2016-12-04 23:12 GMT+01:00 Peter Geoghegan <p...@bowt.ie>: > On Sat, Dec 3, 2016 at 5:20 PM, Tomas Vondra > <tomas.von...@2ndquadrant.com> wrote: > > So the sort is probably slow because of CPU, as it compares strings. In > > some locales that may be very expensive - not sure which locale is used > > in this case, as it was not mentioned. > > I wonder what it would take to teach the optimizer to consider the > possibility of a "collation strength reduction". In other words, for > aggregates that perform a sort (or for aggregates that rely on the > presence of a sort node without there being some other dependency on > the sort node), it should be possible for the optimizer to determine > that it would be just fine to use the C locale, since the user isn't > entitled to assume anything about the exact sort order. There are of > course cases where this can make a huge difference. >
it is pretty good idea. Regards Pavel > > -- > Peter Geoghegan > > > -- > Sent via pgsql-general mailing list (pgsql-general@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-general >
