On Tue, Sep 09, 2008 at 07:23:03PM -0600, Alex Hunsaker wrote: > On Tue, Sep 9, 2008 at 7:48 AM, Kenneth Marshall <[EMAIL PROTECTED]> wrote: > > I think that the glacial speed for generating a big hash index is > > the same problem that the original code faced. > > Yeah sorry, I was not saying it was a new problem with the patch. Err > at least not trying to :) *Both* of them had been running at 18+ (I > finally killed them sometime Sunday or around +32 hours...) > > > It would be useful to have an equivalent test for the hash-only > > index without the modified int8 hash function, since that would > > be more representative of its performance. The collision rates > > that I was observing in my tests of the old and new mix() functions > > was about 2 * (1/10000) of what you test generated. You could just > > test against the integers between 1 and 2000000. > > Sure but then its pretty much just a general test of patch vs no > patch. i.e. How do we measure how much longer collisions take when > the new patch makes things faster? That's what I was trying to > measure... Though I apologize I don't think that was clearly stated > anywhere...
Right, I agree that we need to benchmark the collision processing time difference. I am not certain that two data points is useful information. There are 469 collisions with our current hash function on the integers from 1 to 2000000. What about testing the performance at power-of-2 multiples of 500, i.e. 500, 1000, 2000, 4000, 8000,... Unless you adjust the fill calculation for the CREATE INDEX, I would stop once the time to create the index spikes. It might also be useful to see if a CLUSTER affects the performance as well. What do you think of that strategy? Regards, Ken > Now of course it still would be interesting... And if its only to > 2,000,000 I can still use the modified int8 or just use the int4 > one... > > Anyway Here are the numbers: > create table test_hash(num int8); > insert into test_hash (num) select generate_series(1, 2000000); > create index test_hash_num_idx on test_hash (num); > > pgbench -c1 -n -t10000 -f bench_index.sql > cvs head: tps = 3161.500511 > v5: tps = 7248.808839 > > BTW Im still planning on doing a wide vs narrow test... sometime... :) > -- Sent via pgsql-patches mailing list (pgsql-patches@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-patches
