[orf]

There have been some messages on the development mailing list about adding support for create index concurrently when using Postgresql, which is a big pain point for larger migrations.

It's a bit tricky as you cannot use it in a transaction though

[tbicr]

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.