Subject: Re: Extremely slow DELETE with cascade foreign keys
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-performance@lists.postgresql.org
References: <8f569ed9-fde9-1fe7-4beb-01945009e040@gmail.com>
 <7973.1512491234@sss.pgh.pa.us>
From: Rodrigo Rosenfeld Rosas <rr.rosas@gmail.com>
Message-ID: <311dd1bb-1295-bf0d-eed7-55742a18484a@gmail.com>
Date: Tue, 5 Dec 2017 15:00:41 -0200
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Em 05-12-2017 14:27, Tom Lane escreveu:
> 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


Thanks, indeed that was the case. I manually inspected about a dozen 
tables referencing field_values and the last one ("references") was 
referenced by another table ("highlighted_texts") and the reference_id 
column that has a foreign key on "references"(id) was missing an index.

Good job :)

Best,

Rodrigo.