Re: Simple delete query is taking too long (never ends) - Mailing list pgsql-performance

From Tom Lane
Subject Re: Simple delete query is taking too long (never ends)
Date
Msg-id 14810.1447342595@sss.pgh.pa.us
Whole thread Raw
In response to Re: Simple delete query is taking too long (never ends)  (Merlin Moncure <mmoncure@gmail.com>)
List pgsql-performance
Merlin Moncure <mmoncure@gmail.com> writes:
> On Wed, Nov 11, 2015 at 1:33 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> If you're not sure which table is the problem, try doing an EXPLAIN
>> ANALYZE of a DELETE that will only remove a few rows.  You should
>> see some time blamed on a trigger associated with the FK constraint.

> You've answered this question (with the same answer) what feels like a
> gazillion times.  I guess the underlying problem is that EXPLAIN is,
> uh, not explaining things very well.

In principle, a plain EXPLAIN could list the triggers that would
potentially be fired by the query, but I'm afraid that wouldn't help
much.  The actual performance problem is down inside the trigger,
which is an opaque black box so far as EXPLAIN can possibly know.

            regards, tom lane


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