Re: BUG #6496: Why the SQL is not reported as incorrect? Is there a builtin column named "name"?

luciano(at)geocontrol(dot)com(dot)br writes:
> -- Wrong SQL. Reports no syntax error but yields unexpected data
> SELECT s."name" FROM (SELECT DISTINCT SUBSTRING(bug."name" FROM 1 FOR 3)
> FROM public.is_this_a_bug bug) s;

This is not a bug, exactly, although I'll agree that it's surprising
behavior. What is happening is that the system is taking s."name" as a
coercion from the subquery's composite rowtype to the string type
"name". We got enough complaints about that that 9.1 no longer does it,
cf this release note entry:

Disallow function-style and attribute-style data type casts for
composite types (Tom Lane)

For example, disallow composite_value.text and
text(composite_value). Unintentional uses of this syntax have
frequently resulted in bug reports; although it was not a bug,
it seems better to go back to rejecting such expressions. The
CAST and :: syntaxes are still available for use when a cast of
an entire composite value is actually intended.

There are also some possibly illuminating details here:
http://git.postgresql.org/gitweb/?p=postgresql.git&a=commitdiff&h=543d22fc7423747afd59fe7214f2ddf6259efc62

regards, tom lane