On Friday 06 February 2004 07:19, Octavio Alvarez wrote: > Hi! > > I'd like to know if this is expected behavior. These are two couples of > queries. In each couple, the first one has a WHERE field = function() > condition, just like the second one, but in the form WHERE field = > (SELECT function()). In my opinion, both should have the same execution > plan, as the function has no parameters and, therefore, is constant.
Not necessarily constant - think about random() or timeofday(). Have you set the attributes on your function? http://www.postgresql.org/docs/7.4/static/sql-createfunction.html > pgdb=# explain analyze select count(*) from t_students where period = > (select current_period_id()); It's not entirely clear to me why this form is different from the other form though. -- Richard Huxton Archonet Ltd ---------------------------(end of broadcast)--------------------------- TIP 9: the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match
