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From: Amul Sul <sulamul@gmail.com>
Date: Mon, 30 Mar 2026 18:39:32 +0530
Message-ID: 
 <CAAJ_b959dfJsorK+_vPdVa8F3QYPdOnb-HzJY8oQQR91N9Tq2A@mail.gmail.com>
Subject: Re: CAST(... ON DEFAULT) - WIP build on top of Error-Safe User
 Functions
To: Peter Eisentraut <peter@eisentraut.org>
Cc: jian he <jian.universality@gmail.com>,
 Corey Huinker <corey.huinker@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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Precedence: bulk

On Mon, Mar 30, 2026 at 4:57=E2=80=AFPM Peter Eisentraut <peter@eisentraut.=
org> wrote:
>
>  From the v25 I have committed everything except 0001 and 0009.  I will
> continue reviewing the rest.
>

I=E2=80=99ve had a glance over the remaining patches; here are a few commen=
ts:

V25-0001:

-       if (relation->schemaname)
+       if (escontext =3D=3D NULL)
            ereport(elevel,
-                   (errcode(ERRCODE_UNDEFINED_TABLE),
-                    errmsg("relation \"%s.%s\" does not exist",
-                           relation->schemaname, relation->relname)));
+                   errcode(ERRCODE_LOCK_NOT_AVAILABLE),
+                   relation->schemaname ?
+                   errmsg("relation \"%s.%s\" does not exist",
+                          relation->schemaname, relation->relname) :
+                   errmsg("relation \"%s\" does not exist",
+                          relation->relname));
        else
-           ereport(elevel,
-                   (errcode(ERRCODE_UNDEFINED_TABLE),
-                    errmsg("relation \"%s\" does not exist",
-                           relation->relname)));
+           ereturn(escontext, InvalidOid,
+                   errcode(ERRCODE_LOCK_NOT_AVAILABLE),
+                   relation->schemaname ?
+                   errmsg("relation \"%s.%s\" does not exist",
+                          relation->schemaname, relation->relname) :
+                   errmsg("relation \"%s\" does not exist",
+                          relation->relname));
    }

The error code changed here -- was this intentional?
--

v25-0009 :

+SELECT CAST('abc'::bpchar AS citext DEFAULT NULL ON CONVERSION ERROR); -- =
error
+ERROR:  cannot cast type character to citext when DEFAULT expression
is specified in CAST ... ON CONVERSION ERROR
+LINE 1: SELECT CAST('abc'::bpchar AS citext DEFAULT NULL ON CONVERSI...
+                    ^
+HINT:  Safe type cast for user-defined types are not yet supported.


"Should the HINT be this DETAIL? I believe a hint should provide
guidance for the user to handle the error, but here the user cannot do
anything with the given information.
--

 /* Generic macro for applying evaluate_expr */
-#define ece_evaluate_expr(node) \
+#define ece_evaluate_expr(node, escontext) \
    ((Node *) evaluate_expr((Expr *) (node), \
                            exprType((Node *) (node)), \
                            exprTypmod((Node *) (node)), \
-                           exprCollation((Node *) (node))))
+                           exprCollation((Node *) (node)), \
+                           escontext))


I think we can simply cast escontext to Node * here, instead of
having the caller do it.

Regards,
Amul