Hi Pavel, Thanks a lot for your feedback.
I'll work more on this patch this week, and will send a more complete patch later this week. I'll also try to see how much is the speed up of this method for other types. Thanks, -- Hadi On Mon, Mar 18, 2013 at 10:36 AM, Pavel Stehule <pavel.steh...@gmail.com>wrote: > 2013/3/16 Hadi Moshayedi <h...@moshayedi.net>: > > Revisiting: > > http://www.postgresql.org/message-id/45661be7.4050...@paradise.net.nz > > > > I think the reasons which the numeric average was slow were: > > (1) Using Numeric for count, which is slower than int8 to increment, > > (2) Constructing/deconstructing arrays at each transition step. > > > > This is also discussed at: > > > http://www.citusdata.com/blog/53-postgres-performance-to-avg-or-to-sum-divided-by-count > > > > So, I think we can improve the speed of numeric average by keeping the > > transition state as an struct in the aggregate context, and just passing > the > > pointer to that struct from/to the aggregate transition function. > > > > The attached patch uses this method. > > > > I tested it using the data generated using: > > CREATE TABLE avg_test AS SELECT (random() * 999)::decimal(5,2) as d FROM > > generate_series(1, 10000000) s; > > > > After applying this patch, run time of "SELECT avg(d) FROM avg_test;" > > improves from 10.701 seconds to 5.204 seconds, which seems to be a huge > > improvement. > > > > I think we may also be able to use a similar method to improve > performance > > of some other numeric aggregates (like stddev). But I want to know your > > feedback first. > > > > Is this worth working on? > > I checked this patch and it has a interesting speedup - and a price of > this methoud should not be limited to numeric type only > > Pavel > > > > > Thanks, > > -- Hadi > > > > > > > > -- > > Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) > > To make changes to your subscription: > > http://www.postgresql.org/mailpref/pgsql-hackers > > >
