Message-ID: <15a193c9-e1e8-4ec3-a1b0-8179603bf859@postgresfriends.org>
Date: Fri, 13 Sep 2024 15:38:03 +0200
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Subject: Re: Mutable foreign key constraints
To: Andreas Karlsson <andreas@proxel.se>,
 Laurenz Albe <laurenz.albe@cybertec.at>, Tom Lane <tgl@sss.pgh.pa.us>,
 pgsql-hackers@lists.postgresql.org
References: <4162598.1726176826@sss.pgh.pa.us>
 <560b5873c9b8129a4b7b4fe3239ec32363168599.camel@cybertec.at>
 <7c9f8c8b-e5ca-4675-bc1c-f27789059ee7@proxel.se>
From: Vik Fearing <vik@postgresfriends.org>
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On 9/13/24 15:05, Andreas Karlsson wrote:
> On 9/13/24 4:41 AM, Laurenz Albe wrote:
>> That's very broken and should not be allowed.
> 
> +1
> 
>>> A possible objection is that if anybody has such a setup and
>>> hasn't noticed a problem because they never change their
>>> timezone setting, they might not appreciate us breaking it.
>>
>> I hope that there are few cases of that in the field, and I think it
>> is OK to break them.  After all, it can be fixed with a simple
>>
>>    ALTER TABLE foo ALTER id TYPE timestamptz;
>>
>> If the session time zone is UTC, that wouldn't even require a rewrite.
>>
>> I agree that it cannot be backpatched.
> 
> I unfortunately suspect there might be more cases than we think in the 
> field due to many people not understanding the difference between 
> timestamp and timestamptz but the good thing is that 
> timestamp/timestamptz are rare in foreign keys, even in composite ones.


It will become a lot more common with WITHOUT OVERLAPS, so I think it is 
important to fix this at the same time or earlier as that feature.


> Since this is quite broken and does not have any real world usefulness I 
> think we should just go ahead and disallow it and have a few people 
> complain.


+1
-- 
Vik Fearing