feat: Initial commit

Author: danielptv

.github/dependabot.yml

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+version: 2
+updates:
+  - package-ecosystem: pip
+    directory: "/.github/workflows"
+    schedule:
+      interval: daily
+    commit-message:
+      prefix: "ci: "
+  - package-ecosystem: github-actions
+    directory: "/"
+    schedule:
+      interval: "daily"
+    commit-message:
+      prefix: "ci: "

Dockerfile

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+ARG POSTGRES_TAG=latest
+FROM postgres:${POSTGRES_TAG}
+
+COPY create-multiple-databases.sh /docker-entrypoint-initdb.d/

README

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+<h1 align="center">docker-postgres-multiple-databases 👑</h1>
+
+**Use multiple databases with the official [PostgreSQL Docker Image](https://hub.docker.com/_/postgres/).**
+
+## How To Use 💡
+
+This repository extends the official PostgreSQL Docker Image by adding an additional environment variable `POSTGRES_MULTIPLE_DATABASES`.
+
+Additional databases can be passed as a ***comma-separated list*** in different formats:
+
+### Database, username and password (`database:username:password`):
+
+```yaml
+postgres:
+    image: eu.gcr.io/your-project/postgres-multi-db
+    environment:
+        - POSTGRES_MULTIPLE_DATABASES=database1:username1:password1,database2:username2,password2
+        - POSTGRES_USER=username
+        - POSTGRES_PASSWORD=password
+        - POSTGRES_DB=database
+```
+
+### Database and username (`database:username`)
+
+```yaml
+postgres:
+    image: eu.gcr.io/your-project/postgres-multi-db
+    environment:
+        - POSTGRES_MULTIPLE_DATABASES=database1:username1,database2:username2
+        - POSTGRES_USER=username
+        - POSTGRES_PASSWORD=password
+        - POSTGRES_DB=database
+```
+
+Passwords will default to the value of `POSTGRES_PASSWORD`.
+
+### Database (`database`)
+
+```yaml
+postgres:
+    image: eu.gcr.io/your-project/postgres-multi-db
+    environment:
+        - POSTGRES_MULTIPLE_DATABASES=database1,database2
+        - POSTGRES_USER=username
+        - POSTGRES_PASSWORD=password
+        - POSTGRES_DB=database
+```
+
+Usernames and passwords will default to the values of `POSTGRES_USER` and `POSTGRES_PASSWORD`.
+
+### Mixed
+
+```yaml
+postgres:
+    image: eu.gcr.io/your-project/postgres-multi-db
+    environment:
+        - POSTGRES_MULTIPLE_DATABASES=database1:username1:password1,database2:username2,database3
+        - POSTGRES_USER=username
+        - POSTGRES_PASSWORD=password
+        - POSTGRES_DB=database
+```
+
+Missing usernames and passwords will default to the values of `POSTGRES_USER` and `POSTGRES_PASSWORD`.

create-multiple-databases.sh

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+#!/bin/bash
+
+set -e
+set -u
+
+function create_user_and_database() {
+    local dbinfo=$1
+    IFS=":" read -r database user password <<<"$dbinfo"
+    echo "Creating database '$database' with user '$user'."
+
+    userExists=$(psql -v ON_ERROR_STOP=1 -U "$POSTGRES_USER" -d "$POSTGRES_DB" -c "SELECT 1 FROM pg_user WHERE usename = '$user';")
+    if [[ "$userExists" == *"(0 rows)"* ]]; then
+        psql -v ON_ERROR_STOP=1 -U "$POSTGRES_USER" -d "$POSTGRES_DB" <<-EOSQL
+            CREATE USER "$user";
+            ALTER USER "$user" WITH ENCRYPTED PASSWORD '$password';
+EOSQL
+    fi
+
+    psql -v ON_ERROR_STOP=1 -U "$POSTGRES_USER" -d "$POSTGRES_DB" <<-EOSQL
+      CREATE DATABASE "$database";
+      GRANT ALL PRIVILEGES ON DATABASE "$database" TO "$user";
+EOSQL
+}
+
+if [ -n "$POSTGRES_MULTIPLE_DATABASES" ]; then
+    echo "Multiple database creation requested."
+    for entry in $(echo "$POSTGRES_MULTIPLE_DATABASES" | tr ',' ' '); do
+        entry=$(echo "$entry" | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//')
+
+        num_colons=$(grep -o ":" <<<"$entry" | wc -l)
+
+        if [ "$num_colons" -eq 0 ]; then
+            entry="$entry:$POSTGRES_USER:$POSTGRES_PASSWORD"
+        elif [ "$num_colons" -eq 1 ]; then
+            entry="$entry:$POSTGRES_PASSWORD"
+        fi
+        create_user_and_database "$entry"
+    done
+    echo "Multiple databases created."
+fi