Anyone seen this kind of lock pileup?

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All,

Having an interesting issue on one 8.4 database. Due to poor application design, the application is requesting 8-15 exclusive (update) locks on the same row on parallel connections pretty much simultaneously (i.e. < 50ms apart).

What's odd about this is that the resulting "lock pileup" takes a mysterious 2-3.5 seconds to clear, despite the fact that none of the connections are *doing* anything during that time, nor are there deadlock errors. In theory at least, the locks should clear out in reverse order in less than a second; none of the individual statements takes more than 10ms to execute.

Has anyone else seen something like this?  Any idea what causes it?

--
                                  -- Josh Berkus
                                     PostgreSQL Experts Inc.
                                     http://www.pgexperts.com

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