apache/beam · error · RuntimeException

FieldTypeValue has no value but the field cannot be null.

Error message

FieldTypeValue has no value but the field cannot be null.

What it means

isNullFieldValueFromProto checks a decoded proto FieldValue: if the proto message has no value set (hasNonNullValue false) but the corresponding Beam schema FieldType is not nullable, it throws this RuntimeException. It protects the invariant that non-nullable schema fields must always have a value on the wire.

Source

Thrown at sdks/java/core/src/main/java/org/apache/beam/sdk/schemas/SchemaTranslation.java:622

            .setLogicalTypeValue(logicalTypeToProto(FieldType.INT64, fieldType, value))
            .build();
      case DECIMAL:
        return builder
            .setLogicalTypeValue(logicalTypeToProto(FieldType.BYTES, fieldType, value))
            .build();
      case LOGICAL_TYPE:
        return builder
            .setLogicalTypeValue(logicalTypeToProto(fieldType.getLogicalType(), value))
            .build();
      default:
        return builder.setAtomicValue(primitiveRowFieldToProto(fieldType, value)).build();
    }
  }

  /** Returns if the given field is null and throws exception if it is and can't be. */
  static boolean isNullFieldValueFromProto(FieldType fieldType, boolean hasNonNullValue) {
    if (!hasNonNullValue && !fieldType.getNullable()) {
      throw new RuntimeException("FieldTypeValue has no value but the field cannot be null.");
    }
    return !hasNonNullValue;
  }

  static Object fieldValueFromProto(FieldType fieldType, SchemaApi.FieldValue value) {
    switch (fieldType.getTypeName()) {
      case ARRAY:
        if (isNullFieldValueFromProto(fieldType, value.hasArrayValue())) {
          return null;
        }
        return arrayValueFromProto(fieldType.getCollectionElementType(), value.getArrayValue());
      case ITERABLE:
        if (isNullFieldValueFromProto(fieldType, value.hasIterableValue())) {
          return null;
        }
        return iterableValueFromProto(
            fieldType.getCollectionElementType(), value.getIterableValue());
      case MAP:

View on GitHub (pinned to 12126d8942)

Solutions

1. Make the field nullable in the reading schema to match the data.
2. Re-encode the data with values present for every non-nullable field.
3. Align the schema used for decoding with the schema captured at write time (store schema alongside data).
4. Filter/repair records missing values before decoding (e.g. provide defaults via a map step).

Example fix

// before
Schema.Field field = Schema.Field.of("name", FieldType.STRING);
// after
Schema.Field field = Schema.Field.of("name", FieldType.STRING.withNullable(true));

if (!fieldType.getNullable()) { /* require every decoded FieldValue to have hasValue() true before decode */ }

try { rowFromProto(proto, schema); } catch (RuntimeException e) { if (e.getMessage().contains("no value but the field cannot be null")) { /* align schema nullability with data */ } else { throw e; } }

When it happens

Trigger: fieldValueFromProto calls isNullFieldValueFromProto on a FieldValue proto where hasValue() is false/unset while the target FieldType.getNullable() is false — e.g. proto produced by a writer that allowed nulls, reader schema says non-nullable.

Common situations: Schema evolution: field was nullable when the data was written, later tightened to non-nullable before decoding; proto FieldValue constructed programmatically without setting a value; deserializing into a schema from a different (stricter) source.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• Could not decode bytes as message
• Null value found for field that doesn't support nulls.
• Most (%s) and least (%s) significant bits value shouldn't be
• Received null value for non-nullable field "{}"
• Null collectionElementType at column

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/d98724f9650f5032. Report an issue: GitHub.