Re: HyperLogLog.c and pg_leftmost_one_pos32()
От | Tomas Vondra |
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Тема | Re: HyperLogLog.c and pg_leftmost_one_pos32() |
Дата | |
Msg-id | 20200730171619.3mtqgqg2z6lhmljo@development обсуждение исходный текст |
Ответ на | Re: HyperLogLog.c and pg_leftmost_one_pos32() (Jeff Davis <pgsql@j-davis.com>) |
Ответы |
Re: HyperLogLog.c and pg_leftmost_one_pos32()
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Список | pgsql-hackers |
On Thu, Jul 30, 2020 at 09:21:23AM -0700, Jeff Davis wrote: >On Wed, 2020-07-29 at 17:32 -0700, Peter Geoghegan wrote: >> How did you test this? What kind of difference are we talking about? > >Essentially: > initHyperLogLog(&hll, 5) > for i in 0 .. one billion > addHyperLogLog(&hll, hash(i)) > estimateHyperLogLog > >The numbers are the same regardless of bwidth. > >Before my patch, it takes about 15.6s. After my patch, it takes about >6.6s, so it's more than a 2X speedup (including the hash calculation). > Wow. That's a huge improvements. How does the whole test (data + query) look like? Is it particularly rare / special case, or something reasonable to expect in practice? regards -- Tomas Vondra http://www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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