Hello David http://www.postgresql.org/docs/faqs.TODO.html
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. Regards Pavel Stehule 2008/6/3 David Fetter <[EMAIL PROTECTED]>: > Folks, > > I've noticed that queries of the form > > SELECT DISTNCT foo, bar, baz > FROM quux > WHERE ... > > perform significantly worse than the equivalent using GROUP BY. > > SELECT foo, bar, baz > FROM quux > WHERE ... > GROUP BY foo, bar, baz > > Where would I start looking in order to make them actually equivalent > from the planner's point of view? Also, would back-patching this make > sense? It doesn't change any APIs, but it does make some queries go > faster. > > Cheers, > David. > -- > David Fetter <[EMAIL PROTECTED]> http://fetter.org/ > Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter > Skype: davidfetter XMPP: [EMAIL PROTECTED] > > Remember to vote! > Consider donating to Postgres: http://www.postgresql.org/about/donate > > -- > Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-hackers > -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
