Schema changes and ID-based node storage

git-svn-id: https://svn.alfresco.com/repos/alfresco-enterprise/alfresco/HEAD/root@2727 c4b6b30b-aa2e-2d43-bbcb-ca4b014f7261

source/java/org/alfresco/repo/domain/hibernate/HibernateHelper.java

@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2005 Alfresco, Inc.
+ *
+ * Licensed under the Mozilla Public License version 1.1 
+ * with a permitted attribution clause. You may obtain a
+ * copy of the License at
+ *
+ *   http://www.alfresco.org/legal/license.txt
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
+ * either express or implied. See the License for the specific
+ * language governing permissions and limitations under the
+ * License.
+ */
+package org.alfresco.repo.domain.hibernate;
+
+import org.hibernate.CacheMode;
+import org.hibernate.ObjectDeletedException;
+import org.hibernate.Query;
+import org.hibernate.ScrollMode;
+import org.hibernate.ScrollableResults;
+import org.hibernate.Session;
+
+/**
+ * Helper methods related to Hibernate
+ * 
+ * @author Derek Hulley
+ */
+public class HibernateHelper
+{
+    /**
+     * Helper method to scroll through the results of a query and delete all the
+     * results, performing batch flushes.  This will handle large resultsets by
+     * pulling the results directly in from the query.  For certain circumstances, it
+     * may be better to perform a bulk delete directly instead.
+     * 
+     * @param session the session to use for the deletions
+     * @param query the query with all parameters set
+     * @return Returns the number of entities deleted, regardless of type
+     */
+    public static int deleteQueryResults(Session session, Query query)
+    {
+        ScrollableResults entities = query.setCacheMode(CacheMode.IGNORE).scroll(ScrollMode.FORWARD_ONLY);
+        int count = 0;
+        while (entities.next())
+        {
+            Object[] entityResults = entities.get();
+            for (Object object : entityResults)
+            {
+                try
+                {
+                    session.delete(object);
+                }
+                catch (ObjectDeletedException e)
+                {
+                    // ignore - it's what we wanted
+                }
+                if (++count % 50 == 0)
+                {
+                    session.flush();
+                    session.clear();
+                }
+            }
+        }
+        return count;
+    }
+}