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

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
replacedthe lock in question with ShareUpdateExclusiveLock, the problem disappeared. Attached is the simple patch with
thesechanges. 
>
> 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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