Re: FOR EACH ROW triggers on partitioned tables

From: Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>
To: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Simon Riggs <simon(at)2ndquadrant(dot)com>
Subject: Re: FOR EACH ROW triggers on partitioned tables
Date: 2018-02-16 02:06:12
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On 2018/02/16 6:55, Alvaro Herrera wrote:
> Amit Langote wrote:
>> On 2018/02/15 6:26, Alvaro Herrera wrote:
>>> Another option is to rethink this feature from the ground up: instead of
>>> cloning catalog rows for each children, maybe we should have the trigger
>>> lookup code, when running DML on the child relation (the partition),
>>> obtain trigger entries not only for the child relation itself but also
>>> for its parents recursively -- so triggers defined in the parent are
>>> fired for the partitions, too. I'm not sure what implications this has
>>> for constraint triggers.
>>> The behavior should be the same, except that you cannot modify the
>>> trigger (firing conditions, etc) on the partition individually -- it
>>> works at the level of the whole partitioned table instead.
>> Do you mean to fire these triggers only if the parent table (not a child
>> table/partition) is addressed in the DML, right? If the table directly
>> addressed in the DML is a partition whose parent has a row-level trigger,
>> then that trigger should not get fired I suppose.
> No, I think that would be strange and cause data inconsistencies.
> Inserting directly into the partition is seen as a performance
> optimization (compared to inserted into the partitioned table), so we
> don't get to skip firing the triggers defined on the parent because the
> behavior would become different. In other words, the performance
> optimization breaks the database.

OK, that makes sense.


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