[web-devel] [ Newbie ] [ MongoDB ] Using MongoDB Persistent backend

[Greg Weber]

I upgraded persistent-mongoDB for Persisten 0.6. I also added it to the
scaffolding, although there is still an issue with the scaffolded site. I am
going to try to upgrade persistent-mongoDB to use the new  MongoDB 1.0
driver and then fix the scaffolding.

On Thu, Jul 7, 2011 at 8:30 AM, Greg Weber <greg at gregweber.info> wrote:

> The latest version of persistent-mongoDB on hackage works now. After we get
> some more usage it will be added as a scaffolding option. Here is some basic
> runner code:
>
> import Database.Persist.MongoDB
> import Database.MongoDB.Connection
> import qualified Database.MongoDB as DB
>
> runMongo :: MongoDBReader (GGHandler M M IO) a -> GHandler M M a
> runMongo x = liftIOHandler $
>   withMongoDBConn (DB.Database "test") "127.0.0.1" $ runMongoDBConn x
> DB.safe DB.Master
>
> On Thu, Jun 30, 2011 at 11:26 AM, Michael Snoyman <michael at snoyman.com>wrote:
>
>> OK, simple question: why can't we use a type of MongoDBReader of:
>>
>> newtype MongoDBReader m a = MongoDBReader (Action m a)
>>    deriving (Monad, Trans.MonadIO, Functor, Applicative)
>>
>> Michael
>>
>> On Thu, Jun 30, 2011 at 6:55 PM, Greg Weber <greg at gregweber.info> wrote:
>> > I think it is about time to finally fix this. I am probably the least
>> > knowledgeable about Monad mashing, but seems like a good time to learn!
>> > Here is a simple app we can use:
>> > https://gist.github.com/1056520
>> > But maybe it is best to use the test suite. Here are all the hacks to
>> get
>> > the tests to run right now that need to be removed:
>> > instance Context DB.MasterOrSlaveOk IO where
>> >   context = undefined
>> >   push = undefined
>> > instance Context DB.Database IO where
>> >   context = undefined
>> >   push = undefined
>> > instance Context DB.WriteMode IO where
>> >   context = undefined
>> >   push = undefined
>> > instance Context DB.Pipe IO where
>> >   context = undefined
>> >   push = undefined
>> > instance Control.Monad.Throw.Throw DB.Failure IO where
>> >   throw = undefined
>> >   catch = undefined
>> >
>> > On Wed, Jun 29, 2011 at 1:25 AM, Michael Snoyman <michael at snoyman.com>
>> > wrote:
>> >>
>> >> On Wed, Jun 29, 2011 at 11:17 AM, Kamil Ciemniewski
>> >> <ciemniewski.kamil at gmail.com> wrote:
>> >> > Hi all,
>> >> >
>> >> > I've got some "newbie" problems using MongoDB as backend
>> >> > in Persistent.
>> >> >
>> >> > Basically I've got my app type defined as:
>> >> > data MyApp = MyApp
>> >> >     { getStatic :: Static -- ^ Settings for static file serving.
>> >> >     , connPool :: ConnPool Host
>> >> >     }
>> >> >
>> >> > And I made it an instance of YesodPersist by:
>> >> > instance YesodPersist MyApp where
>> >> >   type YesodDB MyApp = MongoDBReader Host
>> >> >   runDB db = liftIOHandler
>> >> >            $ fmap connPool getYesod >>= (\p -> return (p,
>> "localhost"))
>> >> > >>=
>> >> > runMongoDBConn db
>> >> >
>> >> > And I made it an instance of YesodAuth as well by:
>> >> > instance YesodAuth MyApp where
>> >> >   type AuthId MyApp = UserId
>> >> >
>> >> >   loginDest _ = RootR
>> >> >   logoutDest _ = RootR
>> >> >
>> >> >   getAuthId creds = runDB $ do
>> >> >       x <- getBy $ UniqueUser $ credsIdent creds
>> >> >       case x of
>> >> >       Just (uid, _) -> return $ Just uid
>> >> >       Nothing -> do
>> >> >           fmap Just $ insert $ User (credsIdent creds) Nothing
>> >> >
>> >> >   authPlugins = [ authEmail ]
>> >> >
>> >> > I've defined User model as yesod scaffold tool defines it.
>> >> >
>> >> > Now, when I try to compile it i get:
>> >> >
>> >> > No instances for (Control.Monad.Context.Context
>> >> >                         Database.MongoDB.Connection.MasterOrSlaveOk
>> >> >                         (GGHandler s MyApp IO),
>> >> >                       Control.Monad.Context.Context
>> >> >                         Database.MongoDB.Query.Database (GGHandler s
>> >> > MyApp
>> >> > IO),
>> >> >                       Control.Monad.Context.Context
>> >> >                         Database.MongoDB.Internal.Protocol.Pipe
>> >> > (GGHandler s
>> >> > MyApp IO),
>> >> >                       Control.Monad.Context.Context
>> >> >                         Database.MongoDB.Query.WriteMode (GGHandler s
>> >> > MyApp
>> >> > IO),
>> >> >                       Control.Monad.Throw.Throw
>> >> >                         Database.MongoDB.Query.Failure (GGHandler s
>> >> > MyApp
>> >> > IO))
>> >> >       arising from a use of `insert'
>> >> >     Possible fix:
>> >> >       add instance declarations for
>> >> >       (Control.Monad.Context.Context
>> >> >          Database.MongoDB.Connection.MasterOrSlaveOk
>> >> >          (GGHandler s MyApp IO),
>> >> >        Control.Monad.Context.Context
>> >> >          Database.MongoDB.Query.Database (GGHandler s MyApp IO),
>> >> >        Control.Monad.Context.Context
>> >> >          Database.MongoDB.Internal.Protocol.Pipe (GGHandler s MyApp
>> IO),
>> >> >        Control.Monad.Context.Context
>> >> >          Database.MongoDB.Query.WriteMode (GGHandler s MyApp IO),
>> >> >        Control.Monad.Throw.Throw
>> >> >          Database.MongoDB.Query.Failure (GGHandler s MyApp IO))
>> >> >     In the expression: insert
>> >> >     In the second argument of `($)', namely
>> >> >       `insert $ User (credsIdent creds) Nothing'
>> >> >     In the expression:
>> >> >         fmap Just $ insert $ User (credsIdent creds) Nothing
>> >> >
>> >> > The problem is probably very trivial.. But I've got no ideas how to
>> fix
>> >> > it.
>> >> >
>> >> > Best regards
>> >> > Kamil Ciemniewski
>> >> >
>> >> > _______________________________________________
>> >> > web-devel mailing list
>> >> > web-devel at haskell.org
>> >> > http://www.haskell.org/mailman/listinfo/web-devel
>> >> >
>> >> >
>> >>
>> >> I don't have direct experience with the MongoDB backend, but I can
>> >> give this a shot if I saw some code. I think one possibility would be
>> >> to wrap everything in a liftIO, but then you won't have access to the
>> >> Handler monad features. This would prevent you from doing things like
>> >> setting messages and sending redirects from the database access
>> >> itself, but should otherwise be fine.
>> >>
>> >> Michael
>> >>
>> >> _______________________________________________
>> >> web-devel mailing list
>> >> web-devel at haskell.org
>> >> http://www.haskell.org/mailman/listinfo/web-devel
>> >
>> >
>>
>
>
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