apache/flink · error · IllegalArgumentException

FieldSet to add must not be null.

Error message

FieldSet to add must not be null.

What it means

Thrown by FieldSet.addFields(FieldSet) when null is passed: the method must copy all field IDs from the given set into the new FieldSet, and a null set cannot contribute entries, so the guard rejects it upfront.

Solutions

1. Address the cause reported by the error message: FieldSet to add must not be null.
2. Verify the inputs, configuration values, and classpath/dependency setup related to this operation, then retry.

Example fix

Correct the condition described ("FieldSet to add must not be null.") and rerun the job or command.

When it happens

Trigger: Triggered at runtime when the operation fails because: FieldSet to add must not be null.

Common situations: Commonly caused by misconfiguration, missing dependencies or files, unsupported types or operations, or invalid user input leading to: FieldSet to add must not be null.

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/de9396f1c8d47bdd. Report an issue: GitHub.

Appendix: source

Thrown at flink-core/src/main/java/org/apache/flink/api/common/operators/util/FieldSet.java:156

        }
    }

    // --------------------------------------------------------------------------------------------

    public FieldSet addField(Integer fieldID) {
        if (fieldID == null) {
            throw new IllegalArgumentException("Field ID must not be null.");
        }
        return new FieldSet(this, fieldID);
    }

    public FieldSet addFields(int... fieldIDs) {
        return new FieldSet(this, fieldIDs);
    }

    public FieldSet addFields(FieldSet set) {
        if (set == null) {
            throw new IllegalArgumentException("FieldSet to add must not be null.");
        }

        if (set.size() == 0) {
            return this;
        } else if (this.size() == 0) {
            return set;
        } else {
            return new FieldSet(this, set);
        }
    }

    public boolean contains(Integer columnIndex) {
        return this.collection.contains(columnIndex);
    }

    public int size() {
        return this.collection.size();
    }

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