Concurrency question - Mailing list pgsql-admin

From Mark Steben
Subject Concurrency question
Date
Msg-id 20090707192727.98C9563381A@mail.postgresql.org
Whole thread Raw
Responses Re: Concurrency question  (Scott Marlowe <scott.marlowe@gmail.com>)
List pgsql-admin
Any help here appreciated.

I ran a vacuum verbose analyze on a database over the weekend.  It ran fine
until it tried to vacuum a table less than 2000 pages.  It successfully
acquired a ShareUpdateExclusiveLock as I would expect.
There was an idle thread that had an AccessSharelock on the same table.
Compatible locks I would think. But the vacuum hung until the
AccessSharelock thread was cancelled - 11 hours in all.
This table normally vacuums in less than 15 seconds.   This AccessSharelock
came from a query that formerly was part of a transaction sent from a remote
server.  Could it be that it hung because it was
A transaction?   Even so I thought those lock types were compatible.


As always thanks for your time.

Mark Steben│Database Administrator│
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