cl-postgres convert nil to false

[Marijn Haverbeke]

The distinction between nil and :null in Postmodern is a conscious
decision. It makes the CL type 'boolean neatly correspond to Postgres
booleans, and introduces a new type to indicate nullability. I've also
had to write code to convert nils to :nulls in deep data structures a
few occasions, but I think that this is a less problematic situation
than having to convert boolean nils to :false.

Add to that backwards incompatibility, and I just don't think this is
a worthwhile change to make.

Best,
Marijn

On Fri, Jul 26, 2013 at 5:06 PM, Julien Danjou <julien at danjou.info> wrote:
> Hi there,
>
> I'm dealing with a problem and I'd like some enlightenment.
>
> I've a table with text columns that can't be NULL.
> In my Lisp program, sometimes I'm assigning `nil' as value for this
> column, either via a direct query execution or via the DAO. What I
> would expect in this case, is to PostgreSQL to raise an error.
>
> But this does not happen.
>
> What happens is that (cl-postgres:to-sql-string nil) returns "false",
> and that the query is built to:
>
>   INSERT INTO mytable (mytextfield) VALUES (false);
>
> PostgreSQL implicit type conversion kicks in and insert the string
> 'false' into the field, which does not trigger an error since this it
> not NULL.
>
> The obvious fix here is to patch all my code to convert nil to :null,
> but this is a pain. I don't want to do the type checking I'm doing with
> PostgreSQL one more time in my application.
>
> What I'd like is for cl-postgres to consider nil as being NULL.
> The boolean false value could be mapped as :false, which would also make
> sure no code is inserting false just because a value is actually nil.
>
> The change is pretty trivial and I'm running with it right now, which
> allowed me to debug a lot of implicit nil conversion to 'false' in text
> fields.
>
> I recognize this is something that would break compatibility, so that
> might be enabled via a defparameter or something.
>
> Does that sounds like a good idea, or do I miss an obvious problem?
>
> --
> Julien Danjou
> ;; Free Software hacker ; freelance consultant
> ;; http://julien.danjou.info