Choose the best description of the output for the query below var weekAgo = Date.now() - (1000*60*60*24*7); db.visits_calc.group( { key:{date:true}, cond:{date:{$gt:weekAgo}}, reduce:function(obj, out) {out.day += obj.total}, initial:{day:0} });

What will be the output of two command in MongoDB: db.mycol.insert({'_id':1}) db.mycol.insert({'_id':1})

Which expression can not be used with aggregation?

Best statement that describes: 'why aggregation queries outperform mapreduce for small datasets'.

What is the maximum number of Indexes per collection allowed?

What is the maximum size of an Index key?

Which method will shut down replica set?

how indexing improve query response time

For the query below db.collection.find( { x: 5 } ).sort( { z: 1} ) Choose the best index to support the query

Choose the type of query where indexes can result in slower query response time.

Given the below statement, please choose the most probable reason:- 'You have a web application with mongodb as a backend. A query returns a resultset, however when called a second time the result set is empty.'