We need to calculate the average resolution time for an issue within a Tracker project. Currently i have been using the difference between the created and updated date for all issues which are resolved or closed. However as we use a two stage resolution process, there can be any amount of time between an issue being closed once resolved.

So i need to know how to calculate the length of time an issue takes to becoming resolved OR closed (the first time). Can you help me figure out how i can query the db to extract this data - initial thoughts are to look at the change hisrtory however i am not sure how to do this

Thanks