Migrations

Migrations allow you to evolve your database schema over time. Rather than write schema modifications in pure SQL, migrations allow you to describe changes to your tables.

You can think of each migration as being a new "version" of the database. A schema starts off with nothing in it, and each migration modifies it to add or remove tables, columns, or entries. Strapi knows how to update your schema along this timeline, bringing it from whatever point it is in the history to the latest version.

Create a new migration file

To generate a migration file run:

$ strapi migrate:make connection_name migration_name

For example, if you want to create a migration file named new_car_model for the car API we just generated using the default connection the command looks like:

$ strapi migrate:make default new_car_model

How it works

Migration files for each connection can be found in ./data/migrations.

!!! warning Be careful, migrations are automatically generated based on your current database schema and models. We strongly advise you to manually verify those information.

The migrations use the schema builder to update your database schema.

For every migration there is a up and a down logic. The up logic corresponds to the new updates to apply to the connection. The down logic is the "mirror" of the up logic-- it's the logic to rollback this migration.

Transactions

Transactions are an important feature of relational databases, as they allow correct recovery from failures and keep a database consistent even in cases of system failure. All queries within a transaction are executed on the same database connection, and run the entire set of queries as a single unit of work. Any failure will mean the database will rollback any queries executed on that connection to the pre-transaction state.

By default, each migration is run inside a transaction. Whenever needed, one can disable transactions per-migration, via exposing a boolean property from a migration file:

exports.config = {
  transaction: false
};

Run the migrations

Once you have finished writing the migrations using the schema builder, you can update the database by running:

$ strapi migrate:run connection_name

So if you want to run the previous migration generated for the default connection you need to run:

$ strapi migrate:run default

Seeding

Seed files are created in the ./data/seeds directory.

Seeds allow you to populate your database with inserted data. For every migration there is a seed file.

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