remove nexus between Generators and InsertGeneratedIdentifierDelegates

this is certain a very debatable move, but I think it's necessary to
keep the layering intact - we don't want this very technical construct
hanging off the side of the Generator APIs, which are user-visible

hibernate-core/src/main/java/org/hibernate/id/AbstractPostInsertGenerator.java

@@ -1,41 +0,0 @@
-/*
- * Hibernate, Relational Persistence for Idiomatic Java
- *
- * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
- * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
- */
-package org.hibernate.id;
-
-import org.hibernate.boot.model.relational.SqlStringGenerationContext;
-import org.hibernate.dialect.Dialect;
-import org.hibernate.service.ServiceRegistry;
-import org.hibernate.type.Type;
-
-import java.util.Properties;
-
-/**
- * Basic implementation of the {@link PostInsertIdentifierGenerator} contract.
- *
- * @author Gavin King
- */
-public abstract class AbstractPostInsertGenerator
-		implements PostInsertIdentifierGenerator, BulkInsertionCapableIdentifierGenerator {
-
-	@Override
-	public String determineBulkInsertionIdentifierGenerationSelectFragment(SqlStringGenerationContext context) {
-		return null;
-	}
-
-	@Override
-	public boolean referenceColumnsInSql(Dialect dialect) {
-		return dialect.getIdentityColumnSupport().hasIdentityInsertKeyword();
-	}
-
-	@Override
-	public String[] getReferencedColumnValues(Dialect dialect) {
-		return new String[] { dialect.getIdentityColumnSupport().getIdentityInsertString() };
-	}
-
-	@Override
-	public void configure(Type type, Properties params, ServiceRegistry serviceRegistry) {}
-}

hibernate-core/src/main/java/org/hibernate/id/BulkInsertionCapableIdentifierGenerator.java

@@ -33,5 +33,7 @@ public interface BulkInsertionCapableIdentifierGenerator extends Generator {
 	 *
 	 * @return The identifier value generation fragment (SQL).  {@code null} indicates that no fragment is needed.
 	 */
-	String determineBulkInsertionIdentifierGenerationSelectFragment(SqlStringGenerationContext context);
+	default String determineBulkInsertionIdentifierGenerationSelectFragment(SqlStringGenerationContext context) {
+		return null;
+	}
 }

hibernate-core/src/main/java/org/hibernate/id/IdentityGenerator.java

@@ -6,40 +6,20 @@
  */
 package org.hibernate.id;
 
-import org.hibernate.HibernateException;
-import org.hibernate.dialect.Dialect;
-import org.hibernate.id.insert.BasicSelectingDelegate;
 import org.hibernate.id.insert.InsertGeneratedIdentifierDelegate;
-import org.hibernate.id.insert.InsertReturningDelegate;
+import org.hibernate.persister.entity.EntityPersister;
 
 /**
  * A generator for use with ANSI-SQL IDENTITY columns used as the primary key.
  * The IdentityGenerator for autoincrement/identity key generation.
  * <p>
- * Indicates to the {@code Session} that identity (ie. identity/autoincrement
+ * Indicates to the {@code Session} that identity (i.e. identity/autoincrement
  * column) key generation should be used.
  *
  * @implNote Most of the functionality of this generator is delegated to
- * 		{@link InsertGeneratedIdentifierDelegate} (see
- * 		{@link #getInsertGeneratedIdentifierDelegate}).
+ * 		     {@link InsertGeneratedIdentifierDelegate}.
  *
  * @author Christoph Sturm
  */
-public class IdentityGenerator extends AbstractPostInsertGenerator {
-
-	@Override
-	public InsertGeneratedIdentifierDelegate getInsertGeneratedIdentifierDelegate(
-			PostInsertIdentityPersister persister,
-			Dialect dialect,
-			boolean useGetGeneratedKeys) throws HibernateException {
-		if ( useGetGeneratedKeys ) {
-			return dialect.getIdentityColumnSupport().buildGetGeneratedKeysDelegate( persister, dialect );
-		}
-		else if ( dialect.getIdentityColumnSupport().supportsInsertSelectIdentity() ) {
-			return new InsertReturningDelegate( persister, dialect );
-		}
-		else {
-			return new BasicSelectingDelegate( persister, dialect );
-		}
-	}
+public class IdentityGenerator implements PostInsertIdentifierGenerator, BulkInsertionCapableIdentifierGenerator {
 }

hibernate-core/src/main/java/org/hibernate/id/PostInsertIdentifierGenerator.java

@@ -6,11 +6,13 @@
  */
 package org.hibernate.id;
 
-import org.hibernate.HibernateException;
 import org.hibernate.dialect.Dialect;
-import org.hibernate.id.insert.InsertGeneratedIdentifierDelegate;
+import org.hibernate.service.ServiceRegistry;
 import org.hibernate.tuple.GenerationTiming;
 import org.hibernate.tuple.InDatabaseGenerator;
+import org.hibernate.type.Type;
+
+import java.util.Properties;
 
 import static org.hibernate.tuple.GenerationTiming.INSERT;
 
@@ -18,10 +20,6 @@ import static org.hibernate.tuple.GenerationTiming.INSERT;
  * @author Gavin King
  */
 public interface PostInsertIdentifierGenerator extends InDatabaseGenerator, Configurable {
-	InsertGeneratedIdentifierDelegate getInsertGeneratedIdentifierDelegate(
-			PostInsertIdentityPersister persister,
-			Dialect dialect,
-			boolean isGetGeneratedKeysEnabled) throws HibernateException;
 
 	@Override
 	default GenerationTiming getGenerationTiming() {
@@ -32,4 +30,18 @@ public interface PostInsertIdentifierGenerator extends InDatabaseGenerator, Conf
 	default boolean writePropertyValue() {
 		return false;
 	}
+
+	@Override
+	default boolean referenceColumnsInSql(Dialect dialect) {
+		return dialect.getIdentityColumnSupport().hasIdentityInsertKeyword();
+	}
+
+	@Override
+	default String[] getReferencedColumnValues(Dialect dialect) {
+		return new String[] { dialect.getIdentityColumnSupport().getIdentityInsertString() };
+	}
+
+	@Override
+	default void configure(Type type, Properties params, ServiceRegistry serviceRegistry) {}
+
 }

hibernate-core/src/main/java/org/hibernate/id/SelectGenerator.java

@@ -6,58 +6,39 @@
  */
 package org.hibernate.id;
 
-import java.sql.PreparedStatement;
-import java.sql.ResultSet;
-import java.sql.SQLException;
 import java.util.Properties;
 
-import org.hibernate.HibernateException;
-import org.hibernate.Internal;
-import org.hibernate.MappingException;
-import org.hibernate.boot.model.relational.SqlStringGenerationContext;
-import org.hibernate.dialect.Dialect;
-import org.hibernate.engine.spi.SessionFactoryImplementor;
-import org.hibernate.engine.spi.SharedSessionContractImplementor;
-import org.hibernate.id.insert.AbstractSelectingDelegate;
-import org.hibernate.id.insert.IdentifierGeneratingInsert;
-import org.hibernate.id.insert.InsertGeneratedIdentifierDelegate;
-import org.hibernate.jdbc.Expectation;
-import org.hibernate.metamodel.mapping.BasicEntityIdentifierMapping;
+import org.hibernate.persister.entity.EntityPersister;
 import org.hibernate.service.ServiceRegistry;
-import org.hibernate.sql.model.ast.builder.TableInsertBuilder;
-import org.hibernate.sql.model.ast.builder.TableInsertBuilderStandard;
-import org.hibernate.type.BasicType;
 import org.hibernate.type.Type;
 
 /**
- * A generator that selects the just inserted row to determine the identifier
- * value assigned by the database. The correct row is located using a unique
- * key.
- * <p>
- * One mapping parameter is required: key (unless a natural-id is defined in the mapping).
+ * A generator that {@code select}s the just-inserted row to determine the identifier
+ * value assigned by the database. The correct row is located using a unique key of
+ * the entity, either:
+ * <ul>
+ * <li>the mapped {@linkplain org.hibernate.annotations.NaturalId} of the entity, or
+ * <li>a property specified using the parameter named {@code "key"}.
+ * </ul>
+ * The second approach is provided for backward compatibility with older versions of
+ * Hibernate.
+ *
+ * @see org.hibernate.annotations.NaturalId
  *
  * @author Gavin King
  */
-public class SelectGenerator extends AbstractPostInsertGenerator {
+public class SelectGenerator implements PostInsertIdentifierGenerator, BulkInsertionCapableIdentifierGenerator {
 	private String uniqueKeyPropertyName;
 
 	@Override
-	public void configure(Type type, Properties parameters, ServiceRegistry serviceRegistry) throws MappingException {
+	public void configure(Type type, Properties parameters, ServiceRegistry serviceRegistry) {
 		uniqueKeyPropertyName = parameters.getProperty( "key" );
 	}
 
 	@Override
-	public InsertGeneratedIdentifierDelegate getInsertGeneratedIdentifierDelegate(
-			PostInsertIdentityPersister persister,
-			Dialect dialect,
-			boolean isGetGeneratedKeysEnabled) throws HibernateException {
-		return new SelectGeneratorDelegate( persister, dialect, uniqueKeyPropertyName );
-	}
-
-	@Internal
-	public static String determineNameOfPropertyToUse(PostInsertIdentityPersister persister, String supplied) {
-		if ( supplied != null ) {
-			return supplied;
+	public String getUniqueKeyPropertyName(EntityPersister persister) {
+		if ( uniqueKeyPropertyName != null ) {
+			return uniqueKeyPropertyName;
 		}
 		int[] naturalIdPropertyIndices = persister.getNaturalIdentifierProperties();
 		if ( naturalIdPropertyIndices == null ) {
@@ -80,61 +61,4 @@ public class SelectGenerator extends AbstractPostInsertGenerator {
 		}
 		return persister.getPropertyNames()[naturalIdPropertyIndices[0]];
 	}
-
-	private static class SelectGeneratorDelegate extends AbstractSelectingDelegate {
-		private final PostInsertIdentityPersister persister;
-		private final Dialect dialect;
-
-		private final String uniqueKeyPropertyName;
-		private final Type uniqueKeyType;
-		private final BasicType<?> idType;
-
-		private final String idSelectString;
-
-		public SelectGeneratorDelegate(PostInsertIdentityPersister persister, Dialect dialect, String propertyName) {
-			super( persister );
-
-			this.persister = persister;
-			this.dialect = dialect;
-			this.uniqueKeyPropertyName = determineNameOfPropertyToUse( persister, propertyName );
-
-			idSelectString = persister.getSelectByUniqueKeyString(this.uniqueKeyPropertyName);
-			uniqueKeyType = persister.getPropertyType(this.uniqueKeyPropertyName);
-			idType = (BasicType<?>) persister.getIdentifierType();
-		}
-
-		protected String getSelectSQL() {
-			return idSelectString;
-		}
-
-		@Override
-		public IdentifierGeneratingInsert prepareIdentifierGeneratingInsert(SqlStringGenerationContext context) {
-			return new IdentifierGeneratingInsert( dialect );
-		}
-
-		@Override
-		public TableInsertBuilder createTableInsertBuilder(
-				BasicEntityIdentifierMapping identifierMapping,
-				Expectation expectation,
-				SessionFactoryImplementor sessionFactory) {
-			return new TableInsertBuilderStandard( persister, persister.getIdentifierTableMapping(), sessionFactory );
-		}
-
-		protected void bindParameters(Object entity, PreparedStatement ps, SharedSessionContractImplementor session)
-				throws SQLException {
-			Object uniqueKeyValue = persister.getPropertyValue( entity, uniqueKeyPropertyName );
-			uniqueKeyType.nullSafeSet( ps, uniqueKeyValue, 1, session );
-		}
-
-		@Override
-		protected Object extractGeneratedValue(Object entity, ResultSet rs, SharedSessionContractImplementor session)
-				throws SQLException {
-			if ( !rs.next() ) {
-				throw new IdentifierGenerationException( "the inserted row could not be located by the unique key: "
-						+ uniqueKeyPropertyName );
-			}
-
-			return idType.getJdbcValueExtractor().extract( rs, 1, session );
-		}
-	}
 }

hibernate-core/src/main/java/org/hibernate/id/enhanced/SequenceStyleGenerator.java

@@ -547,7 +547,8 @@ public class SequenceStyleGenerator
 
 	@Override
 	public String determineBulkInsertionIdentifierGenerationSelectFragment(SqlStringGenerationContext context) {
-		return context.getDialect().getSequenceSupport().getSelectSequenceNextValString( context.format( getDatabaseStructure().getPhysicalName() ) );
+		return context.getDialect().getSequenceSupport()
+				.getSelectSequenceNextValString( context.format( getDatabaseStructure().getPhysicalName() ) );
 	}
 
 	/**

hibernate-core/src/main/java/org/hibernate/id/insert/AbstractSelectingDelegate.java

@@ -57,8 +57,7 @@ public abstract class AbstractSelectingDelegate implements InsertGeneratedIdenti
 
 	@Override
 	public PreparedStatement prepareStatement(String insertSql, SharedSessionContractImplementor session) {
-		final MutationStatementPreparer statementPreparer = session.getJdbcCoordinator().getMutationStatementPreparer();
-		return statementPreparer.prepareStatement( insertSql, NO_GENERATED_KEYS );
+		return session.getJdbcCoordinator().getMutationStatementPreparer().prepareStatement( insertSql, NO_GENERATED_KEYS );
 	}
 
 	@Override
@@ -73,8 +72,7 @@ public abstract class AbstractSelectingDelegate implements InsertGeneratedIdenti
 		jdbcServices.getSqlStatementLogger().logStatement( insertStatementDetails.getSqlString() );
 		jdbcValueBindings.beforeStatement( insertStatementDetails, session );
 
-		final PreparedStatement insertStatement = insertStatementDetails.resolveStatement();
-		jdbcCoordinator.getResultSetReturn().executeUpdate( insertStatement );
+		jdbcCoordinator.getResultSetReturn().executeUpdate( insertStatementDetails.resolveStatement() );
 
 		// the insert is complete, select the generated id...
 
@@ -109,21 +107,19 @@ public abstract class AbstractSelectingDelegate implements InsertGeneratedIdenti
 	}
 
 	@Override
-	public final Object performInsert(
-			String insertSQL,
-			SharedSessionContractImplementor session,
-			Binder binder) {
-		StatementPreparer statementPreparer = session.getJdbcCoordinator().getStatementPreparer();
+	public final Object performInsert(String insertSQL, SharedSessionContractImplementor session, Binder binder) {
+		JdbcCoordinator jdbcCoordinator = session.getJdbcCoordinator();
+		StatementPreparer statementPreparer = jdbcCoordinator.getStatementPreparer();
 		try {
 			// prepare and execute the insert
 			PreparedStatement insert = statementPreparer.prepareStatement( insertSQL, NO_GENERATED_KEYS );
 			try {
 				binder.bindValues( insert );
-				session.getJdbcCoordinator().getResultSetReturn().executeUpdate( insert );
+				jdbcCoordinator.getResultSetReturn().executeUpdate( insert );
 			}
 			finally {
-				session.getJdbcCoordinator().getLogicalConnection().getResourceRegistry().release( insert );
-				session.getJdbcCoordinator().afterStatementExecution();
+				jdbcCoordinator.getLogicalConnection().getResourceRegistry().release( insert );
+				jdbcCoordinator.afterStatementExecution();
 			}
 		}
 		catch (SQLException sqle) {
@@ -141,17 +137,17 @@ public abstract class AbstractSelectingDelegate implements InsertGeneratedIdenti
 			PreparedStatement idSelect = statementPreparer.prepareStatement( selectSQL, false );
 			try {
 				bindParameters( binder.getEntity(), idSelect, session );
-				ResultSet rs = session.getJdbcCoordinator().getResultSetReturn().extract( idSelect );
+				ResultSet rs = jdbcCoordinator.getResultSetReturn().extract( idSelect );
 				try {
 					return extractGeneratedValue( binder.getEntity(), rs, session );
 				}
 				finally {
-					session.getJdbcCoordinator().getLogicalConnection().getResourceRegistry().release( rs, idSelect );
+					jdbcCoordinator.getLogicalConnection().getResourceRegistry().release( rs, idSelect );
 				}
 			}
 			finally {
-				session.getJdbcCoordinator().getLogicalConnection().getResourceRegistry().release( idSelect );
-				session.getJdbcCoordinator().afterStatementExecution();
+				jdbcCoordinator.getLogicalConnection().getResourceRegistry().release( idSelect );
+				jdbcCoordinator.afterStatementExecution();
 			}
 
 		}
@@ -159,7 +155,7 @@ public abstract class AbstractSelectingDelegate implements InsertGeneratedIdenti
 			throw session.getJdbcServices().getSqlExceptionHelper().convert(
 					sqle,
 					"could not retrieve generated id after insert: " + MessageHelper.infoString( persister ),
-					insertSQL
+					selectSQL
 			);
 		}
 	}

hibernate-core/src/main/java/org/hibernate/id/insert/BasicSelectingDelegate.java

@@ -11,6 +11,7 @@ import java.sql.SQLException;
 
 import org.hibernate.boot.model.relational.SqlStringGenerationContext;
 import org.hibernate.dialect.Dialect;
+import org.hibernate.dialect.identity.IdentityColumnSupport;
 import org.hibernate.engine.spi.SessionFactoryImplementor;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
 import org.hibernate.id.IdentifierGeneratorHelper;
@@ -20,6 +21,8 @@ import org.hibernate.metamodel.mapping.BasicEntityIdentifierMapping;
 import org.hibernate.sql.model.ast.builder.TableInsertBuilder;
 import org.hibernate.sql.model.ast.builder.TableInsertBuilderStandard;
 
+import static org.hibernate.id.IdentifierGeneratorHelper.getGeneratedIdentity;
+
 /**
  * Delegate for dealing with IDENTITY columns where the dialect requires an
  * additional command execution to retrieve the generated IDENTITY value
@@ -37,7 +40,7 @@ public class BasicSelectingDelegate extends AbstractSelectingDelegate {
 	@Override
 	public IdentifierGeneratingInsert prepareIdentifierGeneratingInsert(SqlStringGenerationContext context) {
 		IdentifierGeneratingInsert insert = new IdentifierGeneratingInsert( dialect );
-		insert.addIdentityColumn( persister.getRootTableKeyColumnNames()[ 0 ] );
+		insert.addIdentityColumn( persister.getRootTableKeyColumnNames()[0] );
 		return insert;
 	}
 
@@ -45,16 +48,17 @@ public class BasicSelectingDelegate extends AbstractSelectingDelegate {
 	public TableInsertBuilder createTableInsertBuilder(
 			BasicEntityIdentifierMapping identifierMapping,
 			Expectation expectation,
-			SessionFactoryImplementor sessionFactory) {
-		final TableInsertBuilder builder = new TableInsertBuilderStandard(
-				persister,
-				persister.getIdentifierTableMapping(),
-				sessionFactory
-		);
+			SessionFactoryImplementor factory) {
+		final TableInsertBuilder builder =
+				new TableInsertBuilderStandard( persister, persister.getIdentifierTableMapping(), factory );
 
-		final String value = dialect.getIdentityColumnSupport().getIdentityInsertString();
-		if ( value != null ) {
-			builder.addKeyColumn( identifierMapping.getSelectionExpression(), value, identifierMapping.getJdbcMapping() );
+		IdentityColumnSupport identityColumnSupport = dialect.getIdentityColumnSupport();
+		if ( identityColumnSupport.hasIdentityInsertKeyword() ) {
+			builder.addKeyColumn(
+					identifierMapping.getSelectionExpression(),
+					identityColumnSupport.getIdentityInsertString(),
+					identifierMapping.getJdbcMapping()
+			);
 		}
 
 		return builder;
@@ -68,10 +72,10 @@ public class BasicSelectingDelegate extends AbstractSelectingDelegate {
 	@Override
 	protected Object extractGeneratedValue(Object entity, ResultSet rs, SharedSessionContractImplementor session)
 			throws SQLException {
-		return IdentifierGeneratorHelper.getGeneratedIdentity(
+		return getGeneratedIdentity(
 				rs,
 				persister.getNavigableRole(),
-				persister.getRootTableKeyColumnNames()[ 0 ],
+				persister.getRootTableKeyColumnNames()[0],
 				persister.getIdentifierType(),
 				session.getJdbcServices().getJdbcEnvironment().getDialect()
 		);

hibernate-core/src/main/java/org/hibernate/id/insert/InsertGeneratedIdentifierDelegate.java

@@ -48,11 +48,6 @@ public interface InsertGeneratedIdentifierDelegate {
 			Object entity,
 			SharedSessionContractImplementor session);
 
-
-
-
-
-
 	/**
 	 * Build a {@link org.hibernate.sql.Insert} specific to the delegate's mode
 	 * of handling generated key values.

hibernate-core/src/main/java/org/hibernate/id/insert/SelectGeneratorDelegate.java

@@ -0,0 +1,79 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ */
+package org.hibernate.id.insert;
+
+import org.hibernate.boot.model.relational.SqlStringGenerationContext;
+import org.hibernate.dialect.Dialect;
+import org.hibernate.engine.spi.SessionFactoryImplementor;
+import org.hibernate.engine.spi.SharedSessionContractImplementor;
+import org.hibernate.id.IdentifierGenerationException;
+import org.hibernate.id.PostInsertIdentityPersister;
+import org.hibernate.jdbc.Expectation;
+import org.hibernate.metamodel.mapping.BasicEntityIdentifierMapping;
+import org.hibernate.sql.model.ast.builder.TableInsertBuilder;
+import org.hibernate.sql.model.ast.builder.TableInsertBuilderStandard;
+import org.hibernate.type.BasicType;
+import org.hibernate.type.Type;
+
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.sql.SQLException;
+
+public class SelectGeneratorDelegate extends AbstractSelectingDelegate {
+	private final PostInsertIdentityPersister persister;
+	private final Dialect dialect;
+
+	private final String uniqueKeyPropertyName;
+	private final Type uniqueKeyType;
+	private final BasicType<?> idType;
+
+	private final String idSelectString;
+
+	public SelectGeneratorDelegate(PostInsertIdentityPersister persister, Dialect dialect, String uniqueKeyPropertyName) {
+		super( persister );
+
+		this.persister = persister;
+		this.dialect = dialect;
+		this.uniqueKeyPropertyName = uniqueKeyPropertyName;
+
+		idSelectString = persister.getSelectByUniqueKeyString(this.uniqueKeyPropertyName);
+		uniqueKeyType = persister.getPropertyType(this.uniqueKeyPropertyName);
+		idType = (BasicType<?>) persister.getIdentifierType();
+	}
+
+	protected String getSelectSQL() {
+		return idSelectString;
+	}
+
+	@Override
+	public IdentifierGeneratingInsert prepareIdentifierGeneratingInsert(SqlStringGenerationContext context) {
+		return new IdentifierGeneratingInsert( dialect );
+	}
+
+	@Override
+	public TableInsertBuilder createTableInsertBuilder(
+			BasicEntityIdentifierMapping identifierMapping,
+			Expectation expectation,
+			SessionFactoryImplementor factory) {
+		return new TableInsertBuilderStandard( persister, persister.getIdentifierTableMapping(), factory );
+	}
+
+	protected void bindParameters(Object entity, PreparedStatement ps, SharedSessionContractImplementor session)
+			throws SQLException {
+		uniqueKeyType.nullSafeSet( ps, persister.getPropertyValue( entity, uniqueKeyPropertyName ), 1, session );
+	}
+
+	@Override
+	protected Object extractGeneratedValue(Object entity, ResultSet rs, SharedSessionContractImplementor session)
+			throws SQLException {
+		if ( !rs.next() ) {
+			throw new IdentifierGenerationException("the inserted row could not be located by the unique key: "
+					+ uniqueKeyPropertyName);
+		}
+		return idType.getJdbcValueExtractor().extract( rs, 1, session );
+	}
+}

hibernate-core/src/main/java/org/hibernate/persister/entity/AbstractEntityPersister.java

@@ -99,8 +99,11 @@ import org.hibernate.id.IdentifierGenerator;
 import org.hibernate.id.OptimizableGenerator;
 import org.hibernate.id.PostInsertIdentifierGenerator;
 import org.hibernate.id.PostInsertIdentityPersister;
+import org.hibernate.id.insert.SelectGeneratorDelegate;
 import org.hibernate.id.enhanced.Optimizer;
+import org.hibernate.id.insert.BasicSelectingDelegate;
 import org.hibernate.id.insert.InsertGeneratedIdentifierDelegate;
+import org.hibernate.id.insert.InsertReturningDelegate;
 import org.hibernate.internal.CoreLogging;
 import org.hibernate.internal.CoreMessageLogger;
 import org.hibernate.internal.FilterAliasGenerator;
@@ -259,7 +262,6 @@ import org.hibernate.stat.spi.StatisticsImplementor;
 import org.hibernate.tuple.Generator;
 import org.hibernate.tuple.InDatabaseGenerator;
 import org.hibernate.tuple.GenerationTiming;
-import org.hibernate.tuple.InMemoryGenerator;
 import org.hibernate.tuple.NonIdentifierAttribute;
 import org.hibernate.tuple.entity.EntityBasedAssociationAttribute;
 import org.hibernate.tuple.entity.EntityMetamodel;
@@ -2868,6 +2870,25 @@ public abstract class AbstractEntityPersister
 		return getFactory().getSessionFactoryOptions().isGetGeneratedKeysEnabled();
 	}
 
+	public InsertGeneratedIdentifierDelegate getGeneratedIdentifierDelegate() {
+		Dialect dialect = getFactory().getJdbcServices().getDialect();
+		if ( useGetGeneratedKeys() ) {
+			return dialect.getIdentityColumnSupport().buildGetGeneratedKeysDelegate(this, dialect );
+		}
+		else if ( dialect.getIdentityColumnSupport().supportsInsertSelectIdentity() ) {
+			return new InsertReturningDelegate(this, dialect );
+		}
+		else {
+			return new BasicSelectingDelegate(this, dialect );
+		}
+	}
+
+	@Override
+	public InsertGeneratedIdentifierDelegate getGeneratedIdentifierDelegateForProperty(String uniqueKeyPropertyName) {
+		Dialect dialect = getFactory().getJdbcServices().getDialect();
+		return new SelectGeneratorDelegate( this, dialect, uniqueKeyPropertyName );
+	}
+
 	@Override
 	public String getIdentitySelectString() {
 		//TODO: cache this in an instvar
@@ -3179,12 +3200,11 @@ public abstract class AbstractEntityPersister
 
 	private void doLateInit() {
 		if ( isIdentifierAssignedByInsert() ) {
-			final PostInsertIdentifierGenerator idGenerator = (PostInsertIdentifierGenerator) getGenerator();
-			identityDelegate = idGenerator.getInsertGeneratedIdentifierDelegate(
-					this,
-					getFactory().getJdbcServices().getDialect(),
-					useGetGeneratedKeys()
-			);
+			final InDatabaseGenerator generator = (InDatabaseGenerator) getGenerator();
+			final String uniqueKeyPropertyName = generator.getUniqueKeyPropertyName(this);
+			identityDelegate = uniqueKeyPropertyName == null
+					? getGeneratedIdentifierDelegate()
+					: getGeneratedIdentifierDelegateForProperty( uniqueKeyPropertyName );
 		}
 
 		tableMappings = buildTableMappings();

hibernate-core/src/main/java/org/hibernate/persister/entity/EntityPersister.java

@@ -28,6 +28,7 @@ import org.hibernate.engine.spi.SessionImplementor;
 import org.hibernate.engine.spi.SharedSessionContractImplementor;
 import org.hibernate.event.spi.EventSource;
 import org.hibernate.id.IdentifierGenerator;
+import org.hibernate.id.insert.InsertGeneratedIdentifierDelegate;
 import org.hibernate.internal.FilterAliasGenerator;
 import org.hibernate.internal.TableGroupFilterAliasGenerator;
 import org.hibernate.loader.ast.spi.Loadable;
@@ -1002,6 +1003,14 @@ public interface EntityPersister
 
 	boolean canUseReferenceCacheEntries();
 
+	default InsertGeneratedIdentifierDelegate getGeneratedIdentifierDelegate() {
+		return null;
+	}
+
+	default InsertGeneratedIdentifierDelegate getGeneratedIdentifierDelegateForProperty(String uniqueKeyPropertyName) {
+		return null;
+	}
+
 	/**
 	 * The property name of the "special" identifier property in HQL
 	 *

hibernate-core/src/main/java/org/hibernate/query/sqm/mutation/internal/temptable/InsertExecutionDelegate.java

@@ -36,6 +36,7 @@ import org.hibernate.metamodel.mapping.EntityMappingType;
 import org.hibernate.metamodel.mapping.MappingModelExpressible;
 import org.hibernate.metamodel.mapping.ModelPartContainer;
 import org.hibernate.persister.entity.AbstractEntityPersister;
+import org.hibernate.persister.entity.EntityPersister;
 import org.hibernate.query.SemanticException;
 import org.hibernate.query.results.TableGroupImpl;
 import org.hibernate.query.spi.DomainQueryExecutionContext;
@@ -74,6 +75,7 @@ import org.hibernate.sql.results.graph.basic.BasicFetch;
 import org.hibernate.sql.results.internal.SqlSelectionImpl;
 import org.hibernate.sql.results.spi.ListResultsConsumer;
 import org.hibernate.tuple.Generator;
+import org.hibernate.tuple.InDatabaseGenerator;
 import org.hibernate.tuple.InMemoryGenerator;
 import org.hibernate.type.descriptor.ValueBinder;
 
@@ -302,7 +304,8 @@ public class InsertExecutionDelegate implements TableBasedInsertHandler.Executio
 				true
 		);
 
-		final Generator generator = entityDescriptor.getEntityPersister().getGenerator();
+		final EntityPersister entityPersister = entityDescriptor.getEntityPersister();
+		final Generator generator = entityPersister.getGenerator();
 		final List<Assignment> assignments = assignmentsByTable.get( updatingTableReference );
 		if ( ( assignments == null || assignments.isEmpty() )
 				&& !generator.generatedByDatabase()
@@ -556,13 +559,11 @@ public class InsertExecutionDelegate implements TableBasedInsertHandler.Executio
 				.translate( null, executionContext.getQueryOptions() );
 
 		if ( generator.generatedByDatabase() ) {
-			final PostInsertIdentifierGenerator postInsertGenerator = (PostInsertIdentifierGenerator) generator;
-			final boolean generatedKeysEnabled = sessionFactory.getSessionFactoryOptions().isGetGeneratedKeysEnabled();
-			final InsertGeneratedIdentifierDelegate identifierDelegate = postInsertGenerator.getInsertGeneratedIdentifierDelegate(
-					(PostInsertIdentityPersister) entityDescriptor.getEntityPersister(),
-					jdbcServices.getDialect(),
-					generatedKeysEnabled
-			);
+			final InDatabaseGenerator databaseGenerator = (InDatabaseGenerator) generator;
+			final String uniqueKeyPropertyName = databaseGenerator.getUniqueKeyPropertyName( entityPersister );
+			final InsertGeneratedIdentifierDelegate identifierDelegate = uniqueKeyPropertyName == null
+					? entityPersister.getGeneratedIdentifierDelegate()
+					: entityPersister.getGeneratedIdentifierDelegateForProperty( uniqueKeyPropertyName );
 			final String finalSql = identifierDelegate.prepareIdentifierGeneratingInsert( jdbcInsert.getSqlString() );
 			final BasicEntityIdentifierMapping identifierMapping = (BasicEntityIdentifierMapping) entityDescriptor.getIdentifierMapping();
 			final ValueBinder jdbcValueBinder = identifierMapping.getJdbcMapping().getJdbcValueBinder();

hibernate-core/src/main/java/org/hibernate/tuple/InDatabaseGenerator.java

@@ -7,6 +7,7 @@
 package org.hibernate.tuple;
 
 import org.hibernate.dialect.Dialect;
+import org.hibernate.persister.entity.EntityPersister;
 
 /**
  * A value generated by the database might be generated implicitly, by a trigger, or using
@@ -62,6 +63,10 @@ public interface InDatabaseGenerator extends Generator {
 	 */
 	String[] getReferencedColumnValues(Dialect dialect);
 
+	default String getUniqueKeyPropertyName(EntityPersister persister) {
+		return null;
+	}
+
 	default boolean generatedByDatabase() {
 		return true;
 	}