From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Andres Freund <andres(at)2ndquadrant(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Josh Berkus <josh(at)agliodbs(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: db_user_namespace a "temporary measure" |
Date: | 2014-03-13 00:54:36 |
Message-ID: | 26386.1394672076@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Wed, Mar 12, 2014 at 9:19 AM, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
>> Except that we don't have the infrastructure to perform such checks
>> (neither partial, nor expression indexes, no exclusion constraints) on
>> system tables atm. So it's not a entirely trivial thing to do.
> I'm probably woefully underinformed here, but it seems like getting
> exclusion constraints working might be simpler than partial indexes or
> expression indexes, because both of those involve being able to
> evaluate arbitrary predicates, whereas exclusion constraints just
> involve invoking index access methods to look for conflicting rows via
> smarts built into your index AM. The latter seems to involve less
> risk of circularity (but I might be wrong).
You might be right. I don't think anyone's ever looked at what it
would take to support that particular case. We have looked at the
other cases and run away screaming ... but I think that was before
exclusion constraints existed.
regards, tom lane
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