Re: Make subquery alias optional in FROM clause

On Fri, Feb 24, 2017 at 9:35 AM, David Fetter <david(at)fetter(dot)org> wrote:

>
> > => SELECT "?column"? FROM (select 1+1 as "?column?", 1+1) AS x;
> > ERROR: 42703: column "?column" does not exist
> > LINE 2: SELECT "?column"? FROM (select 1+1 as "?column?", 1+1) AS x;
> > ^
> > HINT: Perhaps you meant to reference the column "x.?column?" or the
> > column "x.?column?".
>

This is indirectly pointing out the duplication ​since the hint is
specifying the exact same name twice...

I don't know how far comparing apples and oranges gets us here...and the
assignment of names to expression columns lacking aliases is a bit smarter
than given credit for here - e.g., it uses the name of the function in a
simple function call expression.

There is no risk of naming conflicts in pre-existing queries. I say we do
something like: pg_subquery_n and make it known that the value for "n"
will be chosen independent of names already present in the query. We've
recently reserved the pg_ prefix for roles we might as well leverage that.
These names need only be available for internal needs; as a user I'd expect
it is be noted as an implementation detail that should not be relied upon.
Whether it needs to get exposed for technical reasons (e.g., dump/restore
and explain) I do not know.

David J.