Certain operations, such as
1. LOAD DATA
3. Invalidate Metadata
(4. and potentially compute stats)
can be long running DDL. These operations blocks on ExecuteStatement (HS2) or query (beeswax).
Because Hue expects all operations as async, when an user issues such a long running DDL from Hue, Hue might timeout. Also, Impala does not have progress reporting on these operations. The lack of progress reporting makes it hard for our user to tell if it's still running or not.