Transaction Deadlocks on Replay about pgreplay HOT 7 CLOSED

This is the same problem as #12.

As mentioned there, pgreplay can only replay the statements in the order they appear in the log, but it cannot guarantee that they will be processed in that order.

In addition to the workarounds shown there, you could also set lock_timeout to a low value during replay. That will prevent hanging indefinitely long, but it will cause delays, and some statements won't be executed. Still, it might be good enough, if the deadlocks happen only rarely.

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Unfortunately, the deadlocks are very common during replay (but not on the source server) with this workload, and we're talking about several thousand transactions per second. Another possibility is to ignore transaction statements when replaying the queries, which may lead to data integrity issues on the target database (as would the lock_timeout option) but in this workload rollbacks are practically non-existent, so it would be a much better test.

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I see.
There is no option to exclude certain commands, but you could grep all BEGIN and COMMIT statements from the log file before replaying it.
I was under the impression that you are not talking about database deadlocks (which are automatically resolved after a second), but about hangs during replay that are never resolved. Which one is it?
Doing away with transactions would only reduce (not totally avoid!) the first kind of deadlocks, but not ones in pgreplay.

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Good point; excluding those via grep should work.

I am talking about database deadlocks. They do not appear to be resolved after a second. If I don't kill the query in PostgreSQL, it hangs indefinitely. From what I can tell, the locks are caused by update queries that contain select clauses in them. I'll give the grep suggestion a try and let you know what I find.

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That's not database deadlocks then.
They are live locks in the database, but the session that is not hanging is waiting (in pgreplay) for the hanging statement to complete.
Perhaps removing transactions will help, but it is not certain.

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Did it help?

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It's on my list for next week; sorry for the delay.

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