I'm frequently confused by the key choice of Jetreports(JR). When for instance, I do a row lookup with filters on 3 specific fields, sometimes JR will choose to use a key in which only field3 is included while there is a key that covers both field1 and field2 which would be the most logical key to use performance wise. Only after switching the order of the keys, trial and error wise, I seem to be able to get it to pick the correct key.
What is the rule JR uses to determine which key to use?
How does JR determine which key to use.