Re: Optimizing NOT IN plans / verify rewrite

[Dave Crooke <dcrooke@xxxxxxxxx>]

With Oracle, I've found an anti-union (MINUS in Oracle, EXCEPT in PGSQL) to be often a bit better than an anti-join, which is in turn faster than NOT IN. Depends of course on row distribution and index layouts, and a bunch of other details.

Depending on what you're returning, it can pay to make sure this computation is done with the shortest possible rows, if necessary using a subquery.

Cheers
Dave

On Mon, Aug 2, 2010 at 2:49 PM, Kevin Grittner <Kevin.Grittner@xxxxxxxxxxxx> wrote:

Maciek Sakrejda <msakrejda@xxxxxxxxxxx> wrote:

> No NULLs. It looks like it's a good deal slower than the LOJ
> version, but a good deal faster than the original.

On 8.4 and later the NOT EXISTS I suggested is a bit faster than
your fast version, since Tom did some very nice work in this area,
implementing semi join and anti join.  If you've got much load with
this kind of query, it might be worth upgrading.

-Kevin

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