![]() This is a good practice that I recommend you follow as well, because with this variable it is easy to redirect to another database. In my projects I use a DATABASE_URL environment variable to configure the location of the database. The trick to generate this initial migration for a project that uses an up to date database is to temporarily switch to an empty database, just for the flask db migrate command. For an existing project the database is up to date and in sync with the models, so there are no differences, and thus, Alembic thinks that there is nothing to put in the database migration script. In a new project the models are going to be compared against a brand new (empty) database, so the migration script will include all the model definitions. The contents of a migration are obtained by running a comparison between the current model definitions and the current schema of your database. To understand the problem you have to think about how Alembic (the migration engine used by Flask-Migrate) generates database migrations. But how can that be if we are just getting started with migrations in this project? The "No changes in schema detected" message indicates that there is no need to migrate the database. This step does not actually work if you have an existing project that has a populated database: (venv) $ flask db migrate If you look at the documentation, the next step in the process is to create an initial migration for your project, using the migrate command: (venv) $ flask db migrate ![]() Add the directory and all of its contents to source control. This command adds a migrations directory in the root of your project. ![]() Please edit configuration/connection/logging settings in 'migrations/alembic.ini' before proceeding. Generating /Users/mgrinberg/microblog/migrations/alembic.ini. ![]() Generating /Users/mgrinberg/microblog/migrations/README. Generating /Users/mgrinberg/microblog/migrations/env.py. Generating /Users/mgrinberg/microblog/migrations/script.py.mako. doneĬreating directory /Users/mgrinberg/microblog/migrations/versions. To create the repository you can use the init command: (venv) $ flask db initĬreating directory /Users/mgrinberg/microblog/migrations. The migration repository should be considered part of your source code, and should be added to your source control. This is a directory where all the migration scripts are going to be stored. The next step in the process is to create a database migration repository. Stamp 'stamp' the revision table with the given. Show Show the revision denoted by the given. Migrate Autogenerate a new revision file (Alias for. Merge Merge two revisions together, creating a new. History List changeset scripts in chronological. ![]() Heads Show current available heads in the script. Ĭurrent Display the current revision for each. Once the extension is added to the project you will have a flask db command available: (venv) $ flask db In that case you would initialize Flask-Migrate as follows: from flask_migrate import Migrate If you use an application factory function you very likely use the delayed method to create your extensions. If you use the direct method of creating extensions: from flask_migrate import Migrate This involves creating and initializing a Migrate instance. The extension then needs to be added to the project. Assuming you have a project that uses Flask-SQLAlchemy to manage a database, you begin by installing the Flask-Migrate extension: (venv) $ pip install flask-migrate This step is the same for new and existing projects. ![]()
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