How Does JIRA Handle JQL Functions?

Question

If I have the below JQL, when it runs the function, is it running the function against all issues or just the ones that qualify on the other clause (project = CVA).

project = CVA AND issue in subtask("status != Closed")

I'm trying to figure out if functions performs better if there is additional clauses, like the example above that is filtering by project.

Sean Klein1 · Answer

By “JIRA runs every clause and then does the AND/OR”, do you mean that the following would return three separate result sets to be analyzed by the query engine:
project = “CVA” AND status != closed AND summary ~ “migrate”
Or is this how JQL conceptually works, but in truth it has an optimizer that recognizes a more efficient execution plan?
Is there a whitepaper or URL that you can reference for more information on how JIRA executes JQL?

Jobin Kuruvilla [Adaptavist] · Answer

It is running against all issues. JIRA runs every clause and then does the AND/OR on the result set.Following should perform better!

issue in subtask("status != Closed AND project = CVA")