Deleting an event does not delete links to profiles it used

Events, contribution pages, etc. can use profiles. The link between these entities and the profiles they use are stored in the civicrm_uf_join table.

When a contribution page is deleted, the links between the profiles and the contribution page are deleted - this is correct.

When an event is deleted, the links between the event and the profiles it used are not deleted. They persist in the civicrm_uf_join table.

Steps to recreate:

• Create a new profile (eg ID 12)
• Create a new event, which uses this profile
• Select * from civicrm_uf_join where uf_group_id = 12 : You see the reference
• Delete the event
• Repeat the select, you can still see the reference, it hasn't been deleted.
• Repeat the above with a contribution page, note that the reference is correctly deleted.

Steps to resolve:

• Implement the logic to delete all profile references for the event from the civicrm_uf_join table when an event is deleted (custom logic in the BAO - it's not an FK cascade).
• Implement update process code to tidy up the civicrm_uf_join - removing references to events that have already been deleted.