@Override
    public DataType setOutputType(DataType outputType, TypeContext context) {
        super.setOutputType(ArrayDataType.getArray(DataType.STRING), outputType, null, context);
        return DataType.STRING;
    }
The destination the chunks will be written to on the form [schema name].[field name]
indexinglanguage/src/main/java/com/yahoo/vespa/indexinglanguage/expressions/ChunkExpression.java