Performance difference between WHERE option and WHERE statement

Question

Hi, From an I/O perspective, which of these is faster, this:

DATA my_subset;
   SET my_giant_superset (WHERE=(some_filter = 1));
RUN;

Or this:

DATA my_subset;
    SET my_giant_superset;

    WHERE some_filter = 1;
RUN;

I think it would be the first one, but I'm not sure. I tried looking in some lower-level SAS I/O documentation but couldn't find the answer there.

Any help is greatly appreciated - thanks!

Accepted Answer

I'm not aware of any difference in performance between the two, and running some simple tests doesn't turn up any differences

The biggest argument I can think of is that using the where option tends to lead to easier to read code, especially if there are multiple set statements involved:

data a; 
do i = 1 to 10;
output;
end;
run;

data b;
    do i = 5 to 15;
    output;
    end;
run;

data c;
    set a; output;
    set b; output;
    where i > 6;
run;

It's not obvious at a glance (at least to me) what the contents of set c are likely to be!

Note that: http://www2.sas.com/proceedings/sugi30/002-30.pdf suggests that there's a minor performance benefit to using the statement instead of the option, but I'm hesitant to take precision performance data from a paper written for an older version of the software.

Performance difference between WHERE option and WHERE statement

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