From: jean-claude <caml.4.jean.claude.bourut@neverbox.com>
To: caml-list@inria.fr
Subject: Re: Idea for another type safe PostgreSQL interface
Date: Tue, 19 Jul 2005 11:55:26 +0000 (UTC) [thread overview]
Message-ID: <loom.20050719T132835-581@post.gmane.org> (raw)
In-Reply-To: <42DC9D16.1080607@barettadeit.com>
Alex Baretta <alex <at> barettadeit.com> writes:
>
> Richard Jones wrote:
> > [I just throwing this idea out there to see if people find it
> > interesting, or want to shoot it down ... There're only fragments of
> > working code at the moment]
> >
> > I'm thinking about a type safe interface to PostgreSQL. One such
> > interface at the moment is in Xcaml, but it only supports a very small
> > subset of SQL, and I like to use complex SQL. It seems that there is
> > a way to support the whole of PostgreSQL's language from within OCaml
> > programs, in a type safe way.
>
> Every once in a while we extend the Embedded SQL with a new feature, but
> we never planned to support all of PostgreSQL. In fact, what we want to
> have is abstraction over the actual DB implementation.
>
> > The general plan would be to have a camlp4 extension which would use
> > Postgres's new "PREPARE" feature to actually prepare the statements,
> > and Postgres's other new feature, "Describe Statement", to pull out
> > the parameter types and result types from the prepared statement.
> > This allows the camlp4 extension to replace the statement string with
> > a type safe expression, and allow type inference to find mismatches.
> > How a typical program would look is shown at the end of this message.
>
Back in the pre-internet era, Dec implemented a DBMS (Rdb I think), a C++
compiler and a "compile time" coherency check between C++ and Rdb.
Their implementation had the following features
-1) C++ compilation would read Rdb schema,
-2) There was a strong coupling between database schema and C++ program.
-3) Moving from test environment to production lead us to rebuild the code,
(That’s silly but I could not find a way around it).
We just gave up using it.
> I really think XDBS is the the way to go. You define the schema in a
> high level language (OO-Entity-Relationship modeling), supporting lower
> level refinements (logical, physical and virtual schema refinements) and
> compiling to Ocaml and SQL-DDL. This way, the type safety can be
> established at compile time without need for a database connection.
> Also, the type safety does not depend on a specific implementation of
> SQL, which is usually desireable.
>
> Alex
>
Nb: I have never worked with PostgreSQL, BUT, with Oracle, Informix, DB2,
sybase, mssql, the full name of a table ( databasename.login.table ) only binds
to an entry inside a system catalog.
If your application uses several logins, then, checking program structures
against database schema can not really occur before login time.
If the goal is only a sanity check, then using any reference definition can
help, but I don't think it will replase the run time check.
Regards,
prev parent reply other threads:[~2005-07-19 12:12 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-07-18 21:05 Richard Jones
2005-07-19 6:26 ` [Caml-list] " Alex Baretta
2005-07-19 11:53 ` Richard Jones
2005-07-19 16:37 ` Alex Baretta
2005-07-19 11:55 ` jean-claude [this message]
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