HHH-18146 Switch to global temporary tables on H2

hibernate-core/src/main/java/org/hibernate/dialect/H2Dialect.java

@@ -47,9 +47,8 @@ import org.hibernate.persister.entity.mutation.EntityMutationTarget;
 import org.hibernate.query.sqm.FetchClauseType;
 import org.hibernate.query.sqm.IntervalType;
 import org.hibernate.query.sqm.TemporalUnit;
-import org.hibernate.query.sqm.mutation.internal.temptable.BeforeUseAction;
+import org.hibernate.query.sqm.mutation.internal.temptable.GlobalTemporaryTableInsertStrategy;
-import org.hibernate.query.sqm.mutation.internal.temptable.LocalTemporaryTableInsertStrategy;
+import org.hibernate.query.sqm.mutation.internal.temptable.GlobalTemporaryTableMutationStrategy;
-import org.hibernate.query.sqm.mutation.internal.temptable.LocalTemporaryTableMutationStrategy;
 import org.hibernate.query.sqm.mutation.spi.SqmMultiTableInsertStrategy;
 import org.hibernate.query.sqm.mutation.spi.SqmMultiTableMutationStrategy;
 import org.hibernate.service.ServiceRegistry;
@@ -675,7 +674,7 @@ public class H2Dialect extends Dialect {
 	public SqmMultiTableMutationStrategy getFallbackSqmMutationStrategy(
 			EntityMappingType entityDescriptor,
 			RuntimeModelCreationContext runtimeModelCreationContext) {
-		return new LocalTemporaryTableMutationStrategy(
+		return new GlobalTemporaryTableMutationStrategy(
 				TemporaryTable.createIdTable(
 						entityDescriptor,
 						basename -> TemporaryTable.ID_TABLE_PREFIX + basename,
@@ -690,7 +689,7 @@ public class H2Dialect extends Dialect {
 	public SqmMultiTableInsertStrategy getFallbackSqmInsertStrategy(
 			EntityMappingType entityDescriptor,
 			RuntimeModelCreationContext runtimeModelCreationContext) {
-		return new LocalTemporaryTableInsertStrategy(
+		return new GlobalTemporaryTableInsertStrategy(
 				TemporaryTable.createEntityTable(
 						entityDescriptor,
 						name -> TemporaryTable.ENTITY_TABLE_PREFIX + name,
@@ -708,12 +707,7 @@ public class H2Dialect extends Dialect {
 
 	@Override
 	public TemporaryTableKind getSupportedTemporaryTableKind() {
-		return TemporaryTableKind.LOCAL;
+		return TemporaryTableKind.GLOBAL;
-	}
-
-	@Override
-	public BeforeUseAction getTemporaryTableBeforeUseAction() {
-		return BeforeUseAction.CREATE;
 	}
 
 	@Override

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

@@ -22,9 +22,6 @@ import org.hibernate.metamodel.mapping.internal.MappingModelCreationProcess;
 public class LocalTemporaryTableStrategy {
 
 	public static final String SHORT_NAME = "local_temporary";
-	/**
-	 * For H2 dialect avoid setting the drop strategy to true because H2 forces a commit when dropping a temporary table
-	 */
 	public static final String DROP_ID_TABLES = "hibernate.query.mutation_strategy.local_temporary.drop_tables";
 
 	private final TemporaryTable temporaryTable;

hibernate-core/src/test/java/org/hibernate/orm/test/dialect/unit/DialectTempTableNoCommitTest.java

@@ -57,7 +57,7 @@ public class DialectTempTableNoCommitTest {
 	@ServiceRegistry(
 			settings = @Setting(name = LocalTemporaryTableStrategy.DROP_ID_TABLES, value = "true")
 	)
-	@SkipForDialect(dialectClass = H2Dialect.class)
+//	@SkipForDialect(dialectClass = H2Dialect.class)
 	@SessionFactory
 	public void noCommitAfterTempTableCreationAndDropTempTableTest(SessionFactoryScope scope) {
 		scope.inTransaction(

hibernate-core/src/test/java/org/hibernate/orm/test/jpa/connection/DataSourceInjectionTest.java

@@ -21,6 +21,7 @@ import jakarta.persistence.PersistenceException;
 import javax.sql.DataSource;
 
 import org.hibernate.cfg.AvailableSettings;
+import org.hibernate.dialect.DerbyDialect;
 import org.hibernate.dialect.H2Dialect;
 import org.hibernate.engine.spi.SessionFactoryImplementor;
 import org.hibernate.engine.spi.SessionImplementor;
@@ -47,7 +48,7 @@ public class DataSourceInjectionTest {
 					// otherwise the FakeDataSourceException will be eaten trying to resolve the Dialect
 					final Map<String, Object> intgOverrides = Collections.singletonMap(
 							AvailableSettings.DIALECT,
-							H2Dialect.class
+							DerbyDialect.class
 					);
 
 					final HibernatePersistenceProvider provider = new HibernatePersistenceProvider();

migration-guide.adoc

@@ -77,3 +77,8 @@ ORM 6.6 introduced support for `@Embeddable` type inheritance.
 With it, we also enabled the `type()` and `treat()` functions to work with embeddable-typed paths.
 As a consequence, the `SqmTreatedPath#getTreatTarget()` method will now return a generic `ManagedDomainType` object,
 which could in turn be an `EntityDomainType` (as it was before) or also an `EmbeddableDomainType` instance.
+
+[[h2-dialect]]
+== H2 database and bulk mutation strategy
+
+With ORM 6.6 when a bulk mutation involves multiple tables, H2 dialect will make use of global temporary tables instead of local ones.