Re: OLAP CUBE/ROLLUP Operators and GROUP BY grouping sets

Robert Bedell kirjutas N, 18.12.2003 kell 01:02:

> > > These are not simple projects, I know.
> >
> > Might be a tad ambitious for your first venture into backend hacking...
>
> I agree completely. I'm not purporting to jump in quite that quickly, but
> it is something I would like to see added, and am willing to put the time
> towards. If you have any suggestions for items in the TODO list that would
> move me more quickly towards my goal I would appreciate it.

I guess that by adding hash aggregates Tom solved most problems of
adding ROLLUP, CUBE and GROUPING SETS.

OTOH, I'm not sure if hash aggregates can already spill to disk if not
enough memory is available for keeping them all. If not, then adding
this capability would be great push towards their general use for
GROUPING SETS.

ALso, a mix of scan-over-sorted-group-by + hash aggregates for
out-of-order extra groups would be great way to using less memory for
hash aggregates.

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Hannu