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Planning new migrations

With the atlas migrate commands users can implement a kind fo workflow that we call versioned migration authoring. This kind of workflow is a synthesis between declarative workflows, where developers specify the desired state of their database, and versioned migrations where each change is explicitly defined as a migration script with a specific version.

Practically speaking, this means that the developer maintains the schema definition, e.g the desired state, and Atlas maintains the migrations/ directory, which contains the explicit SQL scripts to move from one version to the next.

In addition, Atlas maintains a file name atlas.sum which is used to ensure the integrity of the migration directory and force developers to deal with situations where migration order or contents was modified after the fact.

Learn more about versioned migration authoring

Flags

When using migrate diff to plan a migration users must supply multiple parameters:

  • --dev-url a URL to a Dev-database that will be used to compute the diff.
  • --dir the URL of the migration directory, by default it is file://migrations, e.g a directory named migrations in the current working directory.
  • --to the URL of the desired state, can be an HCL file or another database.

Example

atlas migrate diff --dir file://my/project/migrations --to schema.hcl --dev-url mysql://root:pass@localhost:3306/dev

Reference

CLI Command Reference