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From: Corey Huinker <corey.huinker@gmail.com>
Date: Tue, 17 Mar 2026 23:11:18 -0400
Message-ID: 
 <CADkLM=cmv_bmxBe8KmZd6rEgiqSdoDfHnJa63u7rdRuAsqOwDA@mail.gmail.com>
Subject: Re: CAST(... ON DEFAULT) - WIP build on top of Error-Safe User
 Functions
To: jian he <jian.universality@gmail.com>
Cc: Amul Sul <sulamul@gmail.com>, Kirill Reshke <reshkekirill@gmail.com>,
	Vik Fearing <vik@postgresfriends.org>,
 Isaac Morland <isaac.morland@gmail.com>,
	pgsql-hackers@lists.postgresql.org
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>
> + if (inputElementBaseType == MONEYOID ||
> + targetElementBaseType == MONEYOID ||
> + (inputElementBaseType == CIRCLEOID &&
> + targetElementBaseType == POLYGONOID))
> + {
> + errorsafe_coercion = false;
> + }
>

What if we just reject cast functions with a non-null prosqlbody?


>
> Given the interaction with array and domain coercion, we need to think more
> about error-safe type casts for user-defined range, multirange, and
> composite
> types.  For now, we should disallow error-safe casting for these types.
>

I agree. It's far better to get this working for the majority of cases, and
we can chip away at more obscure types later. There will *always* be user
defined types that we cannot account for.

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<div dir=3D"ltr"><div class=3D"gmail_quote gmail_quote_container"><blockquo=
te class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px =
solid rgb(204,204,204);padding-left:1ex">+ if (inputElementBaseType =3D=3D =
MONEYOID ||<br>
+ targetElementBaseType =3D=3D MONEYOID ||<br>
+ (inputElementBaseType =3D=3D CIRCLEOID &amp;&amp;<br>
+ targetElementBaseType =3D=3D POLYGONOID))<br>
+ {<br>
+ errorsafe_coercion =3D false;<br>
+ }<br></blockquote><div><br></div>What if we just reject cast functions wi=
th a non-null prosqlbody?<div>=C2=A0</div><blockquote class=3D"gmail_quote"=
 style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);p=
adding-left:1ex"><br>
Given the interaction with array and domain coercion, we need to think more=
<br>
about error-safe type casts for user-defined range, multirange, and composi=
te<br>
types.=C2=A0 For now, we should disallow error-safe casting for these types=
.<br></blockquote><div><br></div><div>I agree. It&#39;s far better to get t=
his working for the majority of cases, and we can chip away at more obscure=
 types later. There will *always* be user defined types that we cannot acco=
unt for.</div></div></div>

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