Make close() idempotent for already-closed connections (#1044)

Return True when ibm_db.close() or ibm_db_dbi.Connection.close() is called on an already-closed connection instead of raising.
Add a DBI regression test for double-close behavior.

Author: zenflow

ibm_db.c

@@ -4291,7 +4291,8 @@ static PyObject *ibm_db_bind_param(PyObject *self, PyObject *args)
  *    Specifies an active DB2 client connection.
  *
  * ===Return Values
- * Returns TRUE on success or FALSE on failure.
+ * Returns TRUE on success. If the connection is already closed, returns TRUE.
+ * On failure, an exception is raised and NULL is returned.
  */
 static PyObject *ibm_db_close(PyObject *self, PyObject *args)
 {
@@ -4331,9 +4332,10 @@ static PyObject *ibm_db_close(PyObject *self, PyObject *args)
 
         if (!conn_res->handle_active)
         {
-            LogMsg(EXCEPTION, "Connection is not active");
-            PyErr_SetString(PyExc_Exception, "Connection is not active");
-            return NULL;
+            LogMsg(INFO, "Connection already closed; no action required");
+            Py_INCREF(Py_True);
+            LogMsg(INFO, "exit close()");
+            return Py_True;
         }
 
         if (conn_res->handle_active && !conn_res->flag_pconnect)

ibm_db_dbi.py

@@ -923,20 +923,22 @@ def close(self):
         """This method closes the Database connection associated with
         the Connection object.  It takes no arguments.
 
+        If the connection is already closed, this method is a no-op and
+        returns True.
+
         """
         LogMsg(INFO, "entry close()")
-        self.rollback()
-        try:
-            if self.conn_handler is None:
-                LogMsg(ERROR, "Connection cannot be closed; connection is no longer active.")
-                raise ProgrammingError("Connection cannot be closed; "
-                                       "connection is no longer active.")
-            else:
+        if self.conn_handler is None:
+            return_value = True
+            LogMsg(INFO, "Connection already closed; no action required.")
+        else:
+            self.rollback()
+            try:
                 return_value = ibm_db.close(self.conn_handler)
                 LogMsg(INFO, "Connection closed.")
-        except Exception as inst:
-            LogMsg(EXCEPTION, f"An exception occurred while closing connection: {inst}")
-            raise _get_exception(inst)
+            except Exception as inst:
+                LogMsg(EXCEPTION, f"An exception occurred while closing connection: {inst}")
+                raise _get_exception(inst)
         self.conn_handler = None
         for index in range(len(self._cursor_list)):
             if (self._cursor_list[index]() != None):

ibm_db_tests/test_072_CloseTwice_DBI.py

@@ -0,0 +1,42 @@
+#
+#  Licensed Materials - Property of IBM
+#
+#  (c) Copyright IBM Corp. 2026
+#
+
+from __future__ import print_function
+import sys
+import unittest
+import ibm_db_dbi
+import config
+from testfunctions import IbmDbTestFunctions
+
+
+class IbmDbTestCase(unittest.TestCase):
+
+    def test_072_CloseTwice_DBI(self):
+        obj = IbmDbTestFunctions()
+        obj.assert_expect(self.run_test_072)
+
+    def run_test_072(self):
+        conn = ibm_db_dbi.connect(config.database, config.user, config.password)
+
+        rc1 = conn.close()
+        rc2 = conn.close()
+
+        print(rc1)
+        print(rc2)
+
+#__END__
+#__LUW_EXPECTED__
+#True
+#True
+#__ZOS_EXPECTED__
+#True
+#True
+#__SYSTEMI_EXPECTED__
+#True
+#True
+#__IDS_EXPECTED__
+#True
+#True