Обсуждение: drop table if exists ;

hello,

I've found a small logical issue while writing a migration script:

create table vtest (foo int);

create view vtest_v as select * from vtest;

drop table  if exists vtest_v;

ERROR:  "vtest_v" is not a table

drop view  if exists vtest;

ERROR:  "vtest" is not a view

this may be seen as a nice hint, but in my own opinion

DROP ... IF EXISTS should not throw an error for objects that do not exist.

A warning would be better here.

This would allow such a code to be error proof:

...

drop table if exists foo;

drop view  if exists foo;

...

best regards,

Marc Mamin

On 09/19/2012 07:54 PM, Marc Mamin wrote:
> hello,
>
> I've found a small logical issue while writing a migration script:
>
> create table vtest (foo int);
>
> create view vtest_v as select * from vtest;
>
> drop table  if exists vtest_v;
>
> ERROR:  "vtest_v" is not a table
>
> drop view  if exists vtest;
>
> ERROR:  "vtest" is not a view
>
> this may be seen as a nice hint, but in my own opinion
>
> DROP ... IF EXISTS should not throw an error for objects that do not exist.

... but they do exist. There is another object with that name. It isn't
clear if the script author's intention is to DROP the object despite the
type mismatch, or to ignore it because it's not the type of object they
specified to drop.

When something is ambiguous or unclear, PostgreSQL will tend to report
an error for safety.

--
Craig Ringer