Re: Unexpected behavior of DROP VIEW/TABLE IF EXISTS

2018-06-26 17:48 GMT+02:00 David G. Johnston <david(dot)g(dot)johnston(at)gmail(dot)com>:

> On Tuesday, June 26, 2018, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
>
>> 2018-06-26 17:23 GMT+02:00 Peter Moser <pitiz29a(at)gmail(dot)com>:
>>
>>> Hi,
>>> I want to delete a table X, that may not exist, hence I execute
>>>
>>> DROP TABLE IF EXISTS X;
>>>
>>> However, if X is a view, I get an error
>>>
>>> ERROR: "X" is not a table
>>>
>> HINT: Use DROP VIEW to remove a view.
>>> SQL state: 42809
>>>
>>> That is unexpected and also difficult to handle
>>>
>>
>> DROP TABLE should to remove table and nothing else, like DROP VIEW should
>> to drop just view and nothing else. It is safeguard.
>>
>
> Peter isn't asking for drop table to drop a view though, he's asking for
> the documented behavior:
>
> "Do not throw an error if the table does not exist. A notice is issued in
> this case."
>

This is different issue.

> There is no Table named X in the database so the command should be a noop
> with a notice. I would concur, though I'm open to just fixing it in v12
> and back patching a documentation bug fix stating the exception due to
> relations sharing a namespace but there be lacking a corresponding shared
> namespace "drop relation" command.
>

There are two points

a) documentation issue
b) different behave for DROP TABLE IF EXISTS command

My note is related to @b. I understand to the motivation, but I am not sure
if it is good idea. Tables and views shares one namespace.

Often usage of DROP TABLE IF EXISTS is together with CREATE TABLE

Now if some does bad reference in DROP TABLE command, then this command
fails (first). If we do proposed change, then DROP TABLE do nothing, and
CREATE TABLE fails.

So I am not sure, if proposed change is practical because views and tables
shares same namespace and current behave has sense too.

Regards

Pavel

> David J.
>
>