/*
* 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.conf.view;
import java.nio.ByteBuffer;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import org.apache.cassandra.index.sasi.SSTableIndex;
import org.apache.cassandra.index.sasi.disk.OnDiskIndexBuilder;
import org.apache.cassandra.index.sasi.plan.Expression;
import org.apache.cassandra.index.sasi.utils.trie.KeyAnalyzer;
import org.apache.cassandra.index.sasi.utils.trie.PatriciaTrie;
import org.apache.cassandra.index.sasi.utils.trie.Trie;
import org.apache.cassandra.db.marshal.AbstractType;
import org.apache.cassandra.utils.Interval;
import org.apache.cassandra.utils.IntervalTree;
import com.google.common.collect.Sets;
/**
* This class is an extension over RangeTermTree for string terms,
* it is required because interval tree can't handle matching if search is on the
* prefix of min/max of the range, so for ascii/utf8 fields we build an additional
* prefix trie (including both min/max terms of the index) and do union of the results
* of the prefix tree search and results from the interval tree lookup.
*/
public class PrefixTermTree extends RangeTermTree
{
private final OnDiskIndexBuilder.Mode mode;
private final Trie<ByteBuffer, Set<SSTableIndex>> trie;
public PrefixTermTree(ByteBuffer min, ByteBuffer max,
Trie<ByteBuffer, Set<SSTableIndex>> trie,
IntervalTree<Term, SSTableIndex, Interval<Term, SSTableIndex>> ranges,
OnDiskIndexBuilder.Mode mode,
AbstractType<?> comparator)
{
super(min, max, ranges, comparator);
this.mode = mode;
this.trie = trie;
}
public Set<SSTableIndex> search(Expression e)
{
Map<ByteBuffer, Set<SSTableIndex>> indexes = (e == null || e.lower == null || mode == OnDiskIndexBuilder.Mode.CONTAINS)
? trie : trie.prefixMap(e.lower.value);
Set<SSTableIndex> view = new HashSet<>(indexes.size());
indexes.values().forEach(view::addAll);
return Sets.union(view, super.search(e));
}
public static class Builder extends RangeTermTree.Builder
{
private final PatriciaTrie<ByteBuffer, Set<SSTableIndex>> trie;
protected Builder(OnDiskIndexBuilder.Mode mode, final AbstractType<?> comparator)
{
super(mode, comparator);
trie = new PatriciaTrie<>(new ByteBufferKeyAnalyzer(comparator));
}
public void addIndex(SSTableIndex index)
{
super.addIndex(index);
addTerm(index.minTerm(), index);
addTerm(index.maxTerm(), index);
}
public TermTree build()
{
return new PrefixTermTree(min, max, trie, IntervalTree.build(intervals), mode, comparator);
}
private void addTerm(ByteBuffer term, SSTableIndex index)
{
Set<SSTableIndex> indexes = trie.get(term);
if (indexes == null)
trie.put(term, (indexes = new HashSet<>()));
indexes.add(index);
}
}
private static class ByteBufferKeyAnalyzer implements KeyAnalyzer<ByteBuffer>
{
private final AbstractType<?> comparator;
public ByteBufferKeyAnalyzer(AbstractType<?> comparator)
{
this.comparator = comparator;
}
/**
* A bit mask where the first bit is 1 and the others are zero
*/
private static final int MSB = 1 << Byte.SIZE-1;
public int compare(ByteBuffer a, ByteBuffer b)
{
return comparator.compare(a, b);
}
public int lengthInBits(ByteBuffer o)
{
return o.remaining() * Byte.SIZE;
}
public boolean isBitSet(ByteBuffer key, int bitIndex)
{
if (bitIndex >= lengthInBits(key))
return false;
int index = bitIndex / Byte.SIZE;
int bit = bitIndex % Byte.SIZE;
return (key.get(index) & mask(bit)) != 0;
}
public int bitIndex(ByteBuffer key, ByteBuffer otherKey)
{
int length = Math.max(key.remaining(), otherKey.remaining());
boolean allNull = true;
for (int i = 0; i < length; i++)
{
byte b1 = valueAt(key, i);
byte b2 = valueAt(otherKey, i);
if (b1 != b2)
{
int xor = b1 ^ b2;
for (int j = 0; j < Byte.SIZE; j++)
{
if ((xor & mask(j)) != 0)
return (i * Byte.SIZE) + j;
}
}
if (b1 != 0)
allNull = false;
}
return allNull ? KeyAnalyzer.NULL_BIT_KEY : KeyAnalyzer.EQUAL_BIT_KEY;
}
public boolean isPrefix(ByteBuffer key, ByteBuffer prefix)
{
if (key.remaining() < prefix.remaining())
return false;
for (int i = 0; i < prefix.remaining(); i++)
{
if (key.get(i) != prefix.get(i))
return false;
}
return true;
}
/**
* Returns the {@code byte} value at the given index.
*/
private byte valueAt(ByteBuffer value, int index)
{
return index >= 0 && index < value.remaining() ? value.get(index) : 0;
}
/**
* Returns a bit mask where the given bit is set
*/
private int mask(int bit)
{
return MSB >>> bit;
}
}
}