transactionTag property

A tag used for statistics collection about this transaction.

Both request_tag and transaction_tag can be specified for a read or query that belongs to a transaction. The value of transaction_tag should be the same for all requests belonging to the same transaction. If this request doesn't belong to any transaction, transaction_tag is ignored. Legal characters for transaction_tag values are all printable characters (ASCII 32 - 126) and the length of a transaction_tag is limited to 50 characters. Values that exceed this limit are truncated. Any leading underscore (_) characters are removed from the string.