HHH-8961 Reduce allocation cost of org.hibernate.cache.spi.CacheKey instances

Remove tenantId field from CacheKey: use a different type when tenants are needed.
Also remove the Type as we should be able to rely on the entityOrRoleName String.

hibernate-core/src/main/java/org/hibernate/cache/internal/TenantAwareCacheKey.java

@@ -0,0 +1,54 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * Copyright (c) 2014, 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.cache.internal;
+
+import java.io.Serializable;
+
+import org.hibernate.cache.spi.CacheKey;
+import org.hibernate.engine.spi.SessionFactoryImplementor;
+import org.hibernate.type.Type;
+
+/**
+ * Variation of CacheKey to be used when multi-tenancy is applied.
+ * The tenantId field was not simply added to the superclass because of performance considerations:
+ * CacheKey instances are have a very high allocation frequency and this field would enlarge the
+ * size by 50%.
+ *
+ * @author Sanne Grinovero
+ */
+public class TenantAwareCacheKey extends CacheKey {
+
+	private final String tenantId;
+
+	public TenantAwareCacheKey(Serializable id, Type type, String entityOrRoleName, SessionFactoryImplementor factory, String tenantId) {
+		super( id, type, entityOrRoleName, factory, tenantId );
+		this.tenantId = tenantId;
+	}
+
+	@Override
+	public String getTenantId() {
+		return tenantId;
+	}
+
+}

hibernate-core/src/main/java/org/hibernate/cache/spi/CacheKey.java

@@ -33,14 +33,20 @@ import org.hibernate.type.Type;
  * Allows multiple entity classes / collection roles to be stored in the same cache region. Also allows for composite
  * keys which do not properly implement equals()/hashCode().
  *
+ * Note on performance: this class is allocated very heavily!
+ * Make sure the allocation cost stays as low as possible:
+ * if you need to add fields for not-so-common use cases,
+ * it's probably better to create an ad-hoc implementation
+ * extending this one.
+ *
  * @author Gavin King
  * @author Steve Ebersole
+ * @author Sanne Grinovero
  */
 public class CacheKey implements Serializable {
+
 	private final Serializable key;
 	private final Type type;
-	private final String entityOrRoleName;
-	private final String tenantId;
 	private final int hashCode;
 
 	/**
@@ -58,16 +64,25 @@ public class CacheKey implements Serializable {
 			final Serializable id,
 			final Type type,
 			final String entityOrRoleName,
-			final String tenantId,
 			final SessionFactoryImplementor factory) {
-		this.key = id;
-		this.type = type;
-		this.entityOrRoleName = entityOrRoleName;
-		this.tenantId = tenantId;
-		this.hashCode = calculateHashCode( type, factory );
+		this( id, type, entityOrRoleName, factory, null );
 	}
 
-	private int calculateHashCode(Type type, SessionFactoryImplementor factory) {
+	/**
+	 * Used by subclasses: need to specify a tenantId
+	 */
+	protected CacheKey(
+			final Serializable id,
+			final Type type,
+			final String entityOrRoleName,
+			final SessionFactoryImplementor factory,
+			final String tenantId) {
+		this.key = id;
+		this.type = type;
+		this.hashCode = calculateHashCode( type, factory, tenantId );
+	}
+
+	private int calculateHashCode(Type type, SessionFactoryImplementor factory, String tenantId) {
 		int result = type.getHashCode( key, factory );
 		result = 31 * result + (tenantId != null ? tenantId.hashCode() : 0);
 		return result;
@@ -77,12 +92,8 @@ public class CacheKey implements Serializable {
 		return key;
 	}
 
-	public String getEntityOrRoleName() {
-		return entityOrRoleName;
-	}
-
 	public String getTenantId() {
-		return tenantId;
+		return null;
 	}
 
 	@Override
@@ -97,10 +108,10 @@ public class CacheKey implements Serializable {
 			//hashCode is part of this check since it is pre-calculated and hash must match for equals to be true
 			return false;
 		}
+		//Warning: this equals implementation needs to work correctly also for the subclass
 		final CacheKey that = (CacheKey) other;
-		return EqualsHelper.equals( entityOrRoleName, that.entityOrRoleName )
-				&& type.isEqual( key, that.key )
-				&& EqualsHelper.equals( tenantId, that.tenantId );
+		return EqualsHelper.equals( getTenantId(), that.getTenantId() )
+				&& type.isEqual( key, that.key );
 	}
 
 	@Override
@@ -108,9 +119,4 @@ public class CacheKey implements Serializable {
 		return hashCode;
 	}
 
-	@Override
-	public String toString() {
-		// Used to be required for OSCache
-		return entityOrRoleName + '#' + key.toString();
-	}
 }

hibernate-core/src/main/java/org/hibernate/internal/AbstractSessionImpl.java

@@ -38,6 +38,7 @@ import org.hibernate.ScrollableResults;
 import org.hibernate.SessionEventListener;
 import org.hibernate.SessionException;
 import org.hibernate.SharedSessionContract;
+import org.hibernate.cache.internal.TenantAwareCacheKey;
 import org.hibernate.cache.spi.CacheKey;
 import org.hibernate.engine.jdbc.LobCreationContext;
 import org.hibernate.engine.jdbc.connections.spi.ConnectionProvider;
@@ -329,7 +330,13 @@ public abstract class AbstractSessionImpl
 
 	@Override
 	public CacheKey generateCacheKey(Serializable id, Type type, String entityOrRoleName) {
-		return new CacheKey( id, type, entityOrRoleName, getTenantIdentifier(), getFactory() );
+		final String tenantIdentifier = getTenantIdentifier();
+		if ( tenantIdentifier == null ) {
+			return new CacheKey( id, type, entityOrRoleName, getFactory() );
+		}
+		else {
+			return new TenantAwareCacheKey( id, type, entityOrRoleName, getFactory(), tenantIdentifier );
+		}
 	}
 
 	private transient JdbcConnectionAccess jdbcConnectionAccess;

hibernate-core/src/main/java/org/hibernate/internal/CacheImpl.java

@@ -119,11 +119,11 @@ public class CacheImpl implements CacheImplementor {
 	}
 
 	private CacheKey buildCacheKey(Serializable identifier, EntityPersister p) {
+		// have to assume non tenancy
 		return new CacheKey(
 				identifier,
 				p.getIdentifierType(),
 				p.getRootEntityName(),
-				null,                         // have to assume non tenancy
 				sessionFactory
 		);
 	}
@@ -197,11 +197,11 @@ public class CacheImpl implements CacheImplementor {
 	}
 
 	private CacheKey buildCacheKey(Serializable ownerIdentifier, CollectionPersister p) {
+		// have to assume non tenancy
 		return new CacheKey(
 				ownerIdentifier,
 				p.getKeyType(),
 				p.getRole(),
-				null,                        // have to assume non tenancy
 				sessionFactory
 		);
 	}