---
 lib/notmuch.h |   12 ++++++++++++
 lib/query.cc  |   46 +++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 57 insertions(+), 1 deletions(-)

diff --git a/lib/notmuch.h b/lib/notmuch.h
index babd208..22dd69e 100644
--- a/lib/notmuch.h
+++ b/lib/notmuch.h
@@ -445,6 +445,18 @@ typedef enum {
     NOTMUCH_SORT_UNSORTED
 } notmuch_sort_t;
 
+/* Values for notmuch_query_secondary_search_conjunction */
+typedef enum {
+    NOTMUCH_SECONDARY_SEARCH_NONE,
+    NOTMUCH_SECONDARY_SEARCH_AND,
+    NOTMUCH_SECONDARY_SEARCH_AND_NOT
+} notmuch_ss_conjunction_t;
+
+void
+notmuch_query_set_secondary_search (notmuch_query_t *query,
+				    const char *secondary_search_terms,
+				    notmuch_ss_conjunction_t conjunction);
+
 /* Return the query_string of this query. See notmuch_query_create. */
 const char *
 notmuch_query_get_query_string (notmuch_query_t *query);
diff --git a/lib/query.cc b/lib/query.cc
index 68ac1e4..0faef51 100644
--- a/lib/query.cc
+++ b/lib/query.cc
@@ -26,6 +26,8 @@
 struct _notmuch_query {
     notmuch_database_t *notmuch;
     const char *query_string;
+    const char *secondary_search_terms;
+    notmuch_ss_conjunction_t ss_conjunction;
     notmuch_sort_t sort;
     notmuch_string_list_t *exclude_terms;
     notmuch_bool_t omit_excluded_messages;
@@ -92,6 +94,8 @@ notmuch_query_create (notmuch_database_t *notmuch,
 
     query->exclude_terms = _notmuch_string_list_create (query);
 
+    query->secondary_search_terms = NULL;
+
     query->omit_excluded_messages = FALSE;
 
     return query;
@@ -122,6 +126,15 @@ notmuch_query_get_sort (notmuch_query_t *query)
 }
 
 void
+notmuch_query_set_secondary_search (notmuch_query_t *query,
+				    const char *secondary_search_terms,
+				    notmuch_ss_conjunction_t conjunction)
+{
+    query->secondary_search_terms = talloc_strdup (query, secondary_search_terms);
+    query->ss_conjunction = conjunction;
+}
+
+void
 notmuch_query_add_tag_exclude (notmuch_query_t *query, const char *tag)
 {
     char *term = talloc_asprintf (query, "%s%s", _find_prefix ("tag"), tag);
@@ -454,6 +467,36 @@ notmuch_query_destroy (notmuch_query_t *query)
     talloc_free (query);
 }
 
+/* This function tests whether the thread containing document with id
+ * seed_doc_id satisfies the secondary search terms of query.*/
+notmuch_bool_t
+notmuch_thread_test_secondary_search (notmuch_query_t *query, unsigned int seed_doc_id)
+{
+    int count;
+    notmuch_message_t *seed_message;
+    const char *thread_id;
+    char *thread_id_query_string;
+    notmuch_query_t *thread_id_query;
+
+    if (!query->secondary_search_terms) return TRUE;
+    seed_message = _notmuch_message_create (query, query->notmuch, seed_doc_id, NULL);
+
+    thread_id = notmuch_message_get_thread_id (seed_message);
+    thread_id_query_string = talloc_asprintf (query, "thread:%s and %s",
+					      thread_id,
+					      query->secondary_search_terms);
+    thread_id_query = notmuch_query_create (query->notmuch, thread_id_query_string);
+    count = notmuch_query_count_messages (thread_id_query);
+    switch (query->ss_conjunction) {
+    case NOTMUCH_SECONDARY_SEARCH_AND:
+	return (count > 0);
+    case NOTMUCH_SECONDARY_SEARCH_AND_NOT:
+	return (count == 0);
+    default:
+	return TRUE;
+    }
+}
+
 notmuch_bool_t
 notmuch_threads_valid (notmuch_threads_t *threads)
 {
@@ -462,7 +505,8 @@ notmuch_threads_valid (notmuch_threads_t *threads)
     while (threads->doc_id_pos < threads->doc_ids->len) {
 	doc_id = g_array_index (threads->doc_ids, unsigned int,
 				threads->doc_id_pos);
-	if (_notmuch_doc_id_set_contains (&threads->match_set, doc_id))
+	if (_notmuch_doc_id_set_contains (&threads->match_set, doc_id) &&
+	    notmuch_thread_test_secondary_search (threads->query, doc_id))
 	    break;
 
 	threads->doc_id_pos++;
-- 
1.7.9.1