Re: simple functions, huge overhead, no cache

2010/7/12 Josip Rodin <joy@entuzijast.net>:
> On Mon, Jul 12, 2010 at 04:38:48PM +0200, Pavel Stehule wrote:
>> 2010/7/12 Josip Rodin <joy@entuzijast.net>:
>> > On Mon, Jul 12, 2010 at 02:06:43PM +0800, Craig Ringer wrote:
>> >> Meh, personally I'll stick to the good old profiling methods "is it fast
>> >> enough", "\timing", and "explain analyze".
>> >
>> > I agree. Some hint could be included in 'explain analyze' output, maybe just
>> > to separate the timings for things that are well covered by the query plan
>> > optimizer from those that aren't. I found this in a line like this:
>>
>> it is useles for functions - explain doesn't show lines of executed
>> functions. Can you show some example of some more complex query.
>
> It doesn't have to show me any lines, but it could tell me which part of
> the query is actually being optimized, and OTOH which part is simply being
> executed N times unconditionally because it's a function that is marked as
> volatile. That alone would be a reasonable improvement.

this is different kinds of problems. You can have a very slow a
immutable function or very fast volatile function. And with wrong
function design your functions can be a 10 times slower. yeah - you
can multiply it via wrong or good design with wrong or good stability
flag.

Regards

Pavel Stehule



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