_notmuch_doc_id_set_remove (notmuch_doc_id_set_t *doc_ids,
                             unsigned int doc_id);
 
+/* querying xapian documents by type (e.g. "mail" or "ghost"): */
+notmuch_status_t
+_notmuch_query_search_documents (notmuch_query_t *query,
+                                const char *type,
+                                notmuch_messages_t **out);
+
+notmuch_status_t
+_notmuch_query_count_documents (notmuch_query_t *query,
+                               const char *type,
+                               unsigned *count_out);
+
 /* message.cc */
 
 void
 
 notmuch_status_t
 notmuch_query_search_messages_st (notmuch_query_t *query,
                                  notmuch_messages_t **out)
+{
+    return _notmuch_query_search_documents (query, "mail", out);
+}
+
+notmuch_status_t
+_notmuch_query_search_documents (notmuch_query_t *query,
+                                const char *type,
+                                notmuch_messages_t **out)
 {
     notmuch_database_t *notmuch = query->notmuch;
     const char *query_string = query->query_string;
        Xapian::Enquire enquire (*notmuch->xapian_db);
        Xapian::Query mail_query (talloc_asprintf (query, "%s%s",
                                                   _find_prefix ("type"),
-                                                  "mail"));
+                                                  type));
        Xapian::Query string_query, final_query, exclude_query;
        Xapian::MSet mset;
        Xapian::MSetIterator iterator;
 
 notmuch_status_t
 notmuch_query_count_messages_st (notmuch_query_t *query, unsigned *count_out)
+{
+    return _notmuch_query_count_documents (query, "mail", count_out);
+}
+
+notmuch_status_t
+_notmuch_query_count_documents (notmuch_query_t *query, const char *type, unsigned *count_out)
 {
     notmuch_database_t *notmuch = query->notmuch;
     const char *query_string = query->query_string;
        Xapian::Enquire enquire (*notmuch->xapian_db);
        Xapian::Query mail_query (talloc_asprintf (query, "%s%s",
                                                   _find_prefix ("type"),
-                                                  "mail"));
+                                                  type));
        Xapian::Query string_query, final_query, exclude_query;
        Xapian::MSet mset;
        unsigned int flags = (Xapian::QueryParser::FLAG_BOOLEAN |