db.posts.find( { author: /John/ } )

db.posts.find( { author: /AjohnA/ > )

db.posts.find( { $like: {author: /John/} } )

db.posts.find( { author: {$like: /John/} } )

db.test.ensurelndex( { c:l, a: 1})

db.test.ensurelndex( { a : 1, c: 1, d: 1, b : 1})

CH db.test.ensurelndex( { a :1, c:l})

db.test.ensurelndex( { a: 1, b :1, c:l, d:l})

Providing these parameters in any order does not impact the performance

$sort moves before $match

MongoDB does not do any movements by default and will use the order provided

$match moves before $sort

To help in disaster recovery

To protect agains network partitions

To enable certain read preference settings

To add greather redundancy

For more efficient backup operations

findQ returns all the documents in a collection while findOne() retrieves only the first one.

find.limit(l) is not the same query as findOne()

findOneQ returns the actual first document retrieved from a collection

findQ and findOneQ returns cursors to the collection documents

primary

arbiter

hidden

secondary