T156933 is about intelligently purging/redacting PII data from the EventLogging MySQL slave databases. We also need to ensure that old data is removed from the master database (db1046). This is more for storage purposes than for privacy ones.
I see that the eventlogging_sync.sh replication script used to have a very crude way of doing this. We should make a simple but comprehensive version that is separate from the replication script.
This should work for EventLogging Analytics tables, as well as the eventbus ones that I am about to start importing into MySQL for T150369.