Re: Fixing the representation of ORDER BY/GROUP BY/DISTINCT - Mailing list pgsql-hackers

From Gregory Stark
Subject Re: Fixing the representation of ORDER BY/GROUP BY/DISTINCT
Date
Msg-id 87protgclx.fsf@oxford.xeocode.com
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In response to Fixing the representation of ORDER BY/GROUP BY/DISTINCT  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-hackers
"Tom Lane" <tgl@sss.pgh.pa.us> writes:

> This is important for making the world safe for hashed DISTINCT, since
> AFAICS we probably can't ever use hashing for DISTINCT ON --- its definition
> is too dependent on the assumption of sorting.

I don't think that's true. We could store the sort key in the hash along with
the resulting tuple and replace the resulting tuple iff the new sort key is
less than the old sort key.

--  Gregory Stark EnterpriseDB          http://www.enterprisedb.com Ask me about EnterpriseDB's Slony Replication
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