package org.apache.cassandra.io.sstable;
/*
*
* 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.
*
*/
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.apache.cassandra.config.DatabaseDescriptor;
import org.apache.cassandra.config.Config;
import org.apache.cassandra.db.DecoratedKey;
import org.apache.cassandra.dht.AbstractBounds;
import org.apache.cassandra.dht.Range;
import org.apache.cassandra.utils.Pair;
/**
* Two approaches to building an IndexSummary:
* 1. Call maybeAddEntry with every potential index entry
* 2. Call shouldAddEntry, [addEntry,] incrementRowid
*/
public class IndexSummary
{
private ArrayList<KeyPosition> indexPositions;
private long keysWritten = 0;
public IndexSummary(long expectedKeys)
{
long expectedEntries = expectedKeys / DatabaseDescriptor.getIndexInterval();
if (expectedEntries > Integer.MAX_VALUE)
// TODO: that's a _lot_ of keys, or a very low interval
throw new RuntimeException("Cannot use index_interval of " + DatabaseDescriptor.getIndexInterval() + " with " + expectedKeys + " (expected) keys.");
indexPositions = new ArrayList<KeyPosition>((int)expectedEntries);
}
public void incrementRowid()
{
keysWritten++;
}
public boolean shouldAddEntry()
{
return keysWritten % DatabaseDescriptor.getIndexInterval() == 0;
}
public void addEntry(DecoratedKey decoratedKey, long indexPosition)
{
indexPositions.add(new KeyPosition(decoratedKey, indexPosition));
}
public void maybeAddEntry(DecoratedKey decoratedKey, long indexPosition)
{
if (shouldAddEntry())
addEntry(decoratedKey, indexPosition);
incrementRowid();
}
public List<KeyPosition> getIndexPositions()
{
return indexPositions;
}
public void complete()
{
indexPositions.trimToSize();
}
/**
* @return The offset in indexPositions of the first key less than or equal to dk, or -1.
*/
private int binarySearch(DecoratedKey dk)
{
int index = Collections.binarySearch(indexPositions, new KeyPosition(dk, -1));
if (index >= 0)
// exact match
return index;
// binary search gives us the first index _greater_ than the key searched for,
// i.e., its insertion position
int greaterThan = (index + 1) * -1;
if (greaterThan == 0)
return -1;
return greaterThan - 1;
}
/**
* @return The position in the index file to start scanning to find the given key
* (at most indexInterval keys away)
*/
KeyPosition getIndexScanPosition(DecoratedKey decoratedKey)
{
int index = binarySearch(decoratedKey);
if (index == -1)
// given key is before the beginning of the file
return null;
return indexPositions.get(index);
}
/**
* @return The position in the index file to start scanning to find the given rowid
* (at most indexInterval keys away), and the rowid for the position.
*/
Pair<KeyPosition,Long> getIndexScanPosition(long rowid)
{
int index = (int)(rowid / DatabaseDescriptor.getIndexInterval());
return new Pair<KeyPosition,Long>(indexPositions.get(index),
// round down to the matched rowid
DatabaseDescriptor.getIndexInterval() * (long)index);
}
/**
* @param range An unwrapped AbstractBounds (rhs may either be greater than lhs, or equal to the minimum token).
* TODO: Add a method to AbstractBounds that lets us assert that it is unwrapped.
* @return The approximate min and max rowids (within INDEX_INTERVAL) matched by the given AbstractBound, or null
* if no rows match. Note that because of rounding, the maximum rowid may be past the end of the file.
*/
Pair<Long,Long> getRowidRange(AbstractBounds range)
{
// max (rounded up)
int maxIndex = binarySearch(new DecoratedKey(range.right, null));
if (maxIndex == -1 && Range.isWrapAround(range.left, range.right))
// wrapping range: rhs is "infinite"
maxIndex = indexPositions.size();
else if (maxIndex == -1)
// entire range falls before the beginning of the file
return null;
else
// round up to next position
maxIndex += 1;
long maxRowid = maxIndex * DatabaseDescriptor.getIndexInterval();
// min (already rounded down by summary)
int minIndex = binarySearch(new DecoratedKey(range.left, null));
long minRowid = minIndex == -1 ? 0 : minIndex * DatabaseDescriptor.getIndexInterval();
return new Pair<Long,Long>(minRowid, maxRowid);
}
/**
* This is a simple container for the index Key and its corresponding position
* in the index file. Binary search is performed on a list of these objects
* to find where to start looking for the index entry containing the data position
* (which will be turned into a PositionSize object)
*/
public static final class KeyPosition implements Comparable<KeyPosition>
{
public final DecoratedKey key;
public final long indexPosition;
public KeyPosition(DecoratedKey key, long indexPosition)
{
this.key = key;
this.indexPosition = indexPosition;
}
public int compareTo(KeyPosition kp)
{
return key.compareTo(kp.key);
}
public String toString()
{
return key + ":" + indexPosition;
}
}
}