davsclaus commented on code in PR #26053:
URL: https://github.com/apache/camel/pull/26053#discussion_r3921465499
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components/camel-cassandraql/src/main/java/org/apache/camel/processor/keyvalue/cassandra/CassandraKeyValueRepository.java:
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@@ -319,6 +364,52 @@ public Object putIfAbsent(String key, Object value,
Duration ttl) {
return existingBuffer != null ?
KeyValueRepositoryHelper.deserialize(existingBuffer) : null;
}
+ /**
+ * Atomically replaces the value for the given key only if the current
value equals the expected old value, using
+ * Cassandra's lightweight transaction ({@code UPDATE ... SET value = ?
WHERE key = ? IF value = ?}).
+ *
+ * @param expectedOldValue the value that must currently be associated
with the key
+ * @param newValue the new value to store
+ * @param ttl the time-to-live for the new entry; {@code
null}, zero, or negative means no expiration
+ * @return {@code true} if the value was replaced, {@code
false} if the current value did not match
+ */
+ @Override
+ public boolean replace(String key, Object expectedOldValue, Object
newValue, Duration ttl) {
+ LOGGER.debug("Replacing key {} if value matches, TTL {}", key, ttl);
+ ByteBuffer serializedNewValue =
KeyValueRepositoryHelper.serializeToByteBuffer(newValue);
+ ByteBuffer serializedExpectedValue =
KeyValueRepositoryHelper.serializeToByteBuffer(expectedOldValue);
Review Comment:
The LWT `IF value = ?` compares the **serialized** `ByteBuffer` of
`expectedOldValue` against the stored bytes, whereas the `KeyValueRepository`
SPI default compares deserialized values with `Objects.equals(current,
expectedOldValue)`. These match only if serialization is deterministic and the
caller passes the exact value that was stored.
Edge case: two objects that are `.equals()` but serialize to different bytes
(e.g. maps/sets with different iteration order, or different concrete
collection types) would return `false` here where the default
`replace`/`delete` returns `true`. This is a reasonable and arguably more
correct choice for server-side CAS — a short Javadoc note stating the
comparison is by serialized value (same for `delete(key, expected)`) would make
the contract explicit for callers.
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