lib: Simplify code flow in _resolve_message_id_to_thread_id

[notmuch] / lib / database.cc

diff --git a/lib/database.cc b/lib/database.cc
index c91e97c125940b384a3bd24963df6cbeedd88acb..d4e2f1ed4d705be14184178ab1612753b50ba6b5 100644 (file)
--- a/lib/database.cc
+++ b/lib/database.cc
@@ -1111,12 +1111,40 @@ notmuch_database_get_directory (notmuch_database_t *notmuch,
     return _notmuch_directory_create (notmuch, path, &status);
 }
 
+static const char *
+_notmuch_database_generate_thread_id (notmuch_database_t *notmuch)
+{
+    /* 16 bytes (+ terminator) for hexadecimal representation of
+     * a 64-bit integer. */
+    static char thread_id[17];
+    Xapian::WritableDatabase *db;
+
+    db = static_cast <Xapian::WritableDatabase *> (notmuch->xapian_db);
+
+    notmuch->last_thread_id++;
+
+    sprintf (thread_id, "%016" PRIx64, notmuch->last_thread_id);
+
+    db->set_metadata ("last_thread_id", thread_id);
+
+    return thread_id;
+}
+
+static char *
+_get_metadata_thread_id_key (void *ctx, const char *message_id)
+{
+    return talloc_asprintf (ctx, "thread_id_%s", message_id);
+}
+
 /* Find the thread ID to which the message with 'message_id' belongs.
  *
- * Returns NULL if no message with message ID 'message_id' is in the
- * database.
+ * Always returns a newly talloced string belonging to 'ctx'.
  *
- * Otherwise, returns a newly talloced string belonging to 'ctx'.
+ * Note: If there is no message in the database with the given
+ * 'message_id' then a new thread_id will be allocated for this
+ * message and stored in the database metadata, (where this same
+ * thread ID can be looked up if the message is added to the database
+ * later).
  */
 static const char *
 _resolve_message_id_to_thread_id (notmuch_database_t *notmuch,
@@ -1124,19 +1152,41 @@ _resolve_message_id_to_thread_id (notmuch_database_t *notmuch,
                                  const char *message_id)
 {
     notmuch_message_t *message;
-    const char *ret = NULL;
+    string thread_id_string;
+    const char *thread_id;
+    char *metadata_key;
+    Xapian::WritableDatabase *db;
 
     message = notmuch_database_find_message (notmuch, message_id);
-    if (message == NULL)
-       goto DONE;
 
-    ret = talloc_steal (ctx, notmuch_message_get_thread_id (message));
+    if (message) {
+       thread_id = talloc_steal (ctx, notmuch_message_get_thread_id (message));
 
-  DONE:
-    if (message)
        notmuch_message_destroy (message);
 
-    return ret;
+       return thread_id;
+    }
+
+    /* Message has not been seen yet.
+     *
+     * We may have seen a reference to it already, in which case, we
+     * can return the thread ID stored in the metadata. Otherwise, we
+     * generate a new thread ID and store it there.
+     */
+    db = static_cast <Xapian::WritableDatabase *> (notmuch->xapian_db);
+    metadata_key = _get_metadata_thread_id_key (ctx, message_id);
+    thread_id_string = notmuch->xapian_db->get_metadata (metadata_key);
+
+    if (thread_id_string.empty()) {
+       thread_id = _notmuch_database_generate_thread_id (notmuch);
+       db->set_metadata (metadata_key, thread_id);
+    } else {
+       thread_id = thread_id_string.c_str();
+    }
+
+    talloc_free (metadata_key);
+
+    return thread_id;
 }
 
 static notmuch_status_t
@@ -1295,25 +1345,6 @@ _notmuch_database_link_message_to_children (notmuch_database_t *notmuch,
     return ret;
 }
 
-static const char *
-_notmuch_database_generate_thread_id (notmuch_database_t *notmuch)
-{
-    /* 16 bytes (+ terminator) for hexadecimal representation of
-     * a 64-bit integer. */
-    static char thread_id[17];
-    Xapian::WritableDatabase *db;
-
-    db = static_cast <Xapian::WritableDatabase *> (notmuch->xapian_db);
-
-    notmuch->last_thread_id++;
-
-    sprintf (thread_id, "%016" PRIx64, notmuch->last_thread_id);
-
-    db->set_metadata ("last_thread_id", thread_id);
-
-    return thread_id;
-}
-
 /* Given a (mostly empty) 'message' and its corresponding
  * 'message_file' link it to existing threads in the database.
  *
@@ -1337,6 +1368,19 @@ _notmuch_database_link_message (notmuch_database_t *notmuch,
 {
     notmuch_status_t status;
     const char *thread_id = NULL;
+    char *metadata_key = _get_metadata_thread_id_key (message,
+            notmuch_message_get_message_id (message));
+    /* Check if we have already seen related messages to this one.
+     * If we have then use the thread_id that we stored at that time.
+     */
+    string stored_id = notmuch->xapian_db->get_metadata (metadata_key);
+    if (!stored_id.empty()) {
+        Xapian::WritableDatabase *db = static_cast <Xapian::WritableDatabase *> (notmuch->xapian_db);
+        db->set_metadata (metadata_key, "");
+        thread_id = stored_id.c_str();
+        _notmuch_message_add_term (message, "thread", thread_id);
+    }
+    talloc_free (metadata_key);
 
     status = _notmuch_database_link_message_to_parents (notmuch, message,
                                                        message_file,