Re: stored procedure stats in collector

Neil Conway wrote:
> On Thu, 2007-09-20 at 16:08 +0300, Martin Pihlak wrote:
>> The GUC variable stats_function_level now takes 3 values: on, off and all.
>
> That seems a confusing set of values. Perhaps "off", "pl", and "all"
> would be clearer?

Makes sense. It appears that the stats_ prefixed GUC names are deprecated now.
Will rename to "track_functions" and change values to "off", "pl" and
"all". Or should I use "none" instead of "off"?

> I'm curious if you've measured the performance overhead of enabling this
> functionality.
>

Just finished a simple benchmark comparing unpatched, "off" and "all":

unpatched usr sys total
dummy 21.36 0.68 22.04
rfact 51.52 0.07 51.59
ifact 20.40 0.06 20.45

"off" usr sys total diff x
dummy 21.59 0.39 21.97 1.00
rfact 52.40 0.06 52.46 1.02
ifact 20.78 0.02 20.8 1.02

"all" usr sys total diff x
dummy 21.69 35.18 56.87 2.58
rfact 47.83 38.99 86.83 1.68
ifact 20.65 0.36 21.01 1.03

dummy is blank pl/pgsql function (ran 10000000 times). rfact is recursive factorial,
ifact is iterative (both ran 1000000 times). Comparing median of 3 runs. The usr and
sys values are from log_executor_stats.

It seems that the overhead is unnoticeable if disabled, very visible for lightweight
functions and heavy callers. Almost unnoticeable for more compute intensive functions.

>> PS. Would something like this be a canditate for 8.4 inclusion (if polished up)?
>
> It sounds like a useful feature to me.
>
Good. I'll bring the patch up to date with HEAD.

Regards,
Martin