Multiple databases in docker and docker-compose

According to this Github issue might be possible to achieve multiple databases by using bash scripts which you will have to pass in your Dockerfile

EDIT:

To create multiple Databases you could use the following script:

https://github.com/mrts/docker-postgresql-multiple-databases

or

https://github.com/MartinKaburu/docker-postgresql-multiple-databases

Which suggest that you have to clone one of the above git repos and mount it as a volume to: /docker-entrypoint-initdb.d then you would be able to pass multiple database names by using: POSTGRES_MULTIPLE_DATABASES variable

Usually when I need more than one database in a docker project it's a test database. I find it easier to simply spin up a second docker container, without worrying about scripts or volume separation. The main trick is to not conflict the default ports (e.g. 5432 for postgres) and you're good to go. Then docker-compose can be something as simple as this:

version: '3.0'

services: 

  db:
    image: postgres
    environment: 
      - POSTGRES_DB
      - POSTGRES_USER
      - POSTGRES_PASSWORD
    ports:
      - ${POSTGRES_DEV_PORT}:5432
    volumes:
      - app-volume:/var/lib/postgresql/data

  db-test:
    image: postgres
    environment: 
      - POSTGRES_DB
      - POSTGRES_USER
      - POSTGRES_PASSWORD
    ports:
      - ${POSTGRES_TEST_PORT}:5432
    # Notice I don't even use a volume here since I don't care to persist test data between runs

volumes:
  app-volume: #