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