From b51dc708268a88eed8e7a463c72381cb04c140ca Mon Sep 17 00:00:00 2001
From: starocean999 <40539150+starocean999@users.noreply.github.com>
Date: Fri, 1 Dec 2023 20:05:21 +0800
Subject: [PATCH] [fix](nereids) set operation's result type is wrong if
 decimal overflows (#27872)

pick from master #27870
---
 .../plans/logical/LogicalSetOperation.java    | 32 ++++++++++++++++---
 1 file changed, 28 insertions(+), 4 deletions(-)

diff --git a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/logical/LogicalSetOperation.java b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/logical/LogicalSetOperation.java
index c58b0aa0688a94..1835363bce826b 100644
--- a/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/logical/LogicalSetOperation.java
+++ b/fe/fe-core/src/main/java/org/apache/doris/nereids/trees/plans/logical/LogicalSetOperation.java
@@ -17,6 +17,7 @@
 
 package org.apache.doris.nereids.trees.plans.logical;
 
+import org.apache.doris.catalog.ScalarType;
 import org.apache.doris.catalog.Type;
 import org.apache.doris.nereids.memo.GroupExpression;
 import org.apache.doris.nereids.properties.LogicalProperties;
@@ -137,10 +138,7 @@ private List<List<NamedExpression>> castCommonDataTypeOutputs() {
         for (int i = 0; i < child(0).getOutput().size(); ++i) {
             Slot left = child(0).getOutput().get(i);
             Slot right = child(1).getOutput().get(i);
-            DataType compatibleType = DataType.fromCatalogType(Type.getAssignmentCompatibleType(
-                    left.getDataType().toCatalogDataType(),
-                    right.getDataType().toCatalogDataType(),
-                    false));
+            DataType compatibleType = getAssignmentCompatibleType(left.getDataType(), right.getDataType());
             Expression newLeft = TypeCoercionUtils.castIfNotSameType(left, compatibleType);
             Expression newRight = TypeCoercionUtils.castIfNotSameType(right, compatibleType);
             if (newLeft instanceof Cast) {
@@ -211,4 +209,30 @@ public abstract LogicalSetOperation withChildrenAndTheirOutputs(
     public int getArity() {
         return children.size();
     }
+
+    private DataType getAssignmentCompatibleType(DataType left, DataType right) {
+        if (left.isNullType()) {
+            return right;
+        }
+        if (right.isNullType()) {
+            return left;
+        }
+        if (left.equals(right)) {
+            return left;
+        }
+        Type resultType = Type.getAssignmentCompatibleType(left.toCatalogDataType(),
+                right.toCatalogDataType(), false);
+        if (resultType.isDecimalV3()) {
+            int oldPrecision = resultType.getPrecision();
+            int oldScale = resultType.getDecimalDigits();
+            int integerPart = oldPrecision - oldScale;
+            int maxPrecision = ScalarType.MAX_DECIMAL128_PRECISION;
+            if (oldPrecision > maxPrecision) {
+                int newScale = maxPrecision - integerPart;
+                resultType =
+                        ScalarType.createDecimalType(maxPrecision, newScale < 0 ? 0 : newScale);
+            }
+        }
+        return DataType.fromCatalogType(resultType);
+    }
 }