> On Dec 4, 2021, at 9:41 PM, Jacques Nadeau <jacq...@apache.org> wrote: > > A few thoughts: > > Algebra approach. > > > If I understand the model correctly, I actually implemented this in a > different project last year (not knowing it was now a design pattern). My > main finding was that while it had certain benefits, it was pretty > confusing for most people.
Thanks, Vladimir, for educating us about the algebra approach. I have a feeling that OperandBuilder (used in the Config of many planner rules) uses something like this pattern. I was not aware of the algebraic approach, but OperandBuilder emerged as I tried to make the code type-safe and reusable. The irony of the “algebra approach” is that Calcite is an algebra engine. And a very powerful one at that. People who are new to Calcite often try to use a visitor pattern on their RelNode tree, and we have to direct them to the “algebra approach” of using collections of rewrite rules to accomplish their task. For this reason, I think we should keep the built-in visitors fairly simple. Also, my work in https://issues.apache.org/jira/browse/CALCITE-4559 <https://issues.apache.org/jira/browse/CALCITE-4559> (not finished, sadly) can be viewed as an attempt to convert RexSimplify (which is becoming spaghetti code) into something more algebraic. Julian
