Unless otherwise indicated, the final results from the queries executing in Vertica and DBMS-X are piped from a shell command
into a file on the disk not used by the DBMS. Although it is possible to do an equivalent operation in Hadoop, it is easier (and more
common) to store the results of a MR program into the distributed
file system. This procedure, however, is not analogous to how the
DBMSs produce their output data; rather than storing the results in
a single file, the MR program produces one output file for each Reduce instance and stores them in a single directory. The standard
practice is for developers then to use these output directories as a
single input unit for other MR jobs. If, however, a user wishes to
use this data in a non-MR application, they must first combine the
results into a single file and download it to the local file system.