It would be really useful to have a mechanism to add query hints to the generated SQL from LookML. I have some queries where the optimiser for SQL Server is struggling due to the casting of date columns to character and back to facilitate month date ranges, this is resulting in a cardinality estimate issue, which in turn is resulting in a nested loop join instead of a hash join.
Simply specifiying the HASH hint in the join clause sorts the problem out completely; so having the ability to ensure that these are added via LookML would be very beneficial.