org.hibernate/hibernate-core/4.3.11.Final : org/hibernate/id/enhanced/TableGenerator.java

TableGenerator
http://hibernate.org: The core O/RM functionality as provided by Hibernate (Hibernate.org)
GNU Lesser General Public License
The Hibernate Development Team (Hibernate.org)
/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2010, Red Hat Inc. or third-party contributors as
 * indicated by the @author tags or express copyright attribution
 * statements applied by the authors.  All third-party contributions are
 * distributed under license by Red Hat Inc.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 */
package org.hibernate.id.enhanced;

import java.io.Serializable;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Types;
import java.util.Collections;
import java.util.Map;
import java.util.Properties;

import org.hibernate.HibernateException;
import org.hibernate.LockMode;
import org.hibernate.LockOptions;
import org.hibernate.MappingException;
import org.hibernate.cfg.Environment;
import org.hibernate.cfg.ObjectNameNormalizer;
import org.hibernate.dialect.Dialect;
import org.hibernate.engine.jdbc.internal.FormatStyle;
import org.hibernate.engine.jdbc.spi.JdbcServices;
import org.hibernate.engine.jdbc.spi.SqlStatementLogger;
import org.hibernate.engine.spi.SessionEventListenerManager;
import org.hibernate.engine.spi.SessionImplementor;
import org.hibernate.id.Configurable;
import org.hibernate.id.IdentifierGeneratorHelper;
import org.hibernate.id.IntegralDataTypeHolder;
import org.hibernate.id.PersistentIdentifierGenerator;
import org.hibernate.internal.CoreMessageLogger;
import org.hibernate.internal.util.StringHelper;
import org.hibernate.internal.util.config.ConfigurationHelper;
import org.hibernate.jdbc.AbstractReturningWork;
import org.hibernate.mapping.Table;
import org.hibernate.type.Type;

import org.jboss.logging.Logger;

An enhanced version of table-based id generation.

Unlike the simplistic legacy one (which, btw, was only ever intended for subclassing
support) we "segment" the table into multiple values.  Thus a single table can
actually serve as the persistent storage for multiple independent generators.  One
approach would be to segment the values by the name of the entity for which we are
performing generation, which would mean that we would have a row in the generator
table for each entity name.  Or any configuration really; the setup is very flexible.
 In this respect it is very similar to the legacy MultipleHiLoPerTableGenerator in terms of the underlying storage structure (namely a single table capable of holding multiple generator values). The differentiator is, as with SequenceStyleGenerator as well, the externalized notion of an optimizer. 
NOTE that by default we use a single row for all generators (based on DEF_SEGMENT_VALUE). The configuration parameter CONFIG_PREFER_SEGMENT_PER_ENTITY can be used to change that to instead default to using a row for each entity name. 
Configuration parameters:

	 
    NAME
    DEFAULT
    DESCRIPTION
  
  
    TABLE_PARAM
    DEF_TABLE
    The name of the table to use to store/retrieve values
  
  
    VALUE_COLUMN_PARAM
    DEF_VALUE_COLUMN
    The name of column which holds the sequence value for the given segment
  
  
    SEGMENT_COLUMN_PARAM
    DEF_SEGMENT_COLUMN
    The name of the column which holds the segment key
  
  
    SEGMENT_VALUE_PARAM
    DEF_SEGMENT_VALUE
    The value indicating which segment is used by this generator; refers to values in the SEGMENT_COLUMN_PARAM column
  
  
    SEGMENT_LENGTH_PARAM
    DEF_SEGMENT_LENGTH
    The data length of the SEGMENT_COLUMN_PARAM column; used for schema creation
  
  
    INITIAL_PARAM
    DEFAULT_INITIAL_VALUE
    The initial value to be stored for the given segment
  
  
    INCREMENT_PARAM
    DEFAULT_INCREMENT_SIZE
    The increment size for the underlying segment; see the discussion on Optimizer for more details.
  
  
    OPT_PARAM
    depends on defined increment size
    Allows explicit definition of which optimization strategy to use
  

Author: Steve Ebersole/**
 * An enhanced version of table-based id generation.
 * <p/>
 * Unlike the simplistic legacy one (which, btw, was only ever intended for subclassing
 * support) we "segment" the table into multiple values.  Thus a single table can
 * actually serve as the persistent storage for multiple independent generators.  One
 * approach would be to segment the values by the name of the entity for which we are
 * performing generation, which would mean that we would have a row in the generator
 * table for each entity name.  Or any configuration really; the setup is very flexible.
 * <p/>
 * In this respect it is very similar to the legacy
 * {@link org.hibernate.id.MultipleHiLoPerTableGenerator} in terms of the
 * underlying storage structure (namely a single table capable of holding
 * multiple generator values).  The differentiator is, as with
 * {@link SequenceStyleGenerator} as well, the externalized notion
 * of an optimizer.
 * <p/>
 * <b>NOTE</b> that by default we use a single row for all generators (based
 * on {@link #DEF_SEGMENT_VALUE}).  The configuration parameter
 * {@link #CONFIG_PREFER_SEGMENT_PER_ENTITY} can be used to change that to
 * instead default to using a row for each entity name.
 * <p/>
 * Configuration parameters:
 * <table>
 * 	 <tr>
 *     <td><b>NAME</b></td>
 *     <td><b>DEFAULT</b></td>
 *     <td><b>DESCRIPTION</b></td>
 *   </tr>
 *   <tr>
 *     <td>{@link #TABLE_PARAM}</td>
 *     <td>{@link #DEF_TABLE}</td>
 *     <td>The name of the table to use to store/retrieve values</td>
 *   </tr>
 *   <tr>
 *     <td>{@link #VALUE_COLUMN_PARAM}</td>
 *     <td>{@link #DEF_VALUE_COLUMN}</td>
 *     <td>The name of column which holds the sequence value for the given segment</td>
 *   </tr>
 *   <tr>
 *     <td>{@link #SEGMENT_COLUMN_PARAM}</td>
 *     <td>{@link #DEF_SEGMENT_COLUMN}</td>
 *     <td>The name of the column which holds the segment key</td>
 *   </tr>
 *   <tr>
 *     <td>{@link #SEGMENT_VALUE_PARAM}</td>
 *     <td>{@link #DEF_SEGMENT_VALUE}</td>
 *     <td>The value indicating which segment is used by this generator; refers to values in the {@link #SEGMENT_COLUMN_PARAM} column</td>
 *   </tr>
 *   <tr>
 *     <td>{@link #SEGMENT_LENGTH_PARAM}</td>
 *     <td>{@link #DEF_SEGMENT_LENGTH}</td>
 *     <td>The data length of the {@link #SEGMENT_COLUMN_PARAM} column; used for schema creation</td>
 *   </tr>
 *   <tr>
 *     <td>{@link #INITIAL_PARAM}</td>
 *     <td>{@link #DEFAULT_INITIAL_VALUE}</td>
 *     <td>The initial value to be stored for the given segment</td>
 *   </tr>
 *   <tr>
 *     <td>{@link #INCREMENT_PARAM}</td>
 *     <td>{@link #DEFAULT_INCREMENT_SIZE}</td>
 *     <td>The increment size for the underlying segment; see the discussion on {@link Optimizer} for more details.</td>
 *   </tr>
 *   <tr>
 *     <td>{@link #OPT_PARAM}</td>
 *     <td><i>depends on defined increment size</i></td>
 *     <td>Allows explicit definition of which optimization strategy to use</td>
 *   </tr>
 * </table>
 *
 * @author Steve Ebersole
 */
public class TableGenerator implements PersistentIdentifierGenerator, Configurable {
	private static final CoreMessageLogger LOG = Logger.getMessageLogger(
			CoreMessageLogger.class,
			TableGenerator.class.getName()
	);

	By default (in the absence of a SEGMENT_VALUE_PARAM setting) we use a single row for all generators. This setting can be used to change that to instead default to using a row for each entity name. /**
	 * By default (in the absence of a {@link #SEGMENT_VALUE_PARAM} setting) we use a single row for all
	 * generators.  This setting can be used to change that to instead default to using a row for each entity name.
	 */
	public static final String CONFIG_PREFER_SEGMENT_PER_ENTITY = "prefer_entity_table_as_segment_value";

	Configures the name of the table to use. The default value is DEF_TABLE /**
	 * Configures the name of the table to use.  The default value is {@link #DEF_TABLE}
	 */
	public static final String TABLE_PARAM = "table_name";

	The default TABLE_PARAM value /**
	 * The default {@link #TABLE_PARAM} value
	 */
	public static final String DEF_TABLE = "hibernate_sequences";

	The name of column which holds the sequence value. The default value is DEF_VALUE_COLUMN /**
	 * The name of column which holds the sequence value.  The default value is {@link #DEF_VALUE_COLUMN}
	 */
	public static final String VALUE_COLUMN_PARAM = "value_column_name";

	The default VALUE_COLUMN_PARAM value /**
	 * The default {@link #VALUE_COLUMN_PARAM} value
	 */
	public static final String DEF_VALUE_COLUMN = "next_val";

	The name of the column which holds the segment key. The segment defines the different buckets (segments) of values currently tracked in the table. The default value is DEF_SEGMENT_COLUMN /**
	 * The name of the column which holds the segment key.  The segment defines the different buckets (segments)
	 * of values currently tracked in the table.  The default value is {@link #DEF_SEGMENT_COLUMN}
	 */
	public static final String SEGMENT_COLUMN_PARAM = "segment_column_name";

	The default SEGMENT_COLUMN_PARAM value /**
	 * The default {@link #SEGMENT_COLUMN_PARAM} value
	 */
	public static final String DEF_SEGMENT_COLUMN = "sequence_name";

	The value indicating which segment is used by this generator, as indicated by the actual value stored in the column indicated by SEGMENT_COLUMN_PARAM. The default value for setting is DEF_SEGMENT_VALUE, although CONFIG_PREFER_SEGMENT_PER_ENTITY effects the default as well. /**
	 * The value indicating which segment is used by this generator, as indicated by the actual value stored in the
	 * column indicated by {@link #SEGMENT_COLUMN_PARAM}.  The default value for setting is {@link #DEF_SEGMENT_VALUE},
	 * although {@link #CONFIG_PREFER_SEGMENT_PER_ENTITY} effects the default as well.
	 */
	public static final String SEGMENT_VALUE_PARAM = "segment_value";

	The default SEGMENT_VALUE_PARAM value, unless CONFIG_PREFER_SEGMENT_PER_ENTITY is specified /**
	 * The default {@link #SEGMENT_VALUE_PARAM} value, unless {@link #CONFIG_PREFER_SEGMENT_PER_ENTITY} is specified
	 */
	public static final String DEF_SEGMENT_VALUE = "default";

	Indicates the length of the column defined by SEGMENT_COLUMN_PARAM. Used in schema export. The default value is DEF_SEGMENT_LENGTH /**
	 * Indicates the length of the column defined by {@link #SEGMENT_COLUMN_PARAM}.  Used in schema export.  The
	 * default value is {@link #DEF_SEGMENT_LENGTH}
	 */
	public static final String SEGMENT_LENGTH_PARAM = "segment_value_length";

	The default SEGMENT_LENGTH_PARAM value /**
	 * The default {@link #SEGMENT_LENGTH_PARAM} value
	 */
	public static final int DEF_SEGMENT_LENGTH = 255;

	Indicates the initial value to use. The default value is DEFAULT_INITIAL_VALUE /**
	 * Indicates the initial value to use.  The default value is {@link #DEFAULT_INITIAL_VALUE}
	 */
	public static final String INITIAL_PARAM = "initial_value";

	The default INITIAL_PARAM value /**
	 * The default {@link #INITIAL_PARAM} value
	 */
	public static final int DEFAULT_INITIAL_VALUE = 1;

	Indicates the increment size to use. The default value is DEFAULT_INCREMENT_SIZE /**
	 * Indicates the increment size to use.  The default value is {@link #DEFAULT_INCREMENT_SIZE}
	 */
	public static final String INCREMENT_PARAM = "increment_size";

	The default INCREMENT_PARAM value /**
	 * The default {@link #INCREMENT_PARAM} value
	 */
	public static final int DEFAULT_INCREMENT_SIZE = 1;

	Indicates the optimizer to use, either naming a Optimizer implementation class or by naming a StandardOptimizerDescriptor by name /**
	 * Indicates the optimizer to use, either naming a {@link Optimizer} implementation class or by naming
	 * a {@link StandardOptimizerDescriptor} by name
	 */
	public static final String OPT_PARAM = "optimizer";


	private Type identifierType;

	private String tableName;

	private String segmentColumnName;
	private String segmentValue;
	private int segmentValueLength;

	private String valueColumnName;
	private int initialValue;
	private int incrementSize;

	private String selectQuery;
	private String insertQuery;
	private String updateQuery;

	private Optimizer optimizer;
	private long accessCount;

	@Override
	public Object generatorKey() {
		return tableName;
	}

	Type mapping for the identifier.
Returns: The identifier type mapping./**
	 * Type mapping for the identifier.
	 *
	 * @return The identifier type mapping.
	 */
	public final Type getIdentifierType() {
		return identifierType;
	}

	The name of the table in which we store this generator's persistent state.
Returns: The table name./**
	 * The name of the table in which we store this generator's persistent state.
	 *
	 * @return The table name.
	 */
	public final String getTableName() {
		return tableName;
	}

	The name of the column in which we store the segment to which each row
belongs.  The value here acts as PK.
Returns: The segment column name/**
	 * The name of the column in which we store the segment to which each row
	 * belongs.  The value here acts as PK.
	 *
	 * @return The segment column name
	 */
	public final String getSegmentColumnName() {
		return segmentColumnName;
	}

	The value in segment column which corresponding to this generator instance. In other words this value indicates the row in which this generator instance will store values. 
Returns: The segment value for this generator instance./**
	 * The value in {@link #getSegmentColumnName segment column} which
	 * corresponding to this generator instance.  In other words this value
	 * indicates the row in which this generator instance will store values.
	 *
	 * @return The segment value for this generator instance.
	 */
	public final String getSegmentValue() {
		return segmentValue;
	}

	The size of the segment column in the underlying table. 
NOTE : should really have been called 'segmentColumnLength' or
even better 'segmentColumnSize'
Returns: the column size./**
	 * The size of the {@link #getSegmentColumnName segment column} in the
	 * underlying table.
	 * <p/>
	 * <b>NOTE</b> : should really have been called 'segmentColumnLength' or
	 * even better 'segmentColumnSize'
	 *
	 * @return the column size.
	 */
	public final int getSegmentValueLength() {
		return segmentValueLength;
	}

	The name of the column in which we store our persistent generator value.
Returns: The name of the value column./**
	 * The name of the column in which we store our persistent generator value.
	 *
	 * @return The name of the value column.
	 */
	public final String getValueColumnName() {
		return valueColumnName;
	}

	The initial value to use when we find no previous state in the
generator table corresponding to our sequence.
Returns: The initial value to use./**
	 * The initial value to use when we find no previous state in the
	 * generator table corresponding to our sequence.
	 *
	 * @return The initial value to use.
	 */
	public final int getInitialValue() {
		return initialValue;
	}

	The amount of increment to use. The exact implications of this depends on the optimizer being used. 
Returns: The increment amount./**
	 * The amount of increment to use.  The exact implications of this
	 * depends on the {@link #getOptimizer() optimizer} being used.
	 *
	 * @return The increment amount.
	 */
	public final int getIncrementSize() {
		return incrementSize;
	}

	The optimizer being used by this generator.
Returns: Out optimizer./**
	 * The optimizer being used by this generator.
	 *
	 * @return Out optimizer.
	 */
	public final Optimizer getOptimizer() {
		return optimizer;
	}

	Getter for property 'tableAccessCount'.  Only really useful for unit test
assertions.
Returns: Value for property 'tableAccessCount'./**
	 * Getter for property 'tableAccessCount'.  Only really useful for unit test
	 * assertions.
	 *
	 * @return Value for property 'tableAccessCount'.
	 */
	public final long getTableAccessCount() {
		return accessCount;
	}

	@Override
	public void configure(Type type, Properties params, Dialect dialect) throws MappingException {
		identifierType = type;

		tableName = determineGeneratorTableName( params, dialect );
		segmentColumnName = determineSegmentColumnName( params, dialect );
		valueColumnName = determineValueColumnName( params, dialect );

		segmentValue = determineSegmentValue( params );

		segmentValueLength = determineSegmentColumnSize( params );
		initialValue = determineInitialValue( params );
		incrementSize = determineIncrementSize( params );

		this.selectQuery = buildSelectQuery( dialect );
		this.updateQuery = buildUpdateQuery();
		this.insertQuery = buildInsertQuery();

		// if the increment size is greater than one, we prefer pooled optimization; but we
		// need to see if the user prefers POOL or POOL_LO...
		final String defaultPooledOptimizerStrategy = ConfigurationHelper.getBoolean( Environment.PREFER_POOLED_VALUES_LO, params, false )
				? StandardOptimizerDescriptor.POOLED_LO.getExternalName()
				: StandardOptimizerDescriptor.POOLED.getExternalName();
		final String defaultOptimizerStrategy = incrementSize <= 1
				? StandardOptimizerDescriptor.NONE.getExternalName()
				: defaultPooledOptimizerStrategy;
		final String optimizationStrategy = ConfigurationHelper.getString( OPT_PARAM, params, defaultOptimizerStrategy );
		optimizer = OptimizerFactory.buildOptimizer(
				optimizationStrategy,
				identifierType.getReturnedClass(),
				incrementSize,
				ConfigurationHelper.getInt( INITIAL_PARAM, params, -1 )
		);
	}

	Determine the table name to use for the generator values.
 Called during configuration. 
Params: params – The params supplied in the generator config (plus some standard useful extras).
dialect – The dialect in effect
See Also: getTableName()
Returns: The table name to use./**
	 * Determine the table name to use for the generator values.
	 * <p/>
	 * Called during {@link #configure configuration}.
	 *
	 * @see #getTableName()
	 * @param params The params supplied in the generator config (plus some standard useful extras).
	 * @param dialect The dialect in effect
	 * @return The table name to use.
	 */
	protected String determineGeneratorTableName(Properties params, Dialect dialect) {
		String name = ConfigurationHelper.getString( TABLE_PARAM, params, DEF_TABLE );
		final boolean isGivenNameUnqualified = name.indexOf( '.' ) < 0;
		if ( isGivenNameUnqualified ) {
			final ObjectNameNormalizer normalizer = (ObjectNameNormalizer) params.get( IDENTIFIER_NORMALIZER );
			name = normalizer.normalizeIdentifierQuoting( name );
			// if the given name is un-qualified we may neen to qualify it
			final String schemaName = normalizer.normalizeIdentifierQuoting( params.getProperty( SCHEMA ) );
			final String catalogName = normalizer.normalizeIdentifierQuoting( params.getProperty( CATALOG ) );
			name = Table.qualify(
					dialect.quote( catalogName ),
					dialect.quote( schemaName ),
					dialect.quote( name)
			);
		}
		// if already qualified there is not much we can do in a portable manner so we pass it
		// through and assume the user has set up the name correctly.

		return name;
	}

	Determine the name of the column used to indicate the segment for each
row.  This column acts as the primary key.
 Called during configuration. 
Params: params – The params supplied in the generator config (plus some standard useful extras).
dialect – The dialect in effect
See Also: getSegmentColumnName()
Returns: The name of the segment column/**
	 * Determine the name of the column used to indicate the segment for each
	 * row.  This column acts as the primary key.
	 * <p/>
	 * Called during {@link #configure configuration}.
	 *
	 * @see #getSegmentColumnName()
	 * @param params The params supplied in the generator config (plus some standard useful extras).
	 * @param dialect The dialect in effect
	 * @return The name of the segment column
	 */
	protected String determineSegmentColumnName(Properties params, Dialect dialect) {
		final ObjectNameNormalizer normalizer = (ObjectNameNormalizer) params.get( IDENTIFIER_NORMALIZER );
		final String name = ConfigurationHelper.getString( SEGMENT_COLUMN_PARAM, params, DEF_SEGMENT_COLUMN );
		return dialect.quote( normalizer.normalizeIdentifierQuoting( name ) );
	}

	Determine the name of the column in which we will store the generator persistent value.
 Called during configuration. 
Params: params – The params supplied in the generator config (plus some standard useful extras).
dialect – The dialect in effect
See Also: getValueColumnName()
Returns: The name of the value column/**
	 * Determine the name of the column in which we will store the generator persistent value.
	 * <p/>
	 * Called during {@link #configure configuration}.
	 *
	 * @see #getValueColumnName()
	 * @param params The params supplied in the generator config (plus some standard useful extras).
	 * @param dialect The dialect in effect
	 * @return The name of the value column
	 */
	protected String determineValueColumnName(Properties params, Dialect dialect) {
		final ObjectNameNormalizer normalizer = (ObjectNameNormalizer) params.get( IDENTIFIER_NORMALIZER );
		final String name = ConfigurationHelper.getString( VALUE_COLUMN_PARAM, params, DEF_VALUE_COLUMN );
		return dialect.quote( normalizer.normalizeIdentifierQuoting( name ) );
	}

	Determine the segment value corresponding to this generator instance.
 Called during configuration. 
Params: params – The params supplied in the generator config (plus some standard useful extras).
See Also: getSegmentValue()
Returns: The name of the value column/**
	 * Determine the segment value corresponding to this generator instance.
	 * <p/>
	 * Called during {@link #configure configuration}.
	 *
	 * @see #getSegmentValue()
	 * @param params The params supplied in the generator config (plus some standard useful extras).
	 * @return The name of the value column
	 */
	protected String determineSegmentValue(Properties params) {
		String segmentValue = params.getProperty( SEGMENT_VALUE_PARAM );
		if ( StringHelper.isEmpty( segmentValue ) ) {
			segmentValue = determineDefaultSegmentValue( params );
		}
		return segmentValue;
	}

	Used in the cases where determineSegmentValue is unable to determine the value to use. 
Params: params – The params supplied in the generator config (plus some standard useful extras).
Returns: The default segment value to use./**
	 * Used in the cases where {@link #determineSegmentValue} is unable to
	 * determine the value to use.
	 *
	 * @param params The params supplied in the generator config (plus some standard useful extras).
	 * @return The default segment value to use.
	 */
	protected String determineDefaultSegmentValue(Properties params) {
		final boolean preferSegmentPerEntity = ConfigurationHelper.getBoolean( CONFIG_PREFER_SEGMENT_PER_ENTITY, params, false );
		final String defaultToUse = preferSegmentPerEntity ? params.getProperty( TABLE ) : DEF_SEGMENT_VALUE;
		LOG.usingDefaultIdGeneratorSegmentValue( tableName, segmentColumnName, defaultToUse );
		return defaultToUse;
	}

	Determine the size of the segment column 
 Called during configuration. 
Params: params – The params supplied in the generator config (plus some standard useful extras).
See Also: getSegmentValueLength()
Returns: The size of the segment column/**
	 * Determine the size of the {@link #getSegmentColumnName segment column}
	 * <p/>
	 * Called during {@link #configure configuration}.
	 *
	 * @see #getSegmentValueLength()
	 * @param params The params supplied in the generator config (plus some standard useful extras).
	 * @return The size of the segment column
	 */
	protected int determineSegmentColumnSize(Properties params) {
		return ConfigurationHelper.getInt( SEGMENT_LENGTH_PARAM, params, DEF_SEGMENT_LENGTH );
	}

	protected int determineInitialValue(Properties params) {
		return ConfigurationHelper.getInt( INITIAL_PARAM, params, DEFAULT_INITIAL_VALUE );
	}

	protected int determineIncrementSize(Properties params) {
		return ConfigurationHelper.getInt( INCREMENT_PARAM, params, DEFAULT_INCREMENT_SIZE );
	}

	protected String buildSelectQuery(Dialect dialect) {
		final String alias = "tbl";
		final String query = "select " + StringHelper.qualify( alias, valueColumnName ) +
				" from " + tableName + ' ' + alias +
				" where " + StringHelper.qualify( alias, segmentColumnName ) + "=?";
		final LockOptions lockOptions = new LockOptions( LockMode.PESSIMISTIC_WRITE );
		lockOptions.setAliasSpecificLockMode( alias, LockMode.PESSIMISTIC_WRITE );
		final Map updateTargetColumnsMap = Collections.singletonMap( alias, new String[] { valueColumnName } );
		return dialect.applyLocksToSql( query, lockOptions, updateTargetColumnsMap );
	}

	protected String buildUpdateQuery() {
		return "update " + tableName +
				" set " + valueColumnName + "=? " +
				" where " + valueColumnName + "=? and " + segmentColumnName + "=?";
	}

	protected String buildInsertQuery() {
		return "insert into " + tableName + " (" + segmentColumnName + ", " + valueColumnName + ") " + " values (?,?)";
	}

	private IntegralDataTypeHolder makeValue() {
		return IdentifierGeneratorHelper.getIntegralDataTypeHolder( identifierType.getReturnedClass() );
	}

	@Override
	public Serializable generate(final SessionImplementor session, final Object obj) {
		final SqlStatementLogger statementLogger = session.getFactory().getServiceRegistry()
				.getService( JdbcServices.class )
				.getSqlStatementLogger();
		final SessionEventListenerManager statsCollector = session.getEventListenerManager();

		return optimizer.generate(
				new AccessCallback() {
					@Override
					public IntegralDataTypeHolder getNextValue() {
						return session.getTransactionCoordinator().getTransaction().createIsolationDelegate().delegateWork(
								new AbstractReturningWork<IntegralDataTypeHolder>() {
									@Override
									public IntegralDataTypeHolder execute(Connection connection) throws SQLException {
										final IntegralDataTypeHolder value = makeValue();
										int rows;
										do {
											final PreparedStatement selectPS = prepareStatement( connection, selectQuery, statementLogger, statsCollector );

											try {
												selectPS.setString( 1, segmentValue );
												final ResultSet selectRS = executeQuery( selectPS, statsCollector );
												if ( !selectRS.next() ) {
													value.initialize( initialValue );

													final PreparedStatement insertPS = prepareStatement( connection, insertQuery, statementLogger, statsCollector );
													try {
														insertPS.setString( 1, segmentValue );
														value.bind( insertPS, 2 );
														executeUpdate( insertPS, statsCollector );
													}
													finally {
														insertPS.close();
													}
												}
												else {
													value.initialize( selectRS, 1 );
												}
												selectRS.close();
											}
											catch (SQLException e) {
												LOG.unableToReadOrInitHiValue( e );
												throw e;
											}
											finally {
												selectPS.close();
											}


											final PreparedStatement updatePS = prepareStatement( connection, updateQuery, statementLogger, statsCollector );
											try {
												final IntegralDataTypeHolder updateValue = value.copy();
												if ( optimizer.applyIncrementSizeToSourceValues() ) {
													updateValue.add( incrementSize );
												}
												else {
													updateValue.increment();
												}
												updateValue.bind( updatePS, 1 );
												value.bind( updatePS, 2 );
												updatePS.setString( 3, segmentValue );
												rows = executeUpdate( updatePS, statsCollector );
											}
											catch (SQLException e) {
												LOG.unableToUpdateQueryHiValue( tableName, e );
												throw e;
											}
											finally {
												updatePS.close();
											}
										}
										while ( rows == 0 );

										accessCount++;

										return value;
									}
								},
								true
						);
					}

					@Override
					public String getTenantIdentifier() {
						return session.getTenantIdentifier();
					}
				}
		);
	}

	private PreparedStatement prepareStatement(
			Connection connection,
			String sql,
			SqlStatementLogger statementLogger,
			SessionEventListenerManager statsCollector) throws SQLException {
		statementLogger.logStatement( sql, FormatStyle.BASIC.getFormatter() );
		try {
			statsCollector.jdbcPrepareStatementStart();
			return connection.prepareStatement( sql );
		}
		finally {
			statsCollector.jdbcPrepareStatementEnd();
		}
	}

	private int executeUpdate(PreparedStatement ps, SessionEventListenerManager statsCollector) throws SQLException {
		try {
			statsCollector.jdbcExecuteStatementStart();
			return ps.executeUpdate();
		}
		finally {
			statsCollector.jdbcExecuteStatementEnd();
		}

	}

	private ResultSet executeQuery(PreparedStatement ps, SessionEventListenerManager statsCollector) throws SQLException {
		try {
			statsCollector.jdbcExecuteStatementStart();
			return ps.executeQuery();
		}
		finally {
			statsCollector.jdbcExecuteStatementEnd();
		}
	}

	@Override
	public String[] sqlCreateStrings(Dialect dialect) throws HibernateException {
		return new String[] {
				dialect.getCreateTableString() + ' ' + tableName + " ( "
						+ segmentColumnName + ' ' + dialect.getTypeName( Types.VARCHAR, segmentValueLength, 0, 0 ) + " not null "
						+ ", " + valueColumnName + ' ' + dialect.getTypeName( Types.BIGINT )
						+ ", primary key ( " + segmentColumnName + " ) )" + dialect.getTableTypeString()
		};
	}

	@Override
	public String[] sqlDropStrings(Dialect dialect) throws HibernateException {
		return new String[] { dialect.getDropTableString( tableName ) };
	}
}
NAME	DEFAULT	DESCRIPTION
`TABLE_PARAM`	`DEF_TABLE`	The name of the table to use to store/retrieve values
`VALUE_COLUMN_PARAM`	`DEF_VALUE_COLUMN`	The name of column which holds the sequence value for the given segment
`SEGMENT_COLUMN_PARAM`	`DEF_SEGMENT_COLUMN`	The name of the column which holds the segment key
`SEGMENT_VALUE_PARAM`	`DEF_SEGMENT_VALUE`	The value indicating which segment is used by this generator; refers to values in the `SEGMENT_COLUMN_PARAM` column
`SEGMENT_LENGTH_PARAM`	`DEF_SEGMENT_LENGTH`	The data length of the `SEGMENT_COLUMN_PARAM` column; used for schema creation
`INITIAL_PARAM`	`DEFAULT_INITIAL_VALUE`	The initial value to be stored for the given segment
`INCREMENT_PARAM`	`DEFAULT_INCREMENT_SIZE`	The increment size for the underlying segment; see the discussion on `Optimizer` for more details.
`OPT_PARAM`	depends on defined increment size	Allows explicit definition of which optimization strategy to use
Params:	params – The params supplied in the generator config (plus some standard useful extras). dialect – The dialect in effect
See Also:	getTableName()
Returns:	The table name to use.
/

org.hibernate/ hibernate-core/ 4.3.11.Final/ org/hibernate/id/enhanced/TableGenerator.java
