apache/flink · error · IllegalArgumentException

The field ({}) is invalid.

Error message

The field  ({}) is invalid.

What it means

Thrown by checkForMonotonousOrder when a position is negative. CSV column positions must be >= 0. (The message here is well-formed: 'The field (-1) is invalid.', unlike the parallel check in checkAndCoSort which has a typo.) This is a programming-error guard.

Source

Thrown at flink-core/src/main/java/org/apache/flink/api/common/io/GenericCsvInputFormat.java:571

        int i = 0;
        for (Map.Entry<Integer, Class<?>> entry : map.entrySet()) {
            positions[i] = entry.getKey();
            types[i] = entry.getValue();
            i++;
        }
    }

    protected static void checkForMonotonousOrder(int[] positions, Class<?>[] types) {
        if (positions.length != types.length) {
            throw new IllegalArgumentException(
                    "The positions and types must be of the same length");
        }

        int lastPos = -1;

        for (int i = 0; i < positions.length; i++) {
            if (positions[i] < 0) {
                throw new IllegalArgumentException(
                        "The field " + " (" + positions[i] + ") is invalid.");
            }
            if (types[i] == null) {
                throw new IllegalArgumentException("The type " + i + " is invalid (null)");
            }

            if (positions[i] <= lastPos) {
                throw new IllegalArgumentException(
                        "The positions must be strictly increasing (no permutations are supported).");
            }

            lastPos = positions[i];
        }
    }

    private static int max(int[] ints) {
        checkArgument(ints.length > 0);

View on GitHub (pinned to 2f3c205e92)

Solutions

1. Ensure all positions are >= 0 before calling checkForMonotonousOrder.
2. Audit index arithmetic for off-by-one and 0-vs-1 base mistakes.
3. Strip sentinel/placeholder indices before the call.

Example fix

// before
checkForMonotonousOrder(new int[]{-1,1,2}, types);
// after
checkForMonotonousOrder(new int[]{0,1,2}, types);

for (int p : positions) {
    if (p < 0) throw new IllegalArgumentException("Negative CSV position: " + p);
}
checkForMonotonousOrder(positions, types);

static int nonNegIndex(int i) {
    if (i < 0) throw new IllegalArgumentException("index must be >= 0, got " + i);
    return i;
}

try {
    checkForMonotonousOrder(positions, types);
} catch (IllegalArgumentException e) {
    if (e.getMessage().contains("invalid")) {
        throw new IllegalArgumentException("Negative CSV position: " + Arrays.toString(positions), e);
    }
    throw e;
}

When it happens

Trigger: A subclass passes a positions array containing a negative value, e.g. from off-by-one arithmetic, a sentinel not filtered, or 0-vs-1 based indexing confusion.

Common situations: Index = something - 1 when something is 0; sentinel -1 leaking through; refactor leftover; 1-based source data treated as 0-based.

Related errors

• The positions and types must be of the same length
• The field ({} is invalid.
• The type {} is invalid (null)
• The position {} occurs multiple times.
• The positions must be strictly increasing (no permutations a

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/a98798058c98c1b0. Report an issue: GitHub.