Ziyun Fu created KAFKA-21024:
--------------------------------
Summary: WindowToTimestampedWindowByteStoreAdapter.query() does
not convert results to timestamped format
Key: KAFKA-21024
URL: https://issues.apache.org/jira/browse/KAFKA-21024
Project: Kafka
Issue Type: Improvement
Reporter: Ziyun Fu
{panel}
h3. Context & Problem Statement
*KAFKA-16158* updated {{KeyValueToTimestampedKeyValueByteStoreAdapter}} to
implement {{{}TimestampedBytesStore{}}}, ensuring all read paths ({{{}get{}}},
{{{}range{}}}, {{{}all{}}}, {{{}query{}}}) convert the wrapped store's bytes
via {{{}TimestampedBytesStore#convertToTimestampedFormat{}}}.
{{WindowToTimestampedWindowByteStoreAdapter}} serves a similar wrapper role but
handles its two read paths inconsistently:
*
*{{fetch()}} (and iterator overloads):* Properly converts the wrapped plain
store's bytes to timestamped format (via
{{WindowToTimestampedWindowByteStoreAdapter#fetch(Bytes, long)}} and
{{{}WindowToTimestampedWindowIteratorAdapter{}}}).
*
*{{query()}} (IQv2 path):* Delegates directly to the wrapped store without
conversion, returning raw/plain-format bytes for {{WindowKeyQuery}} and
{{{}WindowRangeQuery{}}}.
Due to this inconsistency, {{WindowToTimestampedWindowByteStoreAdapter}} was
intentionally *not* marked as {{{}TimestampedBytesStore{}}}. Doing so would
cause marker-based callers (e.g., {{{}StateManagerUtil#converterForStore{}}},
{{{}WrappedStateStore#isTimestamped{}}}) to wrongly assume {{query()}} returned
timestamped bytes, breaking IQ read paths for window stores.
h3. Implementation Tasks
#
*Update {{WindowToTimestampedWindowByteStoreAdapter#query()}}*
**
Convert query results to timestamped format for {{{}WindowKeyQuery{}}},
{{{}WindowRangeQuery{}}}, and any other applicable IQv2 query types.
**
Align behavior with {{KeyValueToTimestampedKeyValueByteStoreAdapter#query()}}
(which handles {{{}KeyQuery{}}}, {{{}TimestampedKeyQuery{}}}, and
{{{}RangeQuery{}}}).
#
*Implement {{TimestampedBytesStore}}*
**
Once {{query()}} matches {{fetch()}} in returning timestamped bytes, update
{{WindowToTimestampedWindowByteStoreAdapter}} to implement
{{{}TimestampedBytesStore{}}}.
#
*Clean up {{StateManagerUtil#converterForStore}}*
**
Update or remove the stale comment explaining why the window adapter was
excluded from the marker interface.
**
Revisit whether {{WindowToTimestampedWindowByteStoreAdapter}} needs explicit
listing in the adapter-enumeration branch.
**
_Note:_ {{KeyValueToTimestampedKeyValueByteStoreAdapter}} must remain
explicitly enumerated for restore operations because restore bypasses the
adapter and requires matching the inner store's raw byte format.{panel}
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