[GitHub] [doris] 924060929 commented on a diff in pull request #11043: [feature] (Nereids) Merge memo group recursively

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

924060929 commented on code in PR #11043:
URL: https://github.com/apache/doris/pull/11043#discussion_r926376161


##########
fe/fe-core/src/main/java/org/apache/doris/nereids/memo/Memo.java:
##########
@@ -188,19 +189,24 @@ private void mergeGroup(Group source, Group destination) {
                     children.set(i, destination);
                 }
             }
-            if (groupExpressions.containsKey(groupExpression)) {
-                // TODO: need to merge group recursively
-                groupExpression.getOwnerGroup().removeGroupExpression(groupExpression);
+            GroupExpression that = groupExpressions.get(groupExpression);
+            if (that != null) {
+                mergeGroup(groupExpression.getOwnerGroup(), that.getOwnerGroup());
             } else {
                 groupExpressions.put(groupExpression, groupExpression);
             }
         }
-        for (GroupExpression groupExpression : source.getLogicalExpressions()) {
-            source.removeGroupExpression(groupExpression);
+
+        Iterator<GroupExpression> iterator = source.getLogicalExpressions().iterator();
+        while (iterator.hasNext()) {
+            GroupExpression groupExpression = iterator.next();
+            iterator.remove();
             destination.addGroupExpression(groupExpression);
         }
-        for (GroupExpression groupExpression : source.getPhysicalExpressions()) {
-            source.removeGroupExpression(groupExpression);
+        iterator = source.getPhysicalExpressions().iterator();

Review Comment:
   ```suggestion
           if (source != destination) {
               // copy sourceGroup's physicalExpressions to destination group
               destination.addPhysicalExpressions(source.getPhysicalExpressions());
               source.clearPhysicalExpressions();
           }
   ```



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