In TIBCO Data Virtualization, a complex view built on 6 other views may fail with the following exception:

 "ERROR [jetty thread pool-706359] 2019-02-13 15:50:41.734 +0000 Util - User Exception Occurred com.compositesw.common.UserException: An internal error has occurred. Cause: java.lang.IllegalStateException: Could not find matching selectable for 'tExpr16882.KOKRS' in view. eTree.nodeId=780 [Log ID: 97e597d1-1591-4119-a682-1424bcb69962]"

Note:

• When such an error is seen, the execution plan may fail to generate
• The same view works fine when a Case statement within the view is commented out. 

Root Cause:
Generally, this exception comes up when UNION is used in place of UNION ALL and a couple of underlying views have been built with excessive "UNION ALL" statements.

To resolve this issue, increase the "Maximum Number of Union All and Join Flip Iterations" to 100. This setting is located in TDV Studio->Administration->Configuration->Server->SQL Engine->Overrides Panel.

Here is a screenshot.