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Add stratnum GiST support function

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This is support function 12 for the GiST AM and translates
"well-known" RT*StrategyNumber values into whatever strategy number is
used by the opclass (since no particular numbers are actually
required).  We will use this to support temporal PRIMARY
KEY/UNIQUE/FOREIGN KEY/FOR PORTION OF functionality.

This commit adds two implementations, one for internal GiST opclasses
(just an identity function) and another for btree_gist opclasses.  It
updates btree_gist from 1.7 to 1.8, adding the support function for
all its opclasses.

Author: Paul A. Jungwirth <pj@illuminatedcomputing.com>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Reviewed-by: jian he <jian.universality@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CA+renyUApHgSZF9-nd-a0+OPGharLQLO=mDHcY4_qQ0+noCUVg@mail.gmail.com
This commit is contained in:
Peter Eisentraut
2024-01-19 15:41:44 +01:00
parent b725b7eec4
commit 6db4598fcb
17 changed files with 273 additions and 8 deletions
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65
doc/src/sgml/gist.sgml
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@ -272,7 +272,7 @@ CREATE INDEX ON my_table USING GIST (my_inet_column inet_ops);
<para>
There are five methods that an index operator class for
<acronym>GiST</acronym> must provide, and six that are optional.
<acronym>GiST</acronym> must provide, and seven that are optional.
Correctness of the index is ensured
by proper implementation of the <function>same</function>, <function>consistent</function>
and <function>union</function> methods, while efficiency (size and speed) of the
@ -295,6 +295,10 @@ CREATE INDEX ON my_table USING GIST (my_inet_column inet_ops);
user-specified parameters.
The optional eleventh method <function>sortsupport</function> is used to
speed up building a <acronym>GiST</acronym> index.
The optional twelfth method <function>stratnum</function> is used to
translate well-known <literal>RT*StrategyNumber</literal>s (from
<filename>src/include/access/stratnum.h</filename>) into strategy numbers
used by the operator class.
</para>
<variablelist>
@ -1169,6 +1173,65 @@ my_sortsupport(PG_FUNCTION_ARGS)
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><function>stratnum</function></term>
<listitem>
<para>
Given an <literal>RT*StrategyNumber</literal> value from
<filename>src/include/access/stratnum.h</filename>, returns a strategy
number used by this operator class for matching functionality. The
function should return <literal>InvalidStrategy</literal> if the
operator class has no matching strategy.
</para>
<para>
The <acronym>SQL</acronym> declaration of the function must look like
this:
<programlisting>
CREATE OR REPLACE FUNCTION my_stratnum(integer)
RETURNS integer
AS 'MODULE_PATHNAME'
LANGUAGE C STRICT;
</programlisting>
</para>
<para>
The matching code in the C module could then follow this skeleton:
<programlisting>
PG_FUNCTION_INFO_V1(my_stratnum);
Datum
my_stratnum(PG_FUNCTION_ARGS)
{
StrategyNumber strategy = (StrategyNumber) PG_GETARG_UINT16(1);
StrategyNumber ret = InvalidStrategy;
switch (strategy)
{
case RTEqualStrategyNumber:
ret = BTEqualStrategyNumber;
}
PG_RETURN_UINT16(ret);
}
</programlisting>
</para>
<para>
One translation function is provided by
<productname>PostgreSQL</productname>:
<literal>gist_stratnum_identity</literal> is for operator classes that
already use the <literal>RT*StrategyNumber</literal> constants. It
returns whatever is passed to it. The <literal>btree_gist</literal>
extension defines a second translation function,
<literal>gist_stratnum_btree</literal>, for operator classes that use
the <literal>BT*StrategyNumber</literal> constants.
</para>
</listitem>
</varlistentry>
</variablelist>
<para>