Re: Making the subquery alias optional in the FROM clause
| От | Erwin Brandstetter |
|---|---|
| Тема | Re: Making the subquery alias optional in the FROM clause |
| Дата | |
| Msg-id | CAGHENJ6MUCdJxoh3mebMnJk4w1N_-VJM_kXPA3dcS=YD+t3ytg@mail.gmail.com обсуждение исходный текст |
| Ответ на | Making the subquery alias optional in the FROM clause (Dean Rasheed <dean.a.rasheed@gmail.com>) |
| Ответы |
Re: Making the subquery alias optional in the FROM clause
|
| Список | pgsql-hackers |
On Mon, 2 Oct 2023 at 00:33, Dean Rasheed <dean.a.rasheed@gmail.com> wrote:
The only place that exposes the eref's made-up relation name is the
existing query deparsing code in ruleutils.c, which uniquifies it and
generates SQL spec-compliant output. For example:
I ran into one other place: error messages.
SELECT unnamed_subquery.a
FROM (SELECT 1 AS a)
> ERROR: There is an entry for table "unnamed_subquery", but it cannot be referenced from this part of the query.invalid reference to FROM-clause entry for table "unnamed_subquery"
FROM (SELECT 1 AS a)
> ERROR: There is an entry for table "unnamed_subquery", but it cannot be referenced from this part of the query.invalid reference to FROM-clause entry for table "unnamed_subquery"
Normally, we would find the cited name somewhere in the query. Confusing.
Notably, the same does not happen for "unnamed_subquery_1":
SELECT unnamed_subquery_1.a
FROM (SELECT 1 AS a), (SELECT 1 AS a)
> ERROR: missing FROM-clause entry for table "unnamed_subquery_1"
FROM (SELECT 1 AS a), (SELECT 1 AS a)
> ERROR: missing FROM-clause entry for table "unnamed_subquery_1"
That's the message anybody would expect.
Also makes sense, as "uniquification" only happens in the above quoted case, and all invisible aliases seem to be "unnamed_subquery" at this point? But a bit confusing on a different level.
Maybe error messages should not be aware of invisible aliases, and just complain about "missing FROM-clause entry"?
Not sure whether a fix would be easy, nor whether it would be worth the effort. Just wanted to document the corner case issue in this thread.
Regards
Erwin
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