From: | Theo Schlossnagle <jesus(at)omniti(dot)com> |
---|---|
To: | Andrew Dunstan <andrew(at)dunslane(dot)net> |
Cc: | Theo Schlossnagle <jesus(at)omniti(dot)com>, "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, Heikki Linnakangas <heikki(at)enterprisedb(dot)com>, pgsql-patches(at)postgresql(dot)org |
Subject: | Re: Expose checkpoint start/finish times into SQL. |
Date: | 2008-04-04 01:31:22 |
Message-ID: | 99E74F97-99C1-4EF3-A555-7DC710710BC4@omniti.com |
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Thread: | |
Lists: | pgsql-patches |
On Apr 3, 2008, at 7:08 PM, Andrew Dunstan wrote:
>
>
> Joshua D. Drake wrote:
>>> Theo Schlossnagle wrote:
>>>
>>>> First whack at exposing the start and finish checkpoint times into
>>>> SQL.
>>>>
>>> Why is that useful?
>>>
>>
>> For knowing how long checkpoints are taking. If they are taking too
>> long you may need to adjust your bgwriter settings, and it is a
>> serious drag to parse postgresql logs for this info.
>>
>>
>>
>
> Even if this were true, surely the answer is to improve the logging.
>
> Has this feature been discussed on -hackers? I don't recall it (and
> my memory has plenty of holes in it), but I'm sure that after
> attending my talk last Sunday Theo hasn't sent in a patch for an
> undiscussed feature ;-)
Andrew: I don't think this feature has been discussed on hackers. The
patch took about 15 minutes to author, so it sounds like the most
concise way to start a conversation. Seems silly to start the
conversation on hackers with a patch. :-)
Alvaro: Thanks, I flip that to GetCurrentTimestamp()
Heikki: It it useful for knowing when the last checkpoint occurred.
Like Robert, we have situations where reading the log file is a PITA
-- so this provides that information. I originally planned on only
adding the start time, but figured adding the end would make sense too.
Tom: It worked for me in my testing, though I did not extensively
tested. I didn't see anywhere the stats are zero'd out, so I believe
the timestamp is zero at start and then only ever set to the starttime
during a checkpoint invocation. I admittedly don't have a thorough
understanding of that code -- but that segment (before my patch)
looked pretty concise.
--
Theo Schlossnagle
Esoteric Curio -- http://lethargy.org/
OmniTI Computer Consulting, Inc. -- http://omniti.com/
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