Migrations

2 articles

Software Engineering 15 Sep 2026 5 min read

Schema Renames Create a Compatibility Interval

Renaming a database column is a single catalog operation in many relational systems, but an application deployment can make that apparently atomic change span several software versions. If an old process still sends statements containing old_name after the database exposes only new_name, the schema is valid and the process is valid in isolation, yet their interface no longer matches. The central issue is not the rename operation itself. It is the interval in which multiple application versions can reach one database. During that interval, schema evolution behaves like an API compatibility problem.

Software Engineering Databases

Web Development 01 Sep 2026 5 min read

Safe Database Migrations with the Expand-and-Contract Pattern

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. The expand-and-contract pattern reduces those risks by splitting an incompatible change into compatible stages. Why one-step schema changes are risky Suppose an application wants to rename users.full_name to users.display_name.

Databases SQL