mjsax commented on code in PR #21768:
URL: https://github.com/apache/kafka/pull/21768#discussion_r2944198195
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streams/src/main/java/org/apache/kafka/streams/state/internals/MeteredTimestampedKeyValueStoreWithHeaders.java:
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@@ -294,9 +338,10 @@ private <R> QueryResult<R> runTimestampedRangeQuery(final
Query<R> query,
if (rawResult.isSuccess()) {
final KeyValueIterator<Bytes, byte[]> iterator =
rawResult.getResult();
final KeyValueIterator<K, ValueAndTimestamp<V>> resultIterator =
- (KeyValueIterator<K, ValueAndTimestamp<V>>) new
MeteredTimestampedKeyValueStoreWithHeadersIterator(
+ (KeyValueIterator<K, ValueAndTimestamp<V>>) new
MeteredTimestampedKeyValueStoreWithHeadersQueryIterator(
Review Comment:
It's because of backward compatibility in the DSL. There is existing code,
which uses IQ to access the state stores, and it expects to get back
`ValueAndTimestamp` type. We change all the DSL code to use
metered/caching/changelogging-header-stores and only keep the inner-most
byte-store the default ts-store.
Thus, if users upgrade to 4.3, nothing should change for them, and thus we
cannot just start to return `ValueTimestampHeaders` type -- this would break
app even if they do not enable header stores in the DSL.
Does this make sense? -- It's known feature gap that IQ will not allow to
query header with AK 4.3, and it's something we need a followup KIP to add.
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