Enhanced Search features several JQL functions not available as default in Jira, which are documented in the following sections:
Date Functions - compare two dates on the same issue.
Agile Functions - search issues based on sprint information.
Issue Link Functions - search based on issue links.
Epic Functions - search based on issue links.
Sub-task Functions - return sub-tasks of issues, or parent of sub-tasks.
Match Functions - filter issues based on specified field values.
Expression Function - compare attributes of fields.
Functions can be customised in many ways, and search a variety of fields in Jira. Make a request to the Jira Cloud REST API to see all fields you can use inside of the function expressions. For example,
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 as
assignee - currentuser() are invalid.