[Monetdb-developers] Another big group by query

Stefan de Konink stefan at konink.de
Mon Apr 13 11:23:03 CEST 2009


Stefan Manegold wrote:
> On Mon, Apr 13, 2009 at 02:30:44AM +0200, Stefan de Konink wrote:
>> Martin Kersten wrote:
>>> You can trace the execution even for a server started already using
>>> the stethoscope.
> 
> What does this/you you want to tell/show us?
> I.e., does your query still hang, or did it finish now?

The query finishes as I wrote in the previous email, the output was 
merely an attempt to show were the pain might be.

> I see that aggr.count() (not unexpectedly) is the most expensive one of the
> operations shown below --- but "only" ~100 sec --- not too extreme for
> counting the size of 362105182 groups over 365652137 BUNs ...
> 
> The sum of all shown times is "only" 116865583 usec (i.e., just under 2 min).

Then it is likely the output misses the last actual 'big time consumer', 
while Martin suggested it would show that event.

> Did you compile from CVS or from tarball?

I use CVS head.

> Did you configure with either --disable-assert (CVS) or --enable-assert
> (tarball)?

assert, profile, debug

> If you compiled from CVS without --disable-assert or from tarball with
> --enable-assert, you also might want to start your mserver5 with
> --performance (or at least --debug=33554432) to disable "cleaning" of
> to-be-freed memory just before free() is called --- this might make the ":=
> nil;" assignments (a bit?) faster ...

I am more than happy to try this.



Stefan




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