[gregwebs]

Greg from the TiDB team here. I do share your sentiment, and at the moment you can probably best track or progress on this issue here: https://github.com/pingcap/tidb/issues/8484

The explanation is just that TiDB is being developed with tight feedback from our customers that have many TB of data. The feedback from that scale of users is overwhelmingly that they do not want to take the performance hit of foreign keys. It is worth mentioning though that you can declare foreign keys and that on master we do properly check DDL statements (but there is no DML enforcement).

I am trying to figure out a design that will satisfy users with large and small data alike and even let users use foreign keys for documentation purposes when they are not enforced for performance reasons. It would be great to have more community input on this.