/*
* 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.NoSuchElementException;
import org.apache.cassandra.db.*;
import org.apache.cassandra.db.filter.ColumnFilter;
import org.apache.cassandra.db.rows.*;
import org.apache.cassandra.io.sstable.format.SSTableReader;
import org.apache.cassandra.io.util.FileDataInput;
/**
* A Cell Iterator over SSTable
*/
public class SSTableIterator extends AbstractSSTableIterator
{
public SSTableIterator(SSTableReader sstable, DecoratedKey key, ColumnFilter columns, boolean isForThrift)
{
this(sstable, null, key, sstable.getPosition(key, SSTableReader.Operator.EQ), columns, isForThrift);
}
public SSTableIterator(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 ForwardIndexedReader(indexEntry, file, shouldCloseFile)
: new ForwardReader(file, shouldCloseFile);
}
public boolean isReverseOrder()
{
return false;
}
private class ForwardReader extends Reader
{
// The start of the current slice. This will be null as soon as we know we've passed that bound.
protected Slice.Bound start;
// The end of the current slice. Will never be null.
protected Slice.Bound end = Slice.Bound.TOP;
protected Unfiltered next; // the next element to return: this is computed by hasNextInternal().
protected boolean sliceDone; // set to true once we know we have no more result for the slice. This is in particular
// used by the indexed reader when we know we can't have results based on the index.
private ForwardReader(FileDataInput file, boolean shouldCloseFile)
{
super(file, shouldCloseFile);
}
public void setForSlice(Slice slice) throws IOException
{
start = slice.start() == Slice.Bound.BOTTOM ? null : slice.start();
end = slice.end();
sliceDone = false;
next = null;
}
// Skip all data that comes before the currently set slice.
// Return what should be returned at the end of this, or null if nothing should.
private Unfiltered handlePreSliceData() throws IOException
{
assert deserializer != null;
// Note that the following comparison is not strict. The reason is that the only cases
// where it can be == is if the "next" is a RT start marker (either a '[' of a ')[' boundary),
// and if we had a strict inequality and an open RT marker before this, we would issue
// the open marker first, and then return then next later, which would send in the
// stream both '[' (or '(') and then ')[' for the same clustering value, which is wrong.
// By using a non-strict inequality, we avoid that problem (if we do get ')[' for the same
// clustering value than the slice, we'll simply record it in 'openMarker').
while (deserializer.hasNext() && deserializer.compareNextTo(start) <= 0)
{
if (deserializer.nextIsRow())
deserializer.skipNext();
else
updateOpenMarker((RangeTombstoneMarker)deserializer.readNext());
}
Slice.Bound sliceStart = start;
start = null;
// We've reached the beginning of our queried slice. If we have an open marker
// we should return that first.
if (openMarker != null)
return new RangeTombstoneBoundMarker(sliceStart, openMarker);
return null;
}
// Compute the next element to return, assuming we're in the middle to the slice
// and the next element is either in the slice, or just after it. Returns null
// if we're done with the slice.
protected Unfiltered computeNext() throws IOException
{
assert deserializer != null;
if (!deserializer.hasNext() || deserializer.compareNextTo(end) > 0)
return null;
Unfiltered next = deserializer.readNext();
if (next.kind() == Unfiltered.Kind.RANGE_TOMBSTONE_MARKER)
updateOpenMarker((RangeTombstoneMarker)next);
return next;
}
protected boolean hasNextInternal() throws IOException
{
if (next != null)
return true;
if (sliceDone)
return false;
if (start != null)
{
Unfiltered unfiltered = handlePreSliceData();
if (unfiltered != null)
{
next = unfiltered;
return true;
}
}
next = computeNext();
if (next != null)
return true;
// If we have an open marker, we should close it before finishing
if (openMarker != null)
{
next = new RangeTombstoneBoundMarker(end, getAndClearOpenMarker());
return true;
}
sliceDone = true; // not absolutely necessary but accurate and cheap
return false;
}
protected Unfiltered nextInternal() throws IOException
{
if (!hasNextInternal())
throw new NoSuchElementException();
Unfiltered toReturn = next;
next = null;
return toReturn;
}
}
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, sstable.metadata.comparator, indexEntry, false);
this.lastBlockIdx = indexState.blocksCount(); // if we never call setForSlice, that's where we want to stop
}
@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 (we also don't skip the slice for the old format because we didn't have the openMarker
// info in that case and can't rely on this optimization).
if (indexState.currentBlockIdx() == lastBlockIdx
&& metadata().comparator.compare(slice.end(), indexState.currentIndex().firstName) < 0
&& openMarker == null
&& sstable.descriptor.version.storeRows())
{
sliceDone = true;
}
}
@Override
protected Unfiltered computeNext() throws IOException
{
// 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();
if (next.kind() == Unfiltered.Kind.RANGE_TOMBSTONE_MARKER)
updateOpenMarker((RangeTombstoneMarker)next);
return next;
}
}
}