Re: Optimizing NOT IN plans / verify rewrite
| От | Dave Crooke |
|---|---|
| Тема | Re: Optimizing NOT IN plans / verify rewrite |
| Дата | |
| Msg-id | AANLkTinfjRkXJoKD4p8UTEBYtF4AP5+vPuGNcxp=-J+U@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: Optimizing NOT IN plans / verify rewrite ("Kevin Grittner" <Kevin.Grittner@wicourts.gov>) |
| Ответы |
Re: Optimizing NOT IN plans / verify rewrite
|
| Список | pgsql-performance |
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
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@wicourts.gov> wrote:
> No NULLs. It looks like it's a good deal slower than the LOJOn 8.4 and later the NOT EXISTS I suggested is a bit faster than
> version, but a good deal faster than the original.
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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