diff options
Diffstat (limited to 'doc/src/sgml/gist.sgml')
| -rw-r--r-- | doc/src/sgml/gist.sgml | 25 |
1 files changed, 18 insertions, 7 deletions
diff --git a/doc/src/sgml/gist.sgml b/doc/src/sgml/gist.sgml index a373a8aa4b2..ee86e170055 100644 --- a/doc/src/sgml/gist.sgml +++ b/doc/src/sgml/gist.sgml @@ -1170,7 +1170,7 @@ my_sortsupport(PG_FUNCTION_ARGS) </varlistentry> <varlistentry> - <term><function>stratnum</function></term> + <term><function>translate_cmptype</function></term> <listitem> <para> Given a <literal>CompareType</literal> value from @@ -1189,11 +1189,22 @@ my_sortsupport(PG_FUNCTION_ARGS) </para> <para> + This support function corresponds to the index access method callback + function <structfield>amtranslatecmptype</structfield> (see <xref + linkend="index-functions"/>). The + <structfield>amtranslatecmptype</structfield> callback function for + GiST indexes merely calls down to the + <function>translate_cmptype</function> support function of the + respective operator family, since the GiST index access method has no + fixed strategy numbers itself. + </para> + + <para> The <acronym>SQL</acronym> declaration of the function must look like this: <programlisting> -CREATE OR REPLACE FUNCTION my_stratnum(integer) +CREATE OR REPLACE FUNCTION my_translate_cmptype(integer) RETURNS smallint AS 'MODULE_PATHNAME' LANGUAGE C STRICT; @@ -1202,7 +1213,7 @@ LANGUAGE C STRICT; And the operator family registration must look like this: <programlisting> ALTER OPERATOR FAMILY my_opfamily USING gist ADD - FUNCTION 12 ("any", "any") my_stratnum(int); + FUNCTION 12 ("any", "any") my_translate_cmptype(int); </programlisting> </para> @@ -1210,10 +1221,10 @@ ALTER OPERATOR FAMILY my_opfamily USING gist ADD The matching code in the C module could then follow this skeleton: <programlisting> -PG_FUNCTION_INFO_V1(my_stratnum); +PG_FUNCTION_INFO_V1(my_translate_cmptype); Datum -my_stratnum(PG_FUNCTION_ARGS) +my_translate_cmptype(PG_FUNCTION_ARGS) { CompareType cmptype = PG_GETARG_INT32(0); StrategyNumber ret = InvalidStrategy; @@ -1232,11 +1243,11 @@ my_stratnum(PG_FUNCTION_ARGS) <para> One translation function is provided by <productname>PostgreSQL</productname>: - <literal>gist_stratnum_common</literal> is for operator classes that + <literal>gist_translate_cmptype_common</literal> is for operator classes that use the <literal>RT*StrategyNumber</literal> constants. The <literal>btree_gist</literal> extension defines a second translation function, - <literal>gist_stratnum_btree</literal>, for operator classes that use + <literal>gist_translate_cmptype_btree</literal>, for operator classes that use the <literal>BT*StrategyNumber</literal> constants. </para> </listitem> |