JQL is very powerful and it brings in all the advantages of Issue Navigator. You can combine them with other JQL functions to narrow down the search. Exporting into different formats, different views, sorting etc comes with Issue Navigator and hence JQL!
Can I subscribe using these new JQL functions?
Yes, you can. You can do anything that is possible with the Issue Navigator and filters.
Does it affect the JIRA performance?
No and Yes.
Depends on how it is used! It doesn't affect the JIRA as a whole but can take some time to retrieve the search results depending on the nature of the query. It vastly depends on the number of issues the user has got access to! If a user, maybe an administrator, has got access to hundreds of thousands of issues, he might see a delay when searched for issues with a specified number of attachments. Some of these operations traverses the entire issues and goes to DB as the information on attachments or other info that is not stored in indexes. But in most cases the JQL search is very fast and makes use of lucene indexes. On top of that, a caching is introduced in the plugin to avoid the issues raised in http://jira.atlassian.com/browse/JRA-22256.
Try out an evaluation license to see how it performs for you and your JIRA instance. And check out this page to read what you can do if performance is affected.
There a quite a lot of functions but I am not interested in few of them. Can we have a subset of functions?
Yes, you can. All you need to do is to go to the plugin details under Administration > Plugin page and disable the modules you are not interested in.
One function is failing and everything else works perfect. How do I hide the failing one till it is fixed?
Same as above. Disable the module that has the failing function. We will fix it as fast as we can!
How to trouble shoot?
Start by checking our list of known issues. If that doesn't help, look at the JIRA logs (atlassian-jira.log file) to see if there are any obvious errors. If not, create a support ticket in our JIRA and we will surely be able to help!
HOW DO i request for new functions
Please raise a "New Feature" in our JIRA and we will prioritize it based on the criticality of the request.
What should be the cache delay?
It depends entirely on your instance. The default value of 120s works for most but if the number of issues is more, you might as well make it 5 minutes or even more!
Make sure you understand how the cache works. If the cache is for 5 minutes and the actual issue field values changed before that, you won't see the changes reflected in the search results until the 5 minutes delay is over! It is also possible that contradicting searches can live in cache if the value changed in between. It is a rare case but see JQLT-22 for an example.
Given the benefits, we recommend you to set cache for a small period but you can set 0 if you do not need cache.
Can we use these functions in gadgets?
Of course you can. But make sure you do a thorough evaluation. Some of the functions are quite performance intensive, like hasLinks. It wouldn't be advisable to put them on the dashboard as it can hit the system performance.
Again, it depends on your system resources, number of issue etc.