Re: Check constraint on domain over an array not executed for array literals

Florian G. Pflug wrote:
> While trying to create a domain over an array type to enforce a certain
> shape or certain contents of an array (like the array being only
> one-dimensional or not containing NULLs), I've stumbled over what I
> believe to be a bug in postgresql 8.4
> 
> It seems that check constraints on domains are *not* executed for
> literals of the domain-over-array-type - in other words, for expressions
> like:
> array[...]::<my-domain-over-array-type>.
> 
> They are, however, executed if I first force the array to be of the base
> type, and then cast it to the array type.
> ...
> I still have the feeling that this a bug, though. First, because it
> leaves you with no way at guarantee that values of a given domain always
> fulfill certain constraints. And second because "array[...]::arraytype"
> at least *looks* like a cast, and hence should behave like one too.

Agreed, it's a bug. A simpler example is just:

postgres=# create  domain myintarray as int[] check (value[1] < 10);
CREATE DOMAIN
postgres=# SELECT array['20']::myintarray; -- should fail
 array
───────
 {20}
(1 row)

There's a special case in transformExpr function to handle the
"ARRAY[...]::arraytype" construct, which skips the usual type-casting
and just constructs an ArrayExpr with the right target type. However,
it's not taking into account that the target type can be a domain.

Attached patch fixes that. Anyone see a problem with it?

-- 
  Heikki Linnakangas
  EnterpriseDB   http://www.enterprisedb.com