kafka RocksDBRangeIterator 源码

kafka RocksDBRangeIterator 代码

文件路径：/streams/src/main/java/org/apache/kafka/streams/state/internals/RocksDBRangeIterator.java

/*
 * 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.kafka.streams.state.internals;

import org.apache.kafka.common.utils.Bytes;
import org.apache.kafka.streams.KeyValue;
import org.apache.kafka.streams.state.KeyValueIterator;
import org.rocksdb.RocksIterator;

import java.util.Comparator;
import java.util.Set;

class RocksDBRangeIterator extends RocksDbIterator {
    // RocksDB's JNI interface does not expose getters/setters that allow the
    // comparator to be pluggable, and the default is lexicographic, so it's
    // safe to just force lexicographic comparator here for now.
    private final Comparator<byte[]> comparator = Bytes.BYTES_LEXICO_COMPARATOR;
    private final byte[] rawLastKey;
    private final boolean forward;
    private final boolean toInclusive;

    RocksDBRangeIterator(final String storeName,
                         final RocksIterator iter,
                         final Set<KeyValueIterator<Bytes, byte[]>> openIterators,
                         final Bytes from,
                         final Bytes to,
                         final boolean forward,
                         final boolean toInclusive) {
        super(storeName, iter, openIterators, forward);
        this.forward = forward;
        this.toInclusive = toInclusive;
        if (forward) {
            if (from == null) {
                iter.seekToFirst();
            } else {
                iter.seek(from.get());
            }
            rawLastKey = to == null ? null : to.get();
        } else {
            if (to == null) {
                iter.seekToLast();
            } else {
                iter.seekForPrev(to.get());
            }
            rawLastKey = from == null ? null : from.get();
        }
    }

    @Override
    public KeyValue<Bytes, byte[]> makeNext() {
        final KeyValue<Bytes, byte[]> next = super.makeNext();
        if (next == null) {
            return allDone();
        } else if (rawLastKey == null) {
            //null means range endpoint is open
            return next;

        } else {
            if (forward) {
                if (comparator.compare(next.key.get(), rawLastKey) < 0) {
                    return next;
                } else if (comparator.compare(next.key.get(), rawLastKey) == 0) {
                    return toInclusive ? next : allDone();
                } else {
                    return allDone();
                }
            } else {
                if (comparator.compare(next.key.get(), rawLastKey) >= 0) {
                    return next;
                } else {
                    return allDone();
                }
            }
        }
    }
}

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