👐 Empty aggregation pipeline
An empty aggregation
This code is the equivalent to a SELECT * FROM AUTHORS. Returns a cursor with all documents in the authors collection:
- Atlas UI
- MongoDB Shell
- Open the
Aggregationtab. - Select
Text. - Notice the empty array in the editor denoting an empty aggregation pipeline:
[]
db.authors.aggregate([])
We can iterate over the returned cursor and get more documents typing it.
👐 Return all the documents in the books collection and iterate to get the next page of books.
Answer
db.books.aggregate([])
it
🦸♂️ Cursor methods
info
Extra activity, do it if you have extra time or are following at home, won't be covered during the hands-on Lab
A cursor has several useful methods, for instance we can check the size of the returned cursor with itcount
cursor.itcount()
👐 In our previous example with the empty aggregation, to check the size of the returned cursor, what should we type in?
Answer
// as db.books.aggregate([]) returns a cursor we can just call itcount() on it
db.books.aggregate([]).itcount()