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Re: Check constraints on partition parents only? - Mailing list pgsql-hackers

From Nikhil Sontakke
Subject Re: Check constraints on partition parents only?
Date
Msg-id CABamaqNMDBJFTMQk8FzugZG6uZvvQ+DprBEcbRGnSWkB-qW3EA@mail.gmail.com
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In response to Re: Check constraints on partition parents only?  (Andrew Dunstan <andrew@dunslane.net>)
Responses Re: Check constraints on partition parents only?
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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
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