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Allow aggregate transition states to be serialized and deserialized.

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This is necessary infrastructure for supporting parallel aggregation
for aggregates whose transition type is "internal".  Such values
can't be passed between cooperating processes, because they are
just pointers.

David Rowley, reviewed by Tomas Vondra and by me.
This commit is contained in:
Robert Haas
2016-03-29 15:04:05 -04:00
parent 7f0a2c85fb
commit 5fe5a2cee9
25 changed files with 794 additions and 193 deletions
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18
doc/src/sgml/catalogs.sgml
View File

@ -412,6 +412,18 @@
<entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
<entry>Combine function (zero if none)</entry>
</row>
<row>
<entry><structfield>aggserialfn</structfield></entry>
<entry><type>regproc</type></entry>
<entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
<entry>Serialization function (zero if none)</entry>
</row>
<row>
<entry><structfield>aggdeserialfn</structfield></entry>
<entry><type>regproc</type></entry>
<entry><literal><link linkend="catalog-pg-proc"><structname>pg_proc</structname></link>.oid</literal></entry>
<entry>Deserialization function (zero if none)</entry>
</row>
<row>
<entry><structfield>aggmtransfn</structfield></entry>
<entry><type>regproc</type></entry>
@ -454,6 +466,12 @@
<entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
<entry>Data type of the aggregate function's internal transition (state) data</entry>
</row>
<row>
<entry><structfield>aggserialtype</structfield></entry>
<entry><type>oid</type></entry>
<entry><literal><link linkend="catalog-pg-type"><structname>pg_type</structname></link>.oid</literal></entry>
<entry>Return data type of the aggregate function's serialization function (zero if none)</entry>
</row>
<row>
<entry><structfield>aggtransspace</structfield></entry>
<entry><type>int4</type></entry>

50
doc/src/sgml/ref/create_aggregate.sgml
View File

@ -28,6 +28,9 @@ CREATE AGGREGATE <replaceable class="parameter">name</replaceable> ( [ <replacea
[ , FINALFUNC = <replaceable class="PARAMETER">ffunc</replaceable> ]
[ , FINALFUNC_EXTRA ]
[ , COMBINEFUNC = <replaceable class="PARAMETER">combinefunc</replaceable> ]
[ , SERIALFUNC = <replaceable class="PARAMETER">serialfunc</replaceable> ]
[ , DESERIALFUNC = <replaceable class="PARAMETER">deserialfunc</replaceable> ]
[ , SERIALTYPE = <replaceable class="PARAMETER">serialtype</replaceable> ]
[ , INITCOND = <replaceable class="PARAMETER">initial_condition</replaceable> ]
[ , MSFUNC = <replaceable class="PARAMETER">msfunc</replaceable> ]
[ , MINVFUNC = <replaceable class="PARAMETER">minvfunc</replaceable> ]
@ -47,6 +50,9 @@ CREATE AGGREGATE <replaceable class="parameter">name</replaceable> ( [ [ <replac
[ , FINALFUNC = <replaceable class="PARAMETER">ffunc</replaceable> ]
[ , FINALFUNC_EXTRA ]
[ , COMBINEFUNC = <replaceable class="PARAMETER">combinefunc</replaceable> ]
[ , SERIALFUNC = <replaceable class="PARAMETER">serialfunc</replaceable> ]
[ , DESERIALFUNC = <replaceable class="PARAMETER">deserialfunc</replaceable> ]
[ , SERIALTYPE = <replaceable class="PARAMETER">serialtype</replaceable> ]
[ , INITCOND = <replaceable class="PARAMETER">initial_condition</replaceable> ]
[ , HYPOTHETICAL ]
)
@ -61,6 +67,9 @@ CREATE AGGREGATE <replaceable class="PARAMETER">name</replaceable> (
[ , FINALFUNC = <replaceable class="PARAMETER">ffunc</replaceable> ]
[ , FINALFUNC_EXTRA ]
[ , COMBINEFUNC = <replaceable class="PARAMETER">combinefunc</replaceable> ]
[ , SERIALFUNC = <replaceable class="PARAMETER">serialfunc</replaceable> ]
[ , DESERIALFUNC = <replaceable class="PARAMETER">deserialfunc</replaceable> ]
[ , SERIALTYPE = <replaceable class="PARAMETER">serialtype</replaceable> ]
[ , INITCOND = <replaceable class="PARAMETER">initial_condition</replaceable> ]
[ , MSFUNC = <replaceable class="PARAMETER">msfunc</replaceable> ]
[ , MINVFUNC = <replaceable class="PARAMETER">minvfunc</replaceable> ]
@ -436,6 +445,47 @@ SELECT col FROM tab ORDER BY col USING sortop LIMIT 1;
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">serialfunc</replaceable></term>
<listitem>
<para>
In order to allow aggregate functions with an <literal>INTERNAL</>
<replaceable class="PARAMETER">state_data_type</replaceable> to
participate in parallel aggregation, the aggregate must have a valid
<replaceable class="PARAMETER">serialfunc</replaceable>, which must
serialize the aggregate state into <replaceable class="PARAMETER">
serialtype</replaceable>. This function must take a single argument of
<replaceable class="PARAMETER">state_data_type</replaceable> and return
<replaceable class="PARAMETER">serialtype</replaceable>. A
corresponding <replaceable class="PARAMETER">deserialfunc</replaceable>
is also required.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">deserialfunc</replaceable></term>
<listitem>
<para>
Deserializes a previously serialized aggregate state back into
<replaceable class="PARAMETER">state_data_type</replaceable>. This
function must take a single argument of <replaceable class="PARAMETER">
serialtype</replaceable> and return <replaceable class="PARAMETER">
state_data_type</replaceable>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">serialtype</replaceable></term>
<listitem>
<para>
The data type to into which an <literal>INTERNAL</literal> aggregate
state should be serialized.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><replaceable class="PARAMETER">initial_condition</replaceable></term>
<listitem>