/*
   * (non-Javadoc)
   *
   * @see com.orientechnologies.orient.core.metadata.schema.OSchema#dropClass(java.lang.String)
   */
  public void dropClass(final String className) {
    final ODatabaseDocumentInternal db = getDatabase();
    final OStorage storage = db.getStorage();
    final StringBuilder cmd;

    acquireSchemaWriteLock();
    try {
      if (getDatabase().getTransaction().isActive())
        throw new IllegalStateException("Cannot drop a class inside a transaction");

      if (className == null) throw new IllegalArgumentException("Class name is null");

      getDatabase().checkSecurity(ORule.ResourceGeneric.SCHEMA, ORole.PERMISSION_DELETE);

      final String key = className.toLowerCase();

      OClass cls = classes.get(key);

      if (cls == null)
        throw new OSchemaException("Class '" + className + "' was not found in current database");

      if (!cls.getSubclasses().isEmpty())
        throw new OSchemaException(
            "Class '"
                + className
                + "' cannot be dropped because it has sub classes. Remove the dependencies before trying to drop it again");

      cmd = new StringBuilder("drop class ");
      cmd.append(className);
      cmd.append(" unsafe");

      if (isDistributedCommand()) {
        final OAutoshardedStorage autoshardedStorage = (OAutoshardedStorage) storage;
        OCommandSQL commandSQL = new OCommandSQL(cmd.toString());
        commandSQL.addExcludedNode(autoshardedStorage.getNodeId());
        db.command(commandSQL).execute();

        dropClassInternal(className);
      } else if (storage instanceof OStorageProxy) {
        final OCommandSQL commandSQL = new OCommandSQL(cmd.toString());
        db.command(commandSQL).execute();
        reload();
      } else dropClassInternal(className);

      // FREE THE RECORD CACHE
      getDatabase().getLocalCache().freeCluster(cls.getDefaultClusterId());

    } finally {
      releaseSchemaWriteLock();
    }
  }
  private OClass doCreateClass(
      final String className, final int[] clusterIds, int retry, OClass... superClasses)
      throws ClusterIdsAreEmptyException {
    OClass result;

    final ODatabaseDocumentInternal db = getDatabase();
    final OStorage storage = db.getStorage();
    StringBuilder cmd = null;

    getDatabase().checkSecurity(ORule.ResourceGeneric.SCHEMA, ORole.PERMISSION_CREATE);
    acquireSchemaWriteLock();
    try {

      final String key = className.toLowerCase();
      if (classes.containsKey(key) && retry == 0)
        throw new OSchemaException("Class " + className + " already exists in current database");

      if (!isDistributedCommand()) checkClustersAreAbsent(clusterIds);

      cmd = new StringBuilder("create class ");
      // if (getDatabase().getStorage().getConfiguration().isStrictSql())
      // cmd.append('`');
      cmd.append(className);
      // if (getDatabase().getStorage().getConfiguration().isStrictSql())
      // cmd.append('`');

      List<OClass> superClassesList = new ArrayList<OClass>();
      if (superClasses != null && superClasses.length > 0) {
        boolean first = true;
        for (OClass superClass : superClasses) {
          // Filtering for null
          if (superClass != null) {
            if (first) cmd.append(" extends ");
            else cmd.append(", ");
            cmd.append(superClass.getName());
            first = false;
            superClassesList.add(superClass);
          }
        }
      }

      if (clusterIds != null) {
        if (clusterIds.length == 1 && clusterIds[0] == -1) cmd.append(" abstract");
        else {
          cmd.append(" cluster ");
          for (int i = 0; i < clusterIds.length; ++i) {
            if (i > 0) cmd.append(',');
            else cmd.append(' ');

            cmd.append(clusterIds[i]);
          }
        }
      }

      if (isDistributedCommand()) {
        createClassInternal(className, clusterIds, superClassesList);

        final OAutoshardedStorage autoshardedStorage = (OAutoshardedStorage) storage;
        OCommandSQL commandSQL = new OCommandSQL(cmd.toString());
        commandSQL.addExcludedNode(autoshardedStorage.getNodeId());

        final Object res = db.command(commandSQL).execute();

      } else if (storage instanceof OStorageProxy) {
        db.command(new OCommandSQL(cmd.toString())).execute();
        reload();
      } else createClassInternal(className, clusterIds, superClassesList);

      result = classes.get(className.toLowerCase());

      // WAKE UP DB LIFECYCLE LISTENER
      for (Iterator<ODatabaseLifecycleListener> it = Orient.instance().getDbLifecycleListeners();
          it.hasNext(); ) it.next().onCreateClass(getDatabase(), result);

    } finally {
      releaseSchemaWriteLock();
    }

    return result;
  }