2009/8/17 Jeremy Harris <jgh@xxxxxxxxxxx>: > Could not pgsql *measure* these costs (on a sampling basis, and with long > time-constants)? In theory, sure. In practice, well, there are some engineering challenges to solve. 1) The cost model isn't perfect so the it's not clear exactly what to measure to get the best result. As the cost model stands now you would have to include some of the cpu time as well as the i/o time. 2) Timing is expensive. On many platforms getting the current time takes a long time and would make a big difference to the runtime of the query. -- greg http://mit.edu/~gsstark/resume.pdf -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
