Mongo for Developers - Homework week 6

Week6

Homework 6.1 

- Which of the following statements are true about replication in MongoDB? Check all that apply.

  * The minimun sensible number of voting nodes to a replica set is three.              True
  * MongoDB replication is synchronous.                                                 False
  * By default, using the new MongoClient connection class, w = 1, j = 1.               False
  * The oplog utilizes a capped collection.                                             True
  
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Homework 6.2

- Let's suppose you have a five member replica set and want to assure that writes are committed to the journal and 
  are acknowledged by at least 3 nodes before you proceed forward. What would be the appropriate settings for w and j?
  
  * w = 1, j = 1.           Wrong
  * w = "majority", j = 1.  Correct
  * w = 3, j = 0.           Wrong
  * w = 5, j = 1.           Wrong
  * w = 1, j = 3.           Wrong

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Homework 6.3

- Which of the following statements are true about choosing and using a shard key?

  * The shard key must be unique.                                                                       False
  * There must be a index on the collection that stars with the shard key.                              True
  * MongoDB can not enforce unique indexes on a sharded collection other than the shard key itself,
    or indexes prefixed by the shard key.                                                               True
  * Any update that does not contain the shard key will be sent to all shards.                          True
  * You can change the shard key on a collection if you desire.                                         False
  
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Homework 6.4

- If you ran the query
  > use school
  > db.students.find({'student_id':2000})
  Which shards would be involved in answering the query?
  
  Answer: s1
  
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Homework 6.5 

  > python validate.py
  Validate Code: kjvjkl3290mf0m20f2kjjv
  
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