The experiment desk / Free labs
Choose a PostgreSQL rehearsal.
Pick the failure mode you want to understand. Each small, disposable experiment includes the complete script, original SQL results and a free download. No account required.
Your index retry succeeded. Is the index usable?
After duplicate keys caused a unique-index build to fail, a retry with IF NOT EXISTS exited successfully while the index stayed invalid and not ready.
A three-row duplicate-key experiment, including catalog checks after the skipped retry.
Inspect the retry labYou canceled the build. What did it leave behind?
Three controlled wait stages left three different states. One failed unique index still rejected duplicate writes; the rehearsal follows through to a fresh unique rebuild.
A two-row experiment with lock waits, statement cancellation and recorded cleanup checks.
Inspect the cancellation labTwo clients share a backend. Which settings follow them?
In the tested configuration, each client kept its search path, while a session timeout carried over to the other client. Transaction-local settings ended with COMMIT or ROLLBACK.
Two clients, one reused backend, the same database and user. Records setting values, without testing query timing or tenant isolation.
Inspect the pooling lab
Read the setup with the result.
These are dated local observations using synthetic data. Each lab names its configuration, expected failures and limits. Use that scope when deciding what to rehearse in your own environment; these runs do not establish production performance or approve a deployment.
Planning connection counts? Pair the pooling review with the free connection-budget planner.