Installing hsql and HDBC on GHC 6.10.1

Posted by Thomas Sutton on December 7, 2008

I’ve become more interesting in using Haskell for web development lately, so I’ve started playing around with it a bit. As so much of web development is CRUD, that means I’ll need a database access library. There are a two real options1 to consider when it comes to accessing SQL databases from Haskell: hsql and HDBC. The former has a native MySQL driver and the latter is actually maintained, but neither will build with the current GHC and Cabal without assistance. The rest of this post describes the [small] changes necessary to get both packages built and installed with GHC 6.10.1.

You may encounter numerous errors when trying to build hsql or HDBC, but most of them are pretty trivial to resolve. hsql 1.7 doesn’t import a module that it needs, resulting in and error like this:

Database/HSQL.hsc:66:7:
    Could not find module `System.Time':
      it is a member of package old-time-1.0.0.1, which is hidden

Just add old-time to the list of modules needed to build it in hsql.cabal:

build-depends:  base, old-time

and try again. Next it will complain about a language extension being disabled (the messages mention things like -XRankNTypes). There are a few errors like this. Each time you see a new one, you can just add the extension it mentions (without the -X) to the list in hsql.cabal like so:

extensions:     ForeignFunctionInterface, TypeSynonymInstances, CPP, RankNTypes

Finally, you’ll get an error like:

Database/HSQL/Types.hs:145:23: Not in scope: `throwDyn`

This is because it’s being built against the new base library, when it needs things from the old one. There are two ways2 to fix this: tell Cabal to use the old base library, or change the code to look in the write place in the new base library. To use the old library (quickest and easiest) modify the build-depends line in hsql.cabal to specify a version:

build-depends: base == 3.*, old-time

or pass it in as an argument to the configure phase:

runhaskell Setup.lhs configure --constraint='base<4'

If you want to change the code instead, you’ll need to change references to Control.Exception to Control.OldException3.

You may also encounter these errors when installing the various database driver modules. Just take the same approaches to each type of error and everything should go fine (GHC 6.10.1, Mac OS X 10.5.5).

HDBC suffers from the same “old exception problem”. You can either make it use the old version of base, or change the references to Control.Exception to Control.OldException. One that’s done, you can install HDBC with:

runhaskell Setup.lhs configure
runhaskell Setup.lhs build
runhaskell Setup.lhs haddock
sudo runhaskell Setup.lhs install --global

Once you’ve installed the database driver modules of your choice (I used sqlite3 with both), you should be able to access databases from Haskell.

  1. Takusen is another (very interesting) alternative, but it has a funky Setup.hs that doesn’t work with the Cabal version shipped with GHC. You’ll have to wait for the maintainers to fix it.↩︎

  2. Both solutions were suggested in a haskell-cafe@ thread about building HDBC by Thomas Schilling and Don Stewart↩︎

  3. Mentioned the HDBC bug tracker.↩︎

This post was published on December 7, 2008 and last modified on January 26, 2024. It is tagged with: .