Re: Getting rid of SQLValueFunction

On Wed, Oct 19, 2022 at 03:45:48PM +0900, Michael Paquier wrote:
> With this in mind, would somebody complain if I commit that? That's a
> nice reduction in code, while completing the work done in 40c24bf:
> 25 files changed, 338 insertions(+), 477 deletions(-)

On second look, there is something I have underestimated here with
FigureColnameInternal(). This function would create an attribute name
based on the SQL keyword given in input. For example, on HEAD we
would get that:
=# SELECT * FROM CURRENT_CATALOG;
current_catalog
-----------------
postgres
(1 row)

But the patch enforces the attribute name to be the underlying
function name, switching the previous "current_catalog" to
"current_database". For example:
=# SELECT * FROM CURRENT_CATALOG;
current_database
------------------
postgres
(1 row)

I am not sure how much it matters in practice, but this could break
some queries. One way to tackle that is to extend
FigureColnameInternal() so as we use a compatible name when the node
is a T_FuncCall, but that won't be entirely water-proof as long as
there is not a one-one mapping between the SQL keywords and the
underlying function names, aka we would need a current_catalog.
"user" would be also too generic as a catalog function name, so we
should name its proc entry to a pg_user anyway, requiring a shortcut
in FigureColnameInternal(). Or perhaps I am worrying too much and
keeping the code simpler is better? Does the SQL specification
require that the attribute name has to match its SQL keyword when
specified in a FROM clause when there is no aliases?

Thoughts?
--
Michael