On Sat, Jan 08, 2005 at 08:01:51PM +0200, Tzahi Fadida wrote: > I have been trying for a week now without success to discover > if you can measure the cost of a query (with my c function). > EXPLAIN ANALYZE seems to give you the actual time it took it > to run but the "cost" seems to be a fixed estimate number and not > actual.
"cost" is the planner's estimate of disk page fetches; "actual" is elapsed real time. See "Using EXPLAIN" in the "Performance Tips" chapter of the documentation. > I see in the code many times references to pgstats so > i figure there must be some kind of accounting. > Does anyone have a clue on this? its very important to me > to be able to measure scientifically the costs of a query. Have you looked at the "The Statistics Collector" section in the "Monitoring Database Activity" chapter? The statistics views won't show statistics for a particular query, but if the database is quiescent except for your activity then you might be able to measure queries' I/O costs by observing changes in the gathered statistics. -- Michael Fuhr http://www.fuhr.org/~mfuhr/ ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])
