Keeping track of new record without hammering the database. Keeping track of updates without a dedicated column. Ditto for deletes. Schema drift. Managing d

Keeping track of new record without hammering the database. Keeping track of updates without a dedicated column. Ditto for deletes. Schema drift. Managing datatype differences. I.e., Postgres supports complex datatypes that other DBs do not. Stored procedures. Basically any features of a DB that are beyond the bare minimum necessary to call something a relation database is an edge case. I rolled a solution for Postgres -> BQ by hand and it was much more involved than I expected. I had to set up a read-only replica and completely copying over the databases each run, which is only possible because they are so tiny.