Re: BUG #17696: Creation of deferrable initially deferred constraint breaks before transaction commit

On 11/25/22 03:55, Tom Lane wrote:
> On the whole I share David's guess that the cost/benefit ratio of
> making this happen is unattractive.  I might feel impelled to do
> it anyway if somebody could show that the SQL spec requires it ...
> but I bet you'll search for that in vain, because I doubt that the
> SQL spec requires transactional DDL at all.  (There are too many
> influential implementations that would have a problem with that.)

The spec does require transactional DDL (SQL:2016 4.41.1 General 
description of SQL-transactions) but does not allow mixing of DDL and 
DML in the same transaction.  What happens when you do that is 
implementation-defined.

So in this case it would not really matter when the new constraint is 
verified because the user would have no opportunity to fix the data anyway.
-- 
Vik Fearing