On Tue, Sep 30, 2014 at 8:34 AM, Graeme B. Bell <grb@xxxxxxxxxxxxxxxxx> wrote: > >>> The existing cost estimation >>> code effectively assumes that they're perfectly uniformly distributed; >>> which is a good average-case assumption but can be horribly wrong in >>> the worst case. > > > Sorry, just an outsider jumping in with a quick comment. > > Every year or two the core count goes up. Can/should/does postgres ever attempt two strategies in parallel, in cases where strategy A is generally good but strategy B prevents bad worst case behaviour? Kind of like a Schrödinger's Cat approach to scheduling. > What problems would it raise? Interleaved I/O, that would kill performance for both plans if it happens on rotating media. -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
