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Re: Problem with ALTER TABLE - occasional "tuple concurrently updated" - Mailing list pgsql-bugs

From Alvaro Herrera
Subject Re: Problem with ALTER TABLE - occasional "tuple concurrently updated"
Date
Msg-id 1290105030-sup-5154@alvh.no-ip.org
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In response to Re: Problem with ALTER TABLE - occasional "tuple concurrently updated"  (Robert Haas <robertmhaas@gmail.com>)
Responses Re: Problem with ALTER TABLE - occasional "tuple concurrently updated"  (Alvaro Herrera <alvherre@commandprompt.com>)
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Excerpts from Robert Haas's message of jue nov 18 15:11:37 -0300 2010:

> In the current master branch, it appears that "ALTER TABLE c INHERIT
> p" takes a ShareUpdateExclusiveLock on the child, which seems
> sufficient, and an AccessShareLock on the parent, which seems like it
> might not be; though I'm having a hard time figuring out exactly when
> it wouldn't be, especially since in 8.4 I'm fairly sure any ALTER
> TABLE command takes an AccessExclusiveLock.

What if two of these run at the same time, and the parent doesn't
have children when they start?  They would both try to set
relhassubclass, no?

--
Álvaro Herrera <alvherre@commandprompt.com>
The PostgreSQL Company - Command Prompt, Inc.
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