schema change
Database migration
Database Migration
Also known as · DB migration · schema migration · DDL change
Definition
A versioned change that moves operational data structures or constraints from one state to the next. Successful SQL syntax is a separate judgment from compatibility and recoverability.
Searchable examples
- CREATE INDEX CONCURRENTLY
- forward fix
Short example
create table → verify schema → backfill → verify reads/writes
When a change is already applied, a forward-fix migration may be safer than pretending it never happened.
Compare with
- Single Source of Truthdesign principleA principle that gives one authoritative source the meaning and write authority for a fact while treating other representations as derived state. It clarifies ownership and synchronization boundaries; it does not mean copies never exist.
- Idempotencyretry contractThe property that repeated processing of the same intent converges on the same observable business state as one processing. It limits duplicate effects instead of pretending retries do not happen.