Re: Performance gain from reduction of GROUP BY memory

Alvaro Herrera wrote:
> 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?

I read it as something that _could_ be used by user-defined aggregates,
but not something that would require a changes to a user-defined
aggregate.

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