> Do you ever need to find the distinct values of the correl variable? I do track the required columns in a bitset: https://github.com/vlsi/incubator-calcite/blob/correlate/core/src/main/java/org/apache/calcite/rel/core/Correlate.java#L87
As far as I understand, this approach (bitset field indices) will fail for recursive data types, since we won't have a luxury of RelStructuredTypeFlattener (recursive emp will bark at you if you try to flat-map its attributes all the way down to out of memory error). Vladimir
