com.palantir.atlasdb.keyvalue.rocksdb.impl.RocksComparator.java Source code

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Here is the source code for com.palantir.atlasdb.keyvalue.rocksdb.impl.RocksComparator.java

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/**
 * Copyright 2015 Palantir Technologies
 *
 * Licensed under the BSD-3 License (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://opensource.org/licenses/BSD-3-Clause
 *
 * 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 com.palantir.atlasdb.keyvalue.rocksdb.impl;

import java.util.Arrays;

import org.rocksdb.Comparator;
import org.rocksdb.ComparatorOptions;
import org.rocksdb.Slice;

import com.google.common.primitives.Longs;
import com.google.common.primitives.UnsignedBytes;
import com.palantir.atlasdb.ptobject.EncodingUtils;

public class RocksComparator extends Comparator {
    public static final RocksComparator INSTANCE = new RocksComparator(new ComparatorOptions());

    public RocksComparator(ComparatorOptions copt) {
        super(copt);
    }

    @Override
    public String name() {
        return RocksComparatorName.V2.getComparatorName();
    }

    // This method is a hotspot, logic from RocksDbKeyValueServices.parseCellAndTs
    // is duplicated and tuned for perf.
    @Override
    public int compare(Slice a, Slice b) {
        byte[] adata = a.data();
        byte[] bdata = b.data();
        byte[] rowSizeBytes = new byte[2];
        rowSizeBytes[0] = adata[adata.length - 1];
        rowSizeBytes[1] = adata[adata.length - 2];
        int aRowSize = (int) EncodingUtils.decodeVarLong(rowSizeBytes);
        rowSizeBytes[0] = bdata[bdata.length - 1];
        rowSizeBytes[1] = bdata[bdata.length - 2];
        int bRowSize = (int) EncodingUtils.decodeVarLong(rowSizeBytes);

        int comp = UnsignedBytes.lexicographicalComparator().compare(Arrays.copyOf(adata, aRowSize),
                Arrays.copyOf(bdata, bRowSize));
        if (comp != 0) {
            return comp;
        }

        int aColEnd = adata.length - 8 - EncodingUtils.sizeOfVarLong(aRowSize);
        int bColEnd = bdata.length - 8 - EncodingUtils.sizeOfVarLong(bRowSize);
        comp = UnsignedBytes.lexicographicalComparator().compare(Arrays.copyOfRange(adata, aRowSize, aColEnd),
                Arrays.copyOfRange(bdata, bRowSize, bColEnd));
        if (comp != 0) {
            return comp;
        }

        long aTs = Longs.fromBytes(adata[aColEnd + 0], adata[aColEnd + 1], adata[aColEnd + 2], adata[aColEnd + 3],
                adata[aColEnd + 4], adata[aColEnd + 5], adata[aColEnd + 6], adata[aColEnd + 7]);
        long bTs = Longs.fromBytes(bdata[bColEnd + 0], bdata[bColEnd + 1], bdata[bColEnd + 2], bdata[bColEnd + 3],
                bdata[bColEnd + 4], bdata[bColEnd + 5], bdata[bColEnd + 6], bdata[bColEnd + 7]);

        // Note: Ordering is reversed, later timestamps come before eariler ones.
        return Long.compare(bTs, aTs);
    }
}