/*
* 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.apache.kafka.streams.state.StateSerdes;
import java.util.NoSuchElementException;
/**
* Merges two iterators. Assumes each of them is sorted by key
*
* @param <K>
* @param <V>
*/
abstract class AbstractMergedSortedCacheStoreIterator<K, KS, V> implements KeyValueIterator<K, V> {
private final PeekingKeyValueIterator<Bytes, LRUCacheEntry> cacheIterator;
private final KeyValueIterator<KS, byte[]> storeIterator;
protected final StateSerdes<K, V> serdes;
AbstractMergedSortedCacheStoreIterator(final PeekingKeyValueIterator<Bytes, LRUCacheEntry> cacheIterator,
final KeyValueIterator<KS, byte[]> storeIterator,
final StateSerdes<K, V> serdes) {
this.cacheIterator = cacheIterator;
this.storeIterator = storeIterator;
this.serdes = serdes;
}
abstract int compare(final Bytes cacheKey, final KS storeKey);
abstract K deserializeStoreKey(final KS key);
abstract KeyValue<K, V> deserializeStorePair(final KeyValue<KS, byte[]> pair);
abstract K deserializeCacheKey(final Bytes cacheKey);
private boolean isDeletedCacheEntry(final KeyValue<Bytes, LRUCacheEntry> nextFromCache) {
return nextFromCache.value.value == null;
}
@Override
public boolean hasNext() {
// skip over items deleted from cache, and corresponding store items if they have the same key
while (cacheIterator.hasNext() && isDeletedCacheEntry(cacheIterator.peekNext())) {
if (storeIterator.hasNext()) {
final KS nextStoreKey = storeIterator.peekNextKey();
// advance the store iterator if the key is the same as the deleted cache key
if (compare(cacheIterator.peekNextKey(), nextStoreKey) == 0) {
storeIterator.next();
}
}
cacheIterator.next();
}
return cacheIterator.hasNext() || storeIterator.hasNext();
}
@Override
public KeyValue<K, V> next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
final Bytes nextCacheKey = cacheIterator.hasNext() ? cacheIterator.peekNextKey() : null;
final KS nextStoreKey = storeIterator.hasNext() ? storeIterator.peekNextKey() : null;
if (nextCacheKey == null) {
return nextStoreValue(nextStoreKey);
}
if (nextStoreKey == null) {
return nextCacheValue(nextCacheKey);
}
final int comparison = compare(nextCacheKey, nextStoreKey);
if (comparison > 0) {
return nextStoreValue(nextStoreKey);
} else if (comparison < 0) {
return nextCacheValue(nextCacheKey);
} else {
// skip the same keyed element
storeIterator.next();
return nextCacheValue(nextCacheKey);
}
}
private KeyValue<K, V> nextStoreValue(KS nextStoreKey) {
final KeyValue<KS, byte[]> next = storeIterator.next();
if (!next.key.equals(nextStoreKey)) {
throw new IllegalStateException("Next record key is not the peeked key value; this should not happen");
}
return deserializeStorePair(next);
}
private KeyValue<K, V> nextCacheValue(Bytes nextCacheKey) {
final KeyValue<Bytes, LRUCacheEntry> next = cacheIterator.next();
if (!next.key.equals(nextCacheKey)) {
throw new IllegalStateException("Next record key is not the peeked key value; this should not happen");
}
return KeyValue.pair(deserializeCacheKey(next.key), serdes.valueFrom(next.value.value));
}
@Override
public K peekNextKey() {
if (!hasNext()) {
throw new NoSuchElementException();
}
final Bytes nextCacheKey = cacheIterator.hasNext() ? cacheIterator.peekNextKey() : null;
final KS nextStoreKey = storeIterator.hasNext() ? storeIterator.peekNextKey() : null;
if (nextCacheKey == null) {
return deserializeStoreKey(nextStoreKey);
}
if (nextStoreKey == null) {
return deserializeCacheKey(nextCacheKey);
}
final int comparison = compare(nextCacheKey, nextStoreKey);
if (comparison > 0) {
return deserializeStoreKey(nextStoreKey);
} else if (comparison < 0) {
return deserializeCacheKey(nextCacheKey);
} else {
// skip the same keyed element
storeIterator.next();
return deserializeCacheKey(nextCacheKey);
}
}
@Override
public void remove() {
throw new UnsupportedOperationException("remove() is not supported in " + getClass().getName());
}
@Override
public void close() {
cacheIterator.close();
storeIterator.close();
}
}