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Document BRIN's inclusion opclass framework

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Backpatch to 9.5 -- this should have been part of b0b7be6133, but we
didn't have 38b03caebc either at the time.

Author: Emre Hasegeli
Revised by: Ian Barwick
Discussion:
 http://www.postgresql.org/message-id/CAE2gYzyB39Q9up_-TO6FKhH44pcAM1x6n_Cuj15qKoLoFihUVg@mail.gmail.com
 http://www.postgresql.org/message-id/562DA711.3020305@2ndquadrant.com
pull/7/merge
Alvaro Herrera 10 years ago
parent 21a4e4a4c9
commit c15898c1d5
1 changed files with 191 additions and 5 deletions
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      doc/src/sgml/brin.sgml

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@ -535,7 +535,7 @@ typedef struct BrinOpcInfo
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>
@ -566,19 +566,19 @@ typedef struct BrinOpcInfo
<tbody>
<row>
<entry>Support Procedure 1</entry>
<entry>function <function>brin_minmax_opcinfo()</function></entry>
<entry>internal function <function>brin_minmax_opcinfo()</function></entry>
</row>
<row>
<entry>Support Procedure 2</entry>
<entry>function <function>brin_minmax_add_value()</function></entry>
<entry>internal function <function>brin_minmax_add_value()</function></entry>
</row>
<row>
<entry>Support Procedure 3</entry>
<entry>function <function>brin_minmax_consistent()</function></entry>
<entry>internal function <function>brin_minmax_consistent()</function></entry>
</row>
<row>
<entry>Support Procedure 4</entry>
<entry>function <function>brin_minmax_union()</function></entry>
<entry>internal function <function>brin_minmax_union()</function></entry>
</row>
<row>
<entry>Operator Strategy 1</entry>
@ -603,5 +603,191 @@ typedef struct BrinOpcInfo
</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>

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