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Implement operator class parameters

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PostgreSQL provides set of template index access methods, where opclasses have
much freedom in the semantics of indexing.  These index AMs are GiST, GIN,
SP-GiST and BRIN.  There opclasses define representation of keys, operations on
them and supported search strategies.  So, it's natural that opclasses may be
faced some tradeoffs, which require user-side decision.  This commit implements
opclass parameters allowing users to set some values, which tell opclass how to
index the particular dataset.

This commit doesn't introduce new storage in system catalog.  Instead it uses
pg_attribute.attoptions, which is used for table column storage options but
unused for index attributes.

In order to evade changing signature of each opclass support function, we
implement unified way to pass options to opclass support functions.  Options
are set to fn_expr as the constant bytea expression.  It's possible due to the
fact that opclass support functions are executed outside of expressions, so
fn_expr is unused for them.

This commit comes with some examples of opclass options usage.  We parametrize
signature length in GiST.  That applies to multiple opclasses: tsvector_ops,
gist__intbig_ops, gist_ltree_ops, gist__ltree_ops, gist_trgm_ops and
gist_hstore_ops.  Also we parametrize maximum number of integer ranges for
gist__int_ops.  However, the main future usage of this feature is expected
to be json, where users would be able to specify which way to index particular
json parts.

Catversion is bumped.

Discussion: https://postgr.es/m/d22c3a18-31c7-1879-fc11-4c1ce2f5e5af%40postgrespro.ru
Author: Nikita Glukhov, revised by me
Reviwed-by: Nikolay Shaplov, Robert Haas, Tom Lane, Tomas Vondra, Alvaro Herrera
This commit is contained in:
Alexander Korotkov
2020-03-30 19:17:11 +03:00
parent 1d53432ff9
commit 911e702077
108 changed files with 4086 additions and 924 deletions
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16
doc/src/sgml/ref/create_index.sgml
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@@ -22,7 +22,7 @@ PostgreSQL documentation
<refsynopsisdiv>
<synopsis>
CREATE [ UNIQUE ] INDEX [ CONCURRENTLY ] [ [ IF NOT EXISTS ] <replaceable class="parameter">name</replaceable> ] ON [ ONLY ] <replaceable class="parameter">table_name</replaceable> [ USING <replaceable class="parameter">method</replaceable> ]
( { <replaceable class="parameter">column_name</replaceable> | ( <replaceable class="parameter">expression</replaceable> ) } [ COLLATE <replaceable class="parameter">collation</replaceable> ] [ <replaceable class="parameter">opclass</replaceable> ] [ ASC | DESC ] [ NULLS { FIRST | LAST } ] [, ...] )
( { <replaceable class="parameter">column_name</replaceable> | ( <replaceable class="parameter">expression</replaceable> ) } [ COLLATE <replaceable class="parameter">collation</replaceable> ] { <replaceable class="parameter">opclass</replaceable> | DEFAULT } [ ( <replaceable class="parameter">opclass_parameter</replaceable> = <replaceable class="parameter">value</replaceable> [, ... ] ) ] [ ASC | DESC ] [ NULLS { FIRST | LAST } ] [, ...] )
[ INCLUDE ( <replaceable class="parameter">column_name</replaceable> [, ...] ) ]
[ WITH ( <replaceable class="parameter">storage_parameter</replaceable> = <replaceable class="parameter">value</replaceable> [, ... ] ) ]
[ TABLESPACE <replaceable class="parameter">tablespace_name</replaceable> ]
@@ -285,6 +285,15 @@ CREATE [ UNIQUE ] INDEX [ CONCURRENTLY ] [ [ IF NOT EXISTS ] <replaceable class=
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="parameter">opclass_parameter</replaceable></term>
<listitem>
<para>
The name of an operator class parameter. See below for details.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>ASC</literal></term>
<listitem>
@@ -679,8 +688,9 @@ Indexes:
</para>
<para>
An <firstterm>operator class</firstterm> can be specified for each
column of an index. The operator class identifies the operators to be
An <firstterm>operator class</firstterm> with its optional parameters
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
four-byte integers would use the <literal>int4_ops</literal> class;
this operator class includes comparison functions for four-byte