| From: | Dean Rasheed <dean(dot)a(dot)rasheed(at)gmail(dot)com> |
|---|---|
| To: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
| Cc: | Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, Mark Dilger <hornschnorter(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: improving GROUP BY estimation |
| Date: | 2016-03-31 18:47:44 |
| Message-ID: | CAEZATCWQ3L8rKsp0+GbO-7D2weYjxZU3668fJx1ZgoVa_QL1LA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 30 March 2016 at 14:03, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
> Attached is v4 of the patch
Thanks, I think this is good to go, except that I think we need to use
pow() rather than powl() because AIUI powl() is new to C99, and so
won't necessarily be available on all supported platforms. I don't
think we need worry about loss of precision, since that would only be
an issue if rel->rows / rel->tuples were smaller than maybe 10^-14 or
so, and it seems unlikely we'll get anywhere near that any time soon.
I think this is a good, well thought-out change, so unless anyone
objects I'll push it (probably this weekend).
Regards,
Dean
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