I am connecting Tableau live to Cloudera and using Impala. I have some dimensions in my dashboard that are controllable by parameters. When the user changes them the detail of the graph changes..
For example/ IF [PARAMETER] = 'Client' THEN [Client]
ELSEIF [PARAMETER] = 'Region' THEN [Region]
ELSE 'Other' END
The problem is, I'm finding that Cloudera/Impala is a bit unpredictable when doing this and is often returning NULL values instead of the dimension values. I can't nail down exactly when it is happening but my suspicion is caching is at play.