Fix: return empty results from fetch methods after DDL statements

jaydebeapiarrow/__init__.py

@@ -660,7 +660,7 @@ def _get_iter(self):
 
     def fetchone(self):
         if not self._rs:
-            raise Error()
+            return None
 
         if self._buffer:
             return self._buffer.pop(0)
@@ -677,7 +677,7 @@ def fetchone(self):
 
     def fetchmany(self, size=None):
         if not self._rs:
-            raise Error()
+            return []
 
         if size is None:
             size = self.arraysize
@@ -704,7 +704,7 @@ def fetchmany(self, size=None):
 
     def fetchall(self):
         if not self._rs:
-            raise Error()
+            return []
 
         result = []
         if self._buffer:

mockdriver/src/main/java/org/jaydebeapi/mockdriver/MockConnection.java

@@ -498,4 +498,12 @@ public final void mockMultiColumnResult(int[] sqlTypes, Object[] values) throws
 
     Mockito.when(this.prepareStatement(Mockito.any())).thenReturn(mockPreparedStatement);
   }
+
+  /** Simulate a DDL/DML statement that returns no ResultSet (e.g. CREATE TABLE). */
+  public final void mockDDLResult(int updateCount) throws SQLException {
+    PreparedStatement mockPreparedStatement = Mockito.mock(PreparedStatement.class);
+    Mockito.when(mockPreparedStatement.execute()).thenReturn(false);
+    Mockito.when(mockPreparedStatement.getUpdateCount()).thenReturn(updateCount);
+    Mockito.when(this.prepareStatement(Mockito.any())).thenReturn(mockPreparedStatement);
+  }
 }

test/test_integration.py

@@ -999,6 +999,37 @@ def test_rollback_with_autocommit_disabled(self):
         self.conn.jconn.setAutoCommit(False)
         self.conn.rollback()
 
+    def test_fetchone_after_ddl_returns_none(self):
+        """fetchone() after a DDL statement (CREATE TABLE) should return None."""
+        with self.conn.cursor() as cursor:
+            cursor.execute("DROP TABLE IF EXISTS ddl_test")
+            cursor.execute("CREATE TABLE ddl_test (id INTEGER)")
+            result = cursor.fetchone()
+        self.assertIsNone(result)
+
+    def test_fetchall_after_ddl_returns_empty(self):
+        """fetchall() after a DDL statement (CREATE TABLE) should return []."""
+        with self.conn.cursor() as cursor:
+            cursor.execute("DROP TABLE IF EXISTS ddl_test2")
+            cursor.execute("CREATE TABLE ddl_test2 (id INTEGER)")
+            result = cursor.fetchall()
+        self.assertEqual(result, [])
+
+    def test_fetchmany_after_ddl_returns_empty(self):
+        """fetchmany() after a DDL statement (CREATE TABLE) should return []."""
+        with self.conn.cursor() as cursor:
+            cursor.execute("DROP TABLE IF EXISTS ddl_test3")
+            cursor.execute("CREATE TABLE ddl_test3 (id INTEGER)")
+            result = cursor.fetchmany(5)
+        self.assertEqual(result, [])
+
+    def test_description_after_ddl_is_none(self):
+        """cursor.description should be None after a DDL statement."""
+        with self.conn.cursor() as cursor:
+            cursor.execute("DROP TABLE IF EXISTS ddl_test4")
+            cursor.execute("CREATE TABLE ddl_test4 (id INTEGER)")
+        self.assertIsNone(cursor.description)
+
 
 class PostgresTest(IntegrationTestBase, unittest.TestCase):
 

test/test_mock.py

@@ -1248,7 +1248,6 @@ def test_rollback_called_when_autocommit_disabled(self):
         self.conn.jconn.mockAutoCommit(False)
         self.conn.rollback()
 
-
     def test_lastrowid_exists_and_is_none(self):
         """PEP-249: lastrowid attribute must exist on cursor (fixes #84)."""
         with self.conn.cursor() as cursor:
@@ -1273,6 +1272,46 @@ def test_lastrowid_none_after_executemany(self):
         """lastrowid should be None after executemany (mock driver limitation: skip)."""
         self.skipTest("Mock driver executeBatch returns None; covered by integration test")
 
+    # --- DDL statement tests (issue #76) ---
+
+    def test_fetchone_after_ddl_returns_none(self):
+        """fetchone() after a DDL statement (no ResultSet) should return None, not raise."""
+        self.conn.jconn.mockDDLResult(0)
+        with self.conn.cursor() as cursor:
+            cursor.execute("CREATE TABLE test (id INTEGER)")
+            result = cursor.fetchone()
+        self.assertIsNone(result)
+
+    def test_fetchall_after_ddl_returns_empty(self):
+        """fetchall() after a DDL statement (no ResultSet) should return [], not raise."""
+        self.conn.jconn.mockDDLResult(0)
+        with self.conn.cursor() as cursor:
+            cursor.execute("CREATE TABLE test (id INTEGER)")
+            result = cursor.fetchall()
+        self.assertEqual(result, [])
+
+    def test_fetchmany_after_ddl_returns_empty(self):
+        """fetchmany() after a DDL statement (no ResultSet) should return [], not raise."""
+        self.conn.jconn.mockDDLResult(0)
+        with self.conn.cursor() as cursor:
+            cursor.execute("CREATE TABLE test (id INTEGER)")
+            result = cursor.fetchmany(5)
+        self.assertEqual(result, [])
+
+    def test_description_after_ddl_is_none(self):
+        """cursor.description should be None after a DDL statement."""
+        self.conn.jconn.mockDDLResult(0)
+        with self.conn.cursor() as cursor:
+            cursor.execute("CREATE TABLE test (id INTEGER)")
+        self.assertIsNone(cursor.description)
+
+    def test_rowcount_after_ddl(self):
+        """cursor.rowcount should reflect the update count after DDL."""
+        self.conn.jconn.mockDDLResult(0)
+        with self.conn.cursor() as cursor:
+            cursor.execute("CREATE TABLE test (id INTEGER)")
+        self.assertEqual(cursor.rowcount, 0)
+
 
 class JarPathSpacesTest(unittest.TestCase):
     """Tests for JAR file paths containing spaces (issue #86).