content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * 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.apache.cassandra.db.rows;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import org.apache.cassandra.db.Digest;
  import org.apache.cassandra.db.filter.ColumnFilter;
  import org.apache.cassandra.db.transform.Transformation;
  import org.apache.cassandra.schema.TableMetadata;
  
  /**
   * Static methods to work with row iterators.
   */
  public abstract class RowIterators
  {
      private static final Logger logger = LoggerFactory.getLogger(RowIterators.class);
  
      private RowIterators() {}
  
      public static void digest(RowIterator iterator, Digest digest)
      {
          // TODO: we're not computing digest the same way that old nodes. This is
          // currently ok as this is only used for schema digest and the is no exchange
          // of schema digest between different versions. If this changes however,
          // we'll need to agree on a version.
          digest.update(iterator.partitionKey().getKey());
          iterator.columns().regulars.digest(digest);
          iterator.columns().statics.digest(digest);
          digest.updateWithBoolean(iterator.isReverseOrder());
          iterator.staticRow().digest(digest);
  
          while (iterator.hasNext())
              iterator.next().digest(digest);
      }
  
      /**
       * Filter the provided iterator to only include cells that are selected by the user.
       *
       * @param iterator the iterator to filter.
       * @param filter the {@code ColumnFilter} to use when deciding which cells are queried by the user. This should be the filter
       * that was used when querying {@code iterator}.
       * @return the filtered iterator..
       */
      public static RowIterator withOnlyQueriedData(RowIterator iterator, ColumnFilter filter)
      {
          if (filter.allFetchedColumnsAreQueried())
              return iterator;
  
          return Transformation.apply(iterator, new WithOnlyQueriedData(filter));
      }
  
      /**
       * Wraps the provided iterator so it logs the returned rows for debugging purposes.
       * <p>
       * Note that this is only meant for debugging as this can log a very large amount of
       * logging at INFO.
       */
      public static RowIterator loggingIterator(RowIterator iterator, final String id)
      {
          TableMetadata metadata = iterator.metadata();
          logger.info("[{}] Logging iterator on {}.{}, partition key={}, reversed={}",
                      id,
                      metadata.keyspace,
                      metadata.name,
                      metadata.partitionKeyType.getString(iterator.partitionKey().getKey()),
                      iterator.isReverseOrder());
  
          class Log extends Transformation
          {
              @Override
              public Row applyToStatic(Row row)
              {
                  if (!row.isEmpty())
                      logger.info("[{}] {}", id, row.toString(metadata));
                  return row;
              }
  
              @Override
              public Row applyToRow(Row row)
              {
                  logger.info("[{}] {}", id, row.toString(metadata));
                  return row;
              }
          }
          return Transformation.apply(iterator, new Log());
      }
  }
  