Dear all, For some time now I have been getting issues with getiing materialized view union rewriting to work using the HepPlanner. A few weeks ago I have been able to find the culprit and I was wondering whether this is supposed to be intended behaviour.
in [1] the code suggests that you go through all parents in the query DAG, so any circular reference should be seen at this point. But what it does is it only looks at the direct parents of the node if they are exactly the same. In my case, I had an issue where the parent of that parent (so say a sequence of node A - node B - node A) was exactly the same node, which caused issues. Would you instead return all parents you can then check if the current node is already contained in the parent list and if that is the case, you can just return the current node resolving the circular reference. I don't know if this is intended behaviour of the HepPlanner or not, but I thought it might be useful to report my findings in case someone else in the future will stumble upon this issue. Mark [1] https://github.com/apache/calcite/blob/8c0d792dd735eded2bb11be0c7c195b8f302ae90/core/src/main/java/org/apache/calcite/plan/hep/HepPlanner.java#L723
