MongoDB Online Quiz

Q 1 - Which of the following is correct about MongoDB?

A - MongoDB uses JSON format to represent documents

B - MongoDB supports collection joins

C - MongoDB supports some of the SQL functions

D - MongoDB supports geospatial indexes

Q 2 - What is the maximum size of a MongoDB document?

A - 2 MB

B - 16 MB

C - 12 MB

D - There is no maximum size. It depends on the RAM.

Q 3 - In our posts collection, which command can be used to find all the posts whose author names begin lie between “A” and “C” in dictionary order?

A - db.posts.find( { post_author : { $gte : "A" , $lte : "C" } } );

B - db.posts.find( { post_author : { $gte : "C" , $lte : "A" } } );

C - db.posts.find( { post_author : { $gt : "A" , $lt : "C" } } );

D - This type of search is not supported by MongoDB. $lt and $gt operators are applicable only for numeric values.

Q 4 - Consider that the posts collection contains an array called ratings which contains ratings given to the post by various users in the following format:

{
         _id: 1,
         post_text: “This is my first post”,
         ratings: [5, 4, 2, 5],
         //other elements of document 			
}

Which of the following query will return all the documents where the ratings array contains elements that in some combination satisfy the query conditions?

A - db.inventory.find( { ratings: { $elemMatch: { $gt: 3, $lt: 6 } } } )

B - db.inventory.find( { ratings: { ratings: { $gt: 5, $lt: 9 } } } )

C - db.inventory.find( { ratings: { ratings.$: { $gt: 5, $lt: 9 } } } )

D - db.inventory.find( { ratings: { $elemMatch: { $gte: 3, $lte: 6 } } } )

Q 5 - Consider the following posts document:

{
 	_id: 1,
	post_text: “This is my first post”,
	author: “Tom”,
	tags: [“tutorial”,”quiz”,”facebook”,”learning”,”fun”]
}

Which of the following queries will return the documents but with only the first two tags in the tags array?

A - db.posts.find({author:"Tom"},{tags:{$slice:2}})

B - db.posts.find({author:"Tom"}).limit({tags:2})

C - db.posts.find({author:"Tom"}).limit($slice:{tags:2})

D - Both a and c are valid. $slice works both with projection and limit.

Q 6 - Which is the correct order (lowest to highest) in which MongoDB compares the BSON types?

A - Null, Number, String and Object

B - Number, Null, String and Object

C - String, Null, Number and Object

D - Null, Number, Object and String

Q 7 - In a sharded replica set environment, the w Option provides ability for write concern and j Option provides ability for the data to be written on disk journal. Consider that we have a seven member replica set and we want to assure that the writes are committed to journal as well as acknowledged by at least 3 nodes. What should be the value of w?

A - 0

B - 1

C - 3

D - 7

Q 8 - Given the following posts document:

{
 "_id" : 1, 
 "post_text" : "This post does not matter”, 
  “tags”: [ "tutorial", "fun", "learning"],
  // rest of the document
}

What will be the output of following query:

db.posts.aggregate( [ { $unwind : "$tags" } ] )

A - Return three separate documents for three separate tags

B - Arranges the tags (wind) in ascending order

C - Arranges the tags (wind) in descending order

D - Returns one document but converts the tags array in an object

Q 9 - The oplog (operations log) is a special capped collection that keeps a rolling record of all operations that modify the data stored in your databases. All the replica set members contain a copy of the oplog in the following collection:

A - oplog.rs

B - local.oplog.rs

C - <database>..oplog.rs

D - <replicasetid>.oplog.rs

Q 10 - If you have created a compound index on (A,B, C) which of the following access pattern will not be able to utilize the index?

A - A, B, C

B - A, B

C - B, C

D - A