Warning When Using dplyr Mutate

Kevin Feasel

2017-12-05

R, Spark

John Mount has a warning if you are using dplyr’s mutate function and connecting to Spark or a database:

If you are using the R dplyr package with a database or with Apache Spark: I respectfully advise you inspect your code to ensure you are not using any values created inside a dplyr::mutate() statement inside the same dplyr::mutate() statement. This has been my coding advice for some time, and it is a simple and safe re-factoring to break up such statements into safer sequences (simply by introducing more dplyr::mutate()s).

I have since encountered a non-signaling (or silent) result corruption version of the issue. We are now advising code inspection as we now have confirmation that not seeing a thrown error is not a reliable indication of correct execution and correct results.

Thanks to John for reporting, and hopefully the dplyr team can fix it.

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