Destructive Operations
ALTER TABLE ... DROP COLUMN
ALTER TABLE orders DROP COLUMN legacy_notes;What this does
Metadata-only: the column's storage is not physically removed until the table is next rewritten. The risk is application breakage, not lock duration; any code still reading the column errors immediately.
Safe rewrite
Remove all application references first, then drop in a follow-up migration
-- 1. Stop reading "legacy_notes" in application code.
-- 2. Deploy the code change and verify in production.
-- 3. Drop the column in a separate migration:
ALTER TABLE orders DROP COLUMN IF EXISTS legacy_notes;