presto-main/src/main/java/io/prestosql/operator/aggregation/minmaxby/DoubleAndBlockPositionStateSerializer.java/DoubleAndBlockPositionStateSerializer/readFirstField
class DoubleAndBlockPositionStateSerializer:    @Override
    void readFirstField(Block block, int position, DoubleAndBlockPositionValueState state)
    {
        state.setFirst(firstType.getDouble(block, position));
    }