On Tue, 2008-09-23 at 09:13 -0400, Tom Lane wrote: > Simon Riggs <[EMAIL PROTECTED]> writes: > > Thinks: Why not just sort all of the time and skip the debate entirely? > > The sort is demonstrably a loser for smaller indexes. Admittedly, > if the index is small then the sort can't cost all that much, but if > the (correct) threshold is some large fraction of shared_buffers then > it could still take awhile on installations with lots-o-buffers.
The other realisation is that for large indexes, giving them more maintenance_work_mem probably will make them build faster 'cos we'll be sorting. So "give big indexes more memory" is still true *enough* to be broadly consistent, explainable and understandable. I do explain things in more detail on some courses, but pithy rules help busy people. -- Simon Riggs www.2ndQuadrant.com PostgreSQL Training, Services and Support -- Sent via pgsql-patches mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-patches