org.apache.cassandra.index.sasi.sa.SuffixSA Maven / Gradle / Ivy
/*
* 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.sa;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import org.apache.cassandra.index.sasi.disk.DynamicTokenTreeBuilder;
import org.apache.cassandra.index.sasi.disk.OnDiskIndexBuilder;
import org.apache.cassandra.index.sasi.disk.TokenTreeBuilder;
import org.apache.cassandra.db.marshal.AbstractType;
import org.apache.cassandra.utils.LongTimSort;
import org.apache.cassandra.utils.Pair;
import com.google.common.base.Charsets;
public class SuffixSA extends SA
{
public SuffixSA(AbstractType comparator, OnDiskIndexBuilder.Mode mode)
{
super(comparator, mode);
}
protected Term getTerm(ByteBuffer termValue, TokenTreeBuilder tokens)
{
return new CharTerm(charCount, Charsets.UTF_8.decode(termValue.duplicate()), tokens);
}
public TermIterator finish()
{
return new SASuffixIterator();
}
private class SASuffixIterator extends TermIterator
{
private static final int COMPLETE_BIT = 31;
private final long[] suffixes;
private int current = 0;
private IndexedTerm lastProcessedSuffix;
private TokenTreeBuilder container;
public SASuffixIterator()
{
// each element has term index and char position encoded as two 32-bit integers
// to avoid binary search per suffix while sorting suffix array.
suffixes = new long[charCount];
long termIndex = -1, currentTermLength = -1;
boolean isComplete = false;
for (int i = 0; i < charCount; i++)
{
if (i >= currentTermLength || currentTermLength == -1)
{
Term currentTerm = terms.get((int) ++termIndex);
currentTermLength = currentTerm.getPosition() + currentTerm.length();
isComplete = true;
}
suffixes[i] = (termIndex << 32) | i;
if (isComplete)
suffixes[i] |= (1L << COMPLETE_BIT);
isComplete = false;
}
LongTimSort.sort(suffixes, (a, b) -> {
Term aTerm = terms.get((int) (a >>> 32));
Term bTerm = terms.get((int) (b >>> 32));
return comparator.compare(aTerm.getSuffix(clearCompleteBit(a) - aTerm.getPosition()),
bTerm.getSuffix(clearCompleteBit(b) - bTerm.getPosition()));
});
}
private int clearCompleteBit(long value)
{
return (int) (value & ~(1L << COMPLETE_BIT));
}
private Pair suffixAt(int position)
{
long index = suffixes[position];
Term term = terms.get((int) (index >>> 32));
boolean isPartitial = (index & ((long) 1 << 31)) == 0;
return Pair.create(new IndexedTerm(term.getSuffix(clearCompleteBit(index) - term.getPosition()), isPartitial), term.getTokens());
}
public ByteBuffer minTerm()
{
return suffixAt(0).left.getBytes();
}
public ByteBuffer maxTerm()
{
return suffixAt(suffixes.length - 1).left.getBytes();
}
protected Pair computeNext()
{
while (true)
{
if (current >= suffixes.length)
{
if (lastProcessedSuffix == null)
return endOfData();
Pair result = finishSuffix();
lastProcessedSuffix = null;
return result;
}
Pair suffix = suffixAt(current++);
if (lastProcessedSuffix == null)
{
lastProcessedSuffix = suffix.left;
container = new DynamicTokenTreeBuilder(suffix.right);
}
else if (comparator.compare(lastProcessedSuffix.getBytes(), suffix.left.getBytes()) == 0)
{
lastProcessedSuffix = suffix.left;
container.add(suffix.right);
}
else
{
Pair result = finishSuffix();
lastProcessedSuffix = suffix.left;
container = new DynamicTokenTreeBuilder(suffix.right);
return result;
}
}
}
private Pair finishSuffix()
{
return Pair.create(lastProcessedSuffix, container.finish());
}
}
}