Re: Size of Path nodes

On 12/4/15 5:14 PM, Peter Geoghegan wrote:
> On Fri, Dec 4, 2015 at 2:44 PM, Jim Nasby<Jim.Nasby@bluetreble.com>  wrote:
>> >I suspect Cachegrind[1] would answer a lot of these questions (though I've
>> >never actually used it). I can't get postgres to run under valgrind on my
>> >laptop, but maybe someone that's been successful at valgrind can try
>> >cachegrind (It's just another mode of valgrind).
> I've used Cachegrind, and think it's pretty good. You still need a
> test case that exercises what you're interested in, though.
> Distributed costs are really hard to quantify. Sometimes that's
> because they don't exist, and sometimes it's because they can only be
> quantified as part of a value judgement.

If we had a good way to run cachegrind (and maybe if it was run 
automatically somewhere) then at least we'd know what effect a patch had 
on things. (For those not familiar, there is a tool for diffing too 
cachegrind runs). Knowing is half the battle and all that.

Another interesting possibility would be a standardized perf test. [1] 
makes an argument for that.

Maybe a useful way to set stuff like this up would be to create support 
for things to run in travis-ci. Time-based tools presumably would be 
useless, but something doing analysis like cachegrind would probably be 
OK (though I think they do cap test runs to an hour or something).

[1] https://news.ycombinator.com/item?id=8426302
-- 
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
Experts in Analytics, Data Architecture and PostgreSQL
Data in Trouble? Get it in Treble! http://BlueTreble.com