On 11/4/15 4:55 PM, Stephen Frost wrote: > * Joe Conway (m...@joeconway.com) wrote: >> On 11/04/2015 01:24 PM, Alvaro Herrera wrote: >>> I agree with Pavel. Having a transaction timeout just does not make any >>> sense. I can see absolutely no use for it. An idle-in-transaction >>> timeout, on the other hand, is very useful. >> >> +1 -- agreed > > I'm not sure of that. I can certainly see a use for transaction > timeouts- after all, they hold locks and can be very disruptive in the > long run. Further, there are cases where a transaction is normally very > fast and in a corner case it becomes extremely slow and disruptive to > the rest of the system. In those cases, having a timeout for it is > valuable. > > David (adding him to the CC) actually developed a utility specifically > to identify what transactions are blocking what others and to kill off > other processes if they were running for too long and blocking higher > priority processes. It didn't matter, in that environment, if they were > idle-in-transaction or actively running.
You are remembering correctly, Stephen, though there were different timeouts for blocking transactions that were running and those that were idle-in-transaction. We usually set the idle-in-transaction timeout much lower as it measured not total transaction time but idle time since the last state change. In that environment, at least, an idle-in-transaction session was always due to a stuck process, bug, or user session left open overnight. Because partitions and FKs were continuously being created even ACCESS SHARE locks could be a problem. The important thing about this implementation was that nothing was terminated unless it had exceed a timeout AND was blocking another process. A feature of this particular system was that it had very long running transactions that needed to execute unless there was a conflict. Even then, we'd get an alert some time in advance of the transaction being terminated so we could make the judgement call to terminate the other process(es) instead. -- -David da...@pgmasters.net
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