Not necessarily? It depends on where the locks triggering the issue
are set, if they are all set after the savepoint it could work on a
second attempt.
Don't you mean the deadlock failures where can really help rollback to
Yes, I mean deadlock failures can rollback to a savepoint and work on
a second attempt.
And could you, please, give an example where a rollback to savepoint
can help to end its subtransaction successfully after a serialization
failure?
I do not know whether this is possible with about serialization
failures.
It might be if the stuff before and after the savepoint are somehow
unrelated...
If you mean, for example, the updates of different tables - a rollback
to savepoint doesn't help.
And I'm not sure that we should do all the stuff for savepoints
rollbacks because:
- as I see it now it only makes sense for the deadlock failures;
- if there's a failure what savepoint we should rollback to and start
the execution again? Maybe to go to the last one, if it is not
successful go to the previous one etc.
Retrying the entire transaction may take less time..
[...] I mean that the sum of transactions with serialization failure
and transactions with deadlock failure can be greater then the totally
sum of transactions with failures.
Hmmm. Ok.
A "failure" is a transaction (in the sense of pgbench) that could not
made it to the end, even after retries. If there is a rollback and the
a retry which works, it is not a failure.
Now deadlock or serialization errors, which trigger retries, are worth
counting as well, although they are not "failures". So my format
proposal was over optimistic, and the number of deadlocks and
serializations should better be on a retry count line.
Maybe something like:
...
number of failures: 12 (0.004%)
number of retries: 64 (deadlocks: 29, serialization: 35)
Ok! How to you like the idea to use the same format (the total number of
transactions with failures and the number of retries for each failure
type) in other places (log, aggregation log, progress) if the values are
not "default" (= no failures and no retries)?
--
Marina Polyakova
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company
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