| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
| Cc: | Peter Geoghegan <pg(at)heroku(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: PATCH: Extending the HyperLogLog API a bit |
| Date: | 2016-01-19 17:37:17 |
| Message-ID: | 20160119173717.GA210940@alvherre.pgsql |
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| Thread: | |
| Lists: | pgsql-hackers |
While going over this patch I noticed this commit in HyperLogLog's
upstream:
https://github.com/hideo55/cpp-HyperLogLog/commit/b8cb5e7b856928af15e9535b4b1650f493ba453f
In the first hunk which is what we care about, the author is doing
bit-or of both hash values instead of taking the max value, which is
what we were doing.
Our transcript seems to predate that bugfix commit, so I assume we need
to apply this to our copy too. Sadly, Hideaki-san commit message isn't
very descriptive.
I don't really know how HyperLogLog works, so maybe we can't or
shouldn't apply the patch because of how the hash stuff is used.
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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