HHH-12148 - Add setting indicating if the value stored in the table used by the @TableGenerator is the last value used or the next value to be used

documentation/src/main/asciidoc/userguide/appendices/Configurations.adoc

@@ -186,6 +186,9 @@ If true, generated identifier properties are reset to default values when object
 `*hibernate.id.optimizer.pooled.preferred*` (e.g. `none`, `hilo`, `legacy-hilo`, `pooled` (default value), `pooled-lo`, `pooled-lotl` or a fully-qualified name of the https://docs.jboss.org/hibernate/orm/{majorMinorVersion}/javadocs/org/hibernate/id/enhanced/Optimizer.html[`Optimizer`] implementation)::
 When a generator specified an increment-size and an optimizer was not explicitly specified, which of the _pooled_ optimizers should be preferred?
 
+`*hibernate.id.generator.stored_last_used*` (e.g. `true` (default value) or `false`)::
+If true, the value stored in the table used by the `@TableGenerator` is the last value used, if false the value is the next value to be used.
+
 ==== Quoting options
 
 `*hibernate.globally_quoted_identifiers*` (e.g. `true` or `false` (default value))::

hibernate-core/src/main/java/org/hibernate/cfg/AvailableSettings.java

@@ -1790,4 +1790,13 @@ public interface AvailableSettings {
 	 * @see JpaCompliance#isJpaClosedComplianceEnabled()
 	 */
 	String JPA_CLOSED_COMPLIANCE = "hibernate.jpa.compliance.closed";
+
+	/**
+	 * True/False setting indicating if the value stored in the table used by the {@link javax.persistence.TableGenerator}
+	 * is the last value generated or the next value to be used.
+	 *
+	 * The default value is true.
+	 *
+	 */
+	String TABLE_GENERATOR_STORE_LAST_USED = "hibernate.id.generator.stored_last_used";
 }

hibernate-core/src/main/java/org/hibernate/cfg/BinderHelper.java

@@ -812,9 +812,10 @@ public class BinderHelper {
 						public String table() {
 							return "";
 						}
+
 						@Override
 						public int initialValue() {
-							return 1;
+							return 0;
 						}
 
 						@Override

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

@@ -22,6 +22,7 @@ import org.hibernate.LockOptions;
 import org.hibernate.MappingException;
 import org.hibernate.boot.model.naming.Identifier;
 import org.hibernate.boot.model.relational.Database;
+import org.hibernate.boot.model.relational.InitCommand;
 import org.hibernate.boot.model.relational.Namespace;
 import org.hibernate.boot.model.relational.QualifiedName;
 import org.hibernate.boot.model.relational.QualifiedNameParser;
@@ -226,6 +227,8 @@ public class TableGenerator implements PersistentIdentifierGenerator, Configurab
 	 */
 	public static final String OPT_PARAM = "optimizer";
 
+	private boolean storeLastUsedValue;
+
 
 	private Type identifierType;
 
@@ -355,6 +358,8 @@ public class TableGenerator implements PersistentIdentifierGenerator, Configurab
 
 	@Override
 	public void configure(Type type, Properties params, ServiceRegistry serviceRegistry) throws MappingException {
+		storeLastUsedValue = serviceRegistry.getService( ConfigurationService.class )
+				.getSetting( AvailableSettings.TABLE_GENERATOR_STORE_LAST_USED, StandardConverters.BOOLEAN, true );
 		identifierType = type;
 
 		final JdbcEnvironment jdbcEnvironment = serviceRegistry.getService( JdbcEnvironment.class );
@@ -374,11 +379,12 @@ public class TableGenerator implements PersistentIdentifierGenerator, Configurab
 				params,
 				OptimizerFactory.determineImplicitOptimizerName( incrementSize, params )
 		);
+		int optimizerInitialValue = ConfigurationHelper.getInt( INITIAL_PARAM, params, -1 );
 		optimizer = OptimizerFactory.buildOptimizer(
 				optimizationStrategy,
 				identifierType.getReturnedClass(),
 				incrementSize,
-				ConfigurationHelper.getInt( INITIAL_PARAM, params, -1 )
+				optimizerInitialValue
 		);
 	}
 
@@ -542,6 +548,14 @@ public class TableGenerator implements PersistentIdentifierGenerator, Configurab
 		return "insert into " + renderedTableName + " (" + segmentColumnName + ", " + valueColumnName + ") " + " values (?,?)";
 	}
 
+	protected InitCommand generateInsertInitCommand() {
+		int value = initialValue;
+		if ( storeLastUsedValue ) {
+			value = initialValue - 1;
+		}
+		return new InitCommand( "insert into " + renderedTableName + "(" + segmentColumnName + ", " + valueColumnName + ")" + " values ('" + segmentValue + "'," + ( value ) + ")" );
+	}
+
 	private IntegralDataTypeHolder makeValue() {
 		return IdentifierGeneratorHelper.getIntegralDataTypeHolder( identifierType.getReturnedClass() );
 	}
@@ -574,7 +588,14 @@ public class TableGenerator implements PersistentIdentifierGenerator, Configurab
 												selectPS.setString( 1, segmentValue );
 												final ResultSet selectRS = executeQuery( selectPS, statsCollector );
 												if ( !selectRS.next() ) {
-													value.initialize( initialValue );
+													long initializationValue;
+													if ( storeLastUsedValue ) {
+														initializationValue = initialValue - 1;
+													}
+													else {
+														initializationValue = initialValue;
+													}
+													value.initialize( initializationValue );
 
 													try (PreparedStatement insertPS = prepareStatement(
 															connection,
@@ -589,7 +610,14 @@ public class TableGenerator implements PersistentIdentifierGenerator, Configurab
 													}
 												}
 												else {
-													value.initialize( selectRS, 1 );
+													int defaultValue;
+													if ( storeLastUsedValue ) {
+														defaultValue = 0;
+													}
+													else {
+														defaultValue = 1;
+													}
+													value.initialize( selectRS, defaultValue );
 												}
 												selectRS.close();
 											}
@@ -625,9 +653,13 @@ public class TableGenerator implements PersistentIdentifierGenerator, Configurab
 										while ( rows == 0 );
 
 										accessCount++;
-
+										if ( storeLastUsedValue ) {
+											return value.increment();
+										}
+										else {
 											return value;
 										}
+									}
 								},
 								true
 						);
@@ -734,10 +766,10 @@ public class TableGenerator implements PersistentIdentifierGenerator, Configurab
 				table.getQualifiedTableName(),
 				dialect
 		);
+		table.addInitCommand( generateInsertInitCommand() );
 
 		this.selectQuery = buildSelectQuery( dialect );
 		this.updateQuery = buildUpdateQuery();
 		this.insertQuery = buildInsertQuery();
-
 	}
 }

migration-guide.adoc

@@ -27,3 +27,11 @@ instead of zero-bade parameter binding to be consistent with JPA.  That can temp
 reverted by setting the `hibernate.query.sql.jdbc_style_params_base` setting to `true` which
 reverts to expecting zero-based binding.
 
+== Change in the `@TableGenerator` stored value
+
+In order to be compliant with JPA specifications, the value stored by Hibernate 5.3 in the Table used by the `javax.persistence.TableGenerator` is the last value generated.
+Previous versions of Hibernate instead stored the next value to be used.
+
+For backward compatibility a new setting, `hibernate.id.generator.stored_last_used`, has been introduced that gives the opportunity to fall back to the old Hibernate behaviour.
+Existing applications migrating to 5.3 and using @TableGenerator have to set `hibernate.id.generator.stored_last_used` to `false`.
+