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Date: Thu, 9 Jul 2026 09:18:16 +0200
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Subject: Re: implement CAST(expr AS type FORMAT 'template')
To: jian he <jian.universality@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>,
 Corey Huinker <corey.huinker@gmail.com>,
 Zsolt Parragi <zsolt.parragi@percona.com>,
 Vik Fearing <vik@postgresfriends.org>,
 "David G. Johnston" <david.g.johnston@gmail.com>,
 PostgreSQL-development <pgsql-hackers@postgresql.org>
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From: Peter Eisentraut <peter@eisentraut.org>
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On 04.07.26 03:09, jian he wrote:
>> I don't really understand the purpose of this feature to begin with.
>> You can already call the formatting functions directly.  Does this cast
>> syntax offer anything on top of that?
>>
> 
> https://www.postgresql.org/message-id/762ae707-7fdc-43d8-a77a-3a10d12ce21d%40postgresfriends.org
> 
> After this implemented, we can begin fully supporting:
> 
> <cast specification> ::=
>      CAST <left paren>
>          <cast operand> AS <cast target>
>          [ FORMAT <cast template> ]
>          [ <cast error behavior> ON CONVERSION ERROR ]
>          <right paren>

The ON CONVERSION ERROR feature is independent of the FORMAT feature, 
isn't it?