From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: David G. Johnston <david.g.johnston@gmail.com>
Cc: Vik Fearing <vik@2ndquadrant.fr>
Cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
Cc: denisa.cirstescu@asentinel.com, "pgsql-docs@postgresql.org" <pgsql-docs@postgresql.org>
Subject: Re: Undocumented behavior od DROP SCHEMA ... CASCADE
Date: Fri, 12 Aug 2016 18:26:11 -0400
Message-ID: <20160812222611.GA721702@alvherre.pgsql> (raw)
In-Reply-To: <24531.1471039297@sss.pgh.pa.us>
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Tom Lane wrote:
> > also, object locks need to be acquired, which
> > can be very troublesome if you discover that some frequently-used object
> > is in the set to be dropped, by some unfortunate accident.
>
> You'd need the object locks in any case, to be sure things hold still long
> enough for their dependencies to be examined. It's possible a weaker lock
> type would suffice, but I'm not sure; we generally don't require exclusive
> lock on an object to add or remove dependencies on it.
Of course, using a weak lock could run afoul of somebody changing the
dependencies underneath. But even using a stronger lock is unlikely to
give any actual protection: in UI programs (be it GUI admin programs or
psql), more likely than not many users are going to run a check in one
transaction, then run the actual drop in a different transaction.
> I'm not necessarily against adding a function to report the dependencies
> as a table rather than NOTICE output. But things have been like this
> for quite a few years and I can count the number of requests for such a
> function without running out of thumbs. Doesn't seem very high priority.
Sure. Perhaps this'd be a good item for a novice hacker.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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Cc: alvherre@2ndquadrant.com, tgl@sss.pgh.pa.us, david.g.johnston@gmail.com, vik@2ndquadrant.fr, peter.eisentraut@2ndquadrant.com
Subject: Re: Undocumented behavior od DROP SCHEMA ... CASCADE
In-Reply-To: <20160812222611.GA721702@alvherre.pgsql>
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