named a volume for clarity

docker-files/hadoop/docker-compose.yml

@@ -142,6 +142,8 @@ services:
     container_name: hive-metastore-postgresql
     env_file:
       - ./hadoop-hive.env
+    volumes:
+      - hadoop_metastore_postregresql:/var/lib/postgresql/data
     networks:
       - hadoop
     ports:
@@ -152,6 +154,7 @@ volumes:
   hadoop_datanode_2:
   hadoop_namenode:
   hadoop_historyserver:
+  hadoop_metastore_postregresql:
 
 networks:
   hadoop: