Added a small table to store the schema version

Defined in a dedicated 'pony database', allowing to check only this table
to determine if we need to create the tables, and so existing tables getting
a new attribute won't trigger a table creation

supysonic/db.py

@@ -28,9 +28,18 @@ try:
 except ImportError:
     from urlparse import urlparse, parse_qsl
 
+SCHEMA_VERSION = '20180829'
+
 def now():
     return datetime.now().replace(microsecond = 0)
 
+metadb = Database()
+
+class Meta(metadb.Entity):
+    _table_ = 'meta'
+    key = PrimaryKey(str, 32)
+    value = Required(str, 256)
+
 db = Database()
 
 @db.on_connect(provider = 'sqlite')
@@ -500,18 +509,25 @@ def parse_uri(database_uri):
 
 def init_database(database_uri):
     settings = parse_uri(database_uri)
-    db.bind(**settings)
-    db.generate_mapping(check_tables = False)
+
+    metadb.bind(**settings)
+    metadb.generate_mapping(check_tables = False)
 
     try:
-        db.check_tables()
+        metadb.check_tables()
     except DatabaseError:
         sql = pkg_resources.resource_string(__package__, 'schema/' + settings['provider'] + '.sql').decode('utf-8')
         with db_session:
             for statement in sql.split(';'):
                 statement = statement.strip()
                 if statement:
-                    db.execute(statement)
+                    metadb.execute(statement)
+            Meta(key = 'schema_version', value = SCHEMA_VERSION)
+    finally:
+        metadb.disconnect()
+
+    db.bind(**settings)
+    db.generate_mapping(check_tables = False)
 
 def release_database():
     db.disconnect()

supysonic/schema/mysql.sql

@@ -123,3 +123,8 @@ CREATE TABLE IF NOT EXISTS playlist (
     tracks TEXT
 ) DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
 
+CREATE TABLE meta (
+    key VARCHAR(32) PRIMARY KEY,
+    value VARCHAR(256) NOT NULL
+) DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
+

supysonic/schema/postgres.sql

@@ -123,3 +123,8 @@ CREATE TABLE IF NOT EXISTS playlist (
     tracks TEXT
 );
 
+CREATE TABLE meta (
+    key VARCHAR(32) PRIMARY KEY,
+    value VARCHAR(256) NOT NULL
+);
+

supysonic/schema/sqlite.sql

@@ -127,3 +127,8 @@ CREATE TABLE IF NOT EXISTS playlist (
     tracks TEXT
 );
 
+CREATE TABLE meta (
+    key CHAR(32) PRIMARY KEY,
+    value CHAR(256) NOT NULL
+);
+