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

From: Jean-Luc Lachance <jllachan(at)sympatico(dot)ca>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
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 16:56:26
Message-ID: 40C892BA.8080704@sympatico.ca
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I agree, but it should be a simple rewrite. No?

x IS NULL/IS NOT NULL AND/OR NOT EXISTS

Tom Lane wrote:

> 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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