We have a whole lot of code which maintains the room_stats_historical and user_stats_historical tables (and a config option, bucket_size, which configures how it is populated), but afaict they are never actually used.

It's not obvious to me what the purpose of these tables are for, and I'd argue that unless we have a clear usecase for them, the tables and dead code should be stripped out.

It looks like the concept of historical stats was introduced by @ara4n in the initial commits in #4338, though it subsequently got refactored out of recognition by #5971. @ara4n: any comments on the purpose of this, and/or objections to it being ripped out.

Also of interest (and would need updating) is the doc, https://github.com/matrix-org/synapse/blob/v1.29.0/docs/room_and_user_statistics.md.