Migration linter

A migration linter reads the project's database migrations before they run, and flags operations that lock a busy table, lose data or cannot be undone. Which linter fits depends on the database and the migration tool, both found in the project.

Finding it

Look for the migrations directory and for the migration tool in the dependencies, then in CI and the pre-commit config for a linter already run on them. Its config (.squawk.toml, atlas.hcl) says which rules are turned off.

Using it

• New migrations only: squawk on the changed SQL files, or atlas migrate lint --latest 1 with the project's atlas.hcl, so migrations already applied are not reported again.
• Up, down and up again: each migration is run on a throwaway database in both directions, so the undo is tested, not assumed.
• The production version: the throwaway database runs the version used in production, since what locks a table differs between versions.

Examples: Squawk (PostgreSQL), Atlas, strong_migrations (Ruby on Rails).