Status

Current state: Under Discussion

Discussion thread: here 

JIRA: KAFKA-4499

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

Motivation

Currently, both KTable and windowed-KTable stores can be queried via IQ feature. While ReadOnlyKeyValueStore(for KTable stores) provide method all() to scan the whole store (ie, returns an iterator over all stored key-value pairs), there is no similar API for ReadOnlyWindowStore (for windowed-KTable stores).

This limits the usage of a windowed store, because the user needs to know what keys are stored in order the query it. 

Public Interfaces

Methods similar to the ones found in ReadOnlyKeyValueStore will be introduced into the ReadOnlyWindowStore interface. They are the following:

Collection<Windowed<K>> range(long timeFrom, long timeTo);

KeyValueIterator<Windowed<K>, V> allLatest();

and Collection<Windowed<K>> keys();

Proposed Changes

With the need to test the implementation of these methods in mind, the ReadOnlyWindowStoreStub class will implement these additions (i.e. @Override public Collection<Windowed<K>> range(long timeFrom, long timeTo){...}). The corresponding test will also be modified. (e.g. @Test public void testRange(){...}) 

Following the changes in ReadOnlyWindowStore, CachingWindowStore and other WindowStore API will implement these changes accordingly.

Compatibility, Deprecation, and Migration Plan

Rejected Alternatives