Data Lake Analytics U-SQL EXTRACT speed (Local vs Azure)
See slide 31 of https://www.slideshare.net/MichaelRys/best-practices-and-performance-tuning-of-usql-in-azure-data-lake-sql-konferenz-2018. There is a preview option
SET @@FeaturePreviews="InputFileGrouping:on";
which groups small files into limited vertices.