HHH-18720 Type check on select columns in union all gives SemanticException when there is a null column

Author: dreab8

hibernate-core/src/main/java/org/hibernate/query/sqm/tree/select/SqmQueryGroup.java

@@ -166,7 +166,8 @@ private void validateQueryGroupFetchStructure(List<? extends SqmTypedNode<?>> ty
 				for ( int j = 0; j < firstSelectionSize; j++ ) {
 					final SqmTypedNode<?> firstSqmSelection = typedNodes.get( j );
 					final JavaType<?> firstJavaType = firstSqmSelection.getNodeJavaType();
-					if ( firstJavaType != selections.get( j ).getNodeJavaType() ) {
+					final JavaType<?> nodeJavaType = selections.get( j ).getNodeJavaType();
+					if ( nodeJavaType != null && firstJavaType != null && firstJavaType != nodeJavaType ) {
 						throw new SemanticException(
 								"Select items of the same index must have the same java type across all query parts"
 						);

hibernate-core/src/main/java/org/hibernate/sql/results/jdbc/internal/JdbcValuesMappingProducerProviderStandard.java

@@ -7,9 +7,15 @@
 import org.hibernate.engine.spi.SessionFactoryImplementor;
 import org.hibernate.query.results.ResultSetMapping;
 import org.hibernate.query.results.ResultSetMappingImpl;
+import org.hibernate.sql.ast.spi.SqlSelection;
+import org.hibernate.sql.ast.tree.select.QueryGroup;
+import org.hibernate.sql.ast.tree.select.QueryPart;
 import org.hibernate.sql.ast.tree.select.SelectStatement;
 import org.hibernate.sql.results.jdbc.spi.JdbcValuesMappingProducer;
 import org.hibernate.sql.results.jdbc.spi.JdbcValuesMappingProducerProvider;
+import org.hibernate.type.descriptor.jdbc.NullJdbcType;
+
+import java.util.List;
 
 /**
  * Standard JdbcValuesMappingProducerProvider implementation
@@ -26,10 +32,19 @@ public class JdbcValuesMappingProducerProviderStandard implements JdbcValuesMapp
 	public JdbcValuesMappingProducer buildMappingProducer(
 			SelectStatement sqlAst,
 			SessionFactoryImplementor sessionFactory) {
-		return new JdbcValuesMappingProducerStandard(
-				sqlAst.getQuerySpec().getSelectClause().getSqlSelections(),
-				sqlAst.getDomainResultDescriptors()
-		);
+		return new JdbcValuesMappingProducerStandard( getSelections( sqlAst ), sqlAst.getDomainResultDescriptors() );
+	}
+
+	private static List<SqlSelection> getSelections(SelectStatement selectStatement) {
+		if ( selectStatement.getQueryPart() instanceof QueryGroup queryGroup ) {
+			for ( QueryPart queryPart : queryGroup.getQueryParts() ) {
+				if ( !(queryPart.getFirstQuerySpec().getSelectClause().getSqlSelections()
+						.get( 0 ).getExpressionType().getSingleJdbcMapping().getJdbcType() instanceof NullJdbcType) ) {
+					return queryPart.getFirstQuerySpec().getSelectClause().getSqlSelections();
+				}
+			}
+		}
+		return selectStatement.getQuerySpec().getSelectClause().getSqlSelections();
 	}
 
 	@Override