Looked at this for a bit today.

• • The relevant code is in https://github.com/wikimedia/puppet/blob/78c00704610793e62901e821360e7c7609ef3d75/modules/profile/manifests/labs/db/views.pp
• To run the code locally, also check out both the puppet repo and https://github.com/wikimedia/operations-mediawiki-config , then run python maintain-meta_p.py --databases enwiki nlwiki --dry-run --config-location=../../../../templates/labs/db/views/maintain-views.yaml --mediawiki-config=/home/valhallasw/src/operations-mediawiki-config
• NB. You need to either have a local database server set up, or apply http://gerrit.wikimedia.org/r/432532

There are a few points that need some thought:

• we can probably keep the slice column as deprecated column, and move to a two-table setup (see T186675).
• we need to figure out a way how to do database migrations, as 'create if not exists' cannot be used to add columns
• non-wiki databases (T186675) can be added at a later point -- this needs some thought in how to actually register those databases (centralauth_p is not part of the regular dblist files, it seems)
• there are no tests for the current implementation -- it would be good to have a few basic tests (against an in-memory database, or a temporary database)