On Mon, Sep 13, 2010 at 6:48 PM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote: > Gaetano Mendola <mendola@xxxxxxxxx> writes: >> Of course I'm not suggesting to take away the "sort by" and give the user >> an unsorted result, I'm asking why the the optimizer in cases like: > >> select unique(a) from v_table_with_order_by; > >> doesn't takes away the "order by" inside the view and puts it back "rewriting the >> query like this: > >> select unique(a) from v_table_without_order_by >> order by a; > > That changes the order in which the rows are fed to unique(a). The > principal real-world use for a non-top-level ORDER BY is exactly to > determine the order in which rows are fed to a function, so we will > have a revolt on our hands if we break that. I see your point, but some functions like: unique, count are not affected by the order of values fed, and I don't think either that unique has to give out the unique values in the same fed order. Regards Gaetano Mendola -- cpp-today.blogspot.com -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
