Issue Summary

Much like BSERV-12860, there are no unique constraints on the table bb_label_mapping. This could cause duplicates in the table with same label_id, labelable_id and labelable_type.

Steps to Reproduce

Expected Results

Actual Results

The below exception is thrown in the atlassian.bitbucket.log file:
Upon running a DELETE command against REST call

/rest/api/latest/projects/{projectKey}/repos/{repo_slug)/labels/{label}

can return the below result.

2021-11-17 15:06:15,043 DEBUG [http-nio-7990-exec-70] bbuser *1X8W6DVx906x4137511x14 1jjoc9z 127.0.0.1 "DELETE /bitbucket/rest/api/latest/projects/PROJ_name/repos/repo_name/labels/label-namee HTTP/1.1" c.a.s.i.r.e.ServiceExceptionMapper Mapping ServiceException to REST response 500
com.atlassian.bitbucket.DataStoreException: A database error has occurred.
..
Caused by: org.hibernate.NonUniqueResultException: query did not return a unique result: 5

You can see duplicates in bb_label_mapping (With same label_id, labelable_id and labelable_type).

Workaround

Delete the duplicates manually from the database