Re: Performance problem with DELETE FROM/correlated subqueries

Clemens Ladisch <clemens-P6GI/[email protected]> Fri, 7 Feb 2020 09:25:11 +0100

Newsgroups	gmane.comp.db.sqlite.general
Message-ID	<[email protected]>

Jürgen Baier wrote:
>   CREATE TABLE main ( ATT1 INT, ATT2 INT, PRIMARY KEY (ATT1,ATT2) );
>   CREATE TABLE staging ( ATT1 INT, ATT2 INT );
>
> Then I execute
>
>   DELETE FROM main WHERE EXISTS (SELECT 1 FROM staging WHERE main.att1 = staging.att1 AND main.att2 = staging.att2)
>
> which takes a very long time.

DELETE FROM main WHERE (att1, att2) IN (SELECT att1, att2 FROM staging);


Regards,
Clemens
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