HHH-6736 Added support for SELECT ... FOR UPDATE SKIP LOCKED

documentation/src/main/docbook/devguide/en-US/Locking.xml

@@ -263,6 +263,11 @@
               <entry><para>acquired upon explicit user request using a <code>SELECT ... FOR UPDATE NOWAIT</code> in
               Oracle.</para></entry>
             </row>
+            <row>
+              <entry>LockMode.UPGRADE_SKIPLOCKED</entry>
+              <entry><para>acquired upon explicit user request using a <code>SELECT ... FOR UPDATE SKIP LOCKED</code> in
+              Oracle, or <code>SELECT ... with (rowlock,updlock,readpast) in SQL Server</code>.</para></entry>
+            </row>
             <row>
               <entry>LockMode.READ</entry>
               <entry><para>acquired automatically when Hibernate reads data under <phrase>Repeatable Read</phrase> or
@@ -299,17 +304,18 @@
         </listitem>
       </itemizedlist>
       <para>
-        If you call <methodname>Session.load()</methodname> with option <option>UPGRADE</option> or
+        If you call <methodname>Session.load()</methodname> with option <option>UPGRADE</option>,
-        <option>UPGRADE_NOWAIT</option>, and the requested object is not already loaded by the session, the object is
+        <option>UPGRADE_NOWAIT</option> or <option>UPGRADE_SKIPLOCKED</option>, and the requested object is not already
-        loaded using <code>SELECT ... FOR UPDATE</code>. If you call <methodname>load()</methodname> for an object that
+        loaded by the session, the object is loaded using <code>SELECT ... FOR UPDATE</code>. If you call 
-        is already loaded with a less restrictive lock than the one you request, Hibernate calls
+        <methodname>load()</methodname> for an object that is already loaded with a less restrictive lock than the one 
-        <methodname>lock()</methodname> for that object.
+        you request, Hibernate calls <methodname>lock()</methodname> for that object.
       </para>
       <para>
         <methodname>Session.lock()</methodname> performs a version number check if the specified lock mode is
-        <literal>READ</literal>, <literal>UPGRADE</literal>, or <literal>UPGRADE_NOWAIT</literal>. In the case of
+        <literal>READ</literal>, <literal>UPGRADE</literal>, <literal>UPGRADE_NOWAIT</literal> or 
-        <literal>UPGRADE</literal> or <literal>UPGRADE_NOWAIT</literal>, <code>SELECT ... FOR UPDATE</code> syntax is
+        <literal>UPGRADE_SKIPLOCKED</literal>. In the case of <literal>UPGRADE</literal>, 
-        used.
+        <literal>UPGRADE_NOWAIT</literal> or <literal>UPGRADE_SKIPLOCKED</literal>, <code>SELECT ... FOR UPDATE</code> 
+	syntax is used.
       </para>
       <para>
         If the requested lock mode is not supported by the database, Hibernate uses an appropriate alternate mode

hibernate-core/src/main/java/org/hibernate/LockMode.java

@@ -66,6 +66,15 @@ public enum LockMode {
 	 * <tt>UPGRADE</tt>.
 	 */
 	UPGRADE_NOWAIT( 10 ),
+
+	/**
+	 * Attempt to obtain an upgrade lock, using an Oracle-style
+	 * <tt>select for update skip locked</tt>. The semantics of
+	 * this lock mode, once obtained, are the same as
+	 * <tt>UPGRADE</tt>.
+	 */
+	UPGRADE_SKIPLOCKED( 10 ),
+
 	/**
 	 * A <tt>WRITE</tt> lock is obtained when an object is updated
 	 * or inserted.   This lock mode is for internal use only and is

hibernate-core/src/main/java/org/hibernate/LockOptions.java

@@ -64,6 +64,12 @@ public class LockOptions implements Serializable {
 	 */
 	public static final int WAIT_FOREVER = -1;
 
+	/**
+	 * Indicates that rows that are already locked should be skipped.
+	 * @see #getTimeOut()
+	 */
+	public static final int SKIP_LOCKED = -2;
+
 	private LockMode lockMode = LockMode.NONE;
 	private int timeout = WAIT_FOREVER;
 
@@ -221,9 +227,9 @@ public class LockOptions implements Serializable {
 	 * The timeout is the amount of time, in milliseconds, we should instruct the database
 	 * to wait for any requested pessimistic lock acquisition.
 	 * <p/>
-	 * {@link #NO_WAIT} and {@link #WAIT_FOREVER} represent 2 "magic" values.
+	 * {@link #NO_WAIT}, {@link #WAIT_FOREVER} or {@link #SKIP_LOCKED} represent 3 "magic" values.
 	 *
-	 * @return timeout in milliseconds, or {@link #NO_WAIT} or {@link #WAIT_FOREVER}
+	 * @return timeout in milliseconds, {@link #NO_WAIT}, {@link #WAIT_FOREVER} or {@link #SKIP_LOCKED}
 	 */
 	public int getTimeOut() {
 		return timeout;

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

@@ -375,6 +375,9 @@ public abstract class ResultSetMappingBinder {
 		else if ( "upgrade-nowait".equals( lockMode ) ) {
 			return LockMode.UPGRADE_NOWAIT;
 		}
+		else if ( "upgrade-skiplocked".equals( lockMode )) {
+			return LockMode.UPGRADE_SKIPLOCKED;
+		}
 		else if ( "write".equals( lockMode ) ) {
 			return LockMode.WRITE;
 		}

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

@@ -23,40 +23,14 @@
  */
 package org.hibernate.dialect;
 
-import java.io.InputStream;
-import java.io.OutputStream;
-import java.sql.Blob;
-import java.sql.CallableStatement;
-import java.sql.Clob;
-import java.sql.NClob;
-import java.sql.ResultSet;
-import java.sql.SQLException;
-import java.sql.Types;
-import java.util.HashMap;
-import java.util.HashSet;
-import java.util.Iterator;
-import java.util.Map;
-import java.util.Properties;
-import java.util.Set;
-
 import org.hibernate.HibernateException;
 import org.hibernate.LockMode;
 import org.hibernate.LockOptions;
 import org.hibernate.MappingException;
 import org.hibernate.NullPrecedence;
 import org.hibernate.cfg.Environment;
-import org.hibernate.dialect.function.CastFunction;
+import org.hibernate.dialect.function.*;
-import org.hibernate.dialect.function.SQLFunction;
+import org.hibernate.dialect.lock.*;
-import org.hibernate.dialect.function.SQLFunctionTemplate;
-import org.hibernate.dialect.function.StandardAnsiSqlAggregationFunctions;
-import org.hibernate.dialect.function.StandardSQLFunction;
-import org.hibernate.dialect.lock.LockingStrategy;
-import org.hibernate.dialect.lock.OptimisticForceIncrementLockingStrategy;
-import org.hibernate.dialect.lock.OptimisticLockingStrategy;
-import org.hibernate.dialect.lock.PessimisticForceIncrementLockingStrategy;
-import org.hibernate.dialect.lock.PessimisticReadSelectLockingStrategy;
-import org.hibernate.dialect.lock.PessimisticWriteSelectLockingStrategy;
-import org.hibernate.dialect.lock.SelectLockingStrategy;
 import org.hibernate.dialect.pagination.LegacyLimitHandler;
 import org.hibernate.dialect.pagination.LimitHandler;
 import org.hibernate.dialect.unique.DefaultUniqueDelegate;
@@ -78,16 +52,17 @@ import org.hibernate.internal.util.collections.ArrayHelper;
 import org.hibernate.internal.util.io.StreamCopier;
 import org.hibernate.mapping.Column;
 import org.hibernate.persister.entity.Lockable;
-import org.hibernate.sql.ANSICaseFragment;
+import org.hibernate.sql.*;
-import org.hibernate.sql.ANSIJoinFragment;
-import org.hibernate.sql.CaseFragment;
-import org.hibernate.sql.ForUpdateFragment;
-import org.hibernate.sql.JoinFragment;
 import org.hibernate.type.StandardBasicTypes;
 import org.hibernate.type.descriptor.sql.ClobTypeDescriptor;
 import org.hibernate.type.descriptor.sql.SqlTypeDescriptor;
 import org.jboss.logging.Logger;
 
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.sql.*;
+import java.util.*;
+
 /**
  * Represents a dialect of SQL implemented by a particular RDBMS.
  * Subclasses implement Hibernate compatibility with different systems.<br>
@@ -1195,6 +1170,8 @@ public abstract class Dialect implements ConversionContext {
             case FORCE:
             case PESSIMISTIC_FORCE_INCREMENT:
                 return getForUpdateNowaitString();
+            case UPGRADE_SKIPLOCKED:
+                return getForUpdateSkipLockedString();
             default:
                 return "";
         }
@@ -1313,6 +1290,16 @@ public abstract class Dialect implements ConversionContext {
 		return getForUpdateString();
 	}
 
+	/**
+	* Retrieves the <tt>FOR UPDATE SKIP LOCKED</tt> syntax specific to this dialect.
+	*
+	* @return The appropriate <tt>FOR UPDATE SKIP LOCKED</tt> clause string.
+	*/
+	public String getForUpdateSkipLockedString() {
+		// by default we report no support for SKIP_LOCKED lock semantics
+		return getForUpdateString();
+	}
+
 	/**
 	 * Get the <tt>FOR UPDATE OF column_list NOWAIT</tt> fragment appropriate
 	 * for this dialect given the aliases of the columns to be write locked.
@@ -1324,6 +1311,17 @@ public abstract class Dialect implements ConversionContext {
 		return getForUpdateString( aliases );
 	}
 
+ 	/**
+	 * Get the <tt>FOR UPDATE OF column_list SKIP LOCKED</tt> fragment appropriate
+	 * for this dialect given the aliases of the columns to be write locked.
+	 *
+	 * @param aliases The columns to be write locked.
+	 * @return The appropriate <tt>FOR UPDATE colunm_list SKIP LOCKED</tt> clause string.
+	 */
+	public String getForUpdateSkipLockedString(String aliases) {
+		return getForUpdateString( aliases );
+	}
+
 	/**
 	 * Some dialects support an alternative means to <tt>SELECT FOR UPDATE</tt>,
 	 * whereby a "lock hint" is appends to the table name in the from clause.

hibernate-core/src/main/java/org/hibernate/dialect/Oracle10gDialect.java

@@ -22,6 +22,7 @@
  * Boston, MA  02110-1301  USA
  */
 package org.hibernate.dialect;
+import org.hibernate.LockOptions;
 import org.hibernate.sql.ANSIJoinFragment;
 import org.hibernate.sql.JoinFragment;
 
@@ -45,4 +46,21 @@ public class Oracle10gDialect extends Oracle9iDialect {
 	public JoinFragment createOuterJoinFragment() {
 		return new ANSIJoinFragment();
 	}
+
+	public String getWriteLockString(int timeout) {
+		if ( timeout == LockOptions.SKIP_LOCKED ) {
+			return  getForUpdateSkipLockedString();
+		}
+		else {
+			return super.getWriteLockString(timeout);
+		}
+	}
+
+	public String getForUpdateSkipLockedString() {
+		return " for update skip locked";
+	}
+
+	public String getForUpdateSkipLockedString(String aliases) {
+		return getForUpdateString() + " of " + aliases + " skip locked";
+	}
 }

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

@@ -134,6 +134,8 @@ public class SQLServerDialect extends AbstractTransactSQLDialect {
 				return tableName + " with (updlock, rowlock)";
 			case PESSIMISTIC_READ:
 				return tableName + " with (holdlock, rowlock)";
+            case UPGRADE_SKIPLOCKED:
+                return tableName + " with (updlock, rowlock, readpast)";
 			default:
 				return tableName;
 		}

hibernate-core/src/main/java/org/hibernate/dialect/lock/AbstractSelectLockingStrategy.java

@@ -54,11 +54,18 @@ public abstract class AbstractSelectLockingStrategy implements LockingStrategy {
 	protected abstract String generateLockString(int lockTimeout);
 
 	protected String determineSql(int timeout) {
-		return timeout == LockOptions.WAIT_FOREVER
+		if ( timeout == LockOptions.WAIT_FOREVER) {
-				? waitForeverSql
+			return waitForeverSql;
-				: timeout == LockOptions.NO_WAIT
+		}
-						? getNoWaitSql()
+		else if ( timeout == LockOptions.NO_WAIT) {
-						: generateLockString( timeout );
+			return getNoWaitSql();
+		}
+		else if ( timeout == LockOptions.SKIP_LOCKED) {
+			return getSkipLockedSql();
+		}
+		else {
+			return generateLockString( timeout );
+		}
 	}
 
 	private String noWaitSql;
@@ -69,4 +76,13 @@ public abstract class AbstractSelectLockingStrategy implements LockingStrategy {
 		}
 		return noWaitSql;
 	}
+
+	private String skipLockedSql;
+
+	public String getSkipLockedSql() {
+		if ( skipLockedSql == null ) {
+			skipLockedSql = generateLockString( LockOptions.SKIP_LOCKED );
+		}
+		return skipLockedSql;
+	}
 }

hibernate-core/src/main/java/org/hibernate/internal/util/LockModeConverter.java

@@ -57,7 +57,8 @@ public class LockModeConverter {
 		}
 		else if ( lockMode == LockMode.PESSIMISTIC_WRITE
 				|| lockMode == LockMode.UPGRADE
-				|| lockMode == LockMode.UPGRADE_NOWAIT ) {
+				|| lockMode == LockMode.UPGRADE_NOWAIT
+                || lockMode == LockMode.UPGRADE_SKIPLOCKED) {
 			return LockModeType.PESSIMISTIC_WRITE;
 		}
 		else if ( lockMode == LockMode.PESSIMISTIC_FORCE_INCREMENT

hibernate-core/src/main/java/org/hibernate/loader/Loader.java

@@ -254,22 +254,24 @@ public abstract class Loader {
 			Dialect dialect,
 			List<AfterLoadAction> afterLoadActions) {
 		if ( dialect.useFollowOnLocking() ) {
-			LOG.usingFollowOnLocking();
 			// currently only one lock mode is allowed in follow-on locking
 			final LockMode lockMode = determineFollowOnLockMode( parameters.getLockOptions() );
 			final LockOptions lockOptions = new LockOptions( lockMode );
-			lockOptions.setTimeOut( parameters.getLockOptions().getTimeOut() );
+			if ( lockOptions.getLockMode() != LockMode.UPGRADE_SKIPLOCKED ) {
-			lockOptions.setScope( parameters.getLockOptions().getScope() );
+				LOG.usingFollowOnLocking();
-			afterLoadActions.add(
+				lockOptions.setTimeOut( parameters.getLockOptions().getTimeOut() );
-					new AfterLoadAction() {
+				lockOptions.setScope( parameters.getLockOptions().getScope() );
-						@Override
+				afterLoadActions.add(
-						public void afterLoad(SessionImplementor session, Object entity, Loadable persister) {
+						new AfterLoadAction() {
-							( (Session) session ).buildLockRequest( lockOptions ).lock( persister.getEntityName(), entity );
+							@Override
+							public void afterLoad(SessionImplementor session, Object entity, Loadable persister) {
+								( (Session) session ).buildLockRequest( lockOptions ).lock( persister.getEntityName(), entity );
+							}
 						}
-					}
+				);
-			);
+				parameters.setLockOptions( new LockOptions() );
-			parameters.setLockOptions( new LockOptions() );
+				return true;
-			return true;
+			}
 		}
 		return false;
 	}

hibernate-core/src/main/java/org/hibernate/loader/criteria/CriteriaLoader.java

@@ -205,27 +205,28 @@ public class CriteriaLoader extends OuterJoinLoader {
 		}
 
 		if ( dialect.useFollowOnLocking() ) {
-			// Dialect prefers to perform locking in a separate step
+            final LockMode lockMode = determineFollowOnLockMode( lockOptions );
-			LOG.usingFollowOnLocking();
+            if( lockMode != LockMode.UPGRADE_SKIPLOCKED ) {
+				// Dialect prefers to perform locking in a separate step
+				LOG.usingFollowOnLocking();
 
-			final LockMode lockMode = determineFollowOnLockMode( lockOptions );
+				final LockOptions lockOptionsToUse = new LockOptions( lockMode );
-			final LockOptions lockOptionsToUse = new LockOptions( lockMode );
+				lockOptionsToUse.setTimeOut( lockOptions.getTimeOut() );
-			lockOptionsToUse.setTimeOut( lockOptions.getTimeOut() );
+				lockOptionsToUse.setScope( lockOptions.getScope() );
-			lockOptionsToUse.setScope( lockOptions.getScope() );
 
-			afterLoadActions.add(
+				afterLoadActions.add(
-					new AfterLoadAction() {
+						new AfterLoadAction() {
-						@Override
+								@Override
-						public void afterLoad(SessionImplementor session, Object entity, Loadable persister) {
+								public void afterLoad(SessionImplementor session, Object entity, Loadable persister) {
-							( (Session) session ).buildLockRequest( lockOptionsToUse )
+									( (Session) session ).buildLockRequest( lockOptionsToUse )
-									.lock( persister.getEntityName(), entity );
+										.lock( persister.getEntityName(), entity );
-						}
+								}
-					}
+				        }
-			);
+				);
-			parameters.setLockOptions( new LockOptions() );
+				parameters.setLockOptions( new LockOptions() );
-			return sql;
+				return sql;
+			}
 		}
-
 		final LockOptions locks = new LockOptions(lockOptions.getLockMode());
 		locks.setScope( lockOptions.getScope());
 		locks.setTimeOut( lockOptions.getTimeOut());

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

@@ -1910,6 +1910,7 @@ public abstract class AbstractEntityPersister
 		lockers.put( LockMode.READ, generateLocker( LockMode.READ ) );
 		lockers.put( LockMode.UPGRADE, generateLocker( LockMode.UPGRADE ) );
 		lockers.put( LockMode.UPGRADE_NOWAIT, generateLocker( LockMode.UPGRADE_NOWAIT ) );
+		lockers.put( LockMode.UPGRADE_SKIPLOCKED, generateLocker( LockMode.UPGRADE_SKIPLOCKED ) );
 		lockers.put( LockMode.FORCE, generateLocker( LockMode.FORCE ) );
 		lockers.put( LockMode.PESSIMISTIC_READ, generateLocker( LockMode.PESSIMISTIC_READ ) );
 		lockers.put( LockMode.PESSIMISTIC_WRITE, generateLocker( LockMode.PESSIMISTIC_WRITE ) );
@@ -3851,6 +3852,12 @@ public abstract class AbstractEntityPersister
 						readLoader :
 						createEntityLoader( LockMode.UPGRADE_NOWAIT )
 			);
+		loaders.put(
+				LockMode.UPGRADE_SKIPLOCKED,
+				disableForUpdate ?
+						readLoader :
+						createEntityLoader( LockMode.UPGRADE_SKIPLOCKED )
+			);
 		loaders.put(
 				LockMode.FORCE,
 				disableForUpdate ?

hibernate-core/src/main/java/org/hibernate/sql/ForUpdateFragment.java

@@ -39,6 +39,7 @@ import org.hibernate.internal.util.StringHelper;
 public class ForUpdateFragment {
 	private final StringBuilder aliases = new StringBuilder();
 	private boolean isNowaitEnabled;
+	private boolean isSkipLockedEnabled;
 	private final Dialect dialect;
 	private LockMode lockMode;
 	private LockOptions lockOptions;
@@ -89,6 +90,10 @@ public class ForUpdateFragment {
 		if ( upgradeType == LockMode.UPGRADE_NOWAIT ) {
 			setNowaitEnabled( true );
 		}
+
+		if ( upgradeType == LockMode.UPGRADE_SKIPLOCKED ) {
+			setSkipLockedEnabled( true );
+		}
 	}
 
 	public ForUpdateFragment addTableAlias(String alias) {
@@ -110,13 +115,25 @@ public class ForUpdateFragment {
 			return "";
 		}
 		// TODO:  pass lockmode
-		return isNowaitEnabled ?
+		if(isNowaitEnabled) {
-				dialect.getForUpdateNowaitString( aliases.toString() ) :
+			return dialect.getForUpdateNowaitString( aliases.toString() );
-				dialect.getForUpdateString( aliases.toString() );
+		}
+		else if (isSkipLockedEnabled) {
+			return dialect.getForUpdateSkipLockedString( aliases.toString() );
+		}
+		else {
+			return dialect.getForUpdateString( aliases.toString() );
+		}
 	}
 
 	public ForUpdateFragment setNowaitEnabled(boolean nowait) {
 		isNowaitEnabled = nowait;
 		return this;
 	}
+
+	public ForUpdateFragment setSkipLockedEnabled(boolean skipLocked) {
+		isSkipLockedEnabled = skipLocked;
+		return this;
+	}
+
 }

hibernate-core/src/main/resources/org/hibernate/hibernate-mapping-3.0.dtd

@@ -993,7 +993,7 @@ finder methods for named queries -->
 	<!ATTLIST return alias CDATA #IMPLIED>
 	<!ATTLIST return entity-name CDATA #IMPLIED>
 	<!ATTLIST return class CDATA #IMPLIED>
-	<!ATTLIST return lock-mode (none|read|upgrade|upgrade-nowait|write) "read">	
+	<!ATTLIST return lock-mode (none|read|upgrade|upgrade-nowait|upgrade-skiplocked|write) "read">	
 
 <!ELEMENT return-property (return-column*)> 
 	<!ATTLIST return-property name CDATA #REQUIRED>
@@ -1008,12 +1008,12 @@ finder methods for named queries -->
 <!ELEMENT return-join (return-property)*> 
 	<!ATTLIST return-join alias CDATA #REQUIRED>
 	<!ATTLIST return-join property CDATA #REQUIRED>
-	<!ATTLIST return-join lock-mode (none|read|upgrade|upgrade-nowait|write) "read">
+	<!ATTLIST return-join lock-mode (none|read|upgrade|upgrade-nowait|upgrade-skiplocked|write) "read">
 
 <!ELEMENT load-collection (return-property)*> 
 	<!ATTLIST load-collection alias CDATA #REQUIRED>
 	<!ATTLIST load-collection role CDATA #REQUIRED>
-	<!ATTLIST load-collection lock-mode (none|read|upgrade|upgrade-nowait|write) "read">
+	<!ATTLIST load-collection lock-mode (none|read|upgrade|upgrade-nowait|upgrade-skiplocked|write) "read">
 
 <!ELEMENT return-scalar EMPTY>
 	<!ATTLIST return-scalar column CDATA #REQUIRED>

hibernate-core/src/main/resources/org/hibernate/hibernate-mapping-4.0.xsd

@@ -1785,6 +1785,7 @@ arbitrary number of queries, and import declarations of arbitrary classes.
       <xs:enumeration value="read"/>
       <xs:enumeration value="upgrade"/>
       <xs:enumeration value="upgrade-nowait"/>
+      <xs:enumeration value="upgrade-skiplocked"/>
       <xs:enumeration value="write"/>
     </xs:restriction>
   </xs:simpleType>

hibernate-core/src/test/java/org/hibernate/test/legacy/ParentChildTest.java

@@ -1098,10 +1098,13 @@ public class ParentChildTest extends LegacyTestCase {
 		s3.setCount(3);
 		Simple s4 = new Simple( Long.valueOf(4) );
 		s4.setCount(4);
+		Simple s5 = new Simple( Long.valueOf(5) );
+		s5.setCount(5);
 		s.save( s1 );
 		s.save( s2 );
 		s.save( s3 );
 		s.save( s4 );
+		s.save( s5 );
 		assertTrue( s.getCurrentLockMode(s1)==LockMode.WRITE );
 		tx.commit();
 		s.close();
@@ -1116,6 +1119,8 @@ public class ParentChildTest extends LegacyTestCase {
 		assertTrue( s.getCurrentLockMode(s3)==LockMode.UPGRADE );
 		s4 = (Simple) s.get(Simple.class, new Long(4), LockMode.UPGRADE_NOWAIT);
 		assertTrue( s.getCurrentLockMode(s4)==LockMode.UPGRADE_NOWAIT );
+		s5 = (Simple) s.get(Simple.class, new Long(5), LockMode.UPGRADE_SKIPLOCKED);
+		assertTrue( s.getCurrentLockMode(s5)==LockMode.UPGRADE_SKIPLOCKED );
 
 		s1 = (Simple) s.load(Simple.class, new Long(1), LockMode.UPGRADE); //upgrade
 		assertTrue( s.getCurrentLockMode(s1)==LockMode.UPGRADE );
@@ -1125,6 +1130,8 @@ public class ParentChildTest extends LegacyTestCase {
 		assertTrue( s.getCurrentLockMode(s3)==LockMode.UPGRADE );
 		s4 = (Simple) s.load(Simple.class, new Long(4), LockMode.UPGRADE);
 		assertTrue( s.getCurrentLockMode(s4)==LockMode.UPGRADE_NOWAIT );
+		s5 = (Simple) s.load(Simple.class, new Long(5), LockMode.UPGRADE);
+		assertTrue( s.getCurrentLockMode(s5)==LockMode.UPGRADE_SKIPLOCKED );
 
 		s.lock(s2, LockMode.UPGRADE); //upgrade
 		assertTrue( s.getCurrentLockMode(s2)==LockMode.UPGRADE );
@@ -1132,7 +1139,9 @@ public class ParentChildTest extends LegacyTestCase {
 		assertTrue( s.getCurrentLockMode(s3)==LockMode.UPGRADE );
 		s.lock(s1, LockMode.UPGRADE_NOWAIT);
 		s.lock(s4, LockMode.NONE);
+		s.lock(s5, LockMode.UPGRADE_SKIPLOCKED);
 		assertTrue( s.getCurrentLockMode(s4)==LockMode.UPGRADE_NOWAIT );
+		assertTrue( s.getCurrentLockMode(s5)==LockMode.UPGRADE_SKIPLOCKED );
 
 		tx.commit();
 		tx = s.beginTransaction();
@@ -1141,6 +1150,7 @@ public class ParentChildTest extends LegacyTestCase {
 		assertTrue( s.getCurrentLockMode(s1)==LockMode.NONE );
 		assertTrue( s.getCurrentLockMode(s2)==LockMode.NONE );
 		assertTrue( s.getCurrentLockMode(s4)==LockMode.NONE );
+		assertTrue( s.getCurrentLockMode(s5)==LockMode.NONE );
 
 		s.lock(s1, LockMode.READ); //upgrade
 		assertTrue( s.getCurrentLockMode(s1)==LockMode.READ );
@@ -1162,8 +1172,9 @@ public class ParentChildTest extends LegacyTestCase {
 		assertTrue( s.getCurrentLockMode(s1)==LockMode.NONE );
 		assertTrue( s.getCurrentLockMode(s2)==LockMode.NONE );
 		assertTrue( s.getCurrentLockMode(s4)==LockMode.NONE );
+		assertTrue( s.getCurrentLockMode(s5)==LockMode.NONE );
 
-		s.delete(s1); s.delete(s2); s.delete(s3); s.delete(s4);
+		s.delete(s1); s.delete(s2); s.delete(s3); s.delete(s4); s.delete(s5);
 		tx.commit();
 		s.close();
 	}

hibernate-entitymanager/src/main/java/org/hibernate/jpa/spi/AbstractEntityManagerImpl.java

@@ -285,7 +285,10 @@ public abstract class AbstractEntityManagerImpl implements HibernateEntityManage
 			throw new PersistenceException( "Unable to parse " + AvailableSettings.LOCK_TIMEOUT + ": " + lockTimeout );
 		}
 		if ( timeoutSet ) {
-			if ( timeout < 0 ) {
+            if ( timeout == LockOptions.SKIP_LOCKED ) {
+                options.setTimeOut( LockOptions.SKIP_LOCKED );
+            }
+			else if ( timeout < 0 ) {
 				options.setTimeOut( LockOptions.WAIT_FOREVER );
 			}
 			else if ( timeout == 0 ) {