MIME-Version: 1.0
References: 
 <CADkLM=fv1JfY4Ufa-jcwwNbjQixNViskQ8jZu3Tz_p656i_4hQ@mail.gmail.com>
 <CAMsGm5dpfm2PHL8XZvC-JSd+UPkgx3rpReUA=G=4+rUCH+Ntcw@mail.gmail.com>
 <CADkLM=eD_S8mGhPfu5+hXXvXgR0-cxGpGd9dgPzD+nCuO7HFaQ@mail.gmail.com>
 <CACJufxHCMzrHOW=wRe8L30rMhB3sjwAv1LE928Fa7sxMu1Tx-g@mail.gmail.com>
 <04afcd1f-ed7d-4c0a-add1-50e3719ccbf9@postgresfriends.org>
 <CACJufxGRAnwJzu7nMq4ZP=yqa1Sz=qR+mR1TmY0aCDjJoJRRtg@mail.gmail.com>
 <762ae707-7fdc-43d8-a77a-3a10d12ce21d@postgresfriends.org>
 <CACJufxFy+DFpJ2e-czyCTAgSJXNFaQGWFKA4mjbW-LAMGc1YBA@mail.gmail.com>
 <CADkLM=f1Jv81=s5Ckazx3zZq=M5KoBJMJkOZux_-L+gezODCEQ@mail.gmail.com>
 <CACJufxGw_OY7K3rfG4kDb902O2guhT-wgTjTJQ=pWeVWRTHpHQ@mail.gmail.com>
 <CADkLM=cFSg3+6Sk00dLAF7Q7jnrKBk6+N5gRxT5BCxRvaGtR-g@mail.gmail.com>
 <CACJufxE_aO5FtBGwhDym-Fwe7k8oJY7a8jcYDx77=t3maPvG0g@mail.gmail.com>
In-Reply-To: 
 <CACJufxE_aO5FtBGwhDym-Fwe7k8oJY7a8jcYDx77=t3maPvG0g@mail.gmail.com>
From: Corey Huinker <corey.huinker@gmail.com>
Date: Tue, 5 Aug 2025 00:10:33 -0400
Message-ID: 
 <CADkLM=chahh6ddZFjLL6AUdqzL_Px0raTu-5Jzn2WN8yELtmJw@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: Vik Fearing <vik@postgresfriends.org>,
 Isaac Morland <isaac.morland@gmail.com>,
	pgsql-hackers@lists.postgresql.org
Content-Type: multipart/alternative; boundary="000000000000a0af20063b9668f8"
Archived-At: 
 <https://www.postgresql.org/message-id/CADkLM%3Dchahh6ddZFjLL6AUdqzL_Px0raTu-5Jzn2WN8yELtmJw%40mail.gmail.com>
Precedence: bulk

--000000000000a0af20063b9668f8
Content-Type: text/plain; charset="UTF-8"

>
>
> In the end, it seems we need to make all these functions in the below
> query error safe.
> select castsource::regtype, casttarget::regtype, castfunc,
> castcontext,castmethod, pp.prosrc, pp.proname from pg_cast pc join pg_proc
> pp on
> pp.oid = pc.castfunc and pc.castfunc > 0
> order by castsource::regtype;
> It's a lot of work, but seems doable, after playing around with it.
>

It is do-able. But that's just the cast functions that are part of core
postgres.


>
>
> I don't think we need to change the pg_cast catalog entry,
> we just need to make these function (pg_cast.castmethod) errors safe.


That would break any user-defined cast functions that were not also error
safe, which is to say all of them.

We need a way for user-defined cast functions to indicate whether or not
they are error safe, and handle both situations accordingly (i.e. fail a
CAST ON DEFAULT when the user-defined cast is not error-safe).

--000000000000a0af20063b9668f8
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<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"><br>
In the end, it seems we need to make all these functions in the below<br>
query error safe.<br>
select castsource::regtype, casttarget::regtype, castfunc,<br>
castcontext,castmethod, pp.prosrc, pp.proname from pg_cast pc join pg_proc =
pp on<br>
pp.oid =3D pc.castfunc and pc.castfunc &gt; 0<br>
order by castsource::regtype;<br>
It&#39;s a lot of work, but seems doable, after playing around with it.<br>=
</blockquote><div><br></div><div>It is do-able. But that&#39;s just the cas=
t functions that are part of core postgres.=C2=A0</div><div></div><div>=C2=
=A0</div><blockquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8e=
x;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<br>
<br>
I don&#39;t think we need to change the pg_cast catalog entry,<br>
we just need to make these function (pg_cast.castmethod) errors safe.</bloc=
kquote><div><br></div><div>That would break any user-defined cast functions=
 that were not also error safe, which is to say all of them.</div><div><br>=
</div><div><div>We need a way for user-defined cast functions to indicate w=
hether or not they are error safe, and handle both situations accordingly (=
i.e. fail a CAST ON DEFAULT when the user-defined cast is not error-safe).<=
/div>=C2=A0</div></div></div>

--000000000000a0af20063b9668f8--