ClickHouse Migration Deep Dive

Overview

Plan and execute ClickHouse schema migrations: column changes, engine migrations, ORDER BY modifications, and versioned migration runners. ClickHouse ALTER operations behave unlike PostgreSQL/MySQL — most are asynchronous mutations that rewrite data parts in the background, and some changes (ORDER BY, engine) require full table recreation. This skill walks the safe path for each.

Prerequisites

• ClickHouse admin access
• Backup of production data (see clickhouse-prod-checklist)
• Test environment for validation

Instructions

Follow these steps in order. SQL and runner code for each step live in the linked reference files — keep them open while you work.