Greg Stark <[EMAIL PROTECTED]> writes: > There's a dual to this as well. If the results were very close but > the actual time taken to run the node doesn't match the cost > calculated then some optimizer parameter needs to be adjusted.
I was thinking about this, but I couldn't think of how to get it to work properly: (1) The optimizer's cost metric is somewhat bogus to begin with. ISTM that translating a cost of X into an expected runtime of Y msecs is definitely not trivial to do. (2) The size of a node's result relation does not depend upon anything outside of PostgreSQL, whereas the exact time it takes to produce that result relation depends on a wide collection of external factors. For example, if the system is under heavy load, queries will take longer than normal to run. Or, if the query invokes a function that happens to occasionally block waiting on some resource, the execution time of the query could be wildly unpredictable. (3) ISTM we couldn't produce a really helpful hint message, even if we somehow resolved #1 and #2 -Neil ---------------------------(end of broadcast)--------------------------- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])