Re: [Haskelldb-users] data structures over tables

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

Frederik Eaton wrote:
> I'm thinking about implementing special indexing data structures over
> SQL tables in databases that might not support those structures
> natively, for instance an R-tree for multidimensional range queries (I
> think mysql supports only up to dimension 2) or a simple balanced tree
> for fast calculation of a running total of a given column. (data
> structure links would be to primary key columns of tables)

Thiat sounds like an interesting project.

> I thought that haskelldb might be a good candidate for such an
> implementation because of the ability to achieve modularity by
> composing query functions, and also the potential to minimize context
> switches by sending large chunks of SQL code to the server at once...
> But presumably the datatypes would require atomicity in the form of
> locking or transactions, which haskelldb would have to support, as
> well as 'if' statements or 'if' functions for logic. An alternative
> would be to write stored procedures directly in SQL. (can haskelldb
> generate these?) A separate issue is enforcing type constraints, such
> as saying that an 'id' value in a certain column can only be used to
> look up elements of certain other columns, it seems like it could be a
> capability of haskelldb, is it?

HaskellDB already has support for transactions (with MySQL I think you=20
need to set the table type correctly for this to work, see the MySQL=20
manual) and if functions. There is no support for stored procedures,=20
though it could be a nice project for someone to look at.

For the id columns, do you mean that one couldn't get at the actual=20
value, just use it to look up other values? Or what is the type=20
contraint here?

/Bj=F6rn