private void updateOldestTxnTimestamp() {
        Map.Entry<Long, TxnMetadata> firstEntry = ongoingTxns.firstEntry();
        if (firstEntry == null) {
            oldestTxnLastTimestamp = -1;
        } else {
            TxnMetadata oldestTxnMetadata = firstEntry.getValue();
            ProducerStateEntry entry = producers.get(oldestTxnMetadata.producerId);
            oldestTxnLastTimestamp = entry != null ? entry.lastTimestamp() : -1L;
        }
    }
Update the mapping with the given append information
storage/src/main/java/org/apache/kafka/storage/internals/log/ProducerStateManager.java