Can 'persistent-postgresql' support infinity/-infinity?

It seems that we cannot use infinity value (e.g. Date) with persistent-postgresql.

The following is my solution now:

1. Patch persistent-postgresql

https://github.com/txkaduo/persistent/commit/8188599e1029f9be9e1daa2afc924c6b504b4639

2. Create orphan instances for Unbounded a

instance PersistField a => PersistField (Unbounded a) where
  toPersistValue PosInfinity = PersistText "infinity"
  toPersistValue NegInfinity = PersistText "-infinity"
  toPersistValue (Finite x)  = toPersistValue x

  fromPersistValue (PersistText "infinity")        = pure PosInfinity
  fromPersistValue (PersistText "-infinity")       = pure NegInfinity
  fromPersistValue (PersistDbSpecific "infinity")  = pure PosInfinity
  fromPersistValue (PersistDbSpecific "-infinity") = pure NegInfinity
  fromPersistValue (PersistByteString "infinity")  = pure PosInfinity
  fromPersistValue (PersistByteString "-infinity") = pure NegInfinity
  fromPersistValue x                               = fmap Finite $ fromPersistValue x

instance PersistFieldSql a => PersistFieldSql (Unbounded a) where
  sqlType _ = sqlType (Proxy :: Proxy a)


instance FromJSON a => FromJSON (Unbounded a) where
  parseJSON (A.String "infinity")  = pure PosInfinity
  parseJSON (A.String "-infinity") = pure NegInfinity
  parseJSON x                      = fmap Finite $ parseJSON x

instance ToJSON a => ToJSON (Unbounded a) where
  toJSON PosInfinity = A.String "infinity"
  toJSON NegInfinity = A.String "-infinity"
  toJSON (Finite x)  = toJSON x

It works for my application.

Is this proper solution?

Start with the persistent-postgresql support discussed in the issue and review the linked patch, then compare it with the proposed Unbounded instances. The work is done when PostgreSQL infinity and -infinity values can be stored and read correctly without breaking finite values.