<para>
As shown in <xref linkend="xindex-btree-support-table"/>, btree defines
- one required and three optional support functions. The four
+ one required and four optional support functions. The five
user-defined methods are:
</para>
<variablelist>
<para>
There are five user-defined methods that an index operator class for
- <acronym>SP-GiST</acronym> must provide, and one is optional. All five
+ <acronym>SP-GiST</acronym> must provide, and two are optional. All five
mandatory methods follow the convention of accepting two <type>internal</type>
arguments, the first of which is a pointer to a C struct containing input
values for the support method, while the second argument is a pointer to a
cases, the output struct is initialized to zeroes before calling the
user-defined method. The optional sixth method <function>compress</function>
accepts datum to be indexed as the only argument and returns a value suitable
- for physical storage in a leaf tuple.
+ for physical storage in a leaf tuple. The optional seventh method
+ <function>options</function> accepts internal pointer to a C struct, where
+ opclass-specific parameters should be placed, and returns <type>void</type>.
</para>
<para>