Check for database existence, to allow delayed creation

CHANGELOG.md

@@ -4,6 +4,7 @@ Change Log
 Unreleased
 ----------
 - Include alias and materialized fields in queryset results
+- Check for database existence, to allow delayed creation
 
 v1.0.1
 ------

src/infi/clickhouse_orm/database.py

@@ -90,12 +90,14 @@ class Database(object):
         self.username = username
         self.password = password
         self.readonly = False
-        self.db_exists = True
+        self.db_exists = False
+        self.db_exists = self._is_existing_database()
         if readonly:
+            if not self.db_exists:
+                raise DatabaseException('Database does not exist, and cannot be created under readonly connection')
             self.connection_readonly = self._is_connection_readonly()
             self.readonly = True
-        elif autocreate:
-            self.db_exists = False
+        elif autocreate and not self.db_exists:
             self.create_database()
         self.server_version = self._get_server_version()
         # Versions 1.1.53981 and below don't have timezone function
@@ -339,6 +341,10 @@ class Database(object):
             ver = '1.1.0'
         return tuple(int(n) for n in ver.split('.')) if as_tuple else ver
 
+    def _is_existing_database(self):
+        r = self._send("SELECT count() FROM system.databases WHERE name = '%s'" % self.db_name)
+        return r.text.strip() == '1'
+
     def _is_connection_readonly(self):
         r = self._send("SELECT value FROM system.settings WHERE name = 'readonly'")
         return r.text.strip() != '0'

tests/test_database.py

@@ -148,10 +148,13 @@ class DatabaseTestCase(TestCaseWithData):
         db = Database('db_not_here', autocreate=False)
         with self.assertRaises(ServerError) as cm:
             db.create_table(Person)
-
         exc = cm.exception
         self.assertEqual(exc.code, 81)
         self.assertEqual(exc.message, "Database db_not_here doesn't exist")
+        # Now create the database - should succeed
+        db.create_database()
+        db.create_table(Person)
+        db.drop_database()
 
     def test_preexisting_db(self):
         db = Database(self.database.db_name, autocreate=False)

tests/test_readonly.py

@@ -58,6 +58,11 @@ class ReadonlyTestCase(TestCaseWithData):
     def test_drop_readonly_table(self):
         self.database.drop_table(ReadOnlyModel)
 
+    def test_nonexisting_readonly_database(self):
+        with self.assertRaises(DatabaseException) as cm:
+            db = Database('dummy', readonly=True)
+        self.assertEqual(cm.exception.message, 'Database does not exist, and cannot be created under readonly connection')
+
 
 class ReadOnlyModel(Model):
     _readonly = True