Re: Casting Varchar to Numeric

Bruce Momjian <pgman@candle.pha.pa.us> writes:
> I can see problems with automatically casting numeric to text because
> you have to guess the desired format, but going from text to numeric
> seems quite easy to do.  Is there a reason we don't do it?

I do not think it's a good idea to have implicit casts between text and
everything under the sun, because that essentially destroys the type
checking system.  What we need (see previous discussion) is a flag in
pg_proc that says whether a type conversion function may be invoked
implicitly or not.  I've got no problem with offering text(numeric) and
numeric(text) functions that are invoked by explicit function calls or
casts --- I just don't want the system trying to use them to make
sense of a bogus query.

> I can cast to integer and float8 fine:

I don't believe that those should be available as implicit casts either.
They are, at the moment:

regression=# select 33 || 44.0;
 ?column?
----------
 3344
(1 row)

Ugh.

            regards, tom lane