From: Tom Lane <tgl@sss.pgh.pa.us>
To: Rodrigo Rosenfeld Rosas <rr.rosas@gmail.com>
cc: pgsql-performance@lists.postgresql.org
Subject: Re: Extremely slow DELETE with cascade foreign keys
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References: <8f569ed9-fde9-1fe7-4beb-01945009e040@gmail.com>
Comments: In-reply-to Rodrigo Rosenfeld Rosas <rr.rosas@gmail.com>
	message dated "Tue, 05 Dec 2017 14:21:38 -0200"
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Date: Tue, 05 Dec 2017 11:27:14 -0500
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Rodrigo Rosenfeld Rosas <rr.rosas@gmail.com> writes:
> Hi, I think something changed recently in my development environment as 
> I don't recall deletes being so slow before.
> I've created a new dump and restored to a new database, ran VACUUM FULL 
> ANALYSE and a simple delete takes forever as you can see here:

The usual suspect for this is not having an index on some FK referencing
column, thus forcing the FK check trigger to seq-scan the entire
referencing table for each referenced row that is to be deleted.

			regards, tom lane