MongoDB MongoDB Certifications C100DBA Questions & Answers

• Question 31:

  Consider the following example document:

  {

  "_id": Objectld("5360c0a0a655a60674680bbe"),

  "user"

  "login": "irOn"

  "description": "Made of steel"

  "date": ISODate("2014-04-30T09:16:45.836Z"),

  }

  >

  and index creation command:

  db.users.createlndex( { "user.login": 1, "user.date": -1 }, "mylndex" )

  When performing the following query:

  db.users.find( { "user.login": /Air.*/ },

  { "user":1, "_id":0 > ).sort( { "user.date":1 > )

  which of the following statements correctly describe how MongoDB will handle the query? Check all that apply.

  A. As an optimized sort query (scanAndOrder = false) using "mylndex" because we are sorting on an indexed field

  B. As an indexed query using "mylndex" because field "user.login" is indexed

  C. MongoDB will need to do a table/collection scan to find matching documents

  D. None of the above

  E. As a covered query using "mylndex" because we are filtering out "_id" and only returning "user.login"

  Correct Answer: B

• Question 32:

  Which of the following commands will return all the posts with number of likes greater than 100 and less than 200, both inclusive?

  A. db.posts.find({ likes : { $gte : 100 , $lte : 200 } } );

  B. db.posts.find({ likes : { $gt : 100 , $lte : 200 } } );

  C. db.posts.find({ likes : { $gte : 100, $lt : 200 } } );

  D. db.posts.find({ likes : { $gt : 100, $lt : 200 > > );

  Correct Answer: A

• Question 33:

  By default, the MongoDB cursor in mongo shell is configured to return how many documents? To get the next set of documents, which command is used?

  A. 200, more

  B. No limit, none

  C. 20, it

  D. 50, it

  Correct Answer: C

• Question 34:

  You perform the following operation in the shell: db.foo.insert( { } ); What gets inserted?

  A. A document will be inserted with the same _id as the last document inserted

  B. A document that matches the collection's existing schema, but with null fields

  C. A document with an _id assigned to be an Objectld

  D. An empty document

  E. No document will be inserted; an error will be raised

  Correct Answer: C

• Question 35:

  Which of the following commands finds all the documents in the posts collection with post timestamp field as null?

  A. db.posts.find( { post_timestamp: { $fieldtype: null } } )

  B. db.posts.find( { post_timestamp: { $type: null } } )

  C. db.posts.find( { post_timestamp : { $type; 10 > > )

  D. db.posts.find( { post_timestamp: { $fieldtype: 10 } } )

  Correct Answer: C

• Question 36:

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

  

  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: { $gte: 3, $lte: 6 } } } )

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

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

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

  Correct Answer: D

• Question 37:

  Aggregation Pipelines have a limit of:

  A. No limit on document and 100 MB RAM

  B. 2 MB document and no limit on RAM

  C. 2 MB document and 100 MB RAM

  D. 16 MB document and 100 MB RAM

  Correct Answer: D

• Question 38:

  Which is the default mode in which the explain() command runs?

  A. allPlansExecution

  B. customExecutionStats

  C. queryPlanner

  D. executionStats

  Correct Answer: C

• Question 39:

  Addding the index {a:l} can potentially decrease the speed of which of the following operations? Check all that apply.

  A. db.collection.update({b:456>, {$inc: {a:l> })

  B. db.collection.find( {a : 232} )

  C. db.collection.insert( { a:341})

  Correct Answer: AC

• Question 40:

  Which of the following needs to be performed prior to initiate backup on a sharded cluster?

  A. db.stopBalancer( )

  B. sh.stopServer( )

  C. db.stopServer( )

  D. sh.stopBalancer( )

  Correct Answer: D