8. students

 

db.students.insertMany([ { "studentID": 1, "name": "Student1", "age": 22, "city": "New York", "tags": ["tag1", "tag2", "tag3"] }, { "studentID": 2, "name": "Student2", "age": 25, "city": "San Francisco", "tags": ["tag1", "tag2", "tag3"] }, { "studentID": 3, "name": "Student3", "age": 30, "city": "Los Angeles", "tags": ["tag1", "tag2", "tag3"] }, { "studentID": 4, "name": "Student4", "age": 35, "city": "Chicago", "tags": ["tag1", "tag2", "tag3"] }, { "studentID": 5, "name": "Student5", "age": 40, "city": "New York", "tags": ["tag1", "tag2", "tag3"] }, { "studentID": 6, "name": "Student6", "age": 45, "city": "San Francisco", "tags": ["tag1", "tag2", "tag3"] }, { "studentID": 7, "name": "Student7", "age": 50, "city": "Los Angeles", "tags": ["tag1", "tag2", "tag3"] }, { "studentID": 8, "name": "Student8", "age": 20, "city": "Chicago", "tags": ["tag1", "tag2", "tag3"] }, { "studentID": 9, "name": "Student9", "age": 28, "city": "New York", "tags": ["tag1", "tag2", "tag3"] }, { "studentID": 10, "name": "Student10", "age": 32, "city": "San Francisco", "tags": ["tag1", "tag2", "tag3"] }, { "studentID": 11, "name": "Student11", "age": 26, "city": "Los Angeles", "tags": ["tag2", "tag3"] }, { "studentID": 12, "name": "Student12", "age": 33, "city": "Chicago", "tags": ["tag1", "tag3"] }, { "studentID": 13, "name": "Student13", "age": 27, "city": "New York", "tags": ["tag1", "tag2"] }, { "studentID": 14, "name": "Student14", "age": 31, "city": "San Francisco", "tags": ["tag1", "tag2", "tag3"] }, { "studentID": 15, "name": "Student15", "age": 36, "city": "Los Angeles", "tags": ["tag2", "tag3"] }, { "studentID": 16, "name": "Student16", "age": 38, "city": "Chicago", "tags": ["tag1", "tag2"] }, { "studentID": 17, "name": "Student17", "age": 29, "city": "New York", "tags": ["tag1", "tag3"] }, { "studentID": 18, "name": "Student18", "age": 34, "city": "San Francisco", "tags": ["tag1", "tag2", "tag3"] }, { "studentID": 19, "name": "Student19", "age": 23, "city": "Los Angeles", "tags": ["tag1", "tag2"] }, { "studentID": 20, "name": "Student20", "age": 39, "city": "Chicago", "tags": ["tag1", "tag2", "tag3"] }] );

db.students.createIndex({ studentID: 1 }, { unique: true });

db.students.createIndex({ city: 1 }, { sparse: true });

db.students.createIndex({ tags: 1 });

db.students.createIndex({ city: 1, age: 1 });

db.students.getIndexes();

8B

db.students.find({}).sort({age: -1}).limit(1);

db.students.find({}).sort({age: -1}).limit(1).explain();

db.students.find({}).sort({age: -1}).limit(1).explain("executionStats");

db.students.find({}).sort({age:1}).limit(1).explain("executionStats").executionStats.totalDocsExamined;

db.students.find({}).sort({age: -1}).limit(1).explain("executionStats").executionStats.executionTimeMillis;