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Create an official API function for C functions to use to check if they are

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being called as aggregates, and to get the aggregate transition state memory
context if needed.  Use it instead of poking directly into AggState and
WindowAggState in places that shouldn't know so much.

We should have done this in 8.4, probably, but better late than never.

Revised version of a patch by Hitoshi Harada.
This commit is contained in:
Tom Lane
2010-02-08 20:39:52 +00:00
parent 4d3d2e2b03
commit d5768dce10
9 changed files with 124 additions and 110 deletions
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12
doc/src/sgml/xaggr.sgml
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@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/xaggr.sgml,v 1.38 2009/06/20 18:45:28 tgl Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/xaggr.sgml,v 1.39 2010/02/08 20:39:51 tgl Exp $ -->
<sect1 id="xaggr">
<title>User-Defined Aggregates</title>
@ -166,14 +166,10 @@ SELECT attrelid::regclass, array_accum(atttypid::regtype)
<para>
A function written in C can detect that it is being called as an
aggregate transition or final function by seeing if it was passed
an <structname>AggState</> or <structname>WindowAggState</> node
as the function call <quote>context</>,
for example by:
aggregate transition or final function by calling
<function>AggCheckCallContext</>, for example:
<programlisting>
if (fcinfo-&gt;context &amp;&amp;
(IsA(fcinfo-&gt;context, AggState) ||
IsA(fcinfo-&gt;context, WindowAggState)))
if (AggCheckCallContext(fcinfo, NULL))
</programlisting>
One reason for checking this is that when it is true for a transition
function, the first input