netudima commented on PR #1988:
URL:
https://github.com/apache/cassandra-java-driver/pull/1988#issuecomment-2833498912
I double checked the issue and can confirm that it is present.
I have used the following test code to validate it:
```
public static void main(String[] args) throws ExecutionException,
InterruptedException {
try (CqlSession cqlSession = CqlSession.builder()
.addContactPoint(new InetSocketAddress("localhost", 9042))
.withLocalDatacenter("datacenter1")
.build()) {
CodecRegistry codecRegistry =
cqlSession.getContext().getCodecRegistry();
GenericType<List<String>> listOfStringType =
GenericType.listOf(String.class);
int result = 0;
for (int i = 0; i < 500_000_000; i++) {
TypeCodec<List<String>> codec =
codecRegistry.codecFor(listOfStringType);
result ^= codec.hashCode();
}
System.out.println(result);
}
}
}
```
and run it using OpenJDK Runtime Environment Temurin-11.0.15+10 (build
11.0.15+10) with the following VM options to capture a JFR recording:
`-XX:StartFlightRecording=duration=200s,filename=flight.jfr,settings=profile`
Result:
<img width="1299" alt="image"
src="https://github.com/user-attachments/assets/765c1372-c220-4255-b6a0-9e9a05f49ea3";
/>
The allocations are present along the whole time during the test. Originally
I hoped that JVM escape analysis
(https://www.javaspecialists.eu/archive/Issue179-Escape-Analysis.html) should
eliminate such allocations once the logic was compiled by C2 JIT compiler but
it sees does not work in this case for this OpenJDK version.
https://jpbempel.github.io/2020/08/02/when-escape-analysis-fails-you.html
So, the optimization is reasonable from my point of view. Note: CacheKey is
used when we lookup a codec not for a primitive type or explicitly registered,
so the result of the optimization is observable only for workloads when we work
with collection/UDT columns.
From code review point of view - it is ok for me as well.
+1, thank you for reporting it.
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