public void begin(ConnectorTransactionHandle transactionHandle) {
    MemoizedMetadata previousValue =
        transactions.putIfAbsent(transactionHandle, new MemoizedMetadata());
    checkState(previousValue == null);
  }
This is used to guarantee one transaction to one {@link MixedFormatConnectorMetadata}
amoro-format-mixed/amoro-mixed-trino/src/main/java/org/apache/amoro/trino/MixedFormatTransactionManager.java