[Haskell-cafe] pure Haskell database

[Marc Weber]

On Wed, Sep 24, 2008 at 11:17:01PM +0200, Manlio Perillo wrote:
>  Hi.
> 
>  I need a simple, concurrent safe, database, written in Haskell.
>  A database with the interface of Data.Map would be great, since what I need 
>  to to is atomically increment some integer values, and I would like to avoid 
>  to use SQLite.

I've tried writing at least part of that. But it's still higly
experimental and uses template haskell.
It looks like this:
from that some datastructures are defined which look like
tables used in traditional RDBMS such as SQLite..
However if you don't want to use many "tables" you may be a lot faster 
writing down what you need yourself. My lib automacially generates code
for inserting / deleting tuples into multi indexes such as (Map Int (Map
Int PrimIdx)).

$(let cds = defaultTable {
                tblName = "cds"
                , columns = [ ("cdId", conT ''Int) , ("title", conT ''Int) ]
                , primary = PrimaryUniq [ "cdId" ] [| 0 |]
                , indexes = [ Index "title" [] ]
                , tblStates = [ ( "nextCdId", [t| Int |], [| 0 |] ) ]
            }

      tracks = let
             a="a"
             -- updateNumRows n = [| \n -> cdUpdateByPK (\r -> r { num_tracks = (num_tracks r) + $(n) } ) |]
             in defaultTable {
             tblName = "tracks"
             , columns = [ ("trackId", conT ''Int )
                       , ("name", conT ''String)
                       , ("cd", conT ''Int) -- foreign key 
                       ]
             , primary = PrimaryUniq [ "cd", "trackId" ] [| 0 |]
             , indexes = [ Index "cd" [ IndexUnique "trackId" ] ] --the id is uniq foreach cd 
             -- checks = [ foreignConstraint "cd" "cds" "id" ]
             -- triggers =  [ InsertUpdate  (Just ["cd"]) [| cdUpdateByPK ( updateNum_tracks (+1) ) . pk |]
                           -- DeleteUpdate  (Just ["cd"]) [| cdUpdateByPK ( updateNum_tracks (-1) ) . pk |] 
                           -- ]
                 }
      db = defaultDB {
              dbName = "my"
            , tables = [ cds, tracks]
            , statistics = True
            }
  in createDB db)


If you're interested drop me a mail.

Marc