system_assignation/hub/DEPLOYMENT.md

## Installing PostgreSQL Database Server on Linux (Ubuntu) ##
Execute the *install_postgresql_linux.sh* script to install PostgreSQL database
*NB: PostgreSQL DB Server runs on a default port of 5432.*

## Installing PostgreSQL Database Server on Windows ##
1. Download a Windows installer from [this link](https://www.enterprisedb.com/downloads/postgres-postgresql-downloads).
2. Double click on the installer file and follow the prompts of the installation wizard
3. On the component selection page of the installation wizard make sure to select *PostgreSQL Server and Commandline tools*
4. You can optionally select pgAdmin 4 to install a graphical UI to access your database
5. On the password page when prompted, enter the default password (postgres) and confirm it
6. You can change the default password of 5432 on the port page. You should ensure that whatever port number you
provide is not used by another service.
7. Follow the installation wizard prompt to complete your installation. You can verify your installation by
searching for the *psql* tool from your start menu

## Installing PostgreSQL Database Server on Mac OS X ##
1. Download the Mac OS X installer from [this link](https://www.enterprisedb.com/downloads/postgres-postgresql-downloads).
2. Launch the installation wizard by double-clicking it and follow the rest of steps as described above on 
Installing PostgreSQL Database Server on Windows.

NB: Hub has been tested with version 15 of PostgreSQL

## Create Database and Database User ##
1. Connect to the PostgreSQL database server via psql by executing `sudo -u postgres psql`. You will be
be prompted for a password, the default password of *postgres* user is *postgres*. The above command may not work on 
a Windows system using the default command line tool. You can access the psql tool from Windows start menu and follow 
the rest of the instructions from step 2 below
2. Execute `create user <username> with encrypted password '<password>';` in the psql console to create a user.
3. Execute `create database <database-name>;` in the psql console to create a database.
4. Execute `grant all privileges on database <database-name> to <username>;` to grant the all privileges on the database
to the user created in step 2 above. 
5. The created database by default, has on schema named public which you can use. However, if you wish to create
another schema, you can do so by following [this link](https://www.postgresqltutorial.com/postgresql-administration/postgresql-create-schema/).

**NB: You can grant selected privileges to the user on the database using commands  [on this page](https://tableplus.com/blog/2018/04/postgresql-how-to-grant-access-to-users.html).*
The user should however have read and write permission to all tables in the database. You can as well create a database and user using the PgAdmin UI tool*

## Setting Up Database Connection Parameters
1. Create a .env file that contains the configuration parameters as explained in the *Database Configuration Parameters*
section in persistence/README.md file.
2. The .env file should contain the following credentials: database user, database password, database host an,d database port
3. Provide the *absolute path* to the .env file to the persistence importers and exporters whenever using them in your code
as shown below:

```python
from hub.exports.db_factory import DBFactory
from pathlib import Path

dotenv_path = (Path(__file__).parent / '.env').resolve()
factory = DBFactory(db_name='hub_db', app_env='PROD', dotenv_path=dotenv_path)
```


## Create Database Tables ##
Use the *DBSetup* class in the persistence package to create the required database tables as described below

```python
from hub.persistence import DBSetup
from pathlib import Path

dotenv_path = (Path(__file__).parent / '.env').resolve()
DBSetup(db_name='hub_db', app_env='PROD', dotenv_path=dotenv_path)
```
The *DBSetUp* class also creates a default admin user with default credentials that can be changed.
with the import UserFactory class. The admin user (name, email, password and role) is logged into the console after it is created by the 
*constructor of DBSetup*. Use can also manage users (create, read, update and delete) with user import and export factories.

**NB: Make sure to change the default admin user credentials**