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Database migrations

Page summary:

Database migrations run one-time scripts before the schema sync to preserve data during upgrades. Migration files export an up() function and run once, in alphabetical order. During the schema sync that follows, Strapi drops the tables and columns it previously managed that are no longer in the content-types schemas.

Database migrations exist to run one-time queries against the database, typically to modify the tables structure or the data when upgrading the Strapi application. These migrations are run automatically when the application starts and are executed before the automated schema migrations that Strapi also performs on boot.

🚧 Experimental feature

Database migrations are experimental. This feature is still a work in progress and will continue to be updated and improved. In the meantime, feel free to ask for help on GitHub Discussions or on the community Discord.

Understanding database migration files​

Migrations are run using JavaScript migration files stored in ./database/migrations.

Strapi automatically detects migration files and run them once at the next startup in alphabetical order. Every new file is executed once.

What happens on startup​

Understanding the order of operations helps predict what happens to your data. On every startup, Strapi performs the following steps:

  1. Loads the schema: content-types and components are converted into database models, then relations are validated.
  2. Runs pending migrations: your migration files in ./database/migrations run first, followed by Strapi's own internal migrations. Each migration runs in its own transaction, and applied migrations are tracked so they never run twice.
  3. Syncs the database schema: Strapi compares the content-types schemas with the database and applies the differences, creating tables and columns, then dropping the ones that are no longer part of the schema, then altering the rest.
  4. Persists the new schema: the resulting schema is stored in the database and becomes the reference for the next startup.
Caution

Migrations run before the schema sync, so an up() function still sees the database in its previous state. Write migrations against the old schema, not the one you are migrating to.

Note

Steps 2 and 3 are skipped entirely when there is no pending migration and the schema has not changed since the last startup. Strapi detects changes by comparing the content-types schemas, not by inspecting the database, so manual changes made directly to the database are not detected or reverted.

Data loss during the schema sync​

During the schema sync, Strapi drops the tables and columns that it previously managed and that no longer match the content-types schemas. This happens automatically, without any warning or confirmation prompt, and identically in development and in production. Deleting a content-type from your code therefore deletes its table, and its data, on the next startup.

Tables that Strapi has never managed, such as tables you created yourself directly in the database, are left untouched.

Migrations are the way to preserve data across such changes: use them to copy or transform data before the schema sync removes the old structure.

Warning

Strapi does not support down migrations. If you need to revert a migration, you have to do it manually. Down migrations are planned, but no timeline is currently available.

Tip

The forceMigration and runMigrations database configuration parameters fine-tune this behavior. Setting forceMigration to false skips all destructive operations, which is useful to inspect what would be dropped before letting Strapi apply it.

Migration files should export the function up(), which is used when upgrading (e.g. adding a new table my_new_table).

The up() function runs in a database transaction which means if a query fails during the migration, the whole migration is cancelled, and no changes are applied to the database. If another transaction is created within the migration function, it will act as a nested transaction.

Note

There is no CLI to manually execute the database migrations.

Creating a migration file​

To create a migration file:

  1. In the ./database/migrations folder, create a new file named after the date and the name of the migration (e.g. 2022.05.10T00.00.00.name-of-my-migration.js). Make sure that the file name follows this naming pattern, because the alphabetical order of the files defines the order in which the migrations have to run.

  2. Copy and paste the following template in the previously created file:

'use strict'

async function up(knex) {}

module.exports = { up };
  1. Fill in the template by adding actual migration code inside the up() function. up() receives a Knex instance, already in a transaction state, that can be used to run the database queries.
Example of migration file
./database/migrations/2022.05.10T00.00.00.name-of-my-migration.js

module.exports = {
  async up(knex) {
    // You have full access to the Knex.js API with an already initialized connection to the database

    // Example: renaming a table
    await knex.schema.renameTable('oldName', 'newName');

    // Example: renaming a column
    await knex.schema.table('someTable', table => {
      table.renameColumn('oldName', 'newName');
    });

    // Example: updating data
    await knex.from('someTable').update({ columnName: 'newValue' }).where({ columnName: 'oldValue' });
  },
};

Using Strapi Instance for migrations​

Warning

If a user opts not to use Knex directly for migrations and instead utilizes the Strapi instance, it is important to wrap the migration code with strapi.db.transaction(). Failure to do so may result in migrations not rolling back if an error occurs.

Example of migration file with Strapi instance
./database/migrations/2022.05.10T00.00.00.name-of-my-migration.js
module.exports = {
  async up() {
    await strapi.db.transaction(async () => {
      // Your migration code here

      // Example: creating new entries
      await strapi.entityService.create('api::article.article', {
        data: {
          title: 'My Article',
        },
      });

      // Example: custom service method
      await strapi.service('api::article.article').updateRelatedArticles();
    });
  },
};

Using the migration progress heartbeats​

For long-running migrations, Strapi provides a progress heartbeat feature that logs periodic status updates without rewriting terminal output. This is useful when migrations process large datasets and need to show activity to the operator.

The heartbeat logger is time-throttled (default 60 seconds) and reports progress in a format like:

… still running (120s) · files 12000/450000

This feature is automatically enabled for migrations that use the heartbeat logging capability, such as data backfill operations. The progress updates are append-only, making them suitable for long-running operations that don't produce frequent log output.

Handling migrations with TypeScript code​

By default Strapi looks for migration files in the source directory rather than the build directory when using TypeScript. This means that TypeScript migrations won't be found and executed properly unless you configure Strapi to look in the right place.

To enable TypeScript migrations in Strapi, you need to set the useTypescriptMigrations parameter to true in your database configuration. This setting tells Strapi to look for migrations in the build directory instead of the source directory.

Here's how to configure it in your database settings:

/config/database.js
module.exports = ({ env }) => ({
  connection: {
    // Your database connection settings
  },
  settings: {
    useTypescriptMigrations: true
  }
});

Additionally, if you want to continue using existing JavaScript migrations alongside TypeScript migrations, you can set allowJs: true in your tsconfig.json file's compiler options, as mentioned in the database configuration documentation.

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