Subject: Looking for an efficient way to replace efficient NOT IN when landling very large data

From: Shaozhong SHI <[email-masked]>
Date: Tue, 11 Apr 2023 10:27:59 +0100

Select a.id, a.name, b.id, b.name from a_large_table a, definitive b where (
a.id, b.name) not in
(select b.id, b.name from definitive b)

is very slow.

Is there a faster way to do so?

Regards,

David

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From: David Rowley <[email-masked]>
Date: Tue, 11 Apr 2023 21:33:42 +1200

On Tue, 11 Apr 2023 at 21:28, Shaozhong SHI <[email-masked]> wrote:
>
> Select a.id, a.name, b.id, b.name from a_large_table a, definitive b where (a.id, b.name) not in

It depends on what your exact requirements are for the NULL handling
that NOT IN provides.  Do you need the query to return 0 rows if b.id
and b.name are null?  This question is moot if none of the columns or
either table allow NULLs.

If you don't require that, then you'll give the planner more
flexibility to choose a more efficient plan if you use NOT EXISTS
instead.

David

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From: Shaozhong SHI <[email-masked]>
Date: Tue, 11 Apr 2023 10:44:02 +0100

> flexibility to choose a more efficient plan if you use NOT EXISTS

I would like to try out an example of NOT EXISTS way and see how the
replacement works.

Regards,

David