[fix](nereids) set operation's result type is wrong if decimal overfl…

…ows (apache#27872)

pick from master apache#27870

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);
+ }
 }