From 070b1ce429d31e81334e6c4e2b450b02e8bdde8b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E8=BF=9F=E6=88=90?= <chicheng@meituan.com>
Date: Tue, 27 Oct 2020 17:53:29 +0800
Subject: [PATCH] fix union bug (#4772)

---
 .../main/java/org/apache/doris/planner/PlanNode.java  | 11 +++++++++++
 .../org/apache/doris/planner/SingleNodePlanner.java   |  5 ++++-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/fe/fe-core/src/main/java/org/apache/doris/planner/PlanNode.java b/fe/fe-core/src/main/java/org/apache/doris/planner/PlanNode.java
index 6d62ab2889b17e..8a84c1a26732ae 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/planner/PlanNode.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/planner/PlanNode.java
@@ -17,6 +17,7 @@
 
 package org.apache.doris.planner;
 
+import com.google.common.base.Predicates;
 import org.apache.doris.analysis.Analyzer;
 import org.apache.doris.analysis.Expr;
 import org.apache.doris.analysis.ExprSubstitutionMap;
@@ -223,6 +224,16 @@ public void unsetLimit() {
         limit = -1;
     }
 
+    protected List<TupleId> getAllScanTupleIds() {
+        List<TupleId> tupleIds = Lists.newArrayList();
+        List<ScanNode> scanNodes = Lists.newArrayList();
+        collectAll(Predicates.instanceOf(ScanNode.class), scanNodes);
+        for(ScanNode node: scanNodes) {
+            tupleIds.addAll(node.getTupleIds());
+        }
+        return tupleIds;
+    }
+
     public ArrayList<TupleId> getTupleIds() {
         Preconditions.checkState(tupleIds != null);
         return tupleIds;
diff --git a/fe/fe-core/src/main/java/org/apache/doris/planner/SingleNodePlanner.java b/fe/fe-core/src/main/java/org/apache/doris/planner/SingleNodePlanner.java
index 8123c3f0688c27..fd81c33facf3c9 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/planner/SingleNodePlanner.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/planner/SingleNodePlanner.java
@@ -71,6 +71,8 @@
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
+import java.util.HashSet;
+import java.util.Set;
 import java.util.UUID;
 
 /**
@@ -283,7 +285,8 @@ private PlanNode createQueryPlan(QueryStmt stmt, Analyzer analyzer, long default
 
         if (analyzer.hasEmptyResultSet()) {
             // Must clear the scanNodes, otherwise we will get NPE in Coordinator::computeScanRangeAssignment
-            scanNodes.clear();
+            Set<TupleId> scanTupleIds = new HashSet<>(root.getAllScanTupleIds());
+            scanNodes.removeIf(scanNode -> scanTupleIds.contains(scanNode.getTupleIds().get(0)));
             PlanNode node = createEmptyNode(stmt, analyzer);
             // Ensure result exprs will be substituted by right outputSmap
             node.setOutputSmap(root.outputSmap);