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From: jian he <jian.universality@gmail.com>
Date: Tue, 22 Jul 2025 18:19:18 +0800
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Subject: Re: CAST(... ON DEFAULT) - WIP build on top of Error-Safe User
 Functions
To: Vik Fearing <vik@postgresfriends.org>
Cc: Corey Huinker <corey.huinker@gmail.com>,
 Isaac Morland <isaac.morland@gmail.com>,
	pgsql-hackers@lists.postgresql.org
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On Tue, Jul 22, 2025 at 2:45=E2=80=AFPM Vik Fearing <vik@postgresfriends.or=
g> wrote:
>
> It was accepted into the standard after 2023 was released.  I am the
> author of this change in the standard, so feel free to ask me anything
> you're unsure about.
>

is the generally syntax as mentioned in this thread:
CAST(source_expression AS target_type DEFAULT default_expression ON ERROR)

if so, what's the restriction of default_expression?