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Status

Current state:   [One of "Under Discussion", "Accepted", "Rejected"]

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

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

Motivation

Describe the problems you are trying to solve.

Public Interfaces

Briefly list any new interfaces that will be introduced as part of this proposal or any existing interfaces that will be removed or changed. The purpose of this section is to concisely call out the public contract that will come along with this feature.

A public interface is any change to the following:

• Binary log format

• The network protocol and api behavior

• Any class in the public packages under clientsConfiguration, especially client configuration

  • org/apache/kafka/common/serialization

  • org/apache/kafka/common

  • org/apache/kafka/common/errors

  • org/apache/kafka/clients/producer

  • org/apache/kafka/clients/consumer (eventually, once stable)

• Monitoring

• Command line tools and arguments

• Anything else that will likely break existing users in some way when they upgrade

Proposed Changes

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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 an additional argument, keyTo , in the WindowRangeQuery  class, and subsequently update the methods within this class to accommodate this new parameter.
We also add a new method public static <K, V> WindowRangeQuery<K, V> withWindowKeyRange(final K keyFrom,final K keyTo,final Instant timeFrom,final Instant timeTo)  to this class.

public class WindowRangeQuery<K, V> implements Query<KeyValueIterator<Windowed<K>, V>> {
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    private final Optional<K> keyTo;
   
    public static <K, V> WindowRangeQuery<K, V> withKey(final K key)

    public static <K, V> WindowRangeQuery<K, V> withWindowStartRange(final Instant timeFrom,
                                                                     final Instant timeTo)

	public static <K, V> WindowRangeQuery<K, V> withWindowKeyRange(final K keyFrom,
                                                               final K keyTo,
                                                               final Instant timeFrom,
                                                               final Instant timeTo)

    public Optional<K> getKeyFrom()
    
    public Optional<K> getKeyTo()

    public Optional<Instant> getTimeFrom() 

    public Optional<Instant> getTimeTo()

    @Override
    public String toString()
}

Compatibility, Deprecation, and Migration Plan

• What impact (if any) will there be on existing users?
• If we are changing behavior how will we phase out the older behavior?
• If we need special migration tools, describe them here.
• When will we remove the existing behavior?

Test Plan

Describe in few sentences how the KIP will be tested. We are mostly interested in system tests (since unit-tests are specific to implementation details). How will we know that the implementation works as expected? How will we know nothing broke?

Rejected Alternatives

• 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

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 typeIf there are alternative ways of accomplishing the same thing, what were they? The purpose of this section is to motivate why the design is the way it is and not some other way.