The article is about migrating from RDS Postgres 9.5 to RDS Postgres 12, which is only feasible with Bucardo. Major version upgrade is less of a pain point these days with logical replication, and even Google Cloud SQL started to support logical replication since about a week ago, after a painfully long wait.
Meanwhile, you are talking about schema migration? In that case, gh-ost indeed is the best tool available. With Postgres, most types of schema migration can be done instantly with just a metadata change, or otherwise be done concurrently without locking the table. So a tool like gh-ost is not as vital, but still valuable for edge cases such as:
- altering the column type: requires table rewrite
- adding an index concurrently onto a busy server: a throttle would be nice
Meanwhile, you are talking about schema migration? In that case, gh-ost indeed is the best tool available. With Postgres, most types of schema migration can be done instantly with just a metadata change, or otherwise be done concurrently without locking the table. So a tool like gh-ost is not as vital, but still valuable for edge cases such as:
- altering the column type: requires table rewrite
- adding an index concurrently onto a busy server: a throttle would be nice