Re: Check constraints on partition parents only?

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От	Nikhil Sontakke
Тема	Re: Check constraints on partition parents only?
Дата	27 июля 2011 г. 10:40:09
Msg-id	CABamaqNMDBJFTMQk8FzugZG6uZvvQ+DprBEcbRGnSWkB-qW3EA@mail.gmail.com обсуждение исходный текст
Ответ на	Re: Check constraints on partition parents only? (Andrew Dunstan <andrew@dunslane.net>)
Ответы	Re: Check constraints on partition parents only?
Список	pgsql-hackers

Дерево обсуждения

Hi,

Yeah, but I think we need to take that chance. At the very least, we
need to support the equivalent of a non-inherited CHECK (false) on
parent tables.

Indeed. I usually enforce that with a trigger that raises an exception, but of course that doesn't help at all with constraint exclusion, and I saw a result just a few weeks ago (I forget the exact details) where it appeared that the plan chosen was significantly worse because the parent table wasn't excluded, so there's a non-trivial downside from having this restriction.

The downside appears to be non-trivial indeed! I cooked up the attached patch to try to allow ALTER...ONLY...CHECK(false) on parent tables.

If this approach looks acceptable, I can provide a complete patch later with some documentation changes (I think we ought to tell about this special case in the documentation) and a minor test case along with it (if the need be felt for the test case).

Although partitioning ought to be looked at from a different angle completely, maybe this small patch can help out a bit in the current scheme of things, although this is indeed a unusual special casing... Thoughts?

Regards,

Nikhils