Обсуждение: IS JSON predicate support for domain base type as JSON/JSONB/BYTEA/TEXT

hi.

src/backend/executor/execExpr.c

        case T_JsonIsPredicate:
            {
                JsonIsPredicate *pred = (JsonIsPredicate *) node;
                ExecInitExprRec((Expr *) pred->expr, state, resv, resnull);
                scratch.opcode = EEOP_IS_JSON;
                scratch.d.is_json.pred = pred;
                ExprEvalPushStep(state, &scratch);
                break;
            }

gram.y:
a_expr IS json_predicate_type_constraint

the above shows the a_expr will be transformed and then evaluated.
The exprType type of a_expr as domain should work just fine.
The attached patch implements this, and it seems to be quite straightforward.
(extensive regress tests added)

CREATE DOMAIN jd1 AS JSON CHECK ((VALUE ->'a')::text <> '3');
CREATE DOMAIN jd2 AS JSONB CHECK ((VALUE ->'a') = '1'::jsonb);
CREATE DOMAIN jd4 AS bytea CHECK (VALUE <> '\x61');
SELECT NULL::jd1 IS JSON;
SELECT NULL::jd2 IS JSON;
SELECT NULL::jd4 IS JSON;

in the master, the above 3 IS JSON would return error,
with the attached patch, it will return NULL.

I checked the discussion links [1], but couldn’t find the reason domains aren’t
supported. I guess at that time, we didn't think about this issue.

[1] https://git.postgresql.org/cgit/postgresql.git/commit/?id=6ee30209a6f161d0a267a33f090c70c579c87c00

--
jian
https://www.enterprisedb.com/

jian he <jian.universality@gmail.com> writes:
> [ v1-0001-IS-JSON-predicate-work-with-domain-type.patch ]

This looks like a large patch with a small patch struggling to
get out of it.  Why didn't you simply do

-    *exprtype = exprType(expr);
+    *exprtype = getBaseType(exprType(expr));

in transformJsonParseArg?

            regards, tom lane

On Wed, Nov 19, 2025 at 1:01 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> jian he <jian.universality@gmail.com> writes:
> > [ v1-0001-IS-JSON-predicate-work-with-domain-type.patch ]
>
> This looks like a large patch with a small patch struggling to
> get out of it.  Why didn't you simply do
>
> -       *exprtype = exprType(expr);
> +       *exprtype = getBaseType(exprType(expr));
>
> in transformJsonParseArg?
>

yech.
While at it, I added parser_errposition to the transformJsonIsPredicate ereport.

errmsg("cannot use type %s in IS JSON predicate",
            format_type_be(exprtype))
we don't need to worry about exprtype as InvalidOid, because
transformJsonParseArg (exprType(expr)) would fail already in that case.


--
jian
https://www.enterprisedb.com/