M101P: MongoDB for Developers - Chapter 4: Performance

Homework 4.1

(OK)

db.products.find( { $and : [ { price : { $gt : 30 } }, { price : { $lt : 50 } } ] } ).sort( { brand : 1 } )

db.products.find( { 'brand' : "GE" } )

db.products.find( { brand : 'GE' } ).sort( { category : 1, brand : -1 } )

(OK)

db.products.find( { 'brand' : "GE" } ).sort( { price : 1 } )

Homework 4.2

(OK) The query uses an index to determine the order in which to return result documents.

The query uses an index to determine which documents match.

(OK) The query examines 251120 documents.

The query returns 251120 documents.

The query is a covered query.

Homework 4.3

db.posts.createIndex({date:-1})
db.posts.createIndex({tags:1,date:-1})
db.posts.createIndex({permalink:1})

Homework 4.4

> db.profile.find().sort({millis:-1}).limit(1).pretty()
{
"_id" : ObjectId("57c41c92adaa1d1ee896b853"),
"ts" : ISODate("2012-11-20T20:09:49.862Z"),
"op" : "query",
"ns" : "school2.students",
"query" : {
"student_id" : 80
},
"ntoreturn" : 0,
"ntoskip" : 0,
"nscanned" : 10000000,
"keyUpdates" : 0,
"numYield" : 5,
"lockStats" : {
"timeLockedMicros" : {
"r" : 19776550,
"w" : 0
},
"timeAcquiringMicros" : {
"r" : 4134067,
"w" : 5
}
},
"nreturned" : 10,
"responseLength" : 2350,
"millis" : 15820,
"client" : "127.0.0.1",
"user" : ""
}

15820

-eof-