One of the big advantages of most of the new SQL-on-Hadoop query engines is the independence between the three layers. Query engines, file systems and file formats are interchangeable. The consequence is that data can be inserted using, for example, Impala, and accessed afterwards using Drill. Or, a SQL query engine can seamlessly switch from the Apache HDFS file system to the MapR file system or to the Amazon S3 file system.
The big advantage is that this allows us to deploy different query engines, each with its own strengths and weaknesses, on the same data. There is no need to copy and duplicate the data.
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