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* 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.columniterator;
import java.io.IOException;
import java.util.*;
import org.apache.cassandra.config.CFMetaData;
import org.apache.cassandra.db.*;
import org.apache.cassandra.db.filter.ColumnFilter;
import org.apache.cassandra.db.partitions.ImmutableBTreePartition;
import org.apache.cassandra.db.rows.*;
import org.apache.cassandra.io.sstable.format.SSTableReader;
import org.apache.cassandra.io.util.FileDataInput;
import org.apache.cassandra.utils.btree.BTree;
/**
* A Cell Iterator in reversed clustering order over SSTable
*/
public class SSTableReversedIterator extends AbstractSSTableIterator
{
public SSTableReversedIterator(SSTableReader sstable, DecoratedKey key, ColumnFilter columns, boolean isForThrift)
{
this(sstable, null, key, sstable.getPosition(key, SSTableReader.Operator.EQ), columns, isForThrift);
}
public SSTableReversedIterator(SSTableReader sstable,
FileDataInput file,
DecoratedKey key,
RowIndexEntry indexEntry,
ColumnFilter columns,
boolean isForThrift)
{
super(sstable, file, key, indexEntry, columns, isForThrift);
}
protected Reader createReader(RowIndexEntry indexEntry, FileDataInput file, boolean shouldCloseFile)
{
return indexEntry.isIndexed()
? new ReverseIndexedReader(indexEntry, file, shouldCloseFile)
: new ReverseReader(file, shouldCloseFile);
}
public boolean isReverseOrder()
{
return true;
}
private class ReverseReader extends Reader
{
protected ReusablePartitionData buffer;
protected Iterator<Unfiltered> iterator;
private ReverseReader(FileDataInput file, boolean shouldCloseFile)
{
super(file, shouldCloseFile);
}
protected ReusablePartitionData createBuffer(int blocksCount)
{
int estimatedRowCount = 16;
int columnCount = metadata().partitionColumns().regulars.size();
if (columnCount == 0 || metadata().clusteringColumns().isEmpty())
{
estimatedRowCount = 1;
}
else
{
try
{
// To avoid wasted resizing we guess-estimate the number of rows we're likely to read. For that
// we use the stats on the number of rows per partition for that sstable.
// FIXME: so far we only keep stats on cells, so to get a rough estimate on the number of rows,
// we divide by the number of regular columns the table has. We should fix once we collect the
// stats on rows
int estimatedRowsPerPartition = (int)(sstable.getEstimatedColumnCount().percentile(0.75) / columnCount);
estimatedRowCount = Math.max(estimatedRowsPerPartition / blocksCount, 1);
}
catch (IllegalStateException e)
{
// The EstimatedHistogram mean() method can throw this (if it overflows). While such overflow
// shouldn't happen, it's not worth taking the risk of letting the exception bubble up.
}
}
return new ReusablePartitionData(metadata(), partitionKey(), columns(), estimatedRowCount);
}
public void setForSlice(Slice slice) throws IOException
{
// If we have read the data, just create the iterator for the slice. Otherwise, read the data.
if (buffer == null)
{
buffer = createBuffer(1);
// Note that we can reuse that buffer between slices (we could alternatively re-read from disk
// every time, but that feels more wasteful) so we want to include everything from the beginning.
// We can stop at the slice end however since any following slice will be before that.
loadFromDisk(null, slice.end(), true);
}
setIterator(slice);
}
protected void setIterator(Slice slice)
{
assert buffer != null;
iterator = buffer.built.unfilteredIterator(columns, Slices.with(metadata().comparator, slice), true);
}
protected boolean hasNextInternal() throws IOException
{
// If we've never called setForSlice, we're reading everything
if (iterator == null)
setForSlice(Slice.ALL);
return iterator.hasNext();
}
protected Unfiltered nextInternal() throws IOException
{
if (!hasNext())
throw new NoSuchElementException();
return iterator.next();
}
protected boolean stopReadingDisk()
{
return false;
}
// Reads the unfiltered from disk and load them into the reader buffer. It stops reading when either the partition
// is fully read, or when stopReadingDisk() returns true.
protected void loadFromDisk(Slice.Bound start, Slice.Bound end, boolean includeFirst) throws IOException
{
buffer.reset();
boolean isFirst = true;
// If the start might be in this block, skip everything that comes before it.
if (start != null)
{
while (deserializer.hasNext() && deserializer.compareNextTo(start) <= 0 && !stopReadingDisk())
{
isFirst = false;
if (deserializer.nextIsRow())
deserializer.skipNext();
else
updateOpenMarker((RangeTombstoneMarker)deserializer.readNext());
}
}
// If we have an open marker, it's either one from what we just skipped (if start != null), or it's from the previous index block.
if (openMarker != null)
{
RangeTombstone.Bound markerStart = start == null ? RangeTombstone.Bound.BOTTOM : RangeTombstone.Bound.fromSliceBound(start);
buffer.add(new RangeTombstoneBoundMarker(markerStart, openMarker));
}
// Now deserialize everything until we reach our requested end (if we have one)
while (deserializer.hasNext()
&& (end == null || deserializer.compareNextTo(end) <= 0)
&& !stopReadingDisk())
{
Unfiltered unfiltered = deserializer.readNext();
if (!isFirst || includeFirst)
buffer.add(unfiltered);
isFirst = false;
if (unfiltered.isRangeTombstoneMarker())
updateOpenMarker((RangeTombstoneMarker)unfiltered);
}
// If we have an open marker, we should close it before finishing
if (openMarker != null)
{
// If we have no end and still an openMarker, this means we're indexed and the marker is closed in a following block.
RangeTombstone.Bound markerEnd = end == null ? RangeTombstone.Bound.TOP : RangeTombstone.Bound.fromSliceBound(end);
buffer.add(new RangeTombstoneBoundMarker(markerEnd, getAndClearOpenMarker()));
}
buffer.build();
}
}
private class ReverseIndexedReader extends ReverseReader
{
private final IndexState indexState;
// The slice we're currently iterating over
private Slice slice;
// The last index block to consider for the slice
private int lastBlockIdx;
private ReverseIndexedReader(RowIndexEntry indexEntry, FileDataInput file, boolean shouldCloseFile)
{
super(file, shouldCloseFile);
this.indexState = new IndexState(this, sstable.metadata.comparator, indexEntry, true);
}
@Override
public void setForSlice(Slice slice) throws IOException
{
this.slice = slice;
// if our previous slicing already got us past the beginning of the sstable, we're done
if (indexState.isDone())
{
iterator = Collections.emptyIterator();
return;
}
// Find the first index block we'll need to read for the slice.
int startIdx = indexState.findBlockIndex(slice.end(), indexState.currentBlockIdx());
if (startIdx < 0)
{
iterator = Collections.emptyIterator();
return;
}
lastBlockIdx = indexState.findBlockIndex(slice.start(), startIdx);
// If the last block to look (in reverse order) is after the very last block, we have nothing for that slice
if (lastBlockIdx >= indexState.blocksCount())
{
assert startIdx >= indexState.blocksCount();
iterator = Collections.emptyIterator();
return;
}
// If we start (in reverse order) after the very last block, just read from the last one.
if (startIdx >= indexState.blocksCount())
startIdx = indexState.blocksCount() - 1;
if (startIdx != indexState.currentBlockIdx())
{
indexState.setToBlock(startIdx);
readCurrentBlock(true);
}
setIterator(slice);
}
@Override
protected boolean hasNextInternal() throws IOException
{
if (super.hasNextInternal())
return true;
// We have nothing more for our current block, move the previous one.
int previousBlockIdx = indexState.currentBlockIdx() - 1;
if (previousBlockIdx < 0 || previousBlockIdx < lastBlockIdx)
return false;
// The slice start can be in
indexState.setToBlock(previousBlockIdx);
readCurrentBlock(false);
setIterator(slice);
// since that new block is within the bounds we've computed in setToSlice(), we know there will
// always be something matching the slice unless we're on the lastBlockIdx (in which case there
// may or may not be results, but if there isn't, we're done for the slice).
return iterator.hasNext();
}
/**
* Reads the current block, the last one we've set.
*
* @param canIncludeSliceEnd whether the block can include the slice end.
*/
private void readCurrentBlock(boolean canIncludeSliceEnd) throws IOException
{
if (buffer == null)
buffer = createBuffer(indexState.blocksCount());
int currentBlock = indexState.currentBlockIdx();
boolean canIncludeSliceStart = currentBlock == lastBlockIdx;
// When dealing with old format sstable, we have the problem that a row can span 2 index block, i.e. it can
// start at the end of a block and end at the beginning of the next one. That's not a problem per se for
// UnfilteredDeserializer.OldFormatSerializer, since it always read rows entirely, even if they span index
// blocks, but as we reading index block in reverse we must be careful to not read the end of the row at
// beginning of a block before we're reading the beginning of that row. So what we do is that if we detect
// that the row starting this block is also the row ending the previous one, we skip that first result and
// let it be read when we'll read the previous block.
boolean includeFirst = true;
if (!sstable.descriptor.version.storeRows() && currentBlock > 0)
{
ClusteringPrefix lastOfPrevious = indexState.index(currentBlock - 1).lastName;
ClusteringPrefix firstOfCurrent = indexState.index(currentBlock).firstName;
includeFirst = metadata().comparator.compare(lastOfPrevious, firstOfCurrent) != 0;
}
loadFromDisk(canIncludeSliceStart ? slice.start() : null, canIncludeSliceEnd ? slice.end() : null, includeFirst);
}
@Override
protected boolean stopReadingDisk()
{
return indexState.isPastCurrentBlock();
}
}
private class ReusablePartitionData
{
private final CFMetaData metadata;
private final DecoratedKey partitionKey;
private final PartitionColumns columns;
private MutableDeletionInfo.Builder deletionBuilder;
private MutableDeletionInfo deletionInfo;
private BTree.Builder<Row> rowBuilder;
private ImmutableBTreePartition built;
private ReusablePartitionData(CFMetaData metadata,
DecoratedKey partitionKey,
PartitionColumns columns,
int initialRowCapacity)
{
this.metadata = metadata;
this.partitionKey = partitionKey;
this.columns = columns;
this.rowBuilder = BTree.builder(metadata.comparator, initialRowCapacity);
}
public void add(Unfiltered unfiltered)
{
if (unfiltered.isRow())
rowBuilder.add((Row)unfiltered);
else
deletionBuilder.add((RangeTombstoneMarker)unfiltered);
}
public void reset()
{
built = null;
rowBuilder.reuse();
deletionBuilder = MutableDeletionInfo.builder(partitionLevelDeletion, metadata().comparator, false);
}
public void build()
{
deletionInfo = deletionBuilder.build();
built = new ImmutableBTreePartition(metadata, partitionKey, columns, Rows.EMPTY_STATIC_ROW, rowBuilder.build(),
deletionInfo, EncodingStats.NO_STATS);
deletionBuilder = null;
}
}
}