Allowing custom user and password for each database.

README.md

@@ -49,6 +49,24 @@ to the container:
             - POSTGRES_USER: myapp
             - POSTGRES_PASSWORD:
 
+### Custom user and password for each database
+
+If you need to use a custom user and password for each database, you can do it by adding the `POSTGRES_USER_<uppercase database name>`
+and `POSTGRES_PASSWORD_<uppercase database name>` environment variables:
+
+    myapp-postgresql:
+        image: postgres:9.6.2
+        volumes:
+            - ../docker-postgresql-multiple-databases:/docker-entrypoint-initdb.d
+        environment:
+            - POSTGRES_MULTIPLE_DATABASES: db1,db2
+            - POSTGRES_USER: myapp
+            - POSTGRES_PASSWORD:
+            - POSTGRES_USER_DB1: myapp_db1
+            - POSTGRES_PASSWORD_DB1:
+            - POSTGRES_USER_DB2: myapp_db2
+            - POSTGRES_PASSWORD_DB2:
+
 ### Non-standard database names
 
 If you need to use non-standard database names (hyphens, uppercase letters etc), quote them in `POSTGRES_MULTIPLE_DATABASES`:

create-multiple-postgresql-databases.sh

@@ -1,18 +1,116 @@
 #!/bin/bash
+# 
+# Source: https://github.com/mrts/docker-postgresql-multiple-databases
+# Author: Mart Sõmermaa (https://github.com/mrts)
+# contributor: Jens Peter Secher (https://github.com/jpsecher)
+# contributor: Emanuele Scarsella (https://github.com/emanuele-scarsella)
+# License: MIT
+#
 
 set -e
 set -u
 
+# Create a user and a database, if they don't already exist
+# Arguments:
+#   $1 - Database name
 function create_user_and_database() {
 	local database=$1
-	echo "  Creating user and database '$database'"
-	psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" <<-EOSQL
-	    CREATE USER $database;
-	    CREATE DATABASE $database;
-	    GRANT ALL PRIVILEGES ON DATABASE $database TO $database;
-EOSQL
+	local user=$(get_user_for_database $database)
+	local password=$(get_password_for_database $database)
+	if user_exists $user; then
+		echo "User '$user' already exists, skipping"
+	else
+		echo "Creating user '$user' ${password:+(with password)}"
+		create_user $user $password
+	fi
+	if database_exists $database; then
+		echo "Database '$database' already exists, skipping"
+	else
+		echo "Creating database '$database' and granting all privileges to user '$user'"
+		create_database $database $user
+	fi
 }
 
+# Create a PostgreSQL user
+# Arguments:
+#   $1 - User name
+#   $2 - User password (optional)
+function create_user() {
+	local user=$1
+	local password=$2
+	psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" <<-EOSQL
+		CREATE USER "$user" ${password:+WITH PASSWORD '$password'};
+	EOSQL
+}
+
+# Create a PostgreSQL database and assign ownership
+# Arguments:
+#   $1 - Database name
+#   $2 - User name
+function create_database() {
+	local database=$1
+	local user=$2
+	psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" --dbname "$POSTGRES_DB" <<-EOSQL
+		CREATE DATABASE "$database" WITH OWNER "$user";
+		GRANT ALL PRIVILEGES ON DATABASE "$database" TO "$user";
+	EOSQL
+}
+
+# Check if a PostgreSQL user exists
+# Arguments:
+#   $1 - User name
+# Returns:
+#   0 if user exists, 1 otherwise
+function user_exists() {
+	local user=$1
+	local result
+	result=$(psql -t -v ON_ERROR_STOP=1 \
+		--username "$POSTGRES_USER" \
+		--dbname "$POSTGRES_DB" \
+		-c "SELECT 1 FROM pg_roles WHERE rolname = '$user';")
+	if [[ "$result" =~ 1 ]]; then
+		return 0
+	fi
+	return 1
+}
+
+# Check if a PostgreSQL database exists
+# Arguments:
+#   $1 - Database name
+# Returns:
+#   0 if database exists, 1 otherwise
+function database_exists() {
+	local database="$1"
+	if psql -lqt --username "$POSTGRES_USER" | cut -d \| -f 1 | grep -qw "$database"; then
+		return 0
+	else
+		return 1
+	fi
+}
+
+# Retrieve the user for a given database
+# Arguments:
+#   $1 - Database name
+# Returns:
+#   User name derived from environment variables or defaults to database name
+function get_user_for_database() {
+    local database=$1
+    local user_var="POSTGRES_USER_${database^^}"
+    echo "${!user_var:-$database}"
+}
+
+# Retrieve the password for a given database
+# Arguments:
+#   $1 - Database name
+# Returns:
+#   Password derived from environment variables or empty if not set
+function get_password_for_database() {
+    local database=$1
+    local password_var="POSTGRES_PASSWORD_${database^^}"
+    echo "${!password_var:-}"
+}
+
+# Main script logic: Create multiple databases if specified in the environment variable
 if [ -n "$POSTGRES_MULTIPLE_DATABASES" ]; then
 	echo "Multiple database creation requested: $POSTGRES_MULTIPLE_DATABASES"
 	for db in $(echo $POSTGRES_MULTIPLE_DATABASES | tr ',' ' '); do