DB Error on upgrade to 4.7: Duplicate entry activity_tab_filter for key 'index_domain_contact_name'
It seems that you have the same setting that is set twice on your database, and the upgrade to 4.7 enforce it won't happen.

You will need to list your settings as stored in the database, you should see more than one activity_tab_filter for the contact_id 571.

Delete the duplicate(s) and keep only one and then run the upgrade again and you should be fine

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