53 lines
2.4 KiB
Markdown
53 lines
2.4 KiB
Markdown
## Database Persistence ##
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The persistence package includes classes to store different class objects in a Postgres database.
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### models ###
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This defines models for all class objects that we want to persist. It is used for Object Relation Mapping (ORM)
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of the class objects to database table columns
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### repositories ###
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This defines repository classes that contain CRUD methods for database operations. The constructor of all repositories requires
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The database name to connect to and the application environment (PROD or TEST). Tests use a different database
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from the production environment, which is why this is necessary. An example is shown below
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```python
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from hub.persistence import CityRepo
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# instantiate city repo for hub production database
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city_repo = CityRepo(db_name='hub', app_env='PROD')
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```
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All database operations are conducted with the production database (*PROD*) named *hub* in the example above
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### config_db ##
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This Python file is a configuration class that contains variables that map to configuration parameters in a .env file.
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It also contains a method ``def conn_string()`` which returns the connection string to a Postgres database.
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### Base ##
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This class has a constructor that establishes a database connection and returns a reference for database-related CRUD operations.
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### Database Configuration Parameter ###
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A .env file (or environment variables) with configuration parameters described below are needed to establish a database connection:
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```
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# production database credentials
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PROD_DB_USER=postgres-database-user
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PROD_DB_PASSWORD=postgres-database-password
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PROD_DB_HOST=database-host
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PROD_DB_PORT=database-port
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# test database credentials
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TEST_DB_USER=postgres-database-user
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TEST_DB_PASSWORD=postgres-database-password
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TEST_DB_HOST=database-host
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TEST_DB_PORT=database-port
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```
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### Database Related Unit Test
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Unit tests that involve database operations require a Postgres database to be set up.
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The tests connect to the database server using the default postgres user (*postgres*).
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NB: You can provide any credentials for the test to connect to postgres, just make sure
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the credentials are set in your .env file as explained above in *Database Configuration Parameters* section
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When the tests are run, a **test_db** database is created and then the required tables for
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the test. Before the tests run, the *test_db* is deleted to ensure that each test starts
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on a clean slate
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