tbicr

Unfortunately savepoints live only in transaction and ACCESS EXCLUSIVE will be released only on whole transaction commit/rollback, so look like no benefits with savepoints for schema migrations to compare with plain transaction.

Constraints creation also tricky because in transaction it take ACCESS EXCLUSIVE lock (eg. lock table on READ/WRITE) and spend time to constraint validation (CHECK, NOT NULL, FOREIGN KEY), so lock will be released only on transaction commit/rollback.

I found only two caveats:

- it doesn't use transactions, so if migration will down, then you will need to fix state manually (one point of improvement), however you cannot run `CREATE INDEX CONCURRENTLY` in transaction.

- it can use `CHECK (column IS NOT NULL)` constraint for safe `NOT NULL` replacement for huge tables, that isn't compatible with standard django behavior.

So all this cases highlighted in README.