apache/beam · error · IllegalArgumentException

Unsupported vector type

Error message

Unsupported vector type: <type>

What it means

SerializableRow.getVectorValue() converts ColumnVector entries into Java objects for the supported DataType set; an unrecognized vector DataType throws IllegalArgumentException 'Unsupported vector type: <type>'. It is the vectorized counterpart of getValue()'s unsupported-type error and is reached while converting arrays/maps/keys.

Solutions

1. Upgrade the Beam Delta IO connector and io.delta kernel dependencies to versions supporting the nested element type
2. Locate the offending nested column (array element or map key/value type) from the table schema
3. Rewrite the table casting the nested element type to a supported one
4. Flatten or restructure the schema (e.g. store complex values as JSON strings) if the type remains unsupported

Example fix

// before
// map<string, unsupported_nested_type> in the table
PCollection<Row> rows = input.apply(DeltaIO.read().withTable(path).withStartVersion(0L));
// after
-- rewrite the table casting the nested element type (Spark example)
df = spark.read.format("delta").load(path).withColumn("m", expr("map_from_entries(transform(map_entries(m), e -> (e.key, cast(e.value as string))))"))
df.write.format("delta").mode("overwrite").save(path)

// Recursively check nested array/map element types for supported mappings before reading
checkNested(deltaSchema); // throws if any nested element/key/value DataType is unsupported

try {
  rows = input.apply(deltaIO);
} catch (IllegalArgumentException e) {
  if (e.getMessage().startsWith("Unsupported vector type:")) {
    // restructure nested collections to supported element types, or upgrade connector
  } else { throw e; }
}

When it happens

Trigger: While serializing array elements or map keys/values during processElement, a nested ColumnVector carries a Delta DataType with no conversion mapping.

Common situations: Nested arrays/maps containing newer Delta element types the connector doesn't support; version skew between delta kernel and the Beam Delta IO connector; tables written by newer Delta writer versions.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

• Unsupported type
• Unsupported type: <type.getClass()>
• Unsupported vector type: <type.getClass()>
• Azure credential provider type
• Cannot decode object from input stream.

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/fce94ea47ef68ef5. Report an issue: GitHub.

Appendix: source

Thrown at sdks/java/io/delta/src/main/java/org/apache/beam/sdk/io/delta/SerializableRow.java:286

      StructType structType = (StructType) type;
      int numFields = structType.fields().size();
      ColumnVector[] childFields = new ColumnVector[numFields];
      for (int j = 0; j < numFields; j++) {
        childFields[j] = vector.getChild(j);
      }
      return new SerializableRow(new VectorRow(structType, childFields, index));
    } else if (type instanceof DateType) {
      return vector.getInt(index);
    } else if (type instanceof TimestampType) {
      return vector.getLong(index);
    } else if (type instanceof ArrayType) {
      ArrayValue arr = vector.getArray(index);
      return convertArray(arr, (ArrayType) type);
    } else if (type instanceof MapType) {
      MapValue map = vector.getMap(index);
      return convertMap(map, (MapType) type);
    }
    throw new IllegalArgumentException("Unsupported vector type: " + type);
  }

  private static List<@Nullable Object> convertArray(ArrayValue arr, ArrayType arrayType) {
    int size = arr.getSize();
    ColumnVector elements = arr.getElements();
    DataType elementType = arrayType.getElementType();
    List<@Nullable Object> result = new ArrayList<>(size);
    for (int i = 0; i < size; i++) {
      result.add(getVectorValue(elements, i, elementType));
    }
    return result;
  }

  private static Map<Object, @Nullable Object> convertMap(MapValue map, MapType mapType) {
    int size = map.getSize();
    ColumnVector keys = map.getKeys();
    ColumnVector values = map.getValues();
    DataType keyType = mapType.getKeyType();

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