collection name: nycFacilities
This collection had more than 100 documents (condition 1)
sample size (N) is greater than 5% (condition 2)
$stage is the first in Aggregation Pipeline.
if meets the 3 conditions, it will take the pseudo-random-selector but condition 2 failed for pseudo-random-selection. (conditions listed above)
how it selects the pseudo-random-selector for selecting documents within the collection?