HHH-18610 ColumnReferenceKey for discriminator

hibernate-core/src/main/java/org/hibernate/query/results/internal/ResultsHelper.java

@@ -4,6 +4,7 @@
  */
 package org.hibernate.query.results.internal;
 
+import org.hibernate.metamodel.mapping.EntityDiscriminatorMapping;
 import org.hibernate.metamodel.mapping.EntityIdentifierMapping;
 import org.hibernate.metamodel.mapping.ModelPart;
 import org.hibernate.metamodel.mapping.SelectableMapping;
@@ -19,6 +20,7 @@ import org.hibernate.sql.results.graph.basic.BasicFetch;
 import org.hibernate.sql.results.jdbc.spi.JdbcValuesMetadata;
 
 import static org.hibernate.sql.ast.spi.SqlExpressionResolver.createColumnReferenceKey;
+import static org.hibernate.sql.ast.spi.SqlExpressionResolver.createDiscriminatorColumnReferenceKey;
 
 /**
  * @author Steve Ebersole
@@ -65,6 +67,25 @@ public class ResultsHelper {
 		);
 	}
 
+	public static Expression resolveSqlExpression(
+			DomainResultCreationStateImpl resolver,
+			JdbcValuesMetadata jdbcValuesMetadata,
+			TableReference tableReference,
+			EntityDiscriminatorMapping discriminatorMapping,
+			String columnAlias) {
+		return resolver.resolveSqlExpression(
+				createDiscriminatorColumnReferenceKey(
+						tableReference,
+						discriminatorMapping
+				),
+				processingState -> {
+					final int jdbcPosition = jdbcValuesMetadata.resolveColumnPosition( columnAlias );
+					final int valuesArrayPosition = jdbcPositionToValuesArrayPosition( jdbcPosition );
+					return new ResultSetMappingSqlSelection( valuesArrayPosition, discriminatorMapping.getJdbcMapping() );
+				}
+		);
+	}
+
 	public static Expression resolveSqlExpression(
 			DomainResultCreationStateImpl resolver,
 			TableReference tableReference,

hibernate-core/src/main/java/org/hibernate/query/results/internal/dynamic/DynamicResultBuilderEntityStandard.java

@@ -7,6 +7,7 @@ package org.hibernate.query.results.internal.dynamic;
 import org.hibernate.LockMode;
 import org.hibernate.engine.FetchTiming;
 import org.hibernate.metamodel.mapping.CollectionPart;
+import org.hibernate.metamodel.mapping.EntityDiscriminatorMapping;
 import org.hibernate.metamodel.mapping.EntityMappingType;
 import org.hibernate.metamodel.mapping.ModelPart;
 import org.hibernate.metamodel.mapping.PluralAttributeMapping;
@@ -259,7 +260,7 @@ public class DynamicResultBuilderEntityStandard
 		}
 
 		if ( discriminatorColumnName != null ) {
-			resolveSqlSelection(
+			resolveDiscriminatorSqlSelection(
 					discriminatorColumnName,
 					tableReference,
 					entityMapping.getDiscriminatorMapping(),
@@ -284,6 +285,25 @@ public class DynamicResultBuilderEntityStandard
 		}
 	}
 
+	private static void resolveDiscriminatorSqlSelection(String columnAlias, TableReference tableReference, EntityDiscriminatorMapping discriminatorMapping, JdbcValuesMetadata jdbcResultsMetadata, DomainResultCreationState domainResultCreationState) {
+		final DomainResultCreationStateImpl creationStateImpl = impl( domainResultCreationState );
+		creationStateImpl.resolveSqlSelection(
+				ResultsHelper.resolveSqlExpression(
+						creationStateImpl,
+						jdbcResultsMetadata,
+						tableReference,
+						discriminatorMapping,
+						columnAlias
+				),
+				discriminatorMapping.getJdbcMapping().getJdbcJavaType(),
+				null,
+				domainResultCreationState.getSqlAstCreationState()
+						.getCreationContext()
+						.getSessionFactory()
+						.getTypeConfiguration()
+		);
+	}
+
 	private FetchBuilder findIdFetchBuilder() {
 		return findFetchBuilder( entityMapping.getIdentifierMapping() );
 	}

hibernate-core/src/main/java/org/hibernate/sql/ast/spi/SqlExpressionResolver.java

@@ -6,10 +6,10 @@ package org.hibernate.sql.ast.spi;
 
 import java.util.function.Function;
 
+import org.hibernate.metamodel.mapping.EntityDiscriminatorMapping;
 import org.hibernate.metamodel.mapping.JdbcMapping;
 import org.hibernate.metamodel.mapping.SelectableMapping;
 import org.hibernate.metamodel.mapping.SelectablePath;
-import org.hibernate.metamodel.mapping.internal.DiscriminatorTypeImpl;
 import org.hibernate.sql.ast.tree.expression.ColumnReference;
 import org.hibernate.sql.ast.tree.expression.Expression;
 import org.hibernate.sql.ast.tree.expression.NestedColumnReference;
@@ -91,6 +91,15 @@ public interface SqlExpressionResolver {
 		return createColumnReferenceKey( tableReference, selectable.getSelectablePath(), selectable.getJdbcMapping() );
 	}
 
+	/**
+	 * Convenience form for creating a key from TableReference and EntityDiscriminatorMapping
+	 */
+	static ColumnReferenceKey createDiscriminatorColumnReferenceKey(TableReference tableReference, EntityDiscriminatorMapping discriminatorMapping) {
+		assert tableReference.containsAffectedTableName( discriminatorMapping.getContainingTableExpression() )
+				: String.format( ROOT, "Expecting tables to match between TableReference (%s) and SelectableMapping (%s)", tableReference.getTableId(), discriminatorMapping.getContainingTableExpression() );
+		return createColumnReferenceKey( tableReference, discriminatorMapping.getSelectablePath(), discriminatorMapping.getUnderlyingJdbcMapping() );
+	}
+
 	default Expression resolveSqlExpression(TableReference tableReference, SelectableMapping selectableMapping) {
 		return resolveSqlExpression(
 				createColumnReferenceKey( tableReference, selectableMapping ),
@@ -127,12 +136,7 @@ public interface SqlExpressionResolver {
 		public ColumnReferenceKey(String tableQualifier, SelectablePath selectablePath, JdbcMapping jdbcMapping) {
 			this.tableQualifier = tableQualifier;
 			this.selectablePath = selectablePath;
-			if ( jdbcMapping instanceof DiscriminatorTypeImpl discriminatorType ) {
+			this.jdbcMapping = jdbcMapping;
-				this.jdbcMapping = discriminatorType.getUnderlyingJdbcMapping();
-			}
-			else {
-				this.jdbcMapping = jdbcMapping;
-			}
 		}
 
 		@Override