A little late to the party, I just learned about this change today.

I maintain a number of bot tasks and database reports on enwp that rely on cross-wiki joins (mostly page title joins between enwp and Commons) to function properly.  I didn't find the migration instructions very helpful; I run FastilyBot on a Raspberry Pi, and needless to say it would be grossly impractical for me to perform a "join" in the bot's code.

Is there going to be a replacement for this functionality?

Fastily

On Mon, Mar 15, 2021 at 3:09 PM Dan Andreescu <dandreescu@wikimedia.org> wrote:
[4] was made to figure out common use cases and possibilities to enable them again.
...

I just want to highlight this ^ thing Joaquin said and mention that our team (Data Engineering) is also participating in brainstorming ways to bring back not just cross-wiki joins but better datasets to run these queries.  We have some good ideas, so please do participate in the task and give us more input so we can pick the best solution quickly.
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