| From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
|---|---|
| To: | "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com> |
| Cc: | Greg Stark <gsstark(at)mit(dot)edu>, Neil Conway <neilc(at)samurai(dot)com>, "Hans-J?rgen Sch?nig" <postgres(at)cybertec(dot)at>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: DISTINCT vs. GROUP BY |
| Date: | 2005-09-20 21:05:05 |
| Message-ID: | 200509202105.j8KL55f24171@candle.pha.pa.us |
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| Lists: | pgsql-hackers |
Jim C. Nasby wrote:
> On Mon, Sep 19, 2005 at 10:16:36PM -0400, Bruce Momjian wrote:
> >
> > Added to TODO:
> >
> > * Allow DISTINCT to use hashing like GROUP BY
>
> 3 lines above we have...
> Consider using hash buckets to do DISTINCT, rather than sorting
> This would be beneficial when there are few distinct values.
OK, I have merged these items into one.
>
> Can you add
> http://archives.postgresql.org/pgsql-hackers/2005-09/msg00810.php? All I
> could find on the other TODO was
> http://archives.postgresql.org/pgsql-committers/2004-09/msg00028.php,
> which doesn't help much...
What do these URL's have that the current TODO does not?
* Consider using hash buckets to do DISTINCT, rather than sorting
This would be beneficial when there are few distinct values. This is
already used by GROUP BY.
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
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