On 2015/12/11 14:41, Kyotaro HORIGUCHI wrote:
> Sorry, I misunderstood the meaning of PgStat_*.
I should've just said "messages to the stats collector" instead of
> At Fri, 11 Dec 2015 09:41:04 +0900, Amit Langote
> <langote_amit...@lab.ntt.co.jp> wrote
>>> As far as I understand it, the basic reason why this patch exists is
>>> to allow a DBA to have a hint of the progress of a VACUUM that may be
>>> taking minutes, or say hours, which is something we don't have now. So
>>> it seems perfectly fine to me to report this information
>>> asynchronously with a bit of lag. Why would we need so much precision
>>> in the report?
>> Sorry, I didn't mean to overstate this requirement. I agree precise
>> real-time reporting of progress info is not such a stringent requirement
>> from the patch. The point regarding whether we should storm the collector
>> with progress info messages still holds, IMHO.
> Taking a few seconds interval between each messages would be
> sufficient. I personaly think that gettimeofday() per processing
> every buffer (or few buffers) is not so heavy-weight but I
> suppose there's not such a consensus here. However,
> IsCheckpointOnSchedule does that per writing one buffer.
> vacuum_delay_point() seems to be a reasonable point to check the
> interval and send stats since it would be designed to be called
> with the interval also appropriate for this purpose.
Interesting, vacuum_delay_point() may be worth considering.
It seems though that, overall, PgBackendStatus approach may be more suited
for progress tracking. Let's see what the author thinks.
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