On Wed, 2006-10-18 at 17:10 -0500, Jim C. Nasby wrote: > Sorry, don't have the earlier part of this thread, but what about... > > SELECT greatest(max(a), max(b)) ... > > ? To fill you in, we're trying to get the max of a union (a view across two physical tables). It can be done if you're creative with the query; I suggested a query that selected the max of the max()es of the individual tables. Your query could work too. However, the trick would be getting postgresql to recognize that it can transform "SELECT max(x) FROM foo" into that, where foo is a view of a union. If PostgreSQL could sort the result of a union by merging the results of two index scans, I think the problem would be solved. Is there something preventing this, or is it just something that needs to be added to the planner? Regards, Jeff Davis
