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.io.sstable.format.big;
  
  import java.io.IOException;
  
  import org.apache.cassandra.db.DecoratedKey;
  import org.apache.cassandra.db.Slice;
  import org.apache.cassandra.db.Slices;
  import org.apache.cassandra.db.UnfilteredValidation;
  import org.apache.cassandra.db.filter.ColumnFilter;
  import org.apache.cassandra.db.rows.RangeTombstoneMarker;
  import org.apache.cassandra.db.rows.Unfiltered;
  import org.apache.cassandra.io.sstable.AbstractSSTableIterator;
  import org.apache.cassandra.io.sstable.format.SSTableReader;
  import org.apache.cassandra.io.sstable.format.Version;
  import org.apache.cassandra.io.util.FileDataInput;
  import org.apache.cassandra.io.util.FileHandle;
  
  /**
   *  A Cell Iterator over SSTable
   */
  public class SSTableIterator extends AbstractSSTableIterator<RowIndexEntry>
  {
      /**
       * The index of the slice being processed.
       */
      private int slice;
  
      public SSTableIterator(SSTableReader sstable,
                             FileDataInput file,
                             DecoratedKey key,
                             RowIndexEntry indexEntry,
                             Slices slices,
                             ColumnFilter columns,
                             FileHandle ifile)
      {
          super(sstable, file, key, indexEntry, slices, columns, ifile);
      }
  
      protected Reader createReaderInternal(RowIndexEntry indexEntry, FileDataInput file, boolean shouldCloseFile, Version version)
      {
          return indexEntry.isIndexed()
               ? new ForwardIndexedReader(indexEntry, file, shouldCloseFile)
               : new ForwardReader(file, shouldCloseFile);
      }
  
      protected int nextSliceIndex()
      {
          int next = slice;
          slice++;
          return next;
      }
  
      protected boolean hasMoreSlices()
      {
          return slice < slices.size();
      }
  
      public boolean isReverseOrder()
      {
          return false;
      }
  
      private class ForwardIndexedReader extends ForwardReader
      {
          private final IndexState indexState;
  
          private int lastBlockIdx; // the last index block that has data for the current query
  
          private ForwardIndexedReader(RowIndexEntry indexEntry, FileDataInput file, boolean shouldCloseFile)
          {
              super(file, shouldCloseFile);
              this.indexState = new IndexState(this, metadata.comparator, indexEntry, false, ifile);
              this.lastBlockIdx = indexState.blocksCount(); // if we never call setForSlice, that's where we want to stop
          }
  
          @Override
          public void close() throws IOException
          {
              super.close();
              this.indexState.close();
          }
  
          @Override
          public void setForSlice(Slice slice) throws IOException
          {
              super.setForSlice(slice);
  
              // if our previous slicing already got us the biggest row in the sstable, we're done
              if (indexState.isDone())
              {
                  sliceDone = true;
                  return;
              }
  
              // Find the first index block we'll need to read for the slice.
              int startIdx = indexState.findBlockIndex(slice.start(), indexState.currentBlockIdx());
              if (startIdx >= indexState.blocksCount())
              {
                  sliceDone = true;
                  return;
              }
  
              // Find the last index block we'll need to read for the slice.
              lastBlockIdx = indexState.findBlockIndex(slice.end(), startIdx);
  
              // If the slice end is before the very first block, we have nothing for that slice
              if (lastBlockIdx < 0)
              {
                  assert startIdx < 0;
                  sliceDone = true;
                  return;
              }
  
              // If we start before the very first block, just read from the first one.
              if (startIdx < 0)
                  startIdx = 0;
  
              // If that's the last block we were reading, we're already where we want to be. Otherwise,
              // seek to that first block
              if (startIdx != indexState.currentBlockIdx())
                  indexState.setToBlock(startIdx);
  
              // The index search is based on the last name of the index blocks, so at that point we have that:
              //   1) indexes[currentIdx - 1].lastName < slice.start <= indexes[currentIdx].lastName
              //   2) indexes[lastBlockIdx - 1].lastName < slice.end <= indexes[lastBlockIdx].lastName
              // so if currentIdx == lastBlockIdx and slice.end < indexes[currentIdx].firstName, we're guaranteed that the
              // whole slice is between the previous block end and this block start, and thus has no corresponding
              // data. One exception is if the previous block ends with an openMarker as it will cover our slice
              // and we need to return it.
              if (indexState.currentBlockIdx() == lastBlockIdx
                  && metadata().comparator.compare(slice.end(), indexState.currentIndex().firstName) < 0
                  && openMarker == null)
              {
                  sliceDone = true;
              }
          }
  
          @Override
          protected Unfiltered computeNext() throws IOException
          {
              while (true)
              {
                  // Our previous read might have made us cross an index block boundary. If so, update our informations.
                  // If we read from the beginning of the partition, this is also what will initialize the index state.
                  indexState.updateBlock();
  
                  // Return the next unfiltered unless we've reached the end, or we're beyond our slice
                  // end (note that unless we're on the last block for the slice, there is no point
                  // in checking the slice end).
                  if (indexState.isDone()
                      || indexState.currentBlockIdx() > lastBlockIdx
                      || !deserializer.hasNext()
                      || (indexState.currentBlockIdx() == lastBlockIdx && deserializer.compareNextTo(end) >= 0))
                      return null;
  
  
                  Unfiltered next = deserializer.readNext();
                  UnfilteredValidation.maybeValidateUnfiltered(next, metadata(), key, sstable);
                  // We may get empty row for the same reason expressed on UnfilteredSerializer.deserializeOne.
                  if (next.isEmpty())
                      continue;
  
                  if (next.kind() == Unfiltered.Kind.RANGE_TOMBSTONE_MARKER)
                      updateOpenMarker((RangeTombstoneMarker) next);
                  return next;
              }
          }
      }
  
      @Override
      public String toString()
      {
          return sstable.toString();
      }
  }
  