Fix for CONPY-256:

Fix indexing when moving a free connection to used connections
to avoid returning the same connection twice.

Kudos and thanks to G.Mech for reporting this bug and providing
the fix.

Author: 9EOR9

mariadb/connectionpool.py

@@ -218,7 +218,8 @@ def get_connection(self):
 
                 conn._used += 1
                 self._connections_used.append(conn)
-                del self._connections_free[i]
+                idx = self._connections_free.index(conn)
+                del self._connections_free[idx]
                 return conn
 
         raise mariadb.PoolError("No connection available")

testing/test/integration/test_pooling.py

@@ -356,6 +356,18 @@ def test_pool_add(self):
         pool.close()
         self.assertEqual(mariadb._CONNECTION_POOLS, {})
 
+    def test_conpy256(self):
+        size = 10
+        connections = []
+        default_conf = conf()
+        pool = mariadb.ConnectionPool(pool_name="test_conpy256",
+                               pool_size=size, **default_conf)
+        for i in range(size):
+            c= pool.get_connection()
+            self.assertNotEqual(c in connections, True)
+            connections.append(c)
+
+        pool.close()
 
 if __name__ == '__main__':
     unittest.main()