问题
Can we append data in existing file in U-SQL? I have created a CSV file as output in U-SQL. I am writing another U-SQL query and I want to append the output of that query in the existing file. Is it possible?
回答1:
It's not supported, and would go against the design of a robust, distributed, idempotent big data system (although you could implement that behaviour by reading the previous output as a rowset and do UNION ALL).
The best way to deal with this is to use partitions properly, for example, create one or more new partitions for each of your executions: https://msdn.microsoft.com/en-us/library/azure/mt621324.aspx
来源：https://stackoverflow.com/questions/40929858/append-data-in-existing-file-in-u-sql