presto-record-decoder/src/main/java/io/prestosql/decoder/avro/AvroColumnDecoder.java/AvroColumnDecoder/decodeField
class AvroColumnDecoder:    public FieldValueProvider decodeField(GenericRecord avroRecord)
    {
        Object avroColumnValue = locateNode(avroRecord, columnMapping);
        return new ObjectValueProvider(avroColumnValue, columnType, columnName);
    }