+ 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, *id, *comma;
+
+ value_string = doc.get_value (NOTMUCH_VALUE_THREAD);
+ value = value_string.c_str();
+ if (strlen (value)) {
+ id = value;
+ while (*id) {
+ comma = strchr (id, ',');
+ if (comma == NULL)
+ comma = id + strlen (id);
+ g_hash_table_insert (thread_ids,
+ strndup (id, comma - id), NULL);
+ id = comma;
+ if (*id)
+ id++;
+ }
+ }
+}
+
+/* Return one or more thread_ids, (as a GPtrArray of strings), for the
+ * given message based on looking into the database for any messages
+ * referenced in parents, and also for any messages in the database
+ * referencing message_id.
+ *
+ * Caller should free all strings in the array and the array itself,
+ * (g_ptr_array_free) when done. */
+static GPtrArray *
+find_thread_ids (Xapian::Database db,
+ GPtrArray *parents,
+ const char *message_id)
+{
+ Xapian::PostingIterator child, children_end;
+ Xapian::Document doc;
+ GHashTable *thread_ids;
+ GList *keys, *l;
+ unsigned int i;
+ const char *parent_message_id;
+ GPtrArray *result;
+
+ thread_ids = g_hash_table_new_full (g_str_hash, g_str_equal,
+ free, NULL);
+
+ 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);