Create Indexes Concurrently Without Locking
Use CREATE INDEX CONCURRENTLY so the table stays available for reads and writes during the index build.
Task
Apply CREATE INDEX CONCURRENTLY idx_orders_user ON orders (user_id); so the schema change is safe, reversible, and does not lock the table during peak traffic.
When to use this
A migration deploys CREATE INDEX CONCURRENTLY idx_orders_user ON orders (user_id); 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 CREATE INDEX CONCURRENTLY idx_orders_user ON orders (user_id); in the project configuration file with the recommended defaults.
CREATE INDEX CONCURRENTLY idx_orders_user ON orders (user_id);
Expected output: The configuration is accepted and CREATE INDEX CONCURRENTLY idx_orders_user ON orders (user_id); runs without errors on the first invocation.
2. Run the check locally to verify CREATE INDEX CONCURRENTLY idx_orders_user ON orders (user_id); 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 CREATE INDEX CONCURRENTLY idx_orders_user ON orders (user_id); blocks merge on failure.
- name: Run add index creation concurrent
run: pnpm test
Expected output: Pull requests with failing CREATE INDEX CONCURRENTLY idx_orders_user ON orders (user_id); 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. Use CREATE INDEX CONCURRENTLY so the table stays available for reads and writes during the index build. The most common mistake is adding the gate without first confirming it catches the issue you care about. Run CREATE INDEX CONCURRENTLY idx_orders_user ON orders (user_id); against the current codebase and inspect the output before wiring it into CI.
CREATE INDEX CONCURRENTLY idx_orders_user ON orders (user_id);Verify and roll back
Once the gate is in place, make failures actionable. A failing CREATE INDEX CONCURRENTLY idx_orders_user ON orders (user_id); 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.