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Re: Check constraints on partition parents only?

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Nikhil Sontakke <nikhil(dot)sontakke(at)enterprisedb(dot)com>
Cc: Alex Hunsaker <badalex(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Jerry Sievers <gsievers19(at)comcast(dot)net>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Check constraints on partition parents only?
Date: 2011-07-28 13:54:52
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
On Thu, Jul 28, 2011 at 9:43 AM, Nikhil Sontakke
<nikhil(dot)sontakke(at)enterprisedb(dot)com> wrote:
> Alternatively we could bring about the same
> by using a combination of conislocal and coninhcnt. For ONLY constraints, we
> will need to percolate this information down to the point where we define it
> in the code. We can then mark ONLY constraints to have conislocal set to
> TRUE and coninhcnt set to a special value (-1)

This approach certainly can't work, because a table can be both an
inheritance parent and an inheritance child.  It could have an ONLY
constraint, and also inherit a copy of the same constraint for one or
more parents.  IOW, the fact that conislocal = true does not mean that
coninhcount is irrelevant.  I think what you probably want to do is
either (a) add a new column or (b) change conislocal to a char value
and make it three-valued:

n = inherited constraint, no local definition
o = defined locally as an "ONLY" constraint
i = defined locally as a non-ONLY constraint

I think I favor the latter approach as more space-efficient, but I
hear Tom muttering about backward-compatibility...

Robert Haas
The Enterprise PostgreSQL Company

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