Functions can be customised in many ways, and search a variety of fields in Jira. Make a request to theJira Cloud REST APIto see all fields you can use inside of the function expressions. For example,customfield_10024orpriority.id.
Most of the functions require a JQL 'subquery' as the starting point for the function you’ve selected. Providing an empty string (e.g. "") causes the query to match each issue in your Jira instance, making your query very inefficient.
User specific data is not supported in subqueries. So statements such asassignee - currentuser()are invalid.