Re: Performance gain from reduction of GROUP BY memory - Mailing list pgsql-hackers

From Alvaro Herrera
Subject Re: Performance gain from reduction of GROUP BY memory
Date
Msg-id 20050830143952.GI16133@surnet.cl
Whole thread Raw
In response to Re: Performance gain from reduction of GROUP BY memory  (Bruce Momjian <pgman@candle.pha.pa.us>)
Responses Re: Performance gain from reduction of GROUP BY memory  (Bruce Momjian <pgman@candle.pha.pa.us>)
List pgsql-hackers
On Tue, Aug 30, 2005 at 10:23:49AM -0400, Bruce Momjian wrote:

> > > 2005-03-12 15:25  tgl
> > > 
> > >     * contrib/intagg/int_aggregate.c,
> > >     contrib/intagg/int_aggregate.sql.in, doc/src/sgml/xaggr.sgml,
> > >     doc/src/sgml/xfunc.sgml, src/backend/executor/nodeAgg.c,
> > >     src/backend/utils/adt/int8.c: Adjust the API for aggregate function
> > >     calls so that a C-coded function can tell whether it is being used
> > >     as an aggregate or not.  This allows such a function to avoid
> > >     re-pallocing a pass-by-reference transition value; normally it
> > >     would be unsafe for a function to scribble on an input, but in the
> > >     aggregate case it's safe to reuse the old transition value.  Make
> > >     int8inc() do this.  This gets a useful improvement in the speed of
> > >     COUNT(*), at least on narrow tables (it seems to be swamped by I/O
> > >     when the table rows are wide).    Per a discussion in early December
> > >     with Neil Conway.  I also fixed int_aggregate.c to check this,
> > >     thereby turning it into something approaching a supportable
> > >     technique instead of being a crude hack.
> 
> I don't usually document internal API changes in the release notes. 
> Should I?

Doesn't this potentially affect user-defined aggregates?

-- 
Alvaro Herrera <alvherre[]alvh.no-ip.org>      Architect, www.EnterpriseDB.com
"Lo esencial es invisible para los ojos" (A. de Saint Exúpery)


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