Dear Jesus, I think your intuition in this regard is correct. After executing the main program in the HepPlanner the resulting plan contains a lot of circular references. Changing the matching order does not influence this behaviour.
Mark On Thu, 2 May 2019 at 22:14, Jesus Camacho Rodriguez <[email protected]> wrote: > Mark, > > I have an intuition that this happens because the rule creates a partially > contained rewriting with a union, where one side contains a scan over the > materialized view and the other side contains the query itself with a > filter on top excluding the data that is coming from the materialized view. > Then the rule is triggered on the plan representing the original query > again and the process is repeated. Have you tried changing the matching > order for your hep program? > > Thanks, > Jesús > > On Thu, May 2, 2019 at 8:53 AM Mark Pasterkamp < > [email protected]> > wrote: > > > Hi Stamatis, > > > > I have tried to recreate the issue but I have not been able to do that. I > > was however able to create a new exception which I don't quite > understand. > > The error happened when calcite was creating a union rewriting using > > materialized views. But trying to recreate this situation gave me another > > interesting one. > > This time, the planner rewrites one of the children nodes into itself I > > would assume which causes a stack overflow. The method itself can be > found > > here: > > > > > > > https://github.com/mpasterkamp/calcite/blob/768b7928dbde5f6f9775a1119e7466d8eafafb4b/core/src/test/java/org/apache/calcite/test/HepPlannerTest.java#L312 > > > > Perhaps I am doing something wrong, perhaps not? I am not knowledgeable > > enough about this to understand why this is happening. Wish I could help > > more for that. > > > > Also, while investigating this issue I found another interesting artifact > > in de source code of the VolcanoCost. A lot of methods in this class have > > an "if (true)"-statement like here: > > > > > > > https://github.com/apache/calcite/blob/4b4d8037c5073e4eb5702b12bc4ecade31476616/core/src/main/java/org/apache/calcite/plan/volcano/VolcanoCost.java#L100 > > > > Now I was just curious, is there any reason for this to be there that you > > know of? > > > > Thank you for responding and congratulations for your recent promotions. > > > > > > With kind regards, > > > > Mark > > > > > > On Thu, 2 May 2019 at 14:58, Stamatis Zampetakis <[email protected]> > > wrote: > > > > > Said like that it looks like a bug. > > > > > > I think the best would be to reproduce the exception as a unit test in > > > HepPlannerTest [1], RelOptRulesTest [2], or PlannerTest [3] so that we > > > could understand better the use case. > > > > > > [1] > > > > > > > > > https://github.com/apache/calcite/blob/master/core/src/test/java/org/apache/calcite/test/HepPlannerTest.java > > > [2] > > > > > > > > > https://github.com/apache/calcite/blob/master/core/src/test/java/org/apache/calcite/test/RelOptRulesTest.java > > > [3] > > > > > > > > > https://github.com/apache/calcite/blob/master/core/src/test/java/org/apache/calcite/tools/PlannerTest.java > > > > > > On Thu, May 2, 2019 at 7:56 AM Mark Pasterkamp < > > > [email protected]> > > > wrote: > > > > > > > I don't, I would assume that the HepPlanner.findBestExp() calculates > > the > > > > cost somewhere down the line > > > > > > > > On Thu, May 2, 2019, 03:31 Yuzhao Chen <[email protected]> wrote: > > > > > > > > > Why you care about cost when use HepPlanner ? The HepPlanner is > aimed > > > for > > > > > some deterministic planning rules, we usually do not need cost in > > Hep. > > > > Some > > > > > exceptions like Join reorder may need a cost. > > > > > > > > > > What kind of planning promotion you did ? I'm kind of curious about > > it. > > > > > > > > > > Best, > > > > > Danny Chan > > > > > 在 2019年5月1日 +0800 PM9:27，Mark Pasterkamp < > > [email protected] > > > > > >，写道： > > > > > > Dear all, > > > > > > > > > > > > While playing around with the HepPlanner I ran into an issue > where > > > the > > > > > > planner wants to rewrite a query with a union rewrite. When the > > > > > > RelMetaDataQuery computes the cost, the cost instance is a > > > VolcanoCost. > > > > > > Then when it tries to calculate the cost of one of the union's > > > operands > > > > > it > > > > > > is a RelCostImpl which results in the ClassCastException. > > > > > > > > > > > > How would I go about solving this issue? As far as my knowledge > > > goes, I > > > > > am > > > > > > not able to change the costhandler of the RelMetaDataQuery. > Another > > > > > > approach I could see is removing the cast in the VolcanoCost > class, > > > > but I > > > > > > would hope I do not have to do that. > > > > > > > > > > > > > > > > > > With kind regards, > > > > > > > > > > > > Mark > > > > > > > > > > > > > > >
