fix: improved error messages that occur during dataframe autoflushing

src/questdb/dataframe.pxi

@@ -2424,14 +2424,16 @@ cdef void_int _dataframe(
                         _ensure_has_gil(&gs)
                         raise c_err_to_py(err)
 
+                was_auto_flush = True
                 _dataframe_handle_auto_flush(&af, ls_buf, &gs)
+                was_auto_flush = False
         except Exception as e:
             # It would be an internal bug for this to raise.
             if not line_sender_buffer_rewind_to_marker(ls_buf, &err):
                 raise c_err_to_py(err)
 
             if (isinstance(e, IngressError) and
-                    (e.code == IngressErrorCode.InvalidApiCall)):
+                    (e.code == IngressErrorCode.InvalidApiCall) and not was_auto_flush):
                 # TODO: This should be allowed by the database.
                 # It currently isn't so we have to raise an error.
                 raise IngressError(

test/test_dataframe.py

@@ -1523,6 +1523,18 @@ def test_serializing_in_chunks(self):
                     for i in range(index * 10, (index + 1) * 10))
                 self.assertEqual(buf, exp.encode("utf-8"))
 
+        def test_auto_flush_error_msg(self):
+            header = ["x", "y"]
+            x = list(range(10000))
+            y = list(range(10000))
+
+            df = pd.DataFrame(zip(x, y), columns=header)
+
+            with self.assertRaisesRegex(qi.IngressError, 'Could not flush buffer: Buffer size of 21780 exceeds maximum configured allowed size of 1024 bytes'):
+                with qi.Sender.from_conf("http::addr=localhost:9000;auto_flush_rows=1000;max_buf_size=1024;protocol_version=2;") as sender:
+                    sender.dataframe(df, table_name='test_df', at=qi.ServerTimestamp)
+                    sender.flush()
+
         def test_arrow_chunked_array(self):
             # We build a table with chunked arrow arrays as columns.
             chunks_a = [