apache/iceberg · error · IllegalStateException

Unknown type for long field. Type name:

Error message

Unknown type for long field. Type name: 

What it means

StructRowData.getLong converts a struct field into a Flink long, accepting Long, LocalTime (nanos of day), LocalDateTime, OffsetDateTime and Instant (as microseconds). Any other class triggers this IllegalStateException. It means the stored value's Java class does not correspond to the Iceberg long/time/timestamp field it occupies.

Solutions

1. Inspect the class name in the message and ensure long/timestamp fields are written as Long or the supported java.time types.
2. Confirm the Iceberg field is LongType/TimestampType as declared in the schema.
3. Convert the value to the expected type in the producing pipeline before writing.

Example fix

// before
row.setField(pos, someTimestamp); // java.sql.Timestamp not supported here

// after
row.setField(pos, someTimestamp.toLocalDateTime());

Object v = struct.getField(pos);
if (!(v instanceof Long || v instanceof LocalTime || v instanceof LocalDateTime || v instanceof OffsetDateTime || v instanceof Instant)) {
  throw new IllegalArgumentException("Unexpected class for long field: " + v.getClass());
}

boolean isLongCompatible(Object v) {
  return v instanceof Long || v instanceof LocalTime || v instanceof LocalDateTime
      || v instanceof OffsetDateTime || v instanceof Instant;
}

try {
  long value = rowData.getLong(pos);
} catch (IllegalStateException e) {
  // inspect the class name in the message and convert upstream
}

When it happens

Trigger: Calling getLong(pos) where the field object is, e.g., an Integer, String or BigDecimal instead of Long or a supported time type.

Common situations: Writers producing Integer for LongType fields; timestamps stored as String or Timestamp objects rather than the expected java.time classes; mismatched Flink LogicalType vs Iceberg type when bridging.

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

• Unknown type for int field. Type name:
• errMsg(variant, "double")
• errMsg(variant, "int")
• errMsg(variant, "long")
• errMsg(variant, "timestamp")

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/4026c28ab3e13b0a. Report an issue: GitHub.

Appendix: source

Thrown at flink/v2.3/flink/src/main/java/org/apache/iceberg/flink/data/StructRowData.java:152

  @Override
  public long getLong(int pos) {
    Object longVal = struct.get(pos, Object.class);

    if (longVal instanceof Long) {
      return (long) longVal;
    } else if (longVal instanceof OffsetDateTime) {
      return Duration.between(Instant.EPOCH, (OffsetDateTime) longVal).toNanos() / 1000;
    } else if (longVal instanceof LocalDate) {
      return ((LocalDate) longVal).toEpochDay();
    } else if (longVal instanceof LocalTime) {
      return ((LocalTime) longVal).toNanoOfDay();
    } else if (longVal instanceof LocalDateTime) {
      return Duration.between(Instant.EPOCH, ((LocalDateTime) longVal).atOffset(ZoneOffset.UTC))
              .toNanos()
          / 1000;
    } else {
      throw new IllegalStateException(
          "Unknown type for long field. Type name: " + longVal.getClass().getName());
    }
  }

  @Override
  public float getFloat(int pos) {
    return struct.get(pos, Float.class);
  }

  @Override
  public double getDouble(int pos) {
    return struct.get(pos, Double.class);
  }

  @Override
  public StringData getString(int pos) {
    return isNullAt(pos) ? null : getStringDataInternal(pos);
  }

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