azure data lake - Dynamic FROM in U-SQL statement -


i trying generate dynamic clause in u-sql can extract data different files based on previous query outcome. that's this:

@filestoextract = select whatevergeneratesthepaths @foo; <-- query generates rowset file want extract like: [/path/file1.csv, /path/file2.csv] select * @filestoextract; <-- here want extract data file1 , file2

i'm afraid kind of dynamics queries not supported yet, can pointing me out way achieve this? seems feasible approach generate u-sql script , execute afterwards.

thanks in advance.

it not clear question if want file names dynamically retrieved , passed extract statement, or name of tables/rowsets , passed select's clause. or both.

in general, cannot dynamically generate source names u-sql expression. may want file feature request here http://aka.ms/adlfeedback dynamically or statically parameterizable sources.

having said that, depending on exact requirements, there may ways achieve goals without work-around describe.

for example, write code parameterized table-valued function , pass different rowsets different scripts, or - if statically can decide rowset choose - can use if statement.

here pseudo-code example:

declare external @someconditionparameter boolean = true;  if (@someconditionparameter)    @data = extract int, b string @fileset1 using extractors.csv(); else    @data = extract int, b string @file2 using ...; end;  @results = mytablevaluedfunction (@data); ...

if files schematized differently, may able use flexible column sets (currently in preview, see release notes) in tvf handle variability of rowset schema.


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