presto-main/src/main/java/io/prestosql/operator/aggregation/minmaxby/KeyAndBlockPositionValueStateSerializer.java/KeyAndBlockPositionValueStateSerializer/getSerializedType
class KeyAndBlockPositionValueStateSerializer:    @Override
    public Type getSerializedType()
    {
        // Types are: firstNull, secondNull, firstField, secondField
        return RowType.anonymous(ImmutableList.of(BOOLEAN, BOOLEAN, firstType, secondType));
    }