apache/flink · error · NumberFormatException

Empty field.

Error message

Empty field.

What it means

Thrown by IntParser.parseField(byte[], int, int, char) when the field starts with the delimiter byte, i.e. the column is empty. The static parser scans raw bytes and rejects an empty column immediately with NumberFormatException instead of producing a default value.

Source

Thrown at flink-core/src/main/java/org/apache/flink/types/parser/IntParser.java:129

    /**
     * Static utility to parse a field of type int from a byte sequence that represents text
     * characters (such as when read from a file stream).
     *
     * @param bytes The bytes containing the text data that should be parsed.
     * @param startPos The offset to start the parsing.
     * @param length The length of the byte sequence (counting from the offset).
     * @param delimiter The delimiter that terminates the field.
     * @return The parsed value.
     * @throws NumberFormatException Thrown when the value cannot be parsed because the text
     *     represents not a correct number.
     */
    public static final int parseField(byte[] bytes, int startPos, int length, char delimiter) {
        long val = 0;
        boolean neg = false;

        if (bytes[startPos] == delimiter) {
            throw new NumberFormatException("Empty field.");
        }

        if (bytes[startPos] == '-') {
            neg = true;
            startPos++;
            length--;
            if (length == 0 || bytes[startPos] == delimiter) {
                throw new NumberFormatException("Orphaned minus sign.");
            }
        }

        for (; length > 0; startPos++, length--) {
            if (bytes[startPos] == delimiter) {
                return (int) (neg ? -val : val);
            }
            if (bytes[startPos] < 48 || bytes[startPos] > 57) {
                throw new NumberFormatException("Invalid character.");
            }

View on GitHub (pinned to 2f3c205e92)

Solutions

1. Fix source data or delimiter handling so int columns are populated.
2. Guard the call: skip the record or substitute a default when the first byte equals the delimiter.
3. If empty cells are valid, map them explicitly (e.g. to null via a nullable wrapper) rather than calling the strict parser.

Example fix

// before
int v = IntParser.parseField(bytes, start, len, ',');

// after
int v = (len > 0 && bytes[start] == (byte) ',')
    ? 0
    : IntParser.parseField(bytes, start, len, ',');

if (len <= 0 || bytes[start] == (byte) delimiter) {
    return 0; // or flag record as invalid
}

try {
    int v = IntParser.parseField(bytes, start, len, delim);
} catch (NumberFormatException e) {
    // empty/malformed int column: side output with row context
}

When it happens

Trigger: Calling IntParser.parseField(bytes, startPos, length, delimiter) where bytes[startPos] == (byte) delimiter — e.g. "7,,9" with ',' delimiter: the middle empty int column throws.

Common situations: CSV rows with missing numeric cells (consecutive delimiters), trailing delimiter yielding an empty last field, or column misalignment after the header schema changes.

Related errors

• Invalid input: Empty string
• Empty field.
• Orphaned minus sign.
• Invalid character.
• Value overflow/underflow

AI-assisted analysis of apache/flink@2f3c205e92 (2026-08-14). Data as JSON: /api/errors/b66c59d9578dddd8. Report an issue: GitHub.