How do I query for issues in JIRA that have a specific label and only that label?

I have a label in JIRA, say Foo. I want to query for all issues that have that label and that label only. How do I do that?

I've tried

labels = Foo AND NOT(labels NOT IN (Foo))

but that returns issues labelled Foo and Bar as well. I want the issues labelled only Foo.

How do I query for issues in JIRA that have a specific label and only that label?

There's no JQL way of doing this that I'm aware of (obviously, hard to prove a negative but I have fairly decent knowledge of JQL).

The obvious approaches don't work:

• labels != Foo does NOT retun tickets that have Foo, at all (by design, because != is 100% equivalent to NOT ... = as per documentation), so doing labels != Foo AND labels = Foo returns empty set.

• Can't use text matcing ~ or !~ , JIRA will throw JQL errors: The operator '!~' is not supported by 'labels' field. That's because it's a picker/multiple choice field, not a text one.

• The only value you can compare "labels" to using IS/IS NOT is "EMPTY"

The 2.5 workarounds (that all suck, admittedly) are:

1. Find the most used "extra" tags, and build a query excluding them

   ... AND labels = Foo AND labels NOT IN (Bar1, Bar2, ...)
   

   Pros: Pure JQL, simple

   Cons: Doesn't catch less-used labels; needs to be updated when more labels are added; and may not scale well if you have super many extra labels that pair with Foo.

2. Use a macro. This Atlassian Q&A details

   • Install JIRA Misc Custom Fields plugin
   • Create a custom numeric field labels_count, using the formula @@Formula: issue.get("labels").size()
   • Re-index JIRA
   • Include AND labels_count = 1 in your JQL

   Pros: Should work

   Cons: I didn't actually test it so not sure if it will work. It requires installing a new plugin (a useful one!) and reindexing. And I don't know if it will keep the field updated without further reindexing - I think it would but not 100% certain.

3. Not sure if this will work, but you can look at another way to create custom fields:

   • Use Script Runner plugin

   • Create a field with Groovy code to return count of labels.

     Best as I can tell, something like return issue.getlabels().size()

   • Some sample code related to ScriptRunner and labels: ex1; ex2

   Pros: ???

   Cons: Paid plugin, not sure how to get this to work.