Re: Very different query speeds for two similar queries

you might consider connection the stethoscope. It will show what is going on in the system. http://www.monetdb.org/Documentation/Manuals/MonetDB/Profiler/Stethoscope regards, Martin On 29/11/13 12:24, Will Muldrew wrote:

Okay - will do, though it'll probably be several hours!

On 29 November 2013 10:54, Stefan Manegold mailto:Stefan.Manegold@cwi.nl> wrote:

Will,

did / can you run your first (slow) query twice in a row and report the speeds of both runs?

Thanks! Stefan

----- Original Message ----- > > > On 29/11/13 11:36, Will Muldrew wrote: > > Hi > > > > I've been trying out monetdb on a 350M row table (modern linux > > workstation with 24GB RAM + SSD). This table has a sorted TIMESTAMP > > column and a second unsorted VARCHAR(6) column which is non-unique > > (perhaps 50M distinct values fairly randomly distributed). > > > > This query is very slow, spends huge amount of time writing, and has > > very low CPU (intermediate results?): > > > > select count(*) from t_order where orderId = 'XXXXXX' > > > > This takes hours to complete. > > > > However, this query is a lot faster, even though the timestamp clause is > > redundant (all my data is > '2012-01-01'): > It decided it can use parallel processing effectively. > Why it did not in the first query is unknown. > > > > > select count(*) from t_order where orderId = 'XXXXXX' and time > > > '1970-01-01'; > > > > The first run is slowish (10s of seconds - I guess because we're reading > > the orderId column fully), however subsequent runs are sub-second. > Yes, that is caching effect. > > > > Obviously I could write an app which puts the spurious timestamp clause > > into the where, but it's still confusing and not ideal. Is there > > something I can do? > > > regards, Martin > _______________________________________________ > users-list mailing list > users-list@monetdb.org mailto:users-list@monetdb.org > https://www.monetdb.org/mailman/listinfo/users-list >

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