One issue I've come across is that the query optimizer in Clickhouse does not propagate `where` clauses through a join. My terminology might be wrong, so consider this example:

select * from a inner join b using (id) where b.foo = 'bar'

Clickhouse will not evaluate `foo = 'bar'` before performing the join, so you might wind up with a join that produces a large intermediate result before the filtering happens. Postgres (probably other databases) will optimize this for you. To force Clickhouse to filter first, you would need to write something like

select * from a inner join ( select * from b where foo = 'bar' ) b using (id)

Maybe not a strict limitation, but the workaround is a bit janky.