presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/RaptorConnector.java/RaptorConnector/beginDelete
class RaptorConnector:    private synchronized void beginDelete(long tableId, UUID transactionId)
    {
        dao.blockMaintenance(tableId);
        verify(deletions.put(tableId, transactionId));
    }