Re: Do docs miss information about timing of triggers?

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От David G. Johnston
Тема Re: Do docs miss information about timing of triggers?
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Msg-id CAKFQuwakuFOhTuKp6e=t+p4mNJVZHVi6y9Btkwz8vUKA9VpeAw@mail.gmail.com
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Ответ на Do docs miss information about timing of triggers?  (Thomas Güttler <guettliml@thomas-guettler.de>)
Ответы Re: Do docs miss information about timing of triggers?  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-general
On Thu, May 26, 2016 at 8:50 AM, Thomas Güttler <guettliml@thomas-guettler.de> wrote:
I (and a team mate) guess that the docs miss information about the timing of triggers,
which are not constraint triggers:

https://www.postgresql.org/docs/devel/static/sql-createtrigger.html


{{{
When the CONSTRAINT option is specified, this command creates a constraint trigger. This is the same as a regular trigger except that the timing of the trigger firing can be adjusted using SET CONSTRAINTS. Constraint triggers must be AFTER ROW triggers on tables. They can be fired either at the end of the statement causing the triggering event, or at the end of the containing transaction; in the latter case they are said to be deferred. A pending deferred-trigger firing can also be forced to happen immediately by using SET CONSTRAINTS. Constraint triggers are expected to raise an exception when the constraints they implement are violated.
}}}

OK, timing of constraint triggers is explained.

But I think the docs don't state the timing of normal AFTER triggers.

Or am I blind?

​Through omission.  Constraint triggers can optionally be deferred - given the specificity that means normal triggers cannot.

By the time a given statement has completed all relevant normal triggers will have fired.  The various timings of combinations of (before/after + row/statement) are not explicitly documented though there doesn't seem to be non-intuitive behavior going on.

​Maybe knowing why you are asking the question will help us to understand if/how things could be improved.

David J.

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