| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Greg Stark <stark(at)mit(dot)edu> |
| Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Idea for aggregates |
| Date: | 2014-04-04 22:47:57 |
| Message-ID: | 10310.1396651677@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Greg Stark <stark(at)mit(dot)edu> writes:
> The basic idea is to separate the all the properties of the aggregate
> functions except the final function from the final function into a
> separate object. Giving the optimizer the knowledge that multiple
> aggregate functions use the share the same basic machinery and
> semantics for the state is the magic sauce that's a prerequisite for
> the several ideas we were each thinking of.
Why exactly do you need to invent an "aggregate class" concept for this?
Can't the planner just look in pg_aggregate to see that the
sfunc/stype/initcond are the same for two different aggregates?
regards, tom lane
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