[MonetDB-users] Profiling queries
Martin.Kersten at cwi.nl
Wed Dec 5 08:07:42 CET 2007
This is of course a very difficult question to answer ;)
to understand if it is an intrinsic problem with the MonetDB solution or
bug, the best step is to use the profiling tools of MonetDB.
and this trace would be helpfull for us to make better suggestions.
m h wrote:
> Hello all-
> First of all thanks to you guys for your great help these past few
> weeks. I really appreciate it. I've learned a bit, and hopefully
> your product is improving from my bug reports.
> I've managed to pull a bit of my data from my proprietary db into
> monetdb. (Have some 60 million rows in the fact table, pulled in 5
> million)! I even ran a query against it and got the same numbers
> (though in a different order)!
> So I did a very basic poor mans benchmark. My python code can hit the
> old db or monetdb by changing one line. So I took timestamps around
> the query execution portion.
> The old db takes 0.21 seconds when cold. Subsequent queries take
> 0.027-0.072 seconds
> Monetdb takes 0.67 seconds when cold and 0.12-0.23 otherwise.
> It appears that the old db is faster when cold than monetdb is after
> being primed.
> A few more caveats. (Yes, this is a poor benchmark but after reading
> pdfs saying that monetdb was 7 times faster than a 64 way oracle box,
> I thought I'd get quite a bit of speedup.) The old db is running
> under vmware on a Core2 1.86Ghz box. Monetdb is running on my laptop,
> a Pentium M 1.86 Ghz machine.
> Since the query is confidential I can't really put it here, but I can
> describe it. I'm pulling stuff out of my fact table and two other
> dimension tables. The select clause sums a few columns, and on one
> sums the product of one column and the sum of a few others. The
> coalesce function is used to convert NULLs to 0. The where statement
> joins the tables using the = operator and then has two "IN" clauses.
> Then there is a group by (since I'm aggregating in the select) and an
> order by.
> Any hints on how to increase performance? Do I need to tune my query
> or tweak other things? (Yes I know the laptop machine is not apples
> to apples to the vmware machine)
> Am open to suggestions.
> thanks much,
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