Re: BUG #16492: DROP VIEW IF EXISTS error - Mailing list pgsql-bugs

From Pavel Stehule
Subject Re: BUG #16492: DROP VIEW IF EXISTS error
Date
Msg-id CAFj8pRCe1+eAF1+06O_qCgVwrxAXsQkznqG1yTZSK+qnC29-Dw@mail.gmail.com
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In response to Re: BUG #16492: DROP VIEW IF EXISTS error  ("David G. Johnston" <david.g.johnston@gmail.com>)
Responses Re: BUG #16492: DROP VIEW IF EXISTS error
Re: BUG #16492: DROP VIEW IF EXISTS error
List pgsql-bugs


pá 12. 6. 2020 v 21:43 odesílatel David G. Johnston <david.g.johnston@gmail.com> napsal:
On Friday, June 12, 2020, PG Bug reporting form <noreply@postgresql.org> wrote:
The following bug has been logged on the website:

Bug reference:      16492
Logged by:          Nina Marlow
Email address:      postgresql.2020@t-net.ruhr
PostgreSQL version: 12.3
Operating system:   Linux/Docker
Description:       

When trying to use "DROP VIEW IF EXISTS x" while a table named "x" exists,
the DROP statement raises an "Error: x is not a view".

The documentation says about the "IF EXISTS" clause:

> Do not throw an error if the view does not exist. A notice is issued in
this case.

Imho, there shouldn't be an error if the view does not exist regardless of
whether or not a table with this name exists. The observed behavior is
contrary to the sense of the "IF EXISTS" clause as one would have to check
whether a table with the desired name exists before using "DROP VIEW IF
EXISTS". But then you could directly check whether or not the view itself
exists.

This thread from 2018 illustrates the current state of the discussion:


I still concur this is indeed a bug that should be fixed.

It is hard to find an agreement here.  Both alternatives has benefits and disadvantages. Just depends on personal view. One direction is more tolerant behaviour (more user friendly). Second direction is more strict behaviour (developer friendly).
Probably preferences depends if somebody use DROP as an isolated command or not. I use DROP IF EXISTS together with CREATE statement, and for me is natural current design.

DROP TABLE IF EXISTS xxx;
CREATE TABLE xxx;

If the first statement doesn't fail, then the second statement will be successful with very high priority. For me is little bit more intuitive message "cannot to drop some" then "cannot to create some" when first command is DROP, and I have to investigate, why DROP was ignored.

Because I use these statements typically in pair, then I prefer current behaviour. I am not sure what is the best design here, but I don't think so this case is a bug. It is just ambiguous.

Nice evening

Pavel




David J.

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