dilipbiswal commented on issue #24759: [SPARK-27395][SQL][WIP] Improve EXPLAIN command URL: https://github.com/apache/spark/pull/24759#issuecomment-521864064 @maropu > sorry for cutting in, but I like the idea; if we had a visiter-pattern-like logic for pringing plans (I think this can be similar to LogicalPlanVisitor), we could easily implement another custom format for printing plans in future. (since the current logic in master is hard-coded, I think its hard to do so though... Could you please explain your idea a bit more ? Let me outline how things are done currently and then perhaps we can discuss how we want to improve. Let me describe how things work now. 1. We have a infrastructure that prints the plan in a tree form. The method that does that is `generateTreeString` in TreeNode. This is s recursive method that calls helper methods like `simpleString` or `verboseString` on the current node (its working on) and deals with spacing of a child below a parent etc. 2. In this PR, we introduced a new format in which we have two requirement. 2.1 We do want the basic tree structure while printing. Only thing is, we want slightly different content in each line. (this is why we needed a new string method) 2.2 We need a additional footer section, where we want to print detailed node info. 3. In order to fulfill 2, i introduced a `processPlan` function in ExplainUtils, that deals with this new format but utilizing the existing infrastructure that deals with printing the plan in the tree structure and also handles 2.2 to print the footer info. 4. Lets say, we want to introduce a new format in the future. I would imagine, we would require another method in ExplainUtils say `processPlan2` that can do whatever it wants. For example, `processPlan2` could decide to print the plan in JSON. Now could you please explain your idea w.r.t the current processing ? In my thinking, the current infrastructure is extendable and that is the reason we could come up with a newer format (header-footer) by making very small change to the infrastructure.
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