lib: Split the database upgrade into two phases for safer operation.

The first phase copies data from the old format to the new format
without deleting anything. This allows an old notmuch to still use the
database if the upgrade process gets interrupted. The second phase
performs the deletion (after updating the database version number). If
the second phase is interrupted, there will be some unused data in the
database, but it shouldn't cause any actual harm.

1 files changed, 8 insertions, 14 deletions

diff --git a/lib/message.cc b/lib/message.cc
index baeaa469..1cda55a1 100644
--- a/lib/message.cc
+++ b/lib/message.cc
@@ -416,22 +416,16 @@ _notmuch_message_add_filename (notmuch_message_t *message,
     return NOTMUCH_STATUS_SUCCESS;
 }
 
-/* Move the filename from the data field (as it was in database format
- * version 0) to a file-direntry term instead (as in database format
- * version 1).
- */
-void
-_notmuch_message_upgrade_filename_storage (notmuch_message_t *message)
+char *
+_notmuch_message_talloc_copy_data (notmuch_message_t *message)
 {
-    char *filename;
+    return talloc_strdup (message, message->doc.get_data ().c_str ());
+}
 
-    filename = talloc_strdup (message, message->doc.get_data ().c_str ());
-    if (filename && *filename != '\0') {
-	_notmuch_message_add_filename (message, filename);
-	message->doc.set_data ("");
-	_notmuch_message_sync (message);
-    }
-    talloc_free (filename);
+void
+_notmuch_message_clear_data (notmuch_message_t *message)
+{
+    message->doc.set_data ("");
 }
 
 const char *