[zmoazeni]

> which causes MySQL to copy the whole table

This is wrong on a couple levels. First it doesn't copy the whole table: https://dev.mysql.com/doc/refman/5.6/en/innodb-create-index-...

However, it can take a while if MySQL is evaluating the consistency. But you can disable that with `SET FOREIGN_KEY_CHECKS = 0` which turns it into a metadata change (nearly instantaneous).

You still will need to check for violations, but you can do that in a more friendly-to-load manner, and of course will need to deal with any violations manually.

But that strategy is a good middle ground to all-or-nothing FKs.

Edit: Whoops, looks like I was wrong on the table-copy part. Per "Otherwise, only the COPY algorithm is supported." So it does copy the data when `FOREIGN_KEY_CHECKS=1` (the default)