Re: stats for failed transactions (was Re: [GENERAL] VACUUM Question)

Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> writes:
> Tom Lane wrote:
>> I think this is unquestionably
>> a bug, at least for autovacuum's purposes --- though it might be OK
>> for the original intent of the stats system, which was simply to track
>> activity levels.
>>
>> Any thoughts about how it ought to work?

> I don't remember exactly how it works -- I think the activity (insert,
> update, delete) counters are kept separately from commit/rollback
> status, right? Maybe we should keep three separate counters: "current
> transaction counters" and "counters for transactions that were
> aborted/committed". We only send the latter counts, and the former are
> added to them when the transaction ends.

My question was at a higher level, actually: *what* should we be
counting?

I think doubling the number of counters in the stats system, which is
what you seem to be proposing, is probably not acceptable --- we've
already got a problem with the stats file becoming unreasonably bulky.
We need to figure out exactly which counts there is adequate reason
to be tracking.

I don't, for instance, see any percentage in tracking block-level I/O
operations separately for committed and rolled-back transactions.
Those numbers are certainly things you watch only for total activity,
and a failed xact is just as much system load as a committed one.

regards, tom lane