In the NGS migration, many collaboration artists have been deleted and split into separate artist credits. However, there doesn't seem to be a way to actually retrieve the mapping from old MBID -> new artist MBIDs in the NGS data that the migration performed on the data.

Here are some examples of MBIDs that exist in the old schema, but don't appear anywhere in the NGS artist or artist_gid_redirect:

cbf70019-3df3-495b-a4b8-49f943b9e898 Jerry Garcia & David Grisman
d46aac8d-8f03-46da-8516-952b6ddd4eed Ravi Shankar and Philip Glass
55db491a-5c30-46a6-ab15-2ec1eabf4bd0 Brian Eno & John Cale
6423c748-7f74-4dbc-8e9d-61669e9dfd59 David Sylvian & Robert Fripp
430f3c84-b455-4340-8e8a-6a7197ad66cf Elvis Costello with Burt Bacharach
f13338d0-0c04-4fa1-98e1-2429479dde3b Nusrat Fateh Ali Khan & Michael Brook

I think being able to retrieve this mapping will help a lot in moving legacy data to the NGS. Unfortunately, artist_gid_redirect's primary key is GID, so these collaboration artists couldn't fit in this table. Ideally, being able to retrieve the entire mapping would be best, but that would require a change to artist_gid_redirect or have another table for these multi-artist mappings. If this is impossible, I suppose making an artist_gid_redirect entry for these collaboration artists pointing to the first artist would be ok, Lukas suggested this on IRC.

What do you think about this?