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Re: ALTER TABLE .. SET SCHEMA lock strength

From: Robert Haas <robertmhaas(at)gmail(dot)com>
To: Peter Eisentraut <peter_e(at)gmx(dot)net>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: ALTER TABLE .. SET SCHEMA lock strength
Date: 2011-01-01 22:17:17
Message-ID: AANLkTinbHx=gqscD2EOtBvD_-r=N8EdoPCp2q1_G0p4x@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Sat, Jan 1, 2011 at 4:24 PM, Peter Eisentraut <peter_e(at)gmx(dot)net> wrote:
> On lör, 2011-01-01 at 13:17 -0500, Tom Lane wrote:
>> ALTER RENAME and ALTER SET SCHEMA are both in the nature of changing the
>> object's identity.  Consider the fairly typical use-case where you are
>> renaming an "old" instance out of the way and renaming another one into
>> the same schema/name.  Do you really want that to be a low-lock
>> operation?  I find it really hard to envision a use case where it'd be
>> smart to allow some concurrent operations to continue using the the old
>> instance while others start using the new one.
>
> At least in Unix land, that's a handy property.  And we're frequently
> cursing those other operating systems where it doesn't work that way.

Yeah, exactly.  If someone is renaming an old instance out of the way
and sticking a new one in its place, the LAST thing you want to do is
lock out queries unnecessarily.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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