On Tue, Mar 7, 2017 at 6:09 PM, Xidorn Quan <m...@upsuper.org> wrote:
> > This major version change is downgrade-incompatible, so IndexedDB and > > DOM cache won't work in an older version if their profile has been > > upgraded. > > IndexedDB is also used internally, so stuff that depends on it likely > > won't work too. > > There's bug 1246615 [2] where you can find a discussion related to this > > issue. > > It would probably be a good idea to backup the old files when upgrading, > so that old version can at least pick the backup file to use. > Maintaining downgrade compatibility is a lot more complex than people think and we have zero test support for it. It hasn't been safe for *years* (look at IDB db migration code history) and its not going to be safe unless we want to invest a lot in it. We just need to do bug 1246615 to make FF warn when a power user gets themselves into this unsupported mode. Per-channel profiles like dev-edition would be great too. As an example of why "backup the db" is harder than it sounds, you would need to backup the entire storage subsystem. If you lose data in IDB, but don't lose data in other sub-systems like cache API, then an origin can find itself in a corrupted state. If we allows writes at this point it can permanently wedge itself in a corrupted state. From the perspective of preserving user data its much safer to simply refuse to open the storage system when we detect an incompatibility like this. _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
