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Status

Current state: Under Discussion

Discussion thread: https://lists.apache.org/thread/klbjwb0906y1r05dp3wbklowm3bq41zr

JIRA: KAFKA-15795 - Getting issue details... STATUS  

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

Motivation

We aim to enhance the WindowRangeQuery  by supporting a new method: fetch(keyFrom, keyTo, from, to). Currently, WindowRangeQuery  utilizes KeyValueIterator<Windowed<K>, V> fetchAll(Instant timeFrom, Instant timeTo)  for retrieving all key-value pairs within a specified time range. However, we propose to use KeyValueIterator<Windowed<K>, V> fetch(K keyFrom, K keyTo, Instant timeFrom, Instant timeTo)  instead. This new method will provide a KeyValueIterator<Windowed<K>, V>  that allows users to iterate over windowed key-value pairs {<Windowed<K>, value>} , spanning the entire time range.

With this new method, users can retrieve window sessions for specific keys, rather than all keys, which enables a more targeted query. This is an improvement over the fetchAll  method, which only allows retrieval of all key's window sessions without the ability to specify a range of keys.

Additionally, this enhancement also allows the WindowRangeQuery  to support WindowKeyQuery  functionality. Users seeking to query window sessions for a specific key can do so by setting keyFrom  and keyTo  to be equal. This dual functionality provides more flexibility and efficiency in querying windowed keys.

Proposed Changes

We need to introduce several additional arguments, upper, key, newTimeFrom, newTimeTo , in the WindowRangeQuery  class, and subsequently update the methods within this class to accommodate these new parameters.
We also add several new method withAllKey(), fromTime(), toTime(), withKeyRange() to this class.

WindowRangeQuery
public class WindowRangeQuery<K, V> implements Query<KeyValueIterator<Windowed<K>, V>> {

    // newly added
    public static <K, V> WindowRangeQuery<K, V> withAllKey()

    // newly added
    public WindowRangeQuery<K, V> fromTime(final Instant timeFrom) 

    // newly added
    public WindowRangeQuery<K, V> toTime(final Instant timeTo) 

    // newly added
    public static <K, V> WindowRangeQuery<K, V> withKeyRange(final K lower, final K upper) 

    //@Deprecated
    public Optional<Instant> getOldTimeFrom() 

    //@Deprecated
    public Optional<Instant> getOldTimeTo() 

    // newly added
    public Optional<Instant> timeFrom() 

    // newly added
    public Optional<Instant> timeTo() 
	
    // newly added
    public Optional<K> key() 

}


Compatibility, Deprecation, and Migration Plan

  • Utilizing the existing WindowRangeQuery  class, we can make some modifications to realize the concepts of KeyValueIterator<Windowed<K>, V> fetch(K keyFrom, K keyTo, Instant timeFrom, Instant timeTo) . 
  • We want to deprecate WindowKeyQuery  class

Examples

The following example illustrates the use of the WindowRangeQuery class to query a kv-store or ts kv-store.

withWindowKeyRange(2, 2, time=2023-01-01T10:05:00.00Z, time=2023-01-01T10:10:00.00Z), the result is (4, 5)

shouldHandleWindowKeyQuery
 public <V> void shouldHandleWindowRangeQuery(
        final Integer keyFrom,
        final Integer keyTo,
        final Instant timeFrom,
        final Instant timeTo,
        final Function<V, Integer> valueExtactor,
        final Set<Integer> expectedValues) {

	    final WindowRangeQuery<Integer, V> query = WindowRangeQuery.withKeyRange(keyFrom, keyTo).fromTime(timeFrom).toTime(timeTo);

        final StateQueryRequest<KeyValueIterator<Windowed<Integer>, V>> request =
            inStore(STORE_NAME)
                .withQuery(query)
                .withPartitions(mkSet(0, 1))
                .withPositionBound(PositionBound.at(INPUT_POSITION));

        final StateQueryResult<KeyValueIterator<Windowed<Integer>, V>> result =
            IntegrationTestUtils.iqv2WaitForResult(kafkaStreams, request);

        if (result.getGlobalResult() != null) {
            fail("global tables aren't implemented");
        } else {
            final Set<Integer> actualValues = new HashSet<>();
            final Map<Integer, QueryResult<KeyValueIterator<Windowed<Integer>, V>>> queryResult = result.getPartitionResults();
            for (final int partition : queryResult.keySet()) {
                final boolean failure = queryResult.get(partition).isFailure();
                if (failure) {
                    throw new AssertionError(queryResult.toString());
                }
                assertThat(queryResult.get(partition).isSuccess(), is(true));

                assertThrows(
                    IllegalArgumentException.class,
                    queryResult.get(partition)::getFailureReason
                );
                assertThrows(
                    IllegalArgumentException.class,
                    queryResult.get(partition)::getFailureMessage
                );

                try (final KeyValueIterator<Windowed<Integer>, V> iterator = queryResult.get(partition).getResult()) {
                    while (iterator.hasNext()) {
                        actualValues.add(valueExtactor.apply(iterator.next().value));
                    }
                }
                assertThat(queryResult.get(partition).getExecutionInfo(), is(empty()));
            }
            assertThat("Result:" + result, actualValues, is(expectedValues));
            assertThat("Result:" + result, result.getPosition(), is(INPUT_POSITION));
        }
    }  

Test Plan

With the introduction of the new keyTo  argument to the WindowRangeQuery  class, it is necessary to update all associated tests. Since SessionRangeQuery  and WindowKeyQuery  also utilize methods from WindowRangeQuery , we must ensure that the tests covering SessionRangeQuery  and WindowKeyQuery  are revised accordingly.

Rejected Alternatives

We will introduce a new class, WindowRangeQuery2 , designed to facilitate the KeyValueIterator<Windowed<K>, V> fetch(K keyFrom, K keyTo, Instant timeFrom, Instant timeTo)  method. This addition will be an expansion to the IQv2 codebase, ensuring that no existing code is modified; we are merely supplementing with new code and methods to support this enhanced query type.

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