| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Andrew Sullivan <andrew(at)libertyrms(dot)info> |
| Cc: | PostgreSQL general list <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: "NOT IN" predicate hangs result |
| Date: | 2002-04-11 20:41:57 |
| Message-ID: | 18089.1018557717@sss.pgh.pa.us |
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| Lists: | pgsql-general |
Andrew Sullivan <andrew(at)libertyrms(dot)info> writes:
> Just out of curiosity, is there a fundamental reason the optimiser
> doesn't just rewrite NOT IN queries to use the NOT EXISTS form,
There are cases where the NOT IN implementation is better; I'd not like
to see the system forcing one approach to be used.
In the long run we should try to fix IN/NOT IN/EXISTS/NOT EXISTS to be
treated as variant kinds of join, at least for the simple cases that
people tend to use a lot. This has been on the TODO list for awhile
but hasn't risen to the top.
regards, tom lane
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