apache/flink · error · InvalidFieldReferenceException

Wildcard expressions are not allowed here.

Error message

Wildcard expressions are not allowed here.

What it means

Thrown by TupleTypeInfoBase.getTypeAt(String) when a wildcard character ('*' or '_') is used as a field expression. Wildcards are only supported by getFlatFields, not by getTypeAt, which expects a concrete field position like 'f0' or '1'. The method validates the expression against PATTERN_NESTED_FIELDS ((f?)([0-9]+)) and explicitly rejects the SELECT_ALL_CHAR before falling through to the generic invalid-format error.

Source

Thrown at flink-core/src/main/java/org/apache/flink/api/java/typeutils/TupleTypeInfoBase.java:191

                    throw new InvalidFieldReferenceException(
                            "Nested field expression \""
                                    + tail
                                    + "\" not possible on atomic type "
                                    + fieldType
                                    + ".");
                }
            }
        }
    }

    @Override
    public <X> TypeInformation<X> getTypeAt(String fieldExpression) {

        Matcher matcher = PATTERN_NESTED_FIELDS.matcher(fieldExpression);
        if (!matcher.matches()) {
            if (fieldExpression.equals(ExpressionKeys.SELECT_ALL_CHAR)
                    || fieldExpression.equals(ExpressionKeys.SELECT_ALL_CHAR_SCALA)) {
                throw new InvalidFieldReferenceException(
                        "Wildcard expressions are not allowed here.");
            } else {
                throw new InvalidFieldReferenceException(
                        "Invalid format of tuple field expression \"" + fieldExpression + "\".");
            }
        }

        String fieldStr = matcher.group(1);
        Matcher fieldMatcher = PATTERN_FIELD.matcher(fieldStr);
        if (!fieldMatcher.matches()) {
            throw new RuntimeException("Invalid matcher pattern");
        }
        String field = fieldMatcher.group(2);
        int fieldPos = Integer.valueOf(field);

        if (fieldPos >= this.getArity()) {
            throw new InvalidFieldReferenceException(
                    "Tuple field expression \""

View on GitHub (pinned to 2f3c205e92)

Solutions

1. Replace the wildcard with a concrete field index, e.g. getTypeAt("f0") or getTypeAt("0").
2. If you need all fields, use getFlatFields(fieldExpression, offset, result) instead of getTypeAt.
3. Review the calling code to ensure you are not forwarding a user-facing '*' selector into a type-resolution path.

Example fix

// before
tupleType.getTypeAt("*");
// after
tupleType.getTypeAt("f0");

if ("*".equals(fieldExpr) || "_".equals(fieldExpr)) {
    throw new IllegalArgumentException("Wildcard not supported by getTypeAt; use getFlatFields instead.");
}
tupleType.getTypeAt(fieldExpr);

static boolean isValidTupleFieldExpression(String expr) {
    return expr != null && !"*".equals(expr) && !"_".equals(expr)
        && expr.matches("(f?)([0-9]+)(\\.(.+))?");
}

When it happens

Trigger: Calling tupleType.getTypeAt("*") or tupleType.getTypeAt("_") on a TupleTypeInfoBase instance (e.g. TupleTypeInfo for Tuple2). Also triggered indirectly when a join/group/select key selector that uses wildcard notation is resolved through getTypeAt instead of getFlatFields.

Common situations: A developer confuses the field-selection API for keys (which supports '*' for 'all fields') with the type-lookup API. Happens when programmatically building dataflows and passing a wildcard key string where a specific tuple field index is required.

Related errors

• Invalid format of tuple field expression "{}".
• Usage of class Tuple as a type is not allowed. Use a concret
• Tuple needs to be parameterized by using generics.
• Type information extraction for tuples (except Tuple0) canno
• Automatic type extraction is not possible on candidates with

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/a837d126b9be8d85. Report an issue: GitHub.