Re: [htoolkit-users] HSQL, HList

[Bjorn B. <d00...@dt...>]

Frederik Eaton wrote:
> I wrote some functions which can be used with HSQL to make it a lot
> more concise, using the HList concept:
>=20
> http://ofb.net/~frederik/SqlRow/
>=20
> If anybody wants to look at it and give feedback. Maybe it could be
> incorporated into the library.

One difference to the current HSQL is that you access record fields by=20
position rather than by name. Not sure whether this is good or bad. One=20
problem is that there is as little type safety now as before, and it's=20
as easy to access a non-existing field.

The nice thing is that you can get back a whole row at a time, and I=20
like the pattern trick in:

getRows stmt >>=3D
         mapM_ (\ (m :. n :. p :. Nil) ->

All in all I think it is a very good demonstration of what you can do=20
with heterogenous lists, and it's not really worse than HSQL when it=20
comes to type-safety.

You might want to have a look at HaskellDB,=20
http://haskelldb.sourceforge.net/ . It uses a similar scheme for record=20
types. It adds a layer of type safety, and you construct the queries=20
using combinators.

You might want to be careful with collectRowsAsync. We have the same=20
thing in HaskellDB, and it turns out to be a problem with some databases=20
if you run a second query without getting all that data from the first=20
one. I think MySQL with the native drivers does it for example, but not=20
with ODBC.

> Is there anyone on this list?

Yes.

/Bj=F6rn