Álvaro,

Yes, a CREATE OR REPLACE would also be useful.

However, the CREATE IF NOT EXISTS is also useful when you aren't concerned that 
the POLICY is going to change. Same with the existing CREATE TABLE IF NOT 
EXISTS.

Yes I'm aware that the DROP/CREATE can create a security hole, which is why I'd 
like the IF NOT EXISTS. At the moment my use case stops the application prior 
to running this script and the database is in a private network.

-----Original Message-----
From: Álvaro Herrera <[email protected]> 
Sent: October 21, 2025 12:23 AM
To: Paul Austin <[email protected]>
Cc: [email protected]
Subject: Re: Extend CREATE POLICY to add IF EXISTS

On 2025-Oct-20, Paul Austin wrote:

> Adrian,
> 
> The drop policy IF EXISTS does work.
> 
> But it would be nice to have the IF NOT EXISTS on CREATE POLICY so I 
> don't need to do a drop and create.

How would CREATE IF NOT EXISTS handle the case of an existing policy that 
doesn't match the one you want?  I think it would just silently not do 
anything, and in that case you can't really rely on it, can you?  So your 
script would have to extract the current policy, compare with the one you want 
(how?) and then maybe drop it and create it anew, or leave it alone.  Is this 
really useful?

I think what you'd really appreciate is CREATE OR REPLACE: if the policy exists 
and matches the one you ask for, then don't do anything; but otherwise throw it 
away and create it anew.  We have this for views, and it allows for things like 
adding more columns than the original view had.

BTW, the pattern DROP IF EXISTS / CREATE is a bit nasty, because there exists a 
period in between where no policy exists, which could be a security hole.  
Unless you use an explicit transaction block.

-- 
Álvaro Herrera        Breisgau, Deutschland  —  https://www.EnterpriseDB.com/
"I love the Postgres community. It's all about doing things _properly_. :-)"
(David Garamond)

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