On 18:12 Sat 09 Jul , Tom Murphy wrote:

Hi, I've found good explanations of the HaskellDB combinators, but I can't find good information about how to correctly define the database layout. Can anyone point me to a resource, or give a quick example?

Thanks! Tom

_______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe

I don't have any examples at hand, but I'll look through the api with you. There are three ways to create the dblayout interface, manually, through dbinfo or through template haskell. The vanilla way is to use the DBInfo(3) module to describe your database layout. It can also be used to create the database schema, but as the dbinfo language is very restricted, I don't recommend it. DBInfo { dbName "DatabaseName" opts = DBOptions { useBString = False , makeIdent = mkIdentPreserving } tbls = [TInfo {tname = "tablename" cols = [CInfo {cname = "columnname", descr = (IntT, False)}] } ] } This would create a layout describing a database called DatabaseName with one table "tablename" with one column "columnname" which is of type int and can't be null. The mkIdentPreserving is an undocumented function in (5) The description then needs to be created into module files with dbInfoToModuleFiles(4). This creates a root "DatabaseName.hs" file and DatabaseName directory. The root file is uncompilable and can be safely removed. The fact that there is two stages for the compilation, makes it difficult to compile. I believe this restriction is because haskelldb was created when there was no template haskell. With template haskell (2) you could do the following: $(mkDbDirectTable "tablename" [("columnname", [t|Int|])] I don't know how to specify whether the field can be null or not, but at least this way you get your dblayout descriptions at compile time. [1] http://hackage.haskell.org/package/haskelldb [2] http://hackage.haskell.org/package/haskelldb-th [3] http://hackage.haskell.org/packages/archive/haskelldb/2.1.1/doc/html/Databas... [4] http://hackage.haskell.org/packages/archive/haskelldb/2.1.1/doc/html/Databas... [5] http://hackage.haskell.org/packages/archive/haskelldb/2.1.1/doc/html/src/Dat... -- Mats Rauhala MasseR