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SQL/JSON: Fix coercion of constructor outputs to types with typmod

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Ensure SQL/JSON constructor functions that allow specifying the
target type using the RETURNING clause perform implicit cast to
that type.  This ensures that output values that exceed the specified
length produce an error rather than being  silently truncated. This
behavior conforms to the SQL standard.

Reported-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Jian He <jian.universality@gmail.com>
Discussion: https://postgr.es/m/202405271326.5a5rprki64aw%40alvherre.pgsql
This commit is contained in:
Amit Langote
2024-06-28 21:37:14 +09:00
parent 065583cf46
commit c2d93c3802
3 changed files with 52 additions and 1 deletions
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24
src/backend/parser/parse_expr.c
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@ -3583,6 +3583,7 @@ coerceJsonFuncExpr(ParseState *pstate, Node *expr,
Node *res;
int location;
Oid exprtype = exprType(expr);
int32 baseTypmod = returning->typmod;
/* if output type is not specified or equals to function type, return */
if (!OidIsValid(returning->typid) || returning->typid == exprtype)
@ -3611,10 +3612,19 @@ coerceJsonFuncExpr(ParseState *pstate, Node *expr,
return (Node *) fexpr;
}
/*
* For domains, consider the base type's typmod to decide whether to setup
* an implicit or explicit cast.
*/
if (get_typtype(returning->typid) == TYPTYPE_DOMAIN)
(void) getBaseTypeAndTypmod(returning->typid, &baseTypmod);
/* try to coerce expression to the output type */
res = coerce_to_target_type(pstate, expr, exprtype,
returning->typid, returning->typmod,
returning->typid, baseTypmod,
baseTypmod > 0 ? COERCION_IMPLICIT :
COERCION_EXPLICIT,
baseTypmod > 0 ? COERCE_IMPLICIT_CAST :
COERCE_EXPLICIT_CAST,
location);
@ -3640,6 +3650,7 @@ makeJsonConstructorExpr(ParseState *pstate, JsonConstructorType type,
JsonConstructorExpr *jsctor = makeNode(JsonConstructorExpr);
Node *placeholder;
Node *coercion;
int32 baseTypmod = returning->typmod;
jsctor->args = args;
jsctor->func = fexpr;
@ -3677,6 +3688,17 @@ makeJsonConstructorExpr(ParseState *pstate, JsonConstructorType type,
placeholder = (Node *) cte;
}
/*
* Convert the source expression to text, because coerceJsonFuncExpr()
* will create an implicit cast to the RETURNING types with typmod and
* there are no implicit casts from json(b) to such types. For domains,
* the base type's typmod will be considered, so do so here too.
*/
if (get_typtype(returning->typid) == TYPTYPE_DOMAIN)
(void) getBaseTypeAndTypmod(returning->typid, &baseTypmod);
if (baseTypmod > 0)
placeholder = coerce_to_specific_type(pstate, placeholder, TEXTOID,
"JSON_CONSTRUCTOR()");
coercion = coerceJsonFuncExpr(pstate, placeholder, returning, true);
if (coercion != placeholder)