azure data lake - Performance selecting from an External Rowset -


i test performance different types of select external db source.

  1. external datasource_identifier
  2. location csharp_string_literal
  3. execute csharp_string_literal

i'm interested in performance, because 3rd type (execute) effective in case of statement.

am doing wrong, or that's normal u-sql first read rows external table , filter inside adla (the same behaviour location)?

that's problem/ineffective in case table large , need use part of table rows.

can force u-sql filter data before reading external table or location? problem need dynamic statement based on variable.

first control ability push predicates sql server engine remotable_types clause on data source object.

then predicate needs remotable. if doing predicate join u-sql rowset (table), may not easy remote efficiently (i not sure if map join semijoin yet).

since seem able remote predicate use in execute, think there chance write queries in other cases in way can remoted. without seeing queries, hard sure.

if want take look, please contact me email (usql @ microsoft dot com).


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