Horton

Re: 'tuple concurrently updated' error for alter role ... set

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Alexey Klyukin <alexk@commandprompt.com>, pgsql-hackers@postgresql.org
Date: 2011-05-12T22:53:56Z
Lists: pgsql-hackers

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  1. Fix possible "tuple concurrently updated" error in ALTER TABLE.

On Thu, May 12, 2011 at 6:28 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Alexey Klyukin <alexk@commandprompt.com> writes:
>> After digging in the code I've found that a RowExclusiveLock is acquired on a pg_db_role_setting table in AlterSetting(). While the name of the locks suggests that it should conflict with itself, it doesn't. After I've replaced the lock in question with ShareUpdateExclusiveLock, the problem disappeared. Attached is the simple patch with these changes.
>
> We're not likely to do that, first because it's randomly different from
> the handling of every other system catalog update,

We have very robust locking of this type for table-related DDL
operations and just about none for anything else.  I don't consider
the latter to be a feature.

-- 
Robert Haas
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