At the suggestion of Jacques and some others at the Hackathon, I have created a interpreter. You can pass it a logical plan (a tree of RelNodes such as FilterRel and ProjectRel) and execute it to get valid results.
You do not need to go through planning, code-generation, or compilation using Janino. So, the interpreter should be able to execute a simple query very quickly. But the code path is much less efficient than the Enumerable convention (which generates Java code) or other conventions, so you should only use this for small data sets (say a couple of thousand rows). The work done is described in https://issues.apache.org/jira/browse/OPTIQ-416. I have logged https://issues.apache.org/jira/browse/OPTIQ-418 to finish the job. That might be a fun job for someone… Julian
