Обсуждение: pg_dump produces invalid SQL for "group by cast(null as numeric)"

Hi PostgreSQL developers,

in [1], a user reported a failure of pg_dump:

-------- snip ----------
1. Create an empty database.

2. Connect to the database and create these views:

create view foo as select 3;
create view bar as select count(*) from foo group by cast(null as numeric);

3. pg_dump the database to a text file. The file contains

   'CREATE VIEW bar AS
       SELECT count(*) AS count FROM foo GROUP BY 2;'

4. Drop view bar from the database.

5. Run the CREATE VIEW bar..; statement from the text file.

6. The statement fails with

   'ERROR: GROUP BY position 2 is not in select list'
-------- snip ----------

I verified that this is still an issue on 8.3 CVS head.

However, I admit that I'm not sure why "group by cast(null as
numeric)" is useful. However, it actually works in the DB and fails in
pg_dump, so either it is valid and should be handled by pg_dump, or it
is invalid and should not be accepted in the first place.

Thank you!

Martin

[1] https://bugs.launchpad.net/bugs/177382

--=20
Martin Pitt        http://www.piware.de
Ubuntu Developer   http://www.ubuntu.com
Debian Developer   http://www.debian.org

Martin Pitt <martin@piware.de> writes:
> create view bar as select count(*) from foo group by cast(null as numeric);

> 3. pg_dump the database to a text file. The file contains

>    'CREATE VIEW bar AS
>        SELECT count(*) AS count FROM foo GROUP BY 2;'

Actually, this seems to be provoking an Assert failure, if you use
an assert-enabled backend:

$ pg_dump d1
pg_dump: SQL command failed
pg_dump: Error message from server: server closed the connection unexpectedly
        This probably means the server terminated abnormally
        before or while processing the request.
pg_dump: The command was: SELECT pg_catalog.pg_get_viewdef('40965'::pg_catalog.oid) as viewdef

Server log shows

TRAP: FailedAssertion("!(!tle->resjunk)", File: "ruleutils.c", Line: 2267)
LOG:  server process (PID 4507) was terminated by signal 6

So it's a backend problem not pg_dump's fault.

            regards, tom lane

FYI, this was fixed in 8.3.0;  not sure you got the report of the fix.

---------------------------------------------------------------------------

Martin Pitt wrote:
-- Start of PGP signed section.
> Hi PostgreSQL developers,
>
> in [1], a user reported a failure of pg_dump:
>
> -------- snip ----------
> 1. Create an empty database.
>
> 2. Connect to the database and create these views:
>
> create view foo as select 3;
> create view bar as select count(*) from foo group by cast(null as numeric);
>
> 3. pg_dump the database to a text file. The file contains
>
>    'CREATE VIEW bar AS
>        SELECT count(*) AS count FROM foo GROUP BY 2;'
>
> 4. Drop view bar from the database.
>
> 5. Run the CREATE VIEW bar..; statement from the text file.
>
> 6. The statement fails with
>
>    'ERROR: GROUP BY position 2 is not in select list'
> -------- snip ----------
>
> I verified that this is still an issue on 8.3 CVS head.
>
> However, I admit that I'm not sure why "group by cast(null as
> numeric)" is useful. However, it actually works in the DB and fails in
> pg_dump, so either it is valid and should be handled by pg_dump, or it
> is invalid and should not be accepted in the first place.
>
> Thank you!
>
> Martin
>
> [1] https://bugs.launchpad.net/bugs/177382
>
> --
> Martin Pitt        http://www.piware.de
> Ubuntu Developer   http://www.ubuntu.com
> Debian Developer   http://www.debian.org
-- End of PGP section, PGP failed!

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  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://postgres.enterprisedb.com

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