Message-ID: <450ABB85.9060508@logix-tt.com>
Date: Fri, 15 Sep 2006 16:41:09 +0200
From: Markus Schaber <schabi@logix-tt.com>
Organization: Logical Tracking and Tracing International AG, Switzerland
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To: PostgreSQL SQL List <pgsql-sql@postgresql.org>
Subject: Re: Aggregates with internal state type?
References: <45086B40.3000200@logix-tt.com> <16722.1158181987@sss.pgh.pa.us>
	<450875FC.9040907@logix-tt.com>
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Hi, Tom,

Markus Schaber wrote:

>>> This lead me to the question whether it is possible to use "internal" as
>>> state type for an Aggregate whose functions are implemented in C.
>> No, because the system has no idea what the representation of an
>> "internal" state value might be, and in particular how to copy it.
>> The same goes for other pseudotypes.
> Ah, I see. So there's no possibility to pass some void* kind of
> intermediate data, I have to craft at least a dummy PostgreSQL datatype
> for it.
> This also solves the question how such things would be cleaned up in
> case of an intermediate error.

As we are at it:

How would you estimate the chances for a Patch to get included that lets
C functions pass some void* data pointer around in an aggregate, when
the aggregate provides a custom "clean-up" function that gets called
whenever the scan gets aborted prematurely?

I assume that this could help speeding up e. G. Array Aggregates, or
PostGIS geomUnion() or string concatenations etc.

Thanks,
Markus
-- 
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf.     | Software Development GIS

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