Given the following document structure:

    {
      '_id' : 'someid',
      '_rev' : 'somerev',
      'metadata' : {
        'participation' : {
          'read' : [1,2,3,4,5]
        }
      }
    }

I want to find all documents in a database where a specific
value **does not** exist in the `metadata.participation.read`
array

Querying for documents in which **metadata.participation.read**
contains the specific value has been easy:

    function(doc) {
      doc['metadata']['participation']['read'].forEach(function(user_id) {
        emit(user_id, doc._id);
      });
    }