Disable broken test_delay_computation_start (#1533)

tests/tpch/test_optimization.py

@@ -42,9 +42,13 @@ def test_optimization(query, dataset_path, fs, client, scale):
     result.repartition(npartitions=1).optimize()
 
 
+@pytest.mark.skip(
+    reason="This test does not work. See FIXME and https://github.com/dask/distributed/issues/8833."
+)
 def test_delay_computation_start(query, dataset_path, fs, client, scale):
     func = getattr(dask_queries, f"query_{query}")
     result = func(dataset_path, fs, scale).optimize()
-    # Client.compute unblocks as soon as update_graph finishes, i.e. graph is
-    # submitted and parsed. This is the time until the dashboard kicks off
+    # FIXME: Client.compute unblocks only until the graph is serialized and put onto
+    # the comm buffer. It should wait until update_graph finishes, i.e. graph is
+    # submitted, parsed, and the tasks have been added onto the scheduler.
     client.compute(result)