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/**

Copyright (C) SYSTAP, LLC DBA Blazegraph 2006-2016.  All rights reserved.

Contact:
     SYSTAP, LLC DBA Blazegraph
     2501 Calvert ST NW #106
     Washington, DC 20008
     [email protected]

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.

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 General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/
/*
 * Created on Apr 13, 2011
 */
package com.bigdata.rdf.sail;

import org.apache.log4j.Logger;

import com.bigdata.journal.IIndexManager;
import com.bigdata.journal.ITx;
import com.bigdata.journal.Journal;
import com.bigdata.journal.TimestampUtility;
import com.bigdata.rdf.sail.webapp.DatasetNotFoundException;
import com.bigdata.rdf.store.AbstractTripleStore;
import com.bigdata.rdf.task.AbstractApiTask;

/**
 * Task destroys a KB for the given namespace. The correct use of this class is
 * as follows:
 * 
 *  * AbstractApiTask.submitApiTask(indexManager, new DestroyKBTask(namespace)).get();
 * 
 * 
 * @see CreateKBTask
 * 
 * @author Bryan Thompson
 */
public class DestroyKBTask extends AbstractApiTask {

   private static final transient Logger log = Logger
         .getLogger(DestroyKBTask.class);

   public DestroyKBTask(final String namespace) {
    
      super(namespace, ITx.UNISOLATED, true/* isGRSRequired */);
      
   }

   @Override
   final public boolean isReadOnly() {
      return false;
   }

   /**
    * @throws DatasetNotFoundException if the namespace does not exist.
    */
   @Override
   public Void call() throws Exception, DatasetNotFoundException {

      /**
       * Note: Unless group commit is enabled, we need to make this operation
       * mutually exclusive with KB level writers in order to avoid the
       * possibility of a triggering a commit during the middle of a
       * BigdataSailConnection level operation (or visa versa).
       * 
       * Note: When group commit is not enabled, the indexManager will be a
       * Journal class. When it is enabled, it will merely implement the
       * IJournal interface.
       * 
       * @see #1143 (Isolation broken in NSS when groupCommit disabled)
       */
      final IIndexManager indexManager = getIndexManager();
      final boolean isGroupCommit = indexManager.isGroupCommit();
      boolean acquiredConnection = false;
      try {

         if (!isGroupCommit) {
            try {
               // acquire the unisolated connection permit.
               ((Journal) indexManager).acquireUnisolatedConnection();
               acquiredConnection = true;
            } catch (InterruptedException e) {
               throw new RuntimeException(e);
            }
         }

         final AbstractTripleStore tripleStore = getTripleStore();

         if (tripleStore == null) {

            throw new DatasetNotFoundException("Not found: namespace="
                  + namespace + ", timestamp="
                  + TimestampUtility.toString(timestamp));

         }

         // Destroy the KB instance.
         tripleStore.destroy();

         // Note: This is the commit point only if group commit is NOT enabled.
         tripleStore.commit();

         if (log.isInfoEnabled())
            log.info("Destroyed: namespace=" + namespace);

         return null;

      } finally {

         if (!isGroupCommit && acquiredConnection) {

            /**
             * When group commit is not enabled, we need to release the
             * unisolated connection.
             * 
             * @see #1143 (Isolation broken in NSS when groupCommit disabled)
             */
            ((Journal) indexManager).releaseUnisolatedConnection();

         }

      }

   }

}