> online schema alteration AND flexible/semi-structured types (JSON, XML). > Again, MySQL and Postgres are behind the curve on this You may want to remove Pos

> online schema alteration AND flexible/semi-structured types (JSON, XML). > Again, MySQL and Postgres are behind the curve on this You may want to remove PostgreSQL from that list, especially in 2017. PostgreSQL has supported XML for years (long before it supported JSON). And online schema changes are not only possible, but even transaction safe, which is especially nice for migrations.