/*
* 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.ArrayDeque;
import java.util.Deque;
import java.util.List;
import com.google.common.collect.AbstractIterator;
import org.apache.cassandra.db.*;
import org.apache.cassandra.db.composites.CellNameType;
import org.apache.cassandra.db.composites.Composite;
import org.apache.cassandra.db.filter.ColumnSlice;
import org.apache.cassandra.io.sstable.CorruptSSTableException;
import org.apache.cassandra.io.sstable.IndexHelper;
import org.apache.cassandra.io.sstable.IndexHelper.IndexInfo;
import org.apache.cassandra.io.sstable.SSTableReader;
import org.apache.cassandra.io.util.FileDataInput;
import org.apache.cassandra.io.util.FileMark;
import org.apache.cassandra.tracing.Tracing;
import org.apache.cassandra.utils.ByteBufferUtil;
/**
* This is a reader that finds the block for a starting column and returns blocks before/after it for each next call.
* This function assumes that the CF is sorted by name and exploits the name index.
*/
class IndexedSliceReader extends AbstractIterator<OnDiskAtom> implements OnDiskAtomIterator
{
private final ColumnFamily emptyColumnFamily;
private final SSTableReader sstable;
private final List<IndexHelper.IndexInfo> indexes;
private final FileDataInput originalInput;
private FileDataInput file;
private final boolean reversed;
private final ColumnSlice[] slices;
private final BlockFetcher fetcher;
private final Deque<OnDiskAtom> blockColumns = new ArrayDeque<OnDiskAtom>();
private final CellNameType comparator;
// Holds range tombstone in reverse queries. See addColumn()
private final Deque<OnDiskAtom> rangeTombstonesReversed;
/**
* This slice reader assumes that slices are sorted correctly, e.g. that for forward lookup slices are in
* lexicographic order of start elements and that for reverse lookup they are in reverse lexicographic order of
* finish (reverse start) elements. i.e. forward: [a,b],[d,e],[g,h] reverse: [h,g],[e,d],[b,a]. This reader also
* assumes that validation has been performed in terms of intervals (no overlapping intervals).
*/
public IndexedSliceReader(SSTableReader sstable, RowIndexEntry indexEntry, FileDataInput input, ColumnSlice[] slices, boolean reversed)
{
Tracing.trace("Seeking to partition indexed section in data file");
this.sstable = sstable;
this.originalInput = input;
this.reversed = reversed;
this.slices = slices;
this.comparator = sstable.metadata.comparator;
this.rangeTombstonesReversed = reversed ? new ArrayDeque<OnDiskAtom>() : null;
try
{
this.indexes = indexEntry.columnsIndex();
emptyColumnFamily = EmptyColumns.factory.create(sstable.metadata);
if (indexes.isEmpty())
{
setToRowStart(indexEntry, input);
emptyColumnFamily.delete(DeletionTime.serializer.deserialize(file));
fetcher = new SimpleBlockFetcher();
}
else
{
emptyColumnFamily.delete(indexEntry.deletionTime());
fetcher = new IndexedBlockFetcher(indexEntry.position);
}
}
catch (IOException e)
{
sstable.markSuspect();
throw new CorruptSSTableException(e, file.getPath());
}
}
/**
* Sets the seek position to the start of the row for column scanning.
*/
private void setToRowStart(RowIndexEntry rowEntry, FileDataInput in) throws IOException
{
if (in == null)
{
this.file = sstable.getFileDataInput(rowEntry.position);
}
else
{
this.file = in;
in.seek(rowEntry.position);
}
sstable.partitioner.decorateKey(ByteBufferUtil.readWithShortLength(file));
if (sstable.descriptor.version.hasRowSizeAndColumnCount)
file.readLong();
}
public ColumnFamily getColumnFamily()
{
return emptyColumnFamily;
}
public DecoratedKey getKey()
{
throw new UnsupportedOperationException();
}
protected OnDiskAtom computeNext()
{
while (true)
{
if (reversed)
{
// Return all tombstone for the block first (see addColumn() below)
OnDiskAtom column = rangeTombstonesReversed.poll();
if (column != null)
return column;
}
OnDiskAtom column = blockColumns.poll();
if (column == null)
{
if (!fetcher.fetchMoreData())
return endOfData();
}
else
{
return column;
}
}
}
public void close() throws IOException
{
if (originalInput == null && file != null)
file.close();
}
protected void addColumn(OnDiskAtom col)
{
if (reversed)
{
/*
* We put range tomstone markers at the beginning of the range they delete. But for reversed queries,
* the caller still need to know about a RangeTombstone before it sees any column that it covers.
* To make that simple, we keep said tombstones separate and return them all before any column for
* a given block.
*/
if (col instanceof RangeTombstone)
rangeTombstonesReversed.addFirst(col);
else
blockColumns.addFirst(col);
}
else
{
blockColumns.addLast(col);
}
}
private abstract class BlockFetcher
{
protected int currentSliceIdx;
protected BlockFetcher(int sliceIdx)
{
this.currentSliceIdx = sliceIdx;
}
/*
* Return the smallest key selected by the current ColumnSlice.
*/
protected Composite currentStart()
{
return reversed ? slices[currentSliceIdx].finish : slices[currentSliceIdx].start;
}
/*
* Return the biggest key selected by the current ColumnSlice.
*/
protected Composite currentFinish()
{
return reversed ? slices[currentSliceIdx].start : slices[currentSliceIdx].finish;
}
protected abstract boolean setNextSlice();
protected abstract boolean fetchMoreData();
protected boolean isColumnBeforeSliceStart(OnDiskAtom column)
{
return isBeforeSliceStart(column.name());
}
protected boolean isBeforeSliceStart(Composite name)
{
Composite start = currentStart();
return !start.isEmpty() && comparator.compare(name, start) < 0;
}
protected boolean isColumnBeforeSliceFinish(OnDiskAtom column)
{
Composite finish = currentFinish();
return finish.isEmpty() || comparator.compare(column.name(), finish) <= 0;
}
protected boolean isAfterSliceFinish(Composite name)
{
Composite finish = currentFinish();
return !finish.isEmpty() && comparator.compare(name, finish) > 0;
}
}
private class IndexedBlockFetcher extends BlockFetcher
{
// where this row starts
private final long columnsStart;
// the index entry for the next block to deserialize
private int nextIndexIdx = -1;
// index of the last block we've read from disk;
private int lastDeserializedBlock = -1;
// For reversed, keep columns at the beginning of the last deserialized block that
// may still match a slice
private final Deque<OnDiskAtom> prefetched;
public IndexedBlockFetcher(long columnsStart)
{
super(-1);
this.columnsStart = columnsStart;
this.prefetched = reversed ? new ArrayDeque<OnDiskAtom>() : null;
setNextSlice();
}
protected boolean setNextSlice()
{
while (++currentSliceIdx < slices.length)
{
nextIndexIdx = IndexHelper.indexFor(slices[currentSliceIdx].start, indexes, comparator, reversed, nextIndexIdx);
if (nextIndexIdx < 0 || nextIndexIdx >= indexes.size())
// no index block for that slice
continue;
// Check if we can exclude this slice entirely from the index
IndexInfo info = indexes.get(nextIndexIdx);
if (reversed)
{
if (!isBeforeSliceStart(info.lastName))
return true;
}
else
{
if (!isAfterSliceFinish(info.firstName))
return true;
}
}
nextIndexIdx = -1;
return false;
}
protected boolean hasMoreSlice()
{
return currentSliceIdx < slices.length;
}
protected boolean fetchMoreData()
{
if (!hasMoreSlice())
return false;
// If we read blocks in reversed disk order, we may have columns from the previous block to handle.
// Note that prefetched keeps columns in reversed disk order.
if (reversed && !prefetched.isEmpty())
{
boolean gotSome = false;
// Avoids some comparison when we know it's not useful
boolean inSlice = false;
OnDiskAtom prefetchedCol;
while ((prefetchedCol = prefetched.peek() ) != null)
{
// col is before slice, we update the slice
if (isColumnBeforeSliceStart(prefetchedCol))
{
inSlice = false;
if (!setNextSlice())
return false;
}
// col is within slice, all columns
// (we go in reverse, so as soon as we are in a slice, no need to check
// we're after the slice until we change slice)
else if (inSlice || isColumnBeforeSliceFinish(prefetchedCol))
{
blockColumns.addLast(prefetched.poll());
gotSome = true;
inSlice = true;
}
// if col is after slice, ignore
else
{
prefetched.poll();
}
}
if (gotSome)
return true;
}
try
{
return getNextBlock();
}
catch (IOException e)
{
throw new CorruptSSTableException(e, file.getPath());
}
}
private boolean getNextBlock() throws IOException
{
if (lastDeserializedBlock == nextIndexIdx)
{
if (reversed)
nextIndexIdx--;
else
nextIndexIdx++;
}
lastDeserializedBlock = nextIndexIdx;
// Are we done?
if (lastDeserializedBlock < 0 || lastDeserializedBlock >= indexes.size())
return false;
IndexInfo currentIndex = indexes.get(lastDeserializedBlock);
/* seek to the correct offset to the data, and calculate the data size */
long positionToSeek = columnsStart + currentIndex.offset;
// With new promoted indexes, our first seek in the data file will happen at that point.
if (file == null)
file = originalInput == null ? sstable.getFileDataInput(positionToSeek) : originalInput;
AtomDeserializer deserializer = emptyColumnFamily.metadata().getOnDiskDeserializer(file, sstable.descriptor.version);
file.seek(positionToSeek);
FileMark mark = file.mark();
// We remenber when we are whithin a slice to avoid some comparison
boolean inSlice = false;
// scan from index start
while (file.bytesPastMark(mark) < currentIndex.width || deserializer.hasUnprocessed())
{
// col is before slice
// (If in slice, don't bother checking that until we change slice)
Composite start = currentStart();
if (!inSlice && !start.isEmpty() && deserializer.compareNextTo(start) < 0)
{
if (reversed)
{
// the next slice select columns that are before the current one, so it may
// match this column, so keep it around.
prefetched.addFirst(deserializer.readNext());
}
else
{
deserializer.skipNext();
}
}
// col is within slice
else
{
Composite finish = currentFinish();
if (finish.isEmpty() || deserializer.compareNextTo(finish) <= 0)
{
inSlice = true;
addColumn(deserializer.readNext());
}
// col is after slice.
else
{
// When reading forward, if we hit a column that sorts after the current slice, it means we're done with this slice.
// For reversed, this may either mean that we're done with the current slice, or that we need to read the previous
// index block. However, we can be sure that we are in the first case though (the current slice is done) if the first
// columns of the block were not part of the current slice, i.e. if we have columns in prefetched.
if (reversed && prefetched.isEmpty())
break;
if (!setNextSlice())
break;
inSlice = false;
// The next index block now corresponds to the first block that may have columns for the newly set slice.
// So if it's different from the current block, we're done with this block. And in that case, we know
// that our prefetched columns won't match.
if (nextIndexIdx != lastDeserializedBlock)
{
if (reversed)
prefetched.clear();
break;
}
// Even if the next slice may have column in this blocks, if we're reversed, those columns have been
// prefetched and we're done with that block
if (reversed)
break;
// otherwise, we will deal with that column at the next iteration
}
}
}
return true;
}
}
private class SimpleBlockFetcher extends BlockFetcher
{
public SimpleBlockFetcher() throws IOException
{
// Since we have to deserialize in order and will read all slices might as well reverse the slices and
// behave as if it was not reversed
super(reversed ? slices.length - 1 : 0);
// We remenber when we are whithin a slice to avoid some comparison
boolean inSlice = false;
int columnCount = sstable.descriptor.version.hasRowSizeAndColumnCount ? file.readInt() : Integer.MAX_VALUE;
AtomDeserializer deserializer = emptyColumnFamily.metadata().getOnDiskDeserializer(file, sstable.descriptor.version);
int deserialized = 0;
while (deserializer.hasNext() && deserialized < columnCount)
{
// col is before slice
// (If in slice, don't bother checking that until we change slice)
Composite start = currentStart();
if (!inSlice && !start.isEmpty() && deserializer.compareNextTo(start) < 0)
{
deserializer.skipNext();
++deserialized;
continue;
}
// col is within slice
Composite finish = currentFinish();
if (finish.isEmpty() || deserializer.compareNextTo(finish) <= 0)
{
inSlice = true;
addColumn(deserializer.readNext());
++deserialized;
}
// col is after slice. more slices?
else
{
inSlice = false;
if (!setNextSlice())
break;
}
}
}
protected boolean setNextSlice()
{
if (reversed)
{
if (currentSliceIdx <= 0)
return false;
currentSliceIdx--;
}
else
{
if (currentSliceIdx >= slices.length - 1)
return false;
currentSliceIdx++;
}
return true;
}
protected boolean fetchMoreData()
{
return false;
}
}
}