Status

Current state: Under Discussion

Discussion thread: here [Change the link from the KIP proposal email archive to your own email thread]

Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

Motivation

The main goal is supporting interactive queries in presence of versioned state stores (KIP-889) in AK. For this KIP, the following query types are considered to be implemented.

Key Queries:

single-key latest-value lookup
single-key lookup with timestamp (upper) bound
single-key query with timestamp range
single-key all versions query

Range Queries

key-range latest-value query
key-range with lower bound latest-value query
key-range with upper bound latest-value query
all-keys (no bound) latest-value query
key-range query with timestamp (upper) bound
key-range with lower bound with timestamp (upper) bound
key-range with upper bound with timestamp (upper) bound
all-keys (no bound) with timestamp (upper) bound
key-range query with timestamp range
key-range query with lower bound with timestamp range
key-range query with upper bound with timestamp range
all-keys (no bound) with timestamp range
key-range query all-versions
key-range query with lower bound all-versions
key-range query with upper bond all-versions
all-keys query (no bound) all-versions (entire store)

Public Interfaces

In this KIP we propose two new public classes: VersionedKeyQuery and VersionedRangeQuery that will be described in the next section. Moreover, the public interface ValueIterator is used to iterate over different values that are returned from a single-key query (each value corresponds to a timestamp).

Proposed Changes

For single-key queries, VersionedKeyQuery and ValueIterator classes will be used.

ValueIterator.java

package org.apache.kafka.streams.state;

/**
 * Iterator interface of {@link Value}.
 * <p>
 * Users must call its {@code close} method explicitly upon completeness to release resources,
 * or use try-with-resources statement (available since JDK7) for this {@link Closeable} class.
 * Note that {@code remove()} is not supported.
 *
 * @param <V> Type of values
 */
public interface ValueIterator<V> extends Iterator<V>, Closeable {

    @Override
    void close();

    /**
     * Peek at the next key without advancing the iterator
     * @return the key of the next value that would be returned from the next call to next
     */
    V peekNextRecord();
}

VersionedKeyQuery.java

package org.apache.kafka.streams.query;

@Evolving
public final class VersionedKeyQuery<K, V> implements Query<ValueIterator<VersionedRecord<V>>> {

  private final K key;
  private final Optional<Long> asOfTimestamp;
  private final Optional<Long> untilTimestamp;

  private VersionedKeyQuery(final K key, Optional<Long> asOfTimestamp, Optional<Long> untilTimestamp);

  /**
   * Interactive key query that returns one record with the specified key
   * * and with the latest timestamp
   * @param key The key to retrieve
   * @param <K> The key type
   * @param <V> The value type
   */
  public static <K, V> VersionedKeyQuery<K, V> withKeyLatestValue(final K key);

/**
   * Interactive key query that returns one record with the specified key
   * * and with the greatest timestamp <= untilTimeStamp
   * @param key The key to retrieve
   * @param untilTimeStamp The upperbound for timestamp
   * @param <K> The key type
   * @param <V> The value type
   */
  public static <K, V> VersionedKeyQuery<K, V> withKeyWithTimestampBound(final K key, long untilTimeStamp);

  /**
   * Interactive key query that returns the records with the specified key
   * * within the specified time range.
   * @param key The key to retrieve
   * @param <K> The key type
   * @param <V> The value type
   */
  public static <K, V> VersionedKeyQuery<K, V> withKeyWithTimestampRange(final K key, long asOfTimestamp, long untilTimestamp);

  /**
   * Interactive key query that returns all the records in the store with the specified key.
   * @param key The key to retrieve
   * @param <K> The key type
   * @param <V> The value type
   */
  public static <K, V> VersionedKeyQuery<K, V> withKeyAllVersions(final K key);

  /**
   * The key that was specified for this query.
   */
  public K getKey();


  /**
   * The lower bound for timestamp of the query, if specified
   */
  public Optional<Long> getAsOfTimestamp();

  /**
   * The upper bound for timestamp of the query, if specified
   */
  public Optional<Long> getUntilTimestamp();
}

For supporting range queries, VersionedRangeQuery class is used.

VersionedRangeQuery.java

package org.apache.kafka.streams.query;
@Evolving
public final class VersionedRangeQuery<K, V> implements Query<KeyValueIterator<K, VersionedRecord<V>>> {
    private final Optional<K> lower;
    private final Optional<K> upper;
    private final Optional<Long> asOfTimestamp;
    private final Optional<Long> untilTimestamp;

    private VersionedRangeQuery(
        final Optional<K> lower,
        final Optional<K> upper,
        final Optional<Long> asOfTimestamp,
        final Optional<Long> untilTimestamp);

    /**
     * Interactive range query using a lower and upper bound to filter the keys returned.
     * * For each key only the record with the latest timestamp is returned.
     * @param lower The key that specifies the lower bound of the range
     * @param upper The key that specifies the upper bound of the range
     * @param <K> The key type
     * @param <V> The value type
     */
    public static <K, V> VersionedRangeQuery<K, V> keyRangeLatestValue(final K lower, final K upper);

    /**
     * Interactive range query using a lower bound to filter the keys returned.
     * * For each key only the record with the latest timestamp is returned.
     * @param lower The key that specifies the lower bound of the range
     * @param <K> The key type
     * @param <V> The value type
     */
    public static <K, V> VersionedRangeQuery<K, V> withLowerBoundLatestValue(final K lower);

    /**
     * Interactive range query using a lower bound to filter the keys returned.
     * * For each key only the record with the latest timestamp is returned.
     * @param upper The key that specifies the upper bound of the range
     * @param <K> The key type
     * @param <V> The value type
     */
    public static <K, V> VersionedRangeQuery<K, V> withUpperBoundLatestValue(final K upper);

    /**
     * Interactive scan query that returns all records in the store.
     * * For each key only the record with the latest timestamp is returned.
     * @param <K> The key type
     * @param <V> The value type
     */
    public static <K, V> VersionedRangeQuery<K, V> withNoBoundLatestValue();

    /**
     * Interactive range query using a lower and upper bound to filter the keys returned.
     * * For each key all the records with the greatest timestamp <= untilTimeStamp are returned.
     * @param lower The key that specifies the lower bound of the range
     * @param upper The key that specifies the upper bound of the range
     * @param untilTimeStamp The upperbound for timestamp
     * @param <K> The key type
     * @param <V> The value type
     */
    public static <K, V> VersionedRangeQuery<K, V> KeyRangeWithTimestampBound(final K lower, final K upper, final long untilTimeStamp);

    /**
     * Interactive range query using a lower bound to filter the keys returned.
     * * For each key all the records with the greatest timestamp <= untilTimeStamp are returned.
     * @param lower The key that specifies the lower bound of the range
     * @param untilTimeStamp The upperbound for timestamp
     * @param <K> The key type
     * @param <V> The value type
     */
    public static <K, V> VersionedRangeQuery<K, V> withLowerBoundWithTimestampBound(final K lower, final long untilTimeStamp);

    /**
     * Interactive range query using an upper and upper bound to filter the keys returned.
     * * For each key all the records with the greatest timestamp <= untilTimeStamp are returned.
     * @param upper The key that specifies the upper bound of the range
     * @param untilTimeStamp The upperbound for timestamp
     * @param <K> The key type
     * @param <V> The value type
     */
    public static <K, V> VersionedRangeQuery<K, V> withUpperBoundWithTimestampBound(final K upper, final long untilTimeStamp);

    /**
     * Interactive scan query that returns all records in the store.
     * * For each key all the records with the greatest timestamp <= untilTimeStamp are returned.
     * @param untilTimeStamp The upperbound for timestamp
     * @param <K> The key type
     * @param <V> The value type
     */
    public static <K, V> VersionedRangeQuery<K, V> withNoBoundWithTimestampBound(final long untilTimeStamp);

    /**
     * Interactive range query using a lower and upper bound to filter the keys returned.
     * * For each key all the records within the specified time range are returned.
     * @param lower The key that specifies the lower bound of the range
     * @param upper The key that specifies the upper bound of the range
     * @param <K> The key type
     * @param <V> The value type
     */
    public static <K, V> VersionedRangeQuery<K, V> keyRangeWithTimestampRange(final K lower, final K upper, final long asOfTimestamp, final long untilTimestamp);

    /**
     * Interactive range query using a lower bound to filter the keys returned.
     * * For each key all the records within the specified time range are returned.
     * @param lower The key that specifies the lower bound of the range
     * @param <K> The key type
     * @param <V> The value type
     */
    public static <K, V> VersionedRangeQuery<K, V> withLowerBoundWithTimestampRange(final K lower, final long asOfTimestamp, final long untilTimestamp);

    /**
     * Interactive range query using an upper bound to filter the keys returned.
     * * For each key all the records within the specified time range are returned.
     * @param upper The key that specifies the upper bound of the range
     * @param <K> The key type
     * @param <V> The value type
     */
    public static <K, V> VersionedRangeQuery<K, V> withUpperBoundWithTimestampRange(final K upper, final long asOfTimestamp, final long untilTimestamp);

    /**
     * Interactive scan query that returns all records in the store.
     * * For each key all the records within the specified time range are returned.
     * @param <K> The key type
     * @param <V> The value type
     */
    public static <K, V> VersionedRangeQuery<K, V> withNoBoundWithTimestampRange(final long asOfTimestamp, final long untilTimestamp);

    /**
     * Interactive range query using a lower and upper bound to filter the keys returned.
     * For each key all values from the oldest till the newest record existing in the state store
     * * are returned
     * @param lower The key that specifies the lower bound of the range
     * @param upper The key that specifies the upper bound of the range
     * @param <K> The key type
     * @param <V> The value type
     */
    public static <K, V> VersionedRangeQuery<K, V> keyRangeAllVersions(final K lower, final K upper);

    /**
     * Interactive range query using a lower bound to filter the keys returned.
     * For each key all values from the oldest till the newest record existing in the state store
     * * are returned
     * @param lower The key that specifies the lower bound of the range
     * @param <K> The key type
     * @param <V> The value type
     */
    public static <K, V> VersionedRangeQuery<K, V> withLowerBoundAllVersions(final K lower);

    /**
     * Interactive range query using an upper bound to filter the keys returned.
     * For each key all values from the oldest till the newest record existing in the state store
     * * are returned
     * @param upper The key that specifies the lower bound of the range
     * @param <K> The key type
     * @param <V> The value type
     */
    public static <K, V> VersionedRangeQuery<K, V> withUpperBoundAllVersions(final K upper);

    /**
     * Interactive scan query that returns all records in the store.
     * For each key all values from the oldest till the newest record existing in the state store
     * * are returned
     * @param <K> The key type
     * @param <V> The value type
     */
    public static <K, V> VersionedRangeQuery<K, V> withNoBoundAllVersions();

    /**
     * The lower bound of the query, if specified.
     */
    public Optional<K> getLowerBound();

    /**
     * The upper bound of the query, if specified
     */
    public Optional<K> getUpperBound();

    /**
     * The upper bound for timestamp of the query, if specified
     */
    public Optional<Long> getAsOfTimestamp();
    /**
     * The upper bound for timestamp of the query, if specified
     */
    public Optional<Long> getUntilTimestamp();
}

Examples

The following example illustrates the use of the VersionedKeyQuery class to query a versioned state store.

final VersionedKeyQuery<Integer, Integer> query = VersionedKeyQuery.withKeyAllVersions(1);

final StateQueryRequest<ValueIterator<VersionedRecord<Integer>>> request =
        inStore("my_store").withQuery(query);

final StateQueryResult<ValueIterator<VersionedRecord<Integer>>> versionedKeyResult = kafkaStreams.query(request);

// Get the results from all partitions.
final Map<Integer, QueryResult<ValueIterator<VersionedRecord<Integer>>>> partitionResults = versionedKeyResult.getPartitionResults();
for (final Entry<Integer, QueryResult<ValueIterator<VersionedRecord<Integer>>>> entry : partitionResults.entrySet()) {
	try (final ValueIterator<VersionedRecord<Integer>> iterator = entry.getValue().getResult()) {
        while (iterator.hasNext()) {
          final VersionedRecord<Integer> record = iterator.next();
          Long timestamp = record.timestamp();
		  Integer value = record.value();	
        }
     }
}

The following example illustrates the use of the VersionedRangeQuery class to query a versioned state store.

final VersionedRangeQuery<Integer, Integer> query =
        VersionedRangeQuery.keyRangeWithTimestampRange(1, 2, 1690201149, 1690373949);

final StateQueryRequest<KeyValueIterator<Integer, VersionedRecord<Integer>>> request =
        inStore("my_store").withQuery(query);

final StateQueryResult<KeyValueIterator<Integer, VersionedRecord<Integer>>> versionedRangeResult = kafkaStreams.query(request);

// Get the results from all partitions.
final Map<Integer, QueryResult<KeyValueIterator<Integer, VersionedRecord<Integer>>>> partitionResults = versionedRangeResult.getPartitionResults();
for (final Entry<Integer, QueryResult<KeyValueIterator<Integer, VersionedRecord<Integer>>>> entry : partitionResults.entrySet()) {
	try (final KeyValueIterator<Integer, VersionedRecord<Integer>> iterator = entry.getValue().getResult()) {
        while (iterator.hasNext()) {
          final KeyValue<Integer, VersionedRecord<Integer>> record = iterator.next();
          Integer key = record.key;
          Integer value = record.value.value();
          Long timestamp = record.value.timestamp();
        }
     }
}

Compatibility, Deprecation, and Migration Plan

Since this is a completely new set of APIs, no backward compatibility concerns are anticipated.
Since nothing is deprecated in this KIP, users have no need to migrate unless they want to.

Space shortcuts

Child pages

Status

Motivation

Public Interfaces

Proposed Changes

Examples

Compatibility, Deprecation, and Migration Plan

Space shortcuts

Child pages

KIP-960: Support interactive queries (IQv2) for versioned state stores

Status

Motivation

Public Interfaces

Proposed Changes

Examples

Compatibility, Deprecation, and Migration Plan