(PECL solr >= 0.9.2)
SolrQuery::setFacetMissing — Maps to facet.missing
Used to indicate that in addition to the Term-based constraints of a facet field, a count of all matching results which have no value for the field should be computed
TRUE turns this feature on.
FALSE disables it.
The name of the field.
Returns the current SolrQuery object, if the return value is used.