From: | Andrew Dunstan <andrew(at)dunslane(dot)net> |
---|---|
To: | Peter Eisentraut <peter_e(at)gmx(dot)net>, David G Johnston <david(dot)g(dot)johnston(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Add min and max execute statement time in pg_stat_statement |
Date: | 2015-02-18 15:11:31 |
Message-ID: | 54E4ABA3.5090807@dunslane.net |
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Lists: | pgsql-hackers |
On 02/17/2015 08:21 PM, Peter Eisentraut wrote:
> On 1/20/15 6:32 PM, David G Johnston wrote:
>> In fact, as far as
>> the database knows, the values provided to this function do represent an
>> entire population and such a correction would be unnecessary. I guess it
>> boils down to whether "future" queries are considered part of the population
>> or whether the population changes upon each query being run and thus we are
>> calculating the ever-changing population variance.
> I think we should be calculating the population variance. We are
> clearly taking the population to be all past queries (from the last
> reset point). Otherwise calculating min and max wouldn't make sense.
>
>
The difference is likely to be very small in any case where you actually
want to examine the standard deviation, so I feel we're rather arguing
about how many angels can fit on the head of a pin, but if this is the
consensus I'll change it.
cheers
andrew
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