+ term = g_strdup_printf ("%s%s", find_prefix (prefix_name), value);
+
+ *begin = db.postlist_begin (term);
+
+ if (end)
+ *end = db.postlist_end (term);
+
+ free (term);
+}
+
+Xapian::Document
+find_message_by_docid (Xapian::Database db, Xapian::docid docid)
+{
+ return db.get_document (docid);
+}
+
+Xapian::Document
+find_message_by_message_id (Xapian::Database db, const char *message_id)
+{
+ Xapian::PostingIterator i, end;
+
+ find_messages_by_term (db, "msgid", message_id, &i, &end);
+
+ if (i != end)
+ return find_message_by_docid (db, *i);
+ else
+ return Xapian::Document ();
+}
+
+static void
+insert_thread_id (GHashTable *thread_ids, Xapian::Document doc)
+{
+ string value_string;
+ const char *value;
+
+ value_string = doc.get_value (NOTMUCH_VALUE_THREAD);
+ value = value_string.c_str();
+ if (strlen (value))
+ g_hash_table_insert (thread_ids, strdup (value), NULL);
+}
+
+static char *
+find_thread_id (Xapian::Database db,
+ GPtrArray *parents,
+ const char *message_id)
+{
+ Xapian::PostingIterator child, children_end;
+ Xapian::Document doc;
+ GHashTable *thread_ids;
+ GList *keys, *l;
+ GString *result = NULL;
+ unsigned int i;
+ const char *parent_message_id;
+
+ thread_ids = g_hash_table_new (g_str_hash, g_str_equal);
+
+ find_messages_by_term (db, "ref", message_id, &child, &children_end);
+ for ( ; child != children_end; child++) {
+ doc = find_message_by_docid (db, *child);
+ insert_thread_id (thread_ids, doc);
+ }
+
+ for (i = 0; i < parents->len; i++) {
+ parent_message_id = (char *) g_ptr_array_index (parents, i);
+ doc = find_message_by_message_id (db, parent_message_id);
+ insert_thread_id (thread_ids, doc);
+ }
+
+ keys = g_hash_table_get_keys (thread_ids);
+ for (l = keys; l; l = l->next) {
+ char *id = (char *) l->data;
+ if (result == NULL) {
+ result = g_string_new (id);
+ } else {
+ g_string_append_printf (result, ",%s", id);
+ }
+ free (id);
+ }
+
+ if (result)
+ return g_string_free (result, FALSE);
+ else
+ return NULL;
+}
+
+/* Add a term for each message-id in the References header of the
+ * message. */
+static void
+parse_references (GPtrArray *array,
+ const char *refs)
+{
+ const char *end, *next;