Hannu Krosing kirjutas L, 07.12.2002 kell 02:32:
> Tom Lane kirjutas L, 07.12.2002 kell 01:46:
> > "Josh Berkus" <josh(at)agliodbs(dot)com> writes:
> > > What have other Postgres users done to speed up aggregates on large
> > > tables?
> > FWIW, I've implemented hashed aggregation in CVS tip.
> This should also make it easier to implement all kinds of GROUP BY
> ROLLUP|CUBE|GROUPING SETS|() queries.
Of these only ROLLUP can be done in one scan after sort, all others
would generally require several scans without hashing.
I just noticed that we don't even have a TODO for this. I think this
would be a good TODO item.
Bruce, could you add:
* Add ROLLUP, CUBE, GROUPING SETS options to GROUP BY
They are all defined in SQL99 p.79 <group by clause>
Some more background info (from a quick Google search)
a very short overview:
more thorough guide for DB2:
In response to
pgsql-performance by date
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|Subject: Re: Speeding up aggregates|
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