PostgreSQL Database Migrations

A schema migration that works on an empty dev database can fail, lock, or corrupt data on a production table with millions of rows. This guide covers how to assess risk, test against real data, and execute migrations safely.

DDL Lock Reference

Every schema change acquires a lock. The critical question is: does it block reads and writes, and for how long?

Fast, Non-Blocking Operations

These complete in milliseconds regardless of table size. They only hold a brief AccessExclusiveLock for the catalog update, not for data rewriting.