[Haskell-cafe] help with safecopy + acid-state

[Johannes Waldmann]

Felipe Almeida Lessa <felipe.lessa <at> gmail.com> writes:

> > data T_orig = T_orig Foo
> > $(deriveSafeCopy 0 'base ''T_orig)
> > data T = T Foo Bar
> > $(deriveSafeCopy 0 'extension ''T)
> > instance Migrate T where type MigrateFrom T = T_Orig ...
> 
> As you can read from deriveSafeCopy's documentation [1], you need to
> increase the version of your data type (e.g. change that zero to one).

Thanks - which zero? (there are two of them.)

and how does it play together with Data.Acid?

Can I really rename  old.T => new.T_orig ?
It looks as if then tries to load the wrong acid-state snapshot.

Best - J.W.