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https://issues.apache.org/jira/browse/KAFKA-20249?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Alieh Saeedi updated KAFKA-20249:
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Fix Version/s: 4.3.0
> Optimize rawValue methods across all Deserializers
> --------------------------------------------------
>
> Key: KAFKA-20249
> URL: https://issues.apache.org/jira/browse/KAFKA-20249
> Project: Kafka
> Issue Type: Sub-task
> Components: streams
> Reporter: Alieh Saeedi
> Priority: Major
> Labels: kip
> Fix For: 4.3.0
>
>
> Optimize rawValue/{{{}rawAggregationValue{}}} to fast-path the common case of
> empty headers in headers-aware state stores, while preserving correct
> behavior for non-empty headers.
> h3. Background
> In the current header-aware state store encoding, the value layout is:
> * 1st byte: header-length prefix (or start of varint-encoded header size)
> * Next {{N}} bytes: serialized headers
> * Remaining bytes: aggregation value (payload)
> Most state store records are expected to have no headers, so optimizing the
> empty-headers case reduces overhead in hot paths where we need to extract the
> raw aggregation value.
> h3. Proposed Change
> Introduce a specialized implementation of rawValue/{{{}rawAggregationValue.
> {}}}
> ```
> // Fast path for empty headers (most common case)
> if (valueWithHeaders[0] == 0x00) {
> // Headers size is 0, just strip first byte
> final byte[] result = new byte[valueWithHeaders.length - 1];
> System.arraycopy(valueWithHeaders, 1, result, 0, result.length);
> return result;
> }
> // Slow path for actual headers (rare in session stores)
> ...
> ```
> Pros:
> - Optimizes the common case (empty headers)
> - ~50% faster for empty headers (no ByteBuffer, simple arraycopy)
> - Still handles non-empty headers correctly
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