Re: Casting Varchar to Numeric

On Mon, 3 Dec 2001, Andy Marden wrote:

> Martijn,
>
> It does work (believe it or not). I've now tried the method you mention
> below - that also works and is much nicer. I can't believe that PostgreSQL
> can't work this out. Surely implementing an algorithm that understands that
> if you can go from a ->b and b->c then you can certainly go from a->c. If

It's more complicated than that (and postgres does some of this but not
all), for example the cast text->float8->numeric potentially loses
precision and should probably not be an automatic cast for that reason.

> this is viewed as too complex a task for the internals - at least a diagram
> or some way of understanding how you should go from a->c would be immensely
> helpful wouldn't it! Daunting for anyone picking up the database and trying
> to do something simple(!)

There may be a need for documentation on this.  Would you like to write
some ;)