Issues Issues in JIRA can be searched using basic and advanced searches but with certain limitations. You can use JQL use JQL functions to overcome these limitations. For example, you cannot get the user property of a user either in the basic or advanced JQL search. For this, you would need a JQL function. These  These JQL functions can be used in in any place in JIRA where you use JQL: in the Issue Navigator, in a Saved Filter, in the Agile Board query etc. The function is available in the 

JQL functions provided by the add-on

The Jira Misc Custom Fields plugin provides some useful JQL functions for use in your advanced JQL searches. These functions are available in any place in Jira where you use JQL after installing after installing the add-on to your instance.