[GitHub] [incubator-doris] morningman commented on a change in pull request #2957: implement the planner for set operation

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

morningman commented on a change in pull request #2957: implement the planner for set operation
URL: https://github.com/apache/incubator-doris/pull/2957#discussion_r382893199
 
 

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 File path: fe/src/main/java/org/apache/doris/planner/SingleNodePlanner.java
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 @@ -1590,16 +1619,46 @@ private PlanNode createSetOperationPlan(SetOperationStmt setOperationStmt, Analy
         setOperationStmt.materializeRequiredSlots(analyzer);
 
         PlanNode result = null;
-        // create DISTINCT tree
-        if (setOperationStmt.hasDistinctOps()) {
-            result = createUnionPlan(
-                    analyzer, setOperationStmt, setOperationStmt.getDistinctOperands(), null, defaultOrderByLimit);
-            result = new AggregationNode(ctx_.getNextNodeId(), result, setOperationStmt.getDistinctAggInfo());
-            result.init(analyzer);
+        SetOperationStmt.Operation operation = null;
+        SetOperationStmt.Qualifier exceptQualifier = null;
+        List<SetOperationStmt.SetOperand> partialOperands = new ArrayList<>();
+        // create plan for a union b intersect c except b to three fragments
+        // 3:[2:[1:[a union b] intersect c] except c]
+        // EXCEPT operator is NOT commutative, it IS important which query is first,
+        // which second using EXCEPT operator, so EXCEPT operator cannot merge all distinct op to one node all all
+        // op to another node
 
 Review comment:
   Could you add more comment to explain the logic here?
   And better to add Unit test to test it. You can reference to bitmap function test.

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