On Tue, Jan 19, 2016 at 9:37 AM, Alvaro Herrera <alvhe...@2ndquadrant.com> wrote: > 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.
Fortunately, the function mergeHyperLogLog() in our hyperloglog.c currently has no callers. > 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. I think that Hideaki's confusion comes from whether or not this HLL state is a sparse or dense/full representation. The distinction is explained in the README for postgresql-hll: https://github.com/aggregateknowledge/postgresql-hll postgresql-hll has no support for merging HLLs that are sparse: https://github.com/aggregateknowledge/postgresql-hll/blob/master/hll.c#L1888 Can't we just tear mergeHyperLogLog() out? -- Peter Geoghegan -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers