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postgresql-simple v0.1 Release Notes

Release Date: 2012-05-04 // almost 12 years ago

    • Renamed several modules, typeclasses, and functions:

      QueryParams  (renderParams)   -> ToRow   (toRow)
QueryResults (convertResults) -> FromRow (fromRow)
Param  (render)  -> ToField   (toField)
Result (convert) -> FromField (fromField)

    • Added the Database.PostgreSQL.Simple.Ok module, a variation of Either SomeException that has an instance for Alternative and also uses a list of exceptions to track the ways it has failed.

    • Changed the return type of fromField and fromRow from Either SomeException to Ok.

    • Thanks to suggestions from Ozgun Ataman, the FromRow typeclass has been massively improved. The result is simpler definitions and better compositionality. Also, user-defined instances need not be to be concerned about forcing the converted results to WHNF. Here is an example comparing the old to the new:

      instance (Result a, Result b) => QueryResults (a,b) where
    convertResults [fa,fb] [va,vb] = do
        !a <- convert fa va
        !b <- convert fb vb
        return (a,b)
    convertResults fs vs  = convertError fs vs 2

instance (FromField a, FromField b) => FromRow (a,b) where
    fromRow = (,) <$> field <*> field

    • Added (:.), a pair that allows one to compose FromRow instances:

      instance (FromRow a, FromRow b) => FromRow (a :. b) where
    fromRow = (:.) <$> fromRow <*> fromRow

    • Moved the contents Field module into the FromField module.

    • Removed the RawResult type.

    • Added DefaultIsolationLevel as a distinct IsolationLevel option and DefaultReadWriteMode as a distinct ReadWriteMode.