[GitHub] [arrow-datafusion] jackwener commented on issue #4267: [EPIC]: reimplement all rules which contains global-state

[GitBox <gi...@apache.org>]

jackwener commented on issue #4267:
URL: https://github.com/apache/arrow-datafusion/issues/4267#issuecomment-1319545030

   let me explain why.
   
   Due to global-state exists, we can't just optimize a subtree, we must traverse the whole tree.
   
   In fact, I prefer to `Pattern-match`, we match a subtree `pattern`, and just optimize the pattren/subtree.
   
   A example: Merge Limit
   
   ```rust
   match plan {
        Limit =>  {
              match childPlan => {
                 Limit => {  merge(limit, childlimit)  }
                  _ => { don't match pattern, return None or recurse....}
              }
        }
        _ => { don't match pattern, return None or recurse....}
   }
   ```
   
   we just match `limit-limit`, and handle it.
   
   BUT, global-state force we must handle various situations， and we must traverse the tree all.


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