Do not discount Arrows; they are worth more than what they seem to be. Even their thickness imply some meaning.
One important thing arrows determine, via their thickness, is the amount of data being transferred from one operator to another. The thicker an arrow is, the more data is getting transfered.
The size of data implied by the arrow thickness is based on the number of rows, not on the size of data on disc. As an example, 100 rows of bits will result in a thicker arrow than 5 rows each of which is 5000 bits.
Contrary to the previous query, the query below reads only one single row from the same table. Therefore, the arrows will turn to be very thin.