add schema upgrades

src/wormhole/server/database.py

@@ -11,6 +11,12 @@ def get_schema(version):
                                    "db-schemas/v%d.sql" % version)
     return schema_bytes.decode("utf-8")
 
+def get_upgrader(new_version):
+    schema_bytes = resource_string("wormhole.server",
+                                   "db-schemas/upgrade-to-v%d.sql" % new_version)
+    return schema_bytes.decode("utf-8")
+
+TARGET_VERSION = 2
 
 def dict_factory(cursor, row):
     d = {}
@@ -18,23 +24,23 @@ def dict_factory(cursor, row):
         d[col[0]] = row[idx]
     return d
 
-def get_db(dbfile, stderr=sys.stderr):
+def get_db(dbfile, target_version=TARGET_VERSION, stderr=sys.stderr):
     """Open or create the given db file. The parent directory must exist.
     Returns the db connection object, or raises DBError.
     """
 
-    must_create = not os.path.exists(dbfile)
+    must_create = (dbfile == ":memory:") or not os.path.exists(dbfile)
     try:
         db = sqlite3.connect(dbfile)
     except (EnvironmentError, sqlite3.OperationalError) as e:
         raise DBError("Unable to create/open db file %s: %s" % (dbfile, e))
     db.row_factory = dict_factory
 
-    VERSION = 2
     if must_create:
-        schema = get_schema(VERSION)
+        schema = get_schema(target_version)
         db.executescript(schema)
-        db.execute("INSERT INTO version (version) VALUES (?)", (VERSION,))
+        db.execute("INSERT INTO version (version) VALUES (?)",
+                   (target_version,))
         db.commit()
 
     try:
@@ -44,7 +50,17 @@ def get_db(dbfile, stderr=sys.stderr):
         # Perhaps it was created with an old version, or it might be junk.
         raise DBError("db file is unusable: %s" % e)
 
-    if version != VERSION:
+    while version < target_version:
+        try:
+            upgrader = get_upgrader(version+1)
+        except ValueError: # ResourceError??
+            raise DBError("Unable to upgrade %s to version %s, left at %s"
+                          % (dbfile, version+1, version))
+        db.executescript(upgrader)
+        db.commit()
+        version = version+1
+
+    if version != target_version:
         raise DBError("Unable to handle db version %s" % version)
 
     return db