https://nalar.dev/tags/migrations/ Recent content in Migrations on Nalar Hugo en-us Tue, 01 Sep 2026 00:00:00 +0700 https://nalar.dev/safe-database-migrations-expand-contract/ Tue, 01 Sep 2026 00:00:00 +0700 https://nalar.dev/safe-database-migrations-expand-contract/ <p>A schema migration can be syntactically correct and still cause an outage. Production deployments often run old and new application versions at the same time, background workers may lag behind, and a large table can turn a simple-looking DDL statement into a long lock.</p> <p>The expand-and-contract pattern reduces those risks by splitting an incompatible change into compatible stages.</p> <h2 id="why-one-step-schema-changes-are-risky">Why one-step schema changes are risky</h2> <p>Suppose an application wants to rename <code>users.full_name</code> to <code>users.display_name</code>.</p>