Dbmate is a database migration tool, to keep your database schema in sync across multiple developers and your production servers.
It is a standalone command line tool, which can be used with Go, Node.js, Python, Ruby, PHP, or any other language or framework you are using to write database-backed applications. This is especially helpful if you are writing many services in different languages, and want to maintain some sanity with consistent development tools.
For a comparison between dbmate and other popular database schema migration tools, please see the [Alternatives](#alternatives) table.
You can run dbmate using the official docker image (remember to set `--network=host` or see [this comment](https://github.com/amacneil/dbmate/issues/128#issuecomment-615924611) for more tips on using dbmate with docker networking):
If you wish to create or apply migrations, you will need to use Docker's [bind mount](https://docs.docker.com/storage/bind-mounts/) feature to make your local working directory (`pwd`) available inside the dbmate container:
The following options are available with all commands. You must use command line arguments in the order `dbmate [global options] command [command options]`. Most options can also be configured via environment variables (and loaded from your `.env` file, which is helpful to share configuration between team members).
Dbmate locates your database using the `DATABASE_URL` environment variable by default. If you are writing a [twelve-factor app](http://12factor.net/), you should be storing all connection strings in environment variables.
To make this easy in development, dbmate looks for a `.env` file in the current directory, and treats any variables listed there as if they were specified in the current environment (existing environment variables take preference, however).
If you do not already have a `.env` file, create one and add your database connection URL:
Dbmate can also load the connection URL from a different environment variable. For example, before running your test suite, you may wish to drop and recreate the test database. One easy way to do this is to store your test database connection URL in the `TEST_DATABASE_URL` environment variable:
Alternatively, you can specify the url directly on the command line:
```sh
$ dbmate -u "postgres://postgres@127.0.0.1:5432/myapp_test?sslmode=disable" up
```
The only advantage of using `dbmate -e TEST_DATABASE_URL` over `dbmate -u $TEST_DATABASE_URL` is that the former takes advantage of dbmate's automatic `.env` file loading.
When connecting to Postgres, you may need to add the `sslmode=disable` option to your connection string, as dbmate by default requires a TLS connection (some other frameworks/languages allow unencrypted connections by default).
A `search_path` parameter can be used to specify the [current schema](https://www.postgresql.org/docs/13/ddl-schemas.html#DDL-SCHEMAS-PATH) while applying migrations, as well as for dbmate's `schema_migrations` table.
If the schema does not exist, it will be created automatically. If multiple comma-separated schemas are passed, the first will be used for the `schema_migrations` table.
SQLite databases are stored on the filesystem, so you do not need to specify a host. By default, files are relative to the current directory. For example, the following will create a database at `./db/database.sqlite3`:
To create a new migration, run `dbmate new create_users_table`. You can name the migration anything you like. This will create a file `db/migrations/20151127184807_create_users_table.sql` in the current directory:
```sql
-- migrate:up
-- migrate:down
```
To write a migration, simply add your SQL to the `migrate:up` section:
> Note: Migration files are named in the format `[version]_[description].sql`. Only the version (defined as all leading numeric characters in the file name) is recorded in the database, so you can safely rename a migration file without having any effect on its current application state.
> Note: `dbmate up` will create the database if it does not already exist (assuming the current user has permission to create databases). If you want to run migrations without creating the database, run `dbmate migrate`.
Pending migrations are always applied in numerical order. However, dbmate does not prevent migrations from being applied out of order if they are committed independently (for example: if a developer has been working on a branch for a long time, and commits a migration which has a lower version number than other already-applied migrations, dbmate will simply apply the pending migration). See [#159](https://github.com/amacneil/dbmate/issues/159) for a more detailed explanation.
By default, dbmate doesn't know how to roll back a migration. In development, it's often useful to be able to revert your database to a previous state. To accomplish this, implement the `migrate:down` section:
`transaction` is useful if you need to run some SQL which cannot be executed from within a transaction. For example, in Postgres, you would need to disable transactions for migrations that alter an enum type to add a value:
If you use a Docker development environment for your project, you may encounter issues with the database not being immediately ready when running migrations or unit tests. This can be due to the database server having only just started.
In general, your application should be resilient to not having a working database connection on startup. However, for the purpose of running migrations or unit tests, this is not practical. The `wait` command avoids this situation by allowing you to pause a script or other application until the database is available. Dbmate will attempt a connection to the database server every second, up to a maximum of 60 seconds.
If the database is available, `wait` will return no output:
```sh
$ dbmate wait
```
If the database is unavailable, `wait` will block until the database becomes available:
Please note that the `wait` command does not verify whether your specified database exists, only that the server is available and ready (so it will return success if the database server is available, but your database has not yet been created).
When you run the `up`, `migrate`, or `rollback` commands, dbmate will automatically create a `./db/schema.sql` file containing a complete representation of your database schema. Dbmate keeps this file up to date for you, so you should not manually edit it.
It is recommended to check this file into source control, so that you can easily review changes to the schema in commits or pull requests. It's also possible to use this file when you want to quickly load a database schema, without running each migration sequentially (for example in your test harness). However, if you do not wish to save this file, you could add it to your `.gitignore`, or pass the `--no-dump-schema` command line option.
To dump the `schema.sql` file without performing any other actions, run `dbmate dump`. Unlike other dbmate actions, this command relies on the respective `pg_dump`, `mysqldump`, or `sqlite3` commands being available in your PATH. If these tools are not available, dbmate will silenty skip the schema dump step during `up`, `migrate`, or `rollback` actions. You can diagnose the issue by running `dbmate dump` and looking at the output:
On Ubuntu or Debian systems, you can fix this by installing `postgresql-client`, `mysql-client`, or `sqlite3` respectively. Ensure that the package version you install is greater than or equal to the version running on your database server.
> Note: The `schema.sql` file will contain a complete schema for your database, even if some tables or columns were created outside of dbmate migrations.
By default, dbmate stores a record of each applied migration in a `schema_migrations` table. This table will be created for you automatically if it does not already exist. The table schema is very simple:
Dbmate records only the version number of applied migrations, so you can safely rename a migration file without affecting its applied status.
You can customize the name of this table using the `--migrations-table` flag or `$DBMATE_MIGRATIONS_TABLE` environment variable. If you already have a table with this name (possibly from a previous migration tool), you should either manually update it to conform to this schema, or configure dbmate to use a different table name.
Why another database schema migration tool? Dbmate was inspired by many other tools, primarily [Active Record Migrations](http://guides.rubyonrails.org/active_record_migrations.html), with the goals of being trivial to configure, and language & framework independent. Here is a comparison between dbmate and other popular migration tools.
> :eight_pointed_black_star: In theory these tools could be used with other languages, but a Go development environment is required because binary builds are not provided.
*If you notice any inaccuracies in this table, please [propose a change](https://github.com/amacneil/dbmate/edit/master/README.md).*
