Why do certain JOINs not work inside an Okera View?
If a query has a "SELECT DISTINCT" clause with JOINs, creating views inside Okera will not work with the following error:
"Node type not supported: AGGREGATION_NODE"
The error is shown because Okera does not support aggregation functions like DISTINCT/MAX/MIN/COUNT and we don't plan to support them for the foreseeable future, as these are query engine constructs.
To resolve this issue, you can simply create the "SELECT DISTINCT" part of the view as an intermediary table, and then use this intermediary table to create the view internally in Okera, as at this point, the result of the aggregation would be made available from this intermediary table, rather than calculated on the fly.
Another option is to use external views.