"Herouth Maoz" <hero...@unicell.co.il> writes:
> I was instructed to delete old records from one of the tables in our
> production system. The deletion took hours and I had to stop it in
> mid-operation and reschedule it as a night job. But then I had to do the same
> when I got up in the morning and it was still running.
> I got an interesting clue, though, when I canceled the deletion the second
> time around. I got the following error message:
> Cancel request sent
> ERROR: canceling statement due to user request
> CONTEXT: SQL statement "SELECT 1 FROM ONLY "public"."sent_messages" x WHERE
> $1 OPERATOR(pg_catalog.=) "subscription_id" FOR SHARE OF x"
Yup, that's a clue all right. I'll bet a nickel that you don't
have an index on the foreign key's referencing column (ie,
sent_messages.subscription_id). That means each delete in
the referenced table has to seqscan the referencing table to
see if the delete would result in an FK violation.
regards, tom lane
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