Title: High Performance PostgreSQL for Rails: Archiving mentions deleted_at column (p338)

The sql command DELETE FROM trip_positions WHERE created_at < (NOW() - INTERVAL ‘90 days’); has a where clause that references the column created_at. In the paragraph that describes the statement, the sentence “To make it fast, you may need an index covering the deleted_at column” should have referenced the created_at column. The trip_positions table do not use soft deletion in the example schema.