apache/flink · error · IllegalArgumentException

FieldSet to add must not be null.

Error message

FieldSet to add must not be null.

What it means

Error "FieldSet to add must not be null." thrown in apache/flink.

Source

Thrown at flink-core/src/main/java/org/apache/flink/api/common/operators/util/FieldList.java:94

            return this;
        }
        if (size() == 0) {
            return new FieldList(fieldIDs);
        } else {
            ArrayList<Integer> list = new ArrayList<Integer>(size() + fieldIDs.length);
            list.addAll(this.collection);
            for (int i = 0; i < fieldIDs.length; i++) {
                list.add(fieldIDs[i]);
            }

            return new FieldList(Collections.unmodifiableList(list));
        }
    }

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

        if (set.size() == 0) {
            return this;
        } else if (size() == 0 && set instanceof FieldList) {
            return (FieldList) set;
        } else {
            ArrayList<Integer> list = new ArrayList<Integer>(size() + set.size());
            list.addAll(this.collection);
            list.addAll(set.collection);
            return new FieldList(Collections.unmodifiableList(list));
        }
    }

    public Integer get(int pos) {
        return get().get(pos);
    }

View on GitHub (pinned to 2f3c205e92)

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/dcb76052722110fa. Report an issue: GitHub.