Re: BUG #7644: Missing implicit types of Result and failing type-conversion - Mailing list pgsql-bugs

On 10 November 2012 16:20:24 Tom Lane <tgl@sss.pgh.pa.us> wrote:
> rep.dot.nop@gmail.com writes:
> > select distinct on (bug) bug
> > from (
> >         select * from (select 'string one' AS bug from generate_series(0,1))
> > s1
> >         UNION
> >         select * from (select 'string two' bug from generate_series(0,0))
> > s2
> >      ) x
> > ;
> > ERROR:  could not determine which collation to use for string comparison
> > HINT:  Use the COLLATE clause to set the collation explicitly.
>
> > What am i missing or doing wrong?
>
> Leaving out the cast.  An undecorated string literal is not a constant
> of type text --- it is a constant of unknown type, and the parser will
> throw an error if the type can't be resolved from fairly-local context.
> (The same applies to NULL, btw.)

Fair enough but what about the failure for the case with the Result
that fails to merge? There I do have a cast but it fails on the Result
as opposed to a genera e_series(0,0):

select distinct on (bug) bug
from (
        select * from (select 'string one'::text AS bug from
generate_series(0,1)) s1
        UNION
        select * from (select 'string two' bug ) s2

     ) x
;


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