On Wed, Sep 10, 2008 at 09:45:04AM -0400, Jack Orenstein wrote: > Am I on the right track -- does autocommit = false for the BIG scan force > versions of TINY to accumulate? I played around with a JDBC test program, > and so far cannot see how the autocommit mode causes variations in what is > seen by the scan. The behavior I've observed is consistent with the > SERIALIZABLE isolation level, but 1) I thought the default was READ > COMMITTED, and 2) why does the accumulation of row versions have anything > to do with autocommit mode (as opposed to isolation level) on a connection > used for the scan? Vacuum can only clean up stuff older than the oldest open transaction. So if you have a transaction which is open for hours then stuff made since then it can't be vacuumed. The solution is: don't do that. What I don't understand from your description is why your scan is slow and how the autocommit relates to this. Postgresql only cares about when you start and commit transactions, and I can't get from your description when exactly that happens. Rule of thumb: don't hold transaction open unnessarily long. Have a nice day, -- Martijn van Oosterhout <kleptog@xxxxxxxxx> http://svana.org/kleptog/ > Please line up in a tree and maintain the heap invariant while > boarding. Thank you for flying nlogn airlines.
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