Re: BUG #17706: ALTER TYPE leads to crash

On Thu, Dec 8, 2022 at 1:01 PM David G. Johnston <david(dot)g(dot)johnston(at)gmail(dot)com>
wrote:

> We don't need to fix this though (i.e., make the query continue to somehow
> work), we need to detect the situation and return some kind of error as
> opposed to crashing the server. The transaction itself is doing something
> illegal and can be forced to abort. Alternatively, maybe the ALTER TYPE
> command can emit the error that it is unable to alter the type as it is
> already in use by the current session. But that would close off possible
> non-problematic uses of ALTER TYPE in this situation
>

Yeah, that makes sense. If we create a table using type foo, the alter
operation would error out like that.

create table t (a foo);

alter type foo alter attribute b type text;
ERROR: cannot alter type "foo" because column "t.a" uses it

Maybe we can likewise record the dependencies for the type if it's being
used in other more scenarios besides as a column in some table?

Thanks
Richard