Re: *very* inefficient choice made by the planner (regarding

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Jean-Luc Lachance <jllachan(at)sympatico(dot)ca>
Cc: pgsql-performance(at)postgresql(dot)org, Frank van Vugt <ftm(dot)van(dot)vugt(at)foxi(dot)nl>
Subject: Re: *very* inefficient choice made by the planner (regarding
Date: 2004-06-10 15:59:05
Message-ID: 25304.1086883145@sss.pgh.pa.us
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Jean-Luc Lachance <jllachan(at)sympatico(dot)ca> writes:
> If the two statments are functionally equivalent, why can't PG rewrite
> the "NOT IN" version into the more efficient "NOT EXISTS"?

They're not equivalent. In particular, the behavior in the presence of
NULLs is quite different.

regards, tom lane

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