[Haskell-cafe] help with safecopy + acid-state
waldmann at imn.htwk-leipzig.de
Mon Jan 30 19:46:00 CET 2012
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 , 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.
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