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Q 1 - In a collection that contains 100 post documents, what does the following command do?
The maximum BSON document size is 16 megabytes. The maximum document size helps ensure that a single document cannot use excessive amount of RAM or, during transmission, excessive amount of bandwidth.
Q 3 - Which of the following command can be used to check the size of a collection named posts?
To view the statistics for a collection, including the data size, use the db.collection.stats() method from the mongo shell.
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 array ratings contains at least one element between 3 and 6?
$elemMatch operator is used to specify multiple criteria on the elements of an array such that at least one array element satisfies all the specified criteria.
Q 5 - Which option should be used with findAndModify() command to return the modified document instead of the pre-modification document?
When true, returns the modified document rather than the original. The findAndModify() method ignores the new option for remove operations. The default is false.
Q 6 - Which of the following about Capped Collections is correct?
Capped collections are fixed-size collections that support high-throughput operations that insert and retrieve documents based on insertion order. Capped collections work in a way similar to circular buffers: once a collection fills its allocated space, it makes room for new documents by overwriting the oldest documents in the collection.
Q 7 - In a sharded replicas set environment with multiple mongos servers, which of the following would decide the mongos failover?
MongoDB cannot create a unique index on the specified index field(s) if the collection already contains data that would violate the unique constraint for the index. The syntax for the same is db.collection.createIndex( { a: 1 }, { unique: true } )
Q 9 - Which of the following is the correct syntax for starting a new mongod process and specifying its replica set name as rs0:
MongoDB uses multikey indexes to index the content stored in arrays. If you index a field that holds an array value, MongoDB creates separate index entries for every element of the array.
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