Re: Extremely slow DELETE with cascade foreign keys

From: Rodrigo Rosenfeld Rosas <rr(dot)rosas(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-performance(at)lists(dot)postgresql(dot)org
Subject: Re: Extremely slow DELETE with cascade foreign keys
Date: 2017-12-05 17:00:41
Message-ID: 311dd1bb-1295-bf0d-eed7-55742a18484a@gmail.com
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Em 05-12-2017 14:27, Tom Lane escreveu:
> Rodrigo Rosenfeld Rosas <rr(dot)rosas(at)gmail(dot)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.

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