Re: Assignment of valid collation for SET operations on queries with UNKNOWN types.

On Tue, Dec 6, 2016 at 10:42 PM, Rahila Syed <rahilasyed90@gmail.com> wrote:
> Hello,
>
>>And ideally fix things so
>>that the type of the view column will be resolved as text, so that you
>>don't hit this condition in the first place; but there is no good that
>>comes out of allowing a view to be created like this
>
> Thank you for suggestion. Attached is a patch which resolves the columns
> with literal constants as TEXT for view creation.
>
> Following views can be created with literal columns resolved as TEXT.
>
> postgres=# create view v as select 'abc' a;
> CREATE VIEW
> postgres=# create view v1 as select 'def' a;
> CREATE VIEW

There is a similar code pattern for materialized views, see
create_ctas_nodata() where the attribute list is built. Even with your
patch, I get that:
=# create materialized view m as select 'abc' a;
WARNING:  42P16: column "a" has type "unknown"
DETAIL:  Proceeding with relation creation anyway.
LOCATION:  CheckAttributeType, heap.c:499
SELECT 1
Time: 6.566 ms
=# select * from m order by 1;
ERROR:  XX000: failed to find conversion function from unknown to text

Your patch has no regression tests, surely you want some to stress
this code path. And actually, shouldn't this be just a plain error?
-- 
Michael