Have content type Article. Content type Article has a field, called "Need Further Review", of boolean type. This field is not required, default value FALSE. The articles has value TRUE, FALSE, NULL for this field. TRUE: select true FALSE: select false NULL: the previous articles still have no value for this field.
Have a view to list articles. It uses SOLR search.
A filter criteria is this field "Need Further Review", and is exposed. It has options: Any, TRUE, FALSE. When users select TRUE, it will list articles with TRUE value of this field. When users select FALSE, it usually lists articles with FALSE value of this field.
Now I want to list articles with FALSE and NULL value of this field when selecting FALSE. How to use SOLR search hook_search_api_solr_query_alter to do it?