HHH-19774 - Automatic flushing for child session with shared connection/tx

HHH-19808 - Automatic closing for child session with shared connection/tx

Author: sebersole

hibernate-core/src/main/java/org/hibernate/engine/creation/internal/SessionCreationOptionsAdaptor.java

@@ -147,17 +147,7 @@ public TransactionCompletionCallbacksImplementor getTransactionCompletionCallbac
 	}
 
 	@Override
-	public void registerParentSessionObserver(ParentSessionObserver callbacks) {
-		originalSession.getEventListenerManager().addListener( new SessionEventListener() {
-			@Override
-			public void flushStart() {
-				callbacks.onParentFlush();
-			}
-
-			@Override
-			public void end() {
-				callbacks.onParentClose();
-			}
-		} );
+	public void registerParentSessionObserver(ParentSessionObserver observer) {
+		registerParentSessionObserver( observer, originalSession );
 	}
 }

hibernate-core/src/main/java/org/hibernate/engine/creation/internal/SharedSessionBuilderImpl.java

@@ -260,20 +260,9 @@ public SharedSessionBuilderImplementor subselectFetchEnabled(boolean subselectFe
 	// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 	// SharedSessionCreationOptions
 
-
 	@Override
-	public void registerParentSessionObserver(ParentSessionObserver callbacks) {
-		original.getEventListenerManager().addListener( new SessionEventListener() {
-			@Override
-			public void flushEnd(int numberOfEntities, int numberOfCollections) {
-				callbacks.onParentFlush();
-			}
-
-			@Override
-			public void end() {
-				callbacks.onParentClose();
-			}
-		} );
+	public void registerParentSessionObserver(ParentSessionObserver observer) {
+		registerParentSessionObserver( observer, original );
 	}
 
 	@Override

hibernate-core/src/main/java/org/hibernate/engine/creation/internal/SharedSessionCreationOptions.java

@@ -4,8 +4,10 @@
  */
 package org.hibernate.engine.creation.internal;
 
+import org.hibernate.SessionEventListener;
 import org.hibernate.Transaction;
 import org.hibernate.engine.jdbc.spi.JdbcCoordinator;
+import org.hibernate.engine.spi.SharedSessionContractImplementor;
 import org.hibernate.engine.spi.TransactionCompletionCallbacksImplementor;
 import org.hibernate.resource.transaction.spi.TransactionCoordinator;
 
@@ -30,6 +32,28 @@ public interface SharedSessionCreationOptions extends SessionCreationOptions {
 	/**
 	 * Registers callbacks for the child session to integrate with events of the parent session.
 	 */
-	void registerParentSessionObserver(ParentSessionObserver callbacks);
+	void registerParentSessionObserver(ParentSessionObserver observer);
+
+	/**
+	 * Consolidated implementation of adding the parent session observer.
+	 */
+	default void registerParentSessionObserver(ParentSessionObserver observer, SharedSessionContractImplementor original) {
+		original.getEventListenerManager().addListener( new SessionEventListener() {
+			@Override
+			public void flushEnd(int numberOfEntities, int numberOfCollections) {
+				observer.onParentFlush();
+			}
+
+			@Override
+			public void partialFlushEnd(int numberOfEntities, int numberOfCollections) {
+				observer.onParentFlush();
+			}
+
+			@Override
+			public void end() {
+				observer.onParentClose();
+			}
+		} );
+	}
 
 }

hibernate-jfr/src/test/java/org/hibernate/event/jfr/flush/FlushTests.java

@@ -23,6 +23,7 @@
 
 import static org.assertj.core.api.Assertions.assertThat;
 
+@SuppressWarnings("JUnitMalformedDeclaration")
 @JfrEventTest
 @DomainModel(annotatedClasses = {
 		FlushTests.TestEntity.class,
@@ -67,22 +68,21 @@ public void testFlushEvent(SessionFactoryScope scope) {
 
 	@Test
 	@EnableEvent(JdbcBatchExecutionEvent.NAME)
-	public void testFlushNoFired(SessionFactoryScope scope) {
+	public void testFlushNotFired(SessionFactoryScope scope) {
 		jfrEvents.reset();
-		scope.inTransaction(
-				session -> {
-
-				}
-		);
-		List<RecordedEvent> events = jfrEvents.events()
-				.filter(
-						recordedEvent ->
-						{
-							String eventName = recordedEvent.getEventType().getName();
-							return eventName.equals( FlushEvent.NAME );
-						}
-				).toList();
-		assertThat( events ).hasSize( 0 );
+		scope.inTransaction( (session) -> {
+			// do nothing
+		} );
+		List<RecordedEvent> events = jfrEvents.events().filter( (recordedEvent) -> {
+			String eventName = recordedEvent.getEventType().getName();
+			return eventName.equals( FlushEvent.NAME );
+		} ).toList();
+
+		// the flush event should be triggered by the commit
+		assertThat( events ).hasSize( 1 );
+		// however, it should not affect anything
+		assertThat( events.get( 0 ).getInt( "numberOfEntitiesProcessed" ) ).isEqualTo( 0 );
+		assertThat( events.get( 0 ).getInt( "numberOfCollectionsProcessed" ) ).isEqualTo( 0 );
 	}
 
 	@Entity(name = "TestEntity")

migration-guide.adoc

@@ -40,13 +40,6 @@ See the link:{releaseSeriesBase}#whats-new[website] for the list of new features
 
 This section describes changes to contracts (classes, interfaces, methods, etc.) which are considered https://hibernate.org/community/compatibility-policy/#api[API].
 
-* Code underlying the session builder APIs was reengineered, and the behavior of `noInterceptor()` for `SharedSessionBuilder` and `SharedStatelessSessionBuilder` was aligned with the preexisting semantics of this method on `SessionBuilder` and `StatelessSessionBuilder`.
-  The previous behavior may be recovered by calling `noSessionInterceptorCreation()`.
-
-* `org.hibernate.dialect.AzureSQLServerDialect` was deprecated. Use `org.hibernate.dialect.SQLServerDialect` instead.
-  If you set `hibernate.boot.allow_jdbc_metadata_access=false` for offline startup,
-  remember to also set the targeted database version through `jakarta.persistence.database-product-version`;
-  this would be 16.0 for SQL Server 2022 or 17.0 for SQL Server 2025.
 
 // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // SPI changes
@@ -57,7 +50,58 @@ This section describes changes to contracts (classes, interfaces, methods, etc.)
 
 This section describes changes to contracts (classes, interfaces, methods, etc.) which are considered https://hibernate.org/community/compatibility-policy/#spi[SPI].
 
-* Some operations of `TypeConfiguration`, `JavaTypeRegistry`, and `BasicTypeRegistry` used unbound type parameters in the return type. The generic signatures of these methods have been changed for improved type safety.
+[[registry-generic-signatures]]
+=== Registry Generic Signatures
+
+Some operations of `TypeConfiguration`, `JavaTypeRegistry`, and `BasicTypeRegistry` had previously used unbound type parameters in the return type. The generic signatures of these methods have been changed for improved type safety.
+
+
+[[AzureSQLServerDialect]]
+=== AzureSQLServerDialect Deprecation
+
+`org.hibernate.dialect.AzureSQLServerDialect` was deprecated; use `org.hibernate.dialect.SQLServerDialect` instead.
+
+[IMPORTANT]
+====
+If you set `hibernate.boot.allow_jdbc_metadata_access=false` for offline startup,
+remember to also set the targeted database version through `jakarta.persistence.database-product-version` - this would be 16.0 for SQL Server 2022 or 17.0 for SQL Server 2025.
+====
+
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+// Changes in Behavior
+// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+[[behavior-changes]]
+== Changes in Behavior
+
+[[child-session-flush-close]]
+=== Child Session Flush/Close Behavior
+
+`Session` and `StatelessSession` which share transactional context with a parent now have slightly different semantics in regard to flushing and closing -
+
+* when the parent is flushed, the child is flushed
+* when the parent is closed, the child is closed
+
+[NOTE]
+====
+This led to a change in triggering of flush events for both -
+
+* `SessionEventListener` registrations
+* JFR events
+
+In both cases, the events are now triggered regardless of whether any entities or collections were actually flushed.
+Each already carried the number of entities and the number of collections which were actually flushed.
+Previously, when no entities and no collections were flushed to the database no event was generated; the event is now generated and both values will be zero.
+
+Interestingly, this now also aligns with handling for auto-flush events which already always triggered these events.
+====
+
+
+[[child-session-no-interceptor]]
+=== Child Session No-Interceptor Behavior
+
+The behavior of `noInterceptor()` for `SharedSessionBuilder` and (the new) `SharedStatelessSessionBuilder` was aligned with the preexisting semantics of this method on `SessionBuilder` and `StatelessSessionBuilder`.
+The previous behavior may be recovered by calling `noSessionInterceptorCreation()`.
 
 
 // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

whats-new.adoc

@@ -11,6 +11,25 @@ Describes the new features and capabilities added to Hibernate ORM in {version}.
 
 IMPORTANT: If migrating from earlier versions, be sure to also check out the link:{migrationGuide}[Migration Guide] for discussion of impactful changes.
 
+[[child-stateless-sessions]]
+== Child StatelessSession
+
+Creation of child `StatelessSession` is now supported, just as with child `Session`.
+This is a `StatelessSession` which shares "transactional context" with a parent `Session` or `StatelessSession`.
+Use `Session#statelessWithOptions` or `StatelessSession#statelessWithOptions` instead of `#sessionWithOptions`.
+
+====
+[source,java]
+----
+Session parent = ...;
+StatelessSession child = parent
+    .statelessWithOptions()
+    .connection()
+    ...
+    .open();
+----
+====
+
 [[vector-module-enhancements]]
 == Hibernate-Vector module enhancements