Amazon Cloudsearch : Filter if exists

[anirudh179]

I have an amazon cloudsearch domain. The aim is to filter if the field 'xyz' exists. Not all document have a xyz field, and I want to have the ones which do have a 'xyz' filtered with some value xyz:'value' , also the ones that do not have 'xyz' to also be returned.

Is this possible? If so how would it be done using Simple query parser ?