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Diffstat (limited to 'doc/src/sgml/btree.sgml')
| -rw-r--r-- | doc/src/sgml/btree.sgml | 33 |
1 files changed, 33 insertions, 0 deletions
diff --git a/doc/src/sgml/btree.sgml b/doc/src/sgml/btree.sgml index 73947db55cb..2c4dd48ea35 100644 --- a/doc/src/sgml/btree.sgml +++ b/doc/src/sgml/btree.sgml @@ -550,6 +550,39 @@ equalimage(<replaceable>opcintype</replaceable> <type>oid</type>) returns bool </para> </listitem> </varlistentry> + <varlistentry> + <term><function>options</function></term> + <listitem> + <para> + Optionally, a B-tree operator family may provide + <function>options</function> (<quote>operator class specific + options</quote>) support functions, registered under support + function number 5. These functions define set of user-visible + parameters that control operator class behavior. + </para> + <para> + An <function>options</function> support function must have the + signature +<synopsis> +options(<replaceable>relopts</replaceable> <type>local_relopts *</type>) returns void +</synopsis> + The function has given pointer to <replaceable>local_relopts</replaceable> + struct, which needs to be filled with a set of operator class + specific options. The options can be accessed from other support + functions using <literal>PG_HAS_OPCLASS_OPTIONS()</literal> and + <literal>PG_GET_OPCLASS_OPTIONS()</literal> macros. + </para> + <para> + Currently, no B-Tree operator class has <function>options</function> + support function. B-tree doesn't allow flexible representation of keys + like GiST, SP-GiST, GIN and BRIN do. So, <function>options</function> + probably doesn't have much usage in current shape of B-tree index + access method. Nevertheless, this support function was added to B-tree + for uniformity, and probably it will found its usage during further + evolution of B-tree in <productname>PostgreSQL</productname>. + </para> + </listitem> + </varlistentry> </variablelist> </sect1> |