From: | Hans-Juergen Schoenig <postgres(at)cybertec(dot)at> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-hackers(at)postgreSQL(dot)org |
Subject: | Re: Status of DISTINCT-by-hashing work |
Date: | 2008-08-06 13:11:42 |
Message-ID: | 4899A30E.6010101@cybertec.at |
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Lists: | pgsql-hackers |
Tom Lane wrote:
> I've pretty much finished the project I got a bee in my bonnet about
> last week, which is to teach SELECT DISTINCT how to (optionally) use
> hashing for grouping in the same way that GROUP BY has been able to do
> for awhile.
>
> There are still two places in the system that hard-wire the use of
> sorting for duplicate elimination:
>
> * Set operations (UNION/INTERSECT/EXCEPT)
>
> * Aggregate functions with DISTINCT
>
> I'm thinking of trying to fix set operations before I leave this topic,
> but I'm not sure it's worth the trouble to change DISTINCT aggregates.
> They'd be a lot more work (since there's no executor infrastructure
> in place that could be used) and the return on investment seems low.
>
> Comments?
>
> regards, tom lane
>
>
i feel it exactly the same way.
DISTINCT has been a place people wanted to see fixed for a while but set
operations are nothing I would really worry about.
what we have now is absolutely fine.
given the list of more important issues, i'd vote for something else.
best regards,
hans
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PostgreSQL Solutions and Support
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www.postgresql-support.de, www.postgresql-support.com
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