| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | David Fetter <david(at)fetter(dot)org> |
| Cc: | PG Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: GROUPING |
| Date: | 2015-05-20 18:41:49 |
| Message-ID: | 1183.1432147309@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
David Fetter <david(at)fetter(dot)org> writes:
> While kicking the tires on the new GROUPING() feature, I noticed that
> NUMERIC has no cast to bit(n). GROUPING() produces essentially a
> bitmap, although the standard mandates for some reason that it be a
> numeric type.
> I was thinking it should produce NUMERIC rather than int4 as it does
> now in order to accommodate large numbers of columns, but the
> usefulness of the bitmap is greatly increased if there's a simple CAST
> to bit(n).
Maybe INT8 would be a better choice than INT4? But I'm not sure there's
any practical use-case for more than 30 grouping sets anyway. Keep in
mind the actual output volume probably grows like 2^N.
regards, tom lane
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