method</replaceable> ]
( { <replaceable class="parameter">column</replaceable> | ( <replaceable class="parameter">expression</replaceable> ) } [ <replaceable class="parameter">opclass</replaceable> ] [, ...] )
[ WHERE <replaceable class="parameter">predicate</replaceable> ]
</synopsis>
</refsynopsisdiv>
@@ -32,25 +28,22 @@ CREATE [ UNIQUE ] INDEX <replaceable class="parameter">index_name</replaceable>
<para>
<command>CREATE INDEX</command> constructs an index <replaceable
class="parameter">index_name</replaceable> on the specified table.
Indexes are primarily used to enhance database performance. But
inappropriate use will result in slower performance.
Indexes are primarily used to enhance database performance (though
inappropriate use will result in slower performance).
</para>
<para>
In the first syntax shown above, the key field(s) for the
index are specified as column names.
The key field(s) for the index are specified as column names,
or alternatively as expressions written in parentheses.
Multiple fields can be specified if the index method supports
multicolumn indexes.
</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. For example, a functional index on
An index field can be an expression computed from the values of
one or more columns of the table row. This feature can be used
to obtain fast access to data based on some transformation of
the basic data. For example, an index computed on
<literal>upper(col)</> would allow the clause
<literal>WHERE upper(col) = 'JIM'</> to use an index.
</para>
@@ -84,6 +77,7 @@ CREATE [ UNIQUE ] INDEX <replaceable class="parameter">index_name</replaceable>
only to columns of the underlying table (but it can use all columns,
not only the one(s) being indexed). Presently, subqueries and
aggregate expressions are also forbidden in <literal>WHERE</literal>.
The same restrictions apply to index fields that are expressions.
</para>
<para>
@@ -92,8 +86,8 @@ CREATE [ UNIQUE ] INDEX <replaceable class="parameter">index_name</replaceable>
their arguments and never on any outside influence (such as
the contents of another table or the current time). This restriction
ensures that the behavior of the index is well-defined. To use a
user-defined function in an index, remember to mark the function immutable
when you create it.
user-defined function in an index expression or <literal>WHERE</literal>
clause, remember to mark the function immutable when you create it.
</para>
</refsect1>
@@ -156,19 +150,22 @@ CREATE [ UNIQUE ] INDEX <replaceable class="parameter">index_name</replaceable>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">ops_name</replaceable></term>
<term><replaceable class="parameter">expression</replaceable></term>
<listitem>
<para>
An associated operator class. See below for details.
An expression based on one or more columns of the table. The
expression usually must be written with surrounding parentheses,
as shown in the syntax. However, the parentheses may be omitted
if the expression has the form of a function call.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">func_name</replaceable></term>
<term><replaceable class="parameter">opclass</replaceable></term>
<listitem>
<para>
A function, which returns a value that can be indexed.
The name of an operator class. See below for details.
</para>
</listitem>
</varlistentry>
@@ -177,7 +174,7 @@ CREATE [ UNIQUE ] INDEX <replaceable class="parameter">index_name</replaceable>
<term><replaceable class="parameter">predicate</replaceable></term>
<listitem>
<para>
Defines the constraint expression for a partial index.
The constraint expression for a partial index.
</para>
</listitem>
</varlistentry>