Schema Migrations

Automatically run schema migrations against a mirrord DB branch

A DB branch includes the source database's schema as of when it was cloned - or starts with no schema at all, depending on copy.mode. Either way, it won't include migrations that exist only in your working tree and haven't been applied to the source database yet.

The migrations field closes that gap: mirrord runs your schema migrations against the branch automatically when it's created, so the branch comes up with the schema your code expects.

This page covers the migrations field of a DB branch config for MySQL, PostgreSQL, and MSSQL. For general concepts and the full list of config fields, see the DB Branching overview.

Schema migrations require mirrord operator 3.182.0, mirrord CLI 3.230.0, and operator Helm chart 3.182.0.

{
  "feature": {
    "db_branches": [
      {
        "type": "pg",
        "version": "17",
        "name": "users-database-name",
        "connection": { "url": "DATABASE_URL" },
        "migrations": {
          "flavor": "flyway",
          "path": "./migrations"
        }
      }
    ]
  }
}

Field	Description
flavor	Selects the migration tool. Currently flyway.
path	Local directory of migration files, resolved relative to your working directory.
image	(Optional) Override the migration runner image. Defaults to flyway/flyway:12 for flavor: flyway.

Using migrations requires the branch's name field to be set.

Migrations run while the branch is created, before it becomes ready. If they fail, the session aborts, so your app is never started against a half-migrated branch.

A migration that conflicts with one already applied to the branch fails your session only, the branch itself remains usable.

Flyway migrations

Set "flavor": "flyway" to run migrations with Flyway.

To override the runner image, set image:

{
  "migrations": {
    "flavor": "flyway",
    "path": "./migrations",
    "image": "flyway/flyway:12"
  }
}