streams/src/main/java/org/apache/kafka/streams/state/WindowStore.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;

import org.apache.kafka.streams.errors.InvalidStateStoreException;
import org.apache.kafka.streams.internals.ApiUtils;
import org.apache.kafka.streams.kstream.Windowed;
import org.apache.kafka.streams.processor.StateStore;

import java.time.Instant;

import static org.apache.kafka.streams.internals.ApiUtils.prepareMillisCheckFailMsgPrefix;

/**
 * Interface for storing the aggregated values of fixed-size time windows.
 * <p>
 * Note, that the stores' physical key type is {@link Windowed Windowed&lt;K&gt;}.
 *
 * @param <K> Type of keys
 * @param <V> Type of values
 */
public interface WindowStore<K, V> extends StateStore, ReadOnlyWindowStore<K, V> {

    /**
     * Put a key-value pair into the window with given window start timestamp
     * <p>
     * If serialized value bytes are null it is interpreted as delete. Note that deletes will be
     * ignored in the case of an underlying store that retains duplicates.
     *
     * @param key                  The key to associate the value to
     * @param value                The value; can be null
     * @param windowStartTimestamp The timestamp of the beginning of the window to put the key/value into
     * @throws InvalidStateStoreException if the store is not initialized
     * @throws NullPointerException if the given key is {@code null}
     */
    void put(K key, V value, long windowStartTimestamp);

    /**
     * Get all the key-value pairs with the given key and the time range from all the existing windows.
     * <p>
     * This iterator must be closed after use.
     * <p>
     * The time range is inclusive and applies to the starting timestamp of the window.
     * For example, if we have the following windows:
     * <pre>
     * +-------------------------------+
     * |  key  | start time | end time |
     * +-------+------------+----------+
     * |   A   |     10     |    20    |
     * +-------+------------+----------+
     * |   A   |     15     |    25    |
     * +-------+------------+----------+
     * |   A   |     20     |    30    |
     * +-------+------------+----------+
     * |   A   |     25     |    35    |
     * +--------------------------------
     * </pre>
     * And we call {@code store.fetch("A", 10, 20)} then the results will contain the first
     * three windows from the table above, i.e., all those where 10 &lt;= start time &lt;= 20.
     * <p>
     * For each key, the iterator guarantees ordering of windows, starting from the oldest/earliest
     * available window to the newest/latest window.
     *
     * @param key      the key to fetch
     * @param timeFrom time range start (inclusive)
     * @param timeTo   time range end (inclusive)
     * @return an iterator over key-value pairs {@code <timestamp, value>}
     * @throws InvalidStateStoreException if the store is not initialized
     * @throws NullPointerException       if the given key is {@code null}
     */
    // WindowStore keeps a long-based implementation of ReadOnlyWindowStore#fetch Instant-based
    // if super#fetch is removed, keep this implementation as it serves PAPI Stores.
    WindowStoreIterator<V> fetch(K key, long timeFrom, long timeTo);

    @Override
    default WindowStoreIterator<V> fetch(final K key,
                                         final Instant timeFrom,
                                         final Instant timeTo) throws IllegalArgumentException {
        return fetch(
            key,
            ApiUtils.validateMillisecondInstant(timeFrom, prepareMillisCheckFailMsgPrefix(timeFrom, "timeFrom")),
            ApiUtils.validateMillisecondInstant(timeTo, prepareMillisCheckFailMsgPrefix(timeTo, "timeTo")));
    }

    default WindowStoreIterator<V> backwardFetch(final K key,
                                                 final long timeFrom,
                                                 final long timeTo) {
        throw new UnsupportedOperationException();
    }

    @Override
    default WindowStoreIterator<V> backwardFetch(final K key,
                                                 final Instant timeFrom,
                                                 final Instant timeTo) throws IllegalArgumentException {
        return backwardFetch(
            key,
            ApiUtils.validateMillisecondInstant(timeFrom, prepareMillisCheckFailMsgPrefix(timeFrom, "timeFrom")),
            ApiUtils.validateMillisecondInstant(timeTo, prepareMillisCheckFailMsgPrefix(timeTo, "timeTo")));
    }

    /**
     * Get all the key-value pairs in the given key range and time range from all the existing windows.
     * <p>
     * This iterator must be closed after use.
     *
     * @param keyFrom     the first key in the range
     *                    A null value indicates a starting position from the first element in the store.
     * @param keyTo       the last key in the range
     *                    A null value indicates that the range ends with the last element in the store.
     * @param timeFrom time range start (inclusive)
     * @param timeTo   time range end (inclusive)
     * @return an iterator over windowed key-value pairs {@code <Windowed<K>, value>}
     * @throws InvalidStateStoreException if the store is not initialized
     */
    // WindowStore keeps a long-based implementation of ReadOnlyWindowStore#fetch Instant-based
    // if super#fetch is removed, keep this implementation as it serves PAPI Stores.
    KeyValueIterator<Windowed<K>, V> fetch(K keyFrom, K keyTo, long timeFrom, long timeTo);

    @Override
    default KeyValueIterator<Windowed<K>, V> fetch(final K keyFrom,
                                                   final K keyTo,
                                                   final Instant timeFrom,
                                                   final Instant timeTo) throws IllegalArgumentException {
        return fetch(
            keyFrom,
            keyTo,
            ApiUtils.validateMillisecondInstant(timeFrom, prepareMillisCheckFailMsgPrefix(timeFrom, "timeFrom")),
            ApiUtils.validateMillisecondInstant(timeTo, prepareMillisCheckFailMsgPrefix(timeTo, "timeTo")));
    }

    default KeyValueIterator<Windowed<K>, V> backwardFetch(final K keyFrom,
                                                           final K keyTo,
                                                           final long timeFrom,
                                                           final long timeTo) {
        throw new UnsupportedOperationException();
    }

    @Override
    default KeyValueIterator<Windowed<K>, V> backwardFetch(final K keyFrom,
                                                          final K keyTo,
                                                          final Instant timeFrom,
                                                          final Instant timeTo) throws IllegalArgumentException {
        return backwardFetch(
            keyFrom,
            keyTo,
            ApiUtils.validateMillisecondInstant(timeFrom, prepareMillisCheckFailMsgPrefix(timeFrom, "timeFrom")),
            ApiUtils.validateMillisecondInstant(timeTo, prepareMillisCheckFailMsgPrefix(timeTo, "timeTo")));
    }

    /**
     * Gets all the key-value pairs that belong to the windows within in the given time range.
     *
     * @param timeFrom the beginning of the time slot from which to search (inclusive)
     * @param timeTo   the end of the time slot from which to search (inclusive)
     * @return an iterator over windowed key-value pairs {@code <Windowed<K>, value>}
     * @throws InvalidStateStoreException if the store is not initialized
     */
    // WindowStore keeps a long-based implementation of ReadOnlyWindowStore#fetch Instant-based
    // if super#fetch is removed, keep this implementation as it serves PAPI Stores.
    KeyValueIterator<Windowed<K>, V> fetchAll(long timeFrom, long timeTo);

    @Override
    default KeyValueIterator<Windowed<K>, V> fetchAll(final Instant timeFrom, final Instant timeTo) throws IllegalArgumentException {
        return fetchAll(
            ApiUtils.validateMillisecondInstant(timeFrom, prepareMillisCheckFailMsgPrefix(timeFrom, "timeFrom")),
            ApiUtils.validateMillisecondInstant(timeTo, prepareMillisCheckFailMsgPrefix(timeTo, "timeTo")));
    }

    default KeyValueIterator<Windowed<K>, V> backwardFetchAll(final long timeFrom, final long timeTo) {
        throw new UnsupportedOperationException();
    }

    @Override
    default KeyValueIterator<Windowed<K>, V> backwardFetchAll(final Instant timeFrom, final Instant timeTo) throws IllegalArgumentException {
        return backwardFetchAll(
            ApiUtils.validateMillisecondInstant(timeFrom, prepareMillisCheckFailMsgPrefix(timeFrom, "timeFrom")),
            ApiUtils.validateMillisecondInstant(timeTo, prepareMillisCheckFailMsgPrefix(timeTo, "timeTo")));
    }
}