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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
* 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.index.sasi.disk;
import java.io.IOException;
import java.util.*;
import org.apache.cassandra.db.DecoratedKey;
import org.apache.cassandra.index.sasi.utils.AbstractIterator;
import org.apache.cassandra.index.sasi.utils.CombinedValue;
import org.apache.cassandra.index.sasi.utils.MappedBuffer;
import org.apache.cassandra.index.sasi.utils.RangeIterator;
import org.apache.cassandra.utils.MergeIterator;
import com.carrotsearch.hppc.LongHashSet;
import com.carrotsearch.hppc.LongSet;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Function;
import com.google.common.collect.Iterators;
import org.apache.commons.lang3.builder.HashCodeBuilder;
import static org.apache.cassandra.index.sasi.disk.TokenTreeBuilder.EntryType;
// Note: all of the seek-able offsets contained in TokenTree should be sizeof(long)
// even if currently only lower int portion of them if used, because that makes
// it possible to switch to mmap implementation which supports long positions
// without any on-disk format changes and/or re-indexing if one day we'll have a need to.
public class TokenTree
{
private static final int LONG_BYTES = Long.SIZE / 8;
private static final int SHORT_BYTES = Short.SIZE / 8;
private final Descriptor descriptor;
private final MappedBuffer file;
private final long startPos;
private final long treeMinToken;
private final long treeMaxToken;
private final long tokenCount;
@VisibleForTesting
protected TokenTree(MappedBuffer tokenTree)
{
this(Descriptor.CURRENT, tokenTree);
}
public TokenTree(Descriptor d, MappedBuffer tokenTree)
{
descriptor = d;
file = tokenTree;
startPos = file.position();
file.position(startPos + TokenTreeBuilder.SHARED_HEADER_BYTES);
if (!validateMagic())
throw new IllegalArgumentException("invalid token tree");
tokenCount = file.getLong();
treeMinToken = file.getLong();
treeMaxToken = file.getLong();
}
public long getCount()
{
return tokenCount;
}
public RangeIterator iterator(Function keyFetcher)
{
return new TokenTreeIterator(file.duplicate(), keyFetcher);
}
public OnDiskToken get(final long searchToken, Function keyFetcher)
{
seekToLeaf(searchToken, file);
long leafStart = file.position();
short leafSize = file.getShort(leafStart + 1); // skip the info byte
file.position(leafStart + TokenTreeBuilder.BLOCK_HEADER_BYTES); // skip to tokens
short tokenIndex = searchLeaf(searchToken, leafSize);
file.position(leafStart + TokenTreeBuilder.BLOCK_HEADER_BYTES);
OnDiskToken token = OnDiskToken.getTokenAt(file, tokenIndex, leafSize, keyFetcher);
return token.get().equals(searchToken) ? token : null;
}
private boolean validateMagic()
{
switch (descriptor.version.toString())
{
case Descriptor.VERSION_AA:
return true;
case Descriptor.VERSION_AB:
return TokenTreeBuilder.AB_MAGIC == file.getShort();
default:
return false;
}
}
// finds leaf that *could* contain token
private void seekToLeaf(long token, MappedBuffer file)
{
// this loop always seeks forward except for the first iteration
// where it may seek back to the root
long blockStart = startPos;
while (true)
{
file.position(blockStart);
byte info = file.get();
boolean isLeaf = (info & 1) == 1;
if (isLeaf)
{
file.position(blockStart);
break;
}
short tokenCount = file.getShort();
long minToken = file.getLong();
long maxToken = file.getLong();
long seekBase = blockStart + TokenTreeBuilder.BLOCK_HEADER_BYTES;
if (minToken > token)
{
// seek to beginning of child offsets to locate first child
file.position(seekBase + tokenCount * LONG_BYTES);
blockStart = (startPos + (int) file.getLong());
}
else if (maxToken < token)
{
// seek to end of child offsets to locate last child
file.position(seekBase + (2 * tokenCount) * LONG_BYTES);
blockStart = (startPos + (int) file.getLong());
}
else
{
// skip to end of block header/start of interior block tokens
file.position(seekBase);
short offsetIndex = searchBlock(token, tokenCount, file);
// file pointer is now at beginning of offsets
if (offsetIndex == tokenCount)
file.position(file.position() + (offsetIndex * LONG_BYTES));
else
file.position(file.position() + ((tokenCount - offsetIndex - 1) + offsetIndex) * LONG_BYTES);
blockStart = (startPos + (int) file.getLong());
}
}
}
private short searchBlock(long searchToken, short tokenCount, MappedBuffer file)
{
short offsetIndex = 0;
for (int i = 0; i < tokenCount; i++)
{
long readToken = file.getLong();
if (searchToken < readToken)
break;
offsetIndex++;
}
return offsetIndex;
}
private short searchLeaf(long searchToken, short tokenCount)
{
long base = file.position();
int start = 0;
int end = tokenCount;
int middle = 0;
while (start <= end)
{
middle = start + ((end - start) >> 1);
// each entry is 16 bytes wide, token is in bytes 4-11
long token = file.getLong(base + (middle * (2 * LONG_BYTES) + 4));
if (token == searchToken)
break;
if (token < searchToken)
start = middle + 1;
else
end = middle - 1;
}
return (short) middle;
}
public class TokenTreeIterator extends RangeIterator
{
private final Function keyFetcher;
private final MappedBuffer file;
private long currentLeafStart;
private int currentTokenIndex;
private long leafMinToken;
private long leafMaxToken;
private short leafSize;
protected boolean firstIteration = true;
private boolean lastLeaf;
TokenTreeIterator(MappedBuffer file, Function keyFetcher)
{
super(treeMinToken, treeMaxToken, tokenCount);
this.file = file;
this.keyFetcher = keyFetcher;
}
protected Token computeNext()
{
maybeFirstIteration();
if (currentTokenIndex >= leafSize && lastLeaf)
return endOfData();
if (currentTokenIndex < leafSize) // tokens remaining in this leaf
{
return getTokenAt(currentTokenIndex++);
}
else // no more tokens remaining in this leaf
{
assert !lastLeaf;
seekToNextLeaf();
setupBlock();
return computeNext();
}
}
protected void performSkipTo(Long nextToken)
{
maybeFirstIteration();
if (nextToken <= leafMaxToken) // next is in this leaf block
{
searchLeaf(nextToken);
}
else // next is in a leaf block that needs to be found
{
seekToLeaf(nextToken, file);
setupBlock();
findNearest(nextToken);
}
}
private void setupBlock()
{
currentLeafStart = file.position();
currentTokenIndex = 0;
lastLeaf = (file.get() & (1 << TokenTreeBuilder.LAST_LEAF_SHIFT)) > 0;
leafSize = file.getShort();
leafMinToken = file.getLong();
leafMaxToken = file.getLong();
// seek to end of leaf header/start of data
file.position(currentLeafStart + TokenTreeBuilder.BLOCK_HEADER_BYTES);
}
private void findNearest(Long next)
{
if (next > leafMaxToken && !lastLeaf)
{
seekToNextLeaf();
setupBlock();
findNearest(next);
}
else if (next > leafMinToken)
searchLeaf(next);
}
private void searchLeaf(long next)
{
for (int i = currentTokenIndex; i < leafSize; i++)
{
if (compareTokenAt(currentTokenIndex, next) >= 0)
break;
currentTokenIndex++;
}
}
private int compareTokenAt(int idx, long toToken)
{
return Long.compare(file.getLong(getTokenPosition(idx)), toToken);
}
private Token getTokenAt(int idx)
{
return OnDiskToken.getTokenAt(file, idx, leafSize, keyFetcher);
}
private long getTokenPosition(int idx)
{
// skip 4 byte entry header to get position pointing directly at the entry's token
return OnDiskToken.getEntryPosition(idx, file) + (2 * SHORT_BYTES);
}
private void seekToNextLeaf()
{
file.position(currentLeafStart + TokenTreeBuilder.BLOCK_BYTES);
}
public void close() throws IOException
{
// nothing to do here
}
private void maybeFirstIteration()
{
// seek to the first token only when requested for the first time,
// highly predictable branch and saves us a lot by not traversing the tree
// on creation time because it's not at all required.
if (!firstIteration)
return;
seekToLeaf(treeMinToken, file);
setupBlock();
firstIteration = false;
}
}
public static class OnDiskToken extends Token
{
private final Set info = new HashSet<>(2);
private final Set loadedKeys = new TreeSet<>(DecoratedKey.comparator);
public OnDiskToken(MappedBuffer buffer, long position, short leafSize, Function keyFetcher)
{
super(buffer.getLong(position + (2 * SHORT_BYTES)));
info.add(new TokenInfo(buffer, position, leafSize, keyFetcher));
}
public void merge(CombinedValue other)
{
if (!(other instanceof Token))
return;
Token o = (Token) other;
if (token != o.token)
throw new IllegalArgumentException(String.format("%s != %s", token, o.token));
if (o instanceof OnDiskToken)
{
info.addAll(((OnDiskToken) other).info);
}
else
{
Iterators.addAll(loadedKeys, o.iterator());
}
}
public Iterator iterator()
{
List> keys = new ArrayList<>(info.size());
for (TokenInfo i : info)
keys.add(i.iterator());
if (!loadedKeys.isEmpty())
keys.add(loadedKeys.iterator());
return MergeIterator.get(keys, DecoratedKey.comparator, new MergeIterator.Reducer()
{
DecoratedKey reduced = null;
public boolean trivialReduceIsTrivial()
{
return true;
}
public void reduce(int idx, DecoratedKey current)
{
reduced = current;
}
protected DecoratedKey getReduced()
{
return reduced;
}
});
}
public LongSet getOffsets()
{
LongSet offsets = new LongHashSet(4);
for (TokenInfo i : info)
{
for (long offset : i.fetchOffsets())
offsets.add(offset);
}
return offsets;
}
public static OnDiskToken getTokenAt(MappedBuffer buffer, int idx, short leafSize, Function keyFetcher)
{
return new OnDiskToken(buffer, getEntryPosition(idx, buffer), leafSize, keyFetcher);
}
private static long getEntryPosition(int idx, MappedBuffer file)
{
// info (4 bytes) + token (8 bytes) + offset (4 bytes) = 16 bytes
return file.position() + (idx * (2 * LONG_BYTES));
}
}
private static class TokenInfo
{
private final MappedBuffer buffer;
private final Function keyFetcher;
private final long position;
private final short leafSize;
public TokenInfo(MappedBuffer buffer, long position, short leafSize, Function keyFetcher)
{
this.keyFetcher = keyFetcher;
this.buffer = buffer;
this.position = position;
this.leafSize = leafSize;
}
public Iterator iterator()
{
return new KeyIterator(keyFetcher, fetchOffsets());
}
public int hashCode()
{
return new HashCodeBuilder().append(keyFetcher).append(position).append(leafSize).build();
}
public boolean equals(Object other)
{
if (!(other instanceof TokenInfo))
return false;
TokenInfo o = (TokenInfo) other;
return keyFetcher == o.keyFetcher && position == o.position;
}
private long[] fetchOffsets()
{
short info = buffer.getShort(position);
// offset extra is unsigned short (right-most 16 bits of 48 bits allowed for an offset)
int offsetExtra = buffer.getShort(position + SHORT_BYTES) & 0xFFFF;
// is the it left-most (32-bit) base of the actual offset in the index file
int offsetData = buffer.getInt(position + (2 * SHORT_BYTES) + LONG_BYTES);
EntryType type = EntryType.of(info & TokenTreeBuilder.ENTRY_TYPE_MASK);
switch (type)
{
case SIMPLE:
return new long[] { offsetData };
case OVERFLOW:
long[] offsets = new long[offsetExtra]; // offsetShort contains count of tokens
long offsetPos = (buffer.position() + (2 * (leafSize * LONG_BYTES)) + (offsetData * LONG_BYTES));
for (int i = 0; i < offsetExtra; i++)
offsets[i] = buffer.getLong(offsetPos + (i * LONG_BYTES));
return offsets;
case FACTORED:
return new long[] { (((long) offsetData) << Short.SIZE) + offsetExtra };
case PACKED:
return new long[] { offsetExtra, offsetData };
default:
throw new IllegalStateException("Unknown entry type: " + type);
}
}
}
private static class KeyIterator extends AbstractIterator
{
private final Function keyFetcher;
private final long[] offsets;
private int index = 0;
public KeyIterator(Function keyFetcher, long[] offsets)
{
this.keyFetcher = keyFetcher;
this.offsets = offsets;
}
public DecoratedKey computeNext()
{
return index < offsets.length ? keyFetcher.apply(offsets[index++]) : endOfData();
}
}
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