apache/iceberg · error · IllegalArgumentException

Cannot convert to long

Error message

Cannot convert to long: ${value.getClass().getName()}

What it means

Conversion failure in RecordConverter.convertLong: the incoming Kafka Connect value for a long-typed field is neither a Number nor a String, so no coercion path applies. The appended class name identifies the value's actual Java type; the topic's schema disagrees with the Iceberg column type.

Solutions

1. Emit numeric (or numeric-string) values from the producer for long fields.
2. Alter the Iceberg column type to match the real value type.
3. Apply a value transformation SMT to normalize types upstream of the sink.
4. Route malformed records to a DLQ by catching IllegalArgumentException.

Example fix

// before
record.set("ts", "2024-01-01T00:00:00"); // string date into LongType
// after
record.set("ts", 1704067200000L); // epoch millis

Object v = record.get("ts");
if (!(v instanceof Number) && !(v instanceof String)) {
  throw new IllegalArgumentException("ts must be numeric, got " + v.getClass().getSimpleName());
}

boolean isLongConvertible(Object v) {
  return v instanceof Number || v instanceof String;
}

try {
  sink.write(record);
} catch (IllegalArgumentException e) {
  if (e.getMessage() != null && e.getMessage().contains("Cannot convert to long")) {
    sendToDlq(record, e);
  } else throw e;
}

When it happens

Trigger: A field mapped to an Iceberg LongType column carrying a Boolean, byte[], Map, List, or other non-numeric non-string value.

Common situations: Producers emitting booleans/objects where the table expects bigint; JSON without schemas where all values become Booleans; nested structs landing in long columns.

Understand the failure class

Background: Type mismatch errors: IllegalArgumentException, TypeError and type guards across 150 open-source libraries — this error's family across 150 libraries.

Related errors

• Cannot convert to double
• Cannot convert to float
• Cannot convert to int
• Cannot convert date
• Cannot convert time

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/05c808113e133198. Report an issue: GitHub.

Appendix: source

Thrown at kafka-connect/kafka-connect/src/main/java/org/apache/iceberg/connect/data/RecordConverter.java:438

    return result;
  }

  protected int convertInt(Object value) {
    if (value instanceof Number) {
      return ((Number) value).intValue();
    } else if (value instanceof String) {
      return Integer.parseInt((String) value);
    }
    throw new IllegalArgumentException("Cannot convert to int: " + value.getClass().getName());
  }

  protected long convertLong(Object value) {
    if (value instanceof Number) {
      return ((Number) value).longValue();
    } else if (value instanceof String) {
      return Long.parseLong((String) value);
    }
    throw new IllegalArgumentException("Cannot convert to long: " + value.getClass().getName());
  }

  protected float convertFloat(Object value) {
    if (value instanceof Number) {
      return ((Number) value).floatValue();
    } else if (value instanceof String) {
      return Float.parseFloat((String) value);
    }
    throw new IllegalArgumentException("Cannot convert to float: " + value.getClass().getName());
  }

  protected double convertDouble(Object value) {
    if (value instanceof Number) {
      return ((Number) value).doubleValue();
    } else if (value instanceof String) {
      return Double.parseDouble((String) value);
    }
    throw new IllegalArgumentException("Cannot convert to double: " + value.getClass().getName());

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