Migrate from Serial to UUID Primary Keys
Add a UUID column, backfill with generated values, make it the primary key, and drop the serial so offline ID guessing is impossible.
Task
Apply ALTER TABLE orders ADD COLUMN id_uuid UUID DEFAULT gen_random_uuid(); so the schema change is safe, reversible, and does not lock the table during peak traffic.
When to use this
A migration deploys ALTER TABLE orders ADD COLUMN id_uuid UUID DEFAULT gen_random_uuid(); during peak hours, takes a 40-second lock, and causes a connection pool exhaustion.
Prerequisites
- A database with migration tooling configured
- A staging environment mirroring production schema
Steps
1. Configure ALTER TABLE orders ADD COLUMN id_uuid UUID DEFAULT gen_random_uuid(); in the project configuration file with the recommended defaults.
ALTER TABLE orders ADD COLUMN id_uuid UUID DEFAULT gen_random_uuid();
Expected output: The configuration is accepted and ALTER TABLE orders ADD COLUMN id_uuid UUID DEFAULT gen_random_uuid(); runs without errors on the first invocation.
2. Run the check locally to verify ALTER TABLE orders ADD COLUMN id_uuid UUID DEFAULT gen_random_uuid(); produces the expected result before pushing.
pnpm test
Expected output: Local run matches CI behavior; no surprises after push.
3. Add the gate to the CI pipeline so ALTER TABLE orders ADD COLUMN id_uuid UUID DEFAULT gen_random_uuid(); blocks merge on failure.
- name: Run add uuid primary key migration
run: pnpm test
Expected output: Pull requests with failing ALTER TABLE orders ADD COLUMN id_uuid UUID DEFAULT gen_random_uuid(); are blocked from merging.
Troubleshooting
Problem
The check passes locally but fails in CI
Solution
Pin dependency versions and the runtime to match CI exactly; reproduce with the same Docker image or act.
Problem
Configuration is rejected with a schema error
Solution
Check the tool version matches the config schema; older versions may not support newer fields.
Limitations
- The gate only runs on events that trigger the workflow; locally pushed commits bypass it.
- Configuration drift is possible if someone edits settings outside version control.
Make migrations safe
Start by measuring the problem. Add a UUID column, backfill with generated values, make it the primary key, and drop the serial so offline ID guessing is impossible. The most common mistake is adding the gate without first confirming it catches the issue you care about. Run ALTER TABLE orders ADD COLUMN id_uuid UUID DEFAULT gen_random_uuid(); against the current codebase and inspect the output before wiring it into CI.
ALTER TABLE orders ADD COLUMN id_uuid UUID DEFAULT gen_random_uuid();Verify and roll back
Once the gate is in place, make failures actionable. A failing ALTER TABLE orders ADD COLUMN id_uuid UUID DEFAULT gen_random_uuid(); should point to the exact file and line, not a generic error. Pin the tool version in the lockfile so a upstream release does not silently change behavior. Review the gate output in every pull request just like a test result.