At Tue, 30 Jun 2009 19:52:08 +0200, Marc Weber wrote:
Is there anyone interested in helping building a library which a) let's you define kind of model of you data b) let's you store you model in any backend (maybe a relational database) c) does static checking of your queries at compilation time?
Maybe this does already exist and I've missed it?
Happstack-state is close in many respects. Your persistent state can basically be any haskell data type for which you could create instances of Read/Show where, read . show == id. (Note, happstack state doesn't actually use Read/Show, but it does use a similar class with similar restrictions). Your queries are just normal functions in the Reader or State monad. Reader if you only want to read the data, State if you want to read and update the data. So, you don't have to learn any special query language or DSL. And you get all your favorite (pure) haskell functions, static type checking, etc. If you want a relation type storage you can use happstack-ixset. You also get write-ahead logging and checkpointing for recovery, data migration, and more. Additionaly, there is multimater support (though not quite suitable for real deployment yet), and plans for sharding support. It does not currently provide a mechanism for mapping the data to a relational database. In theory it would be possible to write a layer that mapped the current state into a SQL database. That would allow other programs to use SQL to read the values. However, it would not be able to support other apps writing updates to the database. - jeremy