2b) And keep your schema changes as incremental and backwards-compatible as possible. Add new tables, add columns to tables, but don't drop or rename anything.

2b) And keep your schema changes as incremental and backwards-compatible as possible. Add new tables, add columns to tables, but don't drop or rename anything. If you need a flag day, in PG terms just setup a new schema, use triggers to sync the two, and migrate your apps to use the new schema -- when they're all migrated, drop the sync triggers and the old schema.