Fixed bug that caused "ORA-03137: malformed TTC packet from client

rejected" exception to be raised when attempting to call parse() on a
scrollable cursor.

Author: anthony-tuininga

doc/src/release_notes.rst

@@ -25,6 +25,10 @@ Thick Mode Changes
 Common Changes
 ++++++++++++++
 
+#)  Fixed bug that caused ``ORA-03137: malformed TTC packet from client
+    rejected`` exception to be raised when attempting to call
+    :meth:`Cursor.parse()` on a scrollable cursor.
+
 
 oracledb `3.4.0 <https://github.com/oracle/python-oracledb/compare/v3.3.0...v3.4.0>`__ (October 2025)
 -----------------------------------------------------------------------------------------------------

src/oracledb/impl/thin/messages/execute.pyx

@@ -81,7 +81,7 @@ cdef class ExecuteMessage(MessageWithData):
             exec_flags |= TNS_EXEC_FLAGS_IMPLICIT_RESULTSET
             if not self.scroll_operation:
                 options |= TNS_EXEC_OPTION_EXECUTE
-        if cursor_impl.scrollable:
+        if cursor_impl.scrollable and not self.parse_only:
             exec_flags |= TNS_EXEC_FLAGS_SCROLLABLE
         if stmt._cursor_id == 0 or stmt._is_ddl:
             options |= TNS_EXEC_OPTION_PARSE

tests/test_4200_cursor_scrollable.py

@@ -223,3 +223,26 @@ def test_4214(conn):
     (value,) = cursor.fetchone()
     assert value == 6.25
     assert cursor.rowcount == 5
+
+
+def test_4215(conn):
+    "4215 - test parse() on a scrollable cursor"
+    cursor = conn.cursor(scrollable=True)
+    statement = """
+        select 1 from dual
+        union all
+        select 2 from dual
+        union all
+        select 3 from dual
+        union all
+        select 4 from dual
+        union all
+        select 5 from dual
+    """
+    cursor.parse(statement)
+    cursor.execute(statement)
+    (fetched_value,) = cursor.fetchone()
+    assert fetched_value == 1
+    cursor.scroll(mode="last")
+    (fetched_value,) = cursor.fetchone()
+    assert fetched_value == 5

tests/test_8600_cursor_scrollable_async.py

@@ -226,3 +226,26 @@ async def test_8614(async_conn):
     (value,) = await cursor.fetchone()
     assert value == 6.25
     assert cursor.rowcount == 5
+
+
+async def test_8615(async_conn):
+    "8615 - test parse() on a scrollable cursor"
+    cursor = async_conn.cursor(scrollable=True)
+    statement = """
+        select 1 from dual
+        union all
+        select 2 from dual
+        union all
+        select 3 from dual
+        union all
+        select 4 from dual
+        union all
+        select 5 from dual
+    """
+    await cursor.parse(statement)
+    await cursor.execute(statement)
+    (fetched_value,) = await cursor.fetchone()
+    assert fetched_value == 1
+    await cursor.scroll(mode="last")
+    (fetched_value,) = await cursor.fetchone()
+    assert fetched_value == 5