docker-compose and create db in Postgres on init

I have a question. I am pretty new to docker, so what I am trying to do is create a docker-compose file that on compose command will also create the database. Problem is that does not create DB as I ask it nicely. So my docker-compose looks like:

version: '3'

services:
  db:
    image: postgres:latest
    restart: always
    ports:
      - 5432:5432
    environment:
      POSTGRES_PASSWORD: 'postgres'
    volumes:
      - database_data:/var/lib/postgresql/data
      - ./init.sql:/docker-entrypoint-initdb.d/init.sql

volumes:
  database_data:
    driver: local

And when I start docker-compose up in log I can see

db_1  | PostgreSQL Database directory appears to contain a database; Skipping initialization
db_1  |
db_1  | 2020-01-13 11:14:36.259 UTC [1] LOG:  starting PostgreSQL 12.1 (Debian 12.1-1.pgdg100+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 8.3.0-6) 8.3.0, 64-bit
db_1  | 2020-01-13 11:14:36.259 UTC [1] LOG:  listening on IPv4 address "0.0.0.0", port 5432
db_1  | 2020-01-13 11:14:36.260 UTC [1] LOG:  listening on IPv6 address "::", port 5432
db_1  | 2020-01-13 11:14:36.264 UTC [1] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
db_1  | 2020-01-13 11:14:36.277 UTC [29] LOG:  database system was shut down at 2020-01-13 11:10:57 UTC
db_1  | 2020-01-13 11:14:36.280 UTC [1] LOG:  database system is ready to accept connections

In my init SQL there is only 1 line:

CREATE DATABASE "MyDataBase";

As I list DB is Postgres container my DB is nowhere to be found. What could be the source root of this problem?

Solution

According to the documentation of postgres docker image you did everything correct.

If you would like to do additional initialization in an image derived from this one, add one or more *.sql, *.sql.gz, or *.sh scripts under /docker-entrypoint-initdb.d (creating the directory if necessary). After the entrypoint calls initdb to create the default postgres user and database, it will run any *.sql files, run any executable *.sh scripts, and source any non-executable *.sh scripts found in that directory to do further initialization before starting the service.

But, there is a catch which I think you missed based on log that you posted above.

Warning: scripts in /docker-entrypoint-initdb.d are only run if you start the container with a data directory that is empty; any pre-existing database will be left untouched on container startup.

So, I would give it a try to empty database_data directory and run again docker-compose up.