I don’t think we ever considered that case. Can you please log it, so that it is on record.
I haven’t analyzed the issue, but my instinct is that it is a reasonable behavior to want and expect, and that it is not that difficult to fix, and if so, someone should fix it. Julian > On Jul 17, 2019, at 2:29 AM, Mark Pasterkamp <markpasterkamp1...@gmail.com> > wrote: > > 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
