defined by the user for other data types using equivalent definitions,

without having to write any source code; appropriate catalog entries being

declared is enough. Note that assumptions about the semantics of operator

strategies are embedded in the support procedures's source code.

strategies are embedded in the support procedures' source code.

</para>

<para>

<tbody>

<row>

<entry>Support Procedure 1</entry>

<entry>function <function>brin_minmax_opcinfo()</function></entry>

<entry>internalfunction <function>brin_minmax_opcinfo()</function></entry>

</row>

<row>

<entry>Support Procedure 2</entry>

<entry>function <function>brin_minmax_add_value()</function></entry>

<entry>internalfunction <function>brin_minmax_add_value()</function></entry>

</row>

<row>

<entry>Support Procedure 3</entry>

<entry>function <function>brin_minmax_consistent()</function></entry>

<entry>internalfunction <function>brin_minmax_consistent()</function></entry>

</row>

<row>

<entry>Support Procedure 4</entry>

<entry>function <function>brin_minmax_union()</function></entry>

<entry>internalfunction <function>brin_minmax_union()</function></entry>

</row>

<row>

<entry>Operator Strategy 1</entry>

</tbody>

</tgroup>

</table>

<para>

To write an operator class for a complex datatype which has values

included within another type, it's possible to use the inclusion support

procedures alongside the corresponding operators, as shown

in <xref linkend="brin-extensibility-inclusion-table">. It requires

only a single additional function, which can be written in any language.

More functions can be defined for additional functionality. All operators

are optional. Some operators require other operators, as shown as

dependencies on the table.

</para>

<table id="brin-extensibility-inclusion-table">

<title>Procedure and Support Numbers for Inclusion Operator Classes</title>

<tgroup cols="3">

<thead>

<row>

<entry>Operator class member</entry>

<entry>Object</entry>

<entry>Dependency</entry>

</row>

</thead>

<tbody>

<row>

<entry>Support Procedure 1</entry>

<entry>internal function <function>brin_inclusion_opcinfo()</function></entry>

<entry></entry>

</row>

<row>

<entry>Support Procedure 2</entry>

<entry>internal function <function>brin_inclusion_add_value()</function></entry>

<entry></entry>

</row>

<row>

<entry>Support Procedure 3</entry>

<entry>internal function <function>brin_inclusion_consistent()</function></entry>

<entry></entry>

</row>

<row>

<entry>Support Procedure 4</entry>

<entry>internal function <function>brin_inclusion_union()</function></entry>

<entry></entry>

</row>

<row>

<entry>Support Procedure 11</entry>

<entry>function to merge two elements</entry>

<entry></entry>

</row>

<row>

<entry>Support Procedure 12</entry>

<entry>optional function to check whether two elements are mergeable</entry>

<entry></entry>

</row>

<row>

<entry>Support Procedure 13</entry>

<entry>optional function to check if an element is contained within another</entry>

<entry></entry>

</row>

<row>

<entry>Support Procedure 14</entry>

<entry>optional function to check whether an element is empty</entry>

<entry></entry>

</row>

<row>

<entry>Operator Strategy 1</entry>

<entry>operator left-of</entry>

<entry>Operator Strategy 4</entry>

</row>

<row>

<entry>Operator Strategy 2</entry>

<entry>operator does-not-extend-to-the-right-of</entry>

<entry>Operator Strategy 5</entry>

</row>

<row>

<entry>Operator Strategy 3</entry>

<entry>operator overlaps</entry>

<entry></entry>

</row>

<row>

<entry>Operator Strategy 4</entry>

<entry>operator right-of</entry>

<entry>Operator Strategy 2</entry>

</row>

<row>

<entry>Operator Strategy 5</entry>

<entry>operator does-not-extend-to-the-right-of</entry>

<entry>Operator Strategy 1</entry>

</row>

<row>

<entry>Operator Strategy 6, 18</entry>

<entry>operator same-as-or-equal-to</entry>

<entry>Operator Strategy 7</entry>

</row>

<row>

<entry>Operator Strategy 7, 13, 16, 24, 25</entry>

<entry>operator contains-or-equal-to</entry>

<entry></entry>

</row>

<row>

<entry>Operator Strategy 8, 14, 26, 27</entry>

<entry>operator is-contained-by-or-equal-to</entry>

<entry>Operator Strategy 3</entry>

</row>

<row>

<entry>Operator Strategy 9</entry>

<entry>operator does-not-extend-above</entry>

<entry>Operator Strategy 11</entry>

</row>

<row>

<entry>Operator Strategy 10</entry>

<entry>operator is-below</entry>

<entry>Operator Strategy 12</entry>

</row>

<row>

<entry>Operator Strategy 11</entry>

<entry>operator is-above</entry>

<entry>Operator Strategy 9</entry>

</row>

<row>

<entry>Operator Strategy 12</entry>

<entry>operator does-not-extend-below</entry>

<entry>Operator Strategy 10</entry>

</row>

<row>

<entry>Operator Strategy 20</entry>

<entry>operator less-than</entry>

<entry>Operator Strategy 4</entry>

</row>

<row>

<entry>Operator Strategy 21</entry>

<entry>operator less-than-or-equal-to</entry>

<entry>Operator Strategy 4</entry>

</row>

<row>

<entry>Operator Strategy 22</entry>

<entry>operator greater-than</entry>

<entry>Operator Strategy 1</entry>

</row>

<row>

<entry>Operator Strategy 23</entry>

<entry>operator greater-than-or-equal-to</entry>

<entry>Operator Strategy 1</entry>

</row>

</tbody>

</tgroup>

</table>

<para>

Support procedure numbers 1-10 are reserved for the BRIN internal

functions, so the SQL level functions start with number 11. Support

function number 11 is the main function required to build the index.

It should accept two arguments with the same datatype as the opclass,

and return the union of them. The inclusion opclass can store union

values with different datatypes if it is defined with the

<literal>STORAGE</> parameter. The return value of the union

function should match the <literal>STORAGE</> datatype.

</para>

<para>

Support procedure numbers 12 and 14 are provided to support

irregularities of built-in datatypes. Procedure number 12

is used to support network addresses from different families which

are not mergeable. Procedure number 14 is used to support

empty ranges. Procedure number 13 is an optional but

recommended one, which allows the new value to be checked before

it is passed to the union function. As the BRIN framework can shortcut

some operations when the union is not changed, using this

function can improve index performance.

</para>

<para>

Both minmax and inclusion opclasses support cross-datatype

operators, though with these the dependencies become more complicated.

The minmax opclass requires a full set of operators to be

defined with both arguments having the same datatype. It allows

additional datatypes to be supported by defining extra sets

of operators. Inclusion opclass operator strategies are dependent

on another operator strategy as shown in

<xref linkend="brin-extensibility-inclusion-table">, or the same

operator strategy as themselves. They require the dependency

operator to be defined with the <literal>STORAGE</> datatype as the

left-hand-side argument and the other supported datatype to be the

right-hand-side argument of the supported operator. See

<literal>float4_minmax_ops</> as an example of minmax, and

<literal>box_inclusion_ops</> as an example of inclusion.

</para>

</sect1>

</chapter>