Re: 9.2beta1, parallel queries, ReleasePredicateLocks, CheckForSerializableConflictIn in the oprofile

On Wed, 30 May 2012, Merlin Moncure wrote:

> hurk -- ISTM that since IOS is masikng the heap lookups, there must
> be contention on the index itself? Does this working set fit in
> shared memory? If so, what happens when you do a database restart and
> repeat the IOS test?

The dataset fits well in shared buffers

Here are the data sizes
public.idt_photoobservation_small | 521 MB | 528756
public.idt_match_idx | 1084 MB | 528762
public.idt_match_transitid_healpixid_idx | 1522 MB | 1955140
public.idt_match | 2906 MB | 528753

And shared buffers are 10G

If I restart the db the timings do not change significantly. There is always some
variation which I don't really understand, e.g. the parallel runs sometimes
take 18s, or 25 seconds, or 30 seconds per thread. So there is something else affecting
the runs -- I don't know, maybe that's related to which thread starts first,
or what is the starting point of the seq scan... (there is no other
activity on the machine btw).

Cheers,
S

*****************************************************
Sergey E. Koposov, PhD, Research Associate
Institute of Astronomy, University of Cambridge
Madingley road, CB3 0HA, Cambridge, UK
Tel: +44-1223-337-551 Web: http://www.ast.cam.ac.uk/~koposov/