db-plugins 27.4.0

ALeRCE database plugins.

Database Models for ALeRCE

This lib offers database initialization procedures for MongoDB and PostgreSQL, using the ALeRCE core models.

Installing db_plugins

For local development:

db_plugins installation is recommended with poetry. You can clone the repository and then

cd libs/db-plugins
poetry install

Alternatively, you can use pip

cd libs/db-plugins
pip install -e .

As a local dependency:

cd some_package
poetry add ../libs/db-plugins

As a remote dependency .. code-block:: console

poetry add “https://github.com/alercebroker/db-plugins.git#subdirectory=libs/db-plugins”

Database

1. Database Initialization

Database plugins will read the configuration you define in a settings.py file. This file should have a DB_CONFIG dictionary with the database connection parameters.

Here is and example on the params used with the SQL plugin:

DB_CONFIG: {
    "SQL": {
        "SQLALCHEMY_DATABASE_URL": "sqlite:///:memory:"
    }
}

After defining DB_CONFIG you can now initialize your database. To do so, run the initdb command as follows

dbp initdb

2. Migrations (SQL only)

When changes to models are made you would want to update the database without creating it all again, or maybe you want to undo some changes and return to a previous state.

The solution is to create migrations. Migrations keep track of your database changes and let you detect differences between your database and models and update the database accordingly.

Migrations will be created by running dbp make_migrations. This command will read your database credentials from DB_CONFIG inside settings.py.

Then, to update your database to latest changes execute dbp migrate.

Database plugins

1. SQL

Initialize database

Before you connect to your database, make sure you initialize it first. To do that execute the following command from your step root folder

dbp initdb

When you run this command with an empty database it will create the following schema:

Migrations

Migrations keep track of database changes. To fully initialize the database with your step configuration run

dbp make_migrations
dbp migrate

This will set the head state for tracking changes on the database and also execute any migrations that might be present.

The first command dbp make_migrations will create migration files according to differences from dbp models and your database.

The seccond command dbp migrate will execute the migrations and update your database.

What migrations can and can’t detect

Migrations will detect:

• Table additions, removals.

• Column additions, removals.

• Change of nullable status on columns.

• Basic changes in indexes

Migrations can’t detect:

• Changes of table name. These will come out as an add/drop of two different tables, and should be hand-edited into a name change instead.

• Changes of column name. Like table name changes, these are detected as a column add/drop pair, which is not at all the same as a name change.