hpcc-systems/HPCC-Platform — pull request #1824 by ghalliday (2012-03-12 14:29:52+00:00)
Title: Improve implicit field projection for count/exists

- Previously the output record from an activity was required to have at least one
field, which meant that exists/count arbitrarily "used" the first field. With
this change that no longer happens - often reducing the number of fields used.

A record can have a _nonEmpty_ attribute associated with it to ensure
it has a non-zero size (to differenitate it from a skipped row). The
transform clears the byte (to make memory consitant and ensure spilt
files compress properly).

Serialize/Deserialize use the default classes so they will still work.

Signed-off-by: Gavin Halliday