Tom Lane wrote:
> In create_opclass.sgml, not only do we have the list of AMs supporting
> STORAGE, but there is also a paragraph describing which AMs do what
> for input datatypes of FUNCTION members (around line 175).
I placed BRIN together with gist/gin/spgist here, namely that the optype
defaults to the opclass' datatype.
> xindex.sgml has that one list you mentioned, but there's not much
> point in fixing that when BRIN indexes fail to be described either in
> 35.14.2 or 35.14.3, where they certainly should be. And there are
> other places throughout that chapter that say that such-and-such AMs
> support each feature as it's discussed.
In 35.14.2 I added the table of strategies in the "minmax" opclasses;
the list for the "inclusion" opclasses would be much longer. Since GIN
doesn't document anything other than its array support, I'm not really
sure that we want/need to document the "inclusion" opclasses also.
In 35.14.3 I added the table of four basic support procs. I think
that's all that's strictly necessary. For inclusion we have a bunch of
additional support procs.
I also added a paragraph to 35.14.5, indicating that "minmax" is pretty
much the same as btree. "Inclusion" opclasses are supposed to support
cross-datatype operators too (supposedly we could support
above/below/containment etc for points relative to boxes, for example,
if we got around to make a decision regarding floating point comparisons
in geometry operators), but we don't have any, so I hesitate to say
anything about this.
Patch attached.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
diff --git a/doc/src/sgml/ref/create_opclass.sgml b/doc/src/sgml/ref/create_opclass.sgml
index 527f33c..7b9d55d 100644
--- a/doc/src/sgml/ref/create_opclass.sgml
+++ b/doc/src/sgml/ref/create_opclass.sgml
@@ -172,7 +172,7 @@ CREATE OPERATOR CLASS <replaceable class="parameter">name</replaceable> [ DEFAUL
the input data type(s) of the function (for B-tree comparison functions
and hash functions)
or the class's data type (for B-tree sort support functions and all
- functions in GiST, SP-GiST and GIN operator classes). These defaults
+ functions in GiST, SP-GiST, GIN and BRIN operator classes). These defaults
are correct, and so <replaceable
class="parameter">op_type</replaceable> need not be specified in
<literal>FUNCTION</> clauses, except for the case of a B-tree sort
@@ -232,7 +232,7 @@ CREATE OPERATOR CLASS <replaceable class="parameter">name</replaceable> [ DEFAUL
<para>
The data type actually stored in the index. Normally this is
the same as the column data type, but some index methods
- (currently GiST and GIN) allow it to be different. The
+ (currently GiST, GIN and BRIN) allow it to be different. The
<literal>STORAGE</> clause must be omitted unless the index
method allows a different type to be used.
</para>
diff --git a/doc/src/sgml/xindex.sgml b/doc/src/sgml/xindex.sgml
index aaf9d8c..7a81ddd 100644
--- a/doc/src/sgml/xindex.sgml
+++ b/doc/src/sgml/xindex.sgml
@@ -323,6 +323,49 @@
</table>
<para>
+ BRIN indexes are similar to GiST, SP-GiST and GIN indexes in that they
+ don't have a fixed set of strategies either. Instead the support routines
+ of each operator class interpret the strategy nnumbers according to the
+ operator class's definition. As an example, the strategy numbers used by
+ the built-in <literal>Minmax</> operator classes are shown in
+ <xref linkend="xindex-brin-minmax-strat-table">.
+ </para>
+
+ <table tocentry="1" id="xindex-brin-minmax-strat-table">
+ <title>BRIN Minmax Strategies</title>
+ <tgroup cols="2">
+ <thead>
+ <row>
+ <entry>Operation</entry>
+ <entry>Strategy Number</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>less than</entry>
+ <entry>1</entry>
+ </row>
+ <row>
+ <entry>less than or equal</entry>
+ <entry>2</entry>
+ </row>
+ <row>
+ <entry>equal</entry>
+ <entry>3</entry>
+ </row>
+ <row>
+ <entry>greater than or equal</entry>
+ <entry>4</entry>
+ </row>
+ <row>
+ <entry>greater than</entry>
+ <entry>5</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ <para>
Notice that all the operators listed above return Boolean values. In
practice, all operators defined as index method search operators must
return type <type>boolean</type>, since they must appear at the top
@@ -602,6 +645,53 @@
</table>
<para>
+ BRIN indexes have four basic support functions, as shown in
+ <xref linkend="xindex-brin-support-table">; those basic functions
+ may require additional support functions to be provided.
+ (For more information see <xref linkend="brin-extensibility">.)
+ </para>
+
+ <table tocentry="1" id="xindex-brin-support-table">
+ <title>GIN Support Functions</title>
+ <tgroup cols="3">
+ <thead>
+ <row>
+ <entry>Function</entry>
+ <entry>Description</entry>
+ <entry>Support Number</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry><function>opcInfo</></entry>
+ <entry>
+ return internal information describing the indexed columns'
+ summary data
+ </entry>
+ <entry>1</entry>
+ </row>
+ <row>
+ <entry><function>add_value</></entry>
+ <entry>add a new value to an existing summary index tuple</entry>
+ <entry>2</entry>
+ </row>
+ <row>
+ <entry><function>consistent</></entry>
+ <entry>determine whether value matches query condition</entry>
+ <entry>3</entry>
+ </row>
+ <row>
+ <entry><function>union</></entry>
+ <entry>
+ compute union of two summary tuples
+ </entry>
+ <entry>4</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </table>
+
+ <para>
Unlike search operators, support functions return whichever data
type the particular index method expects; for example in the case
of the comparison function for B-trees, a signed integer. The number
@@ -609,7 +699,7 @@
dependent on the index method. For B-tree and hash the comparison and
hashing support functions take the same input data types as do the
operators included in the operator class, but this is not the case for
- most GiST, SP-GiST, and GIN support functions.
+ most GiST, SP-GiST, GIN, and BRIN support functions.
</para>
</sect2>
@@ -994,6 +1084,17 @@ ALTER OPERATOR FAMILY integer_ops USING btree ADD
handle.
</para>
+ <para>
+ In BRIN, the requirements depends on the framework that provides the
+ operator classes. For operator classes based on <literal>Minmax</>,
+ the behavior required is the same as for B-tree operator families:
+ all the operators in the family must sort compatibly, and casts must
+ not change the associated sort ordering.
+ Operator classes based on the <literal>Inclusion</> framework can
+ theoretically support cross-data-type operations, but there's no
+ demonstrating implementation yet.
+ </para>
+
<note>
<para>
Prior to <productname>PostgreSQL</productname> 8.3, there was no concept
@@ -1178,7 +1279,7 @@ CREATE OPERATOR CLASS polygon_ops
STORAGE box;
</programlisting>
- At present, only the GiST and GIN index methods support a
+ At present, only the GiST, GIN and BRIN index methods support a
<literal>STORAGE</> type that's different from the column data type.
The GiST <function>compress</> and <function>decompress</> support
routines must deal with data-type conversion when <literal>STORAGE</>
@@ -1188,6 +1289,10 @@ CREATE OPERATOR CLASS polygon_ops
integer-array columns might have keys that are just integers. The
GIN <function>extractValue</> and <function>extractQuery</> support
routines are responsible for extracting keys from indexed values.
+ BRIN is similar to GIN: the <literal>STORAGE</> type identifies the
+ type of the stored summary values, and operator classes' support
+ procedures are responsible for interpreting the summary values
+ correctly.
</para>
</sect2>
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