The document provides an overview of MongoDB including key concepts like collections, documents, queries, indexes, aggregation, and more. It compares MongoDB to a traditional SQL database and shows examples of common operations like insert, update, find in MongoDB shell and Node.js driver. It also briefly covers more advanced topics like geospatial queries, optimization, replication and sharding.

1. by 桂林

2. All languages used
Browser script: javaS c r ip t
Server script: javaS c r ip t
Database script: javaS c r ip t

3. All languages used
Browser script: javaS c r ip t
Server script: javaS c r ip t
Database script: javaS c r ip t

4. Overview of MongoDB
Patterns of mongoskin

5. Why MongoDB
Agile and Scalable

6. Overview of MongoDB
MySQL
posts
id
comments
id
post_id
tags
id
name
posts_tags
post_id
tag_id

7. Overview of MongoDB
Database >> Database
Table >> Collection
Row >> Document

8. Overview of MongoDB
M on g oD B
{
_id: ObjectId(),
title: 'node and mongodb',
slug: 'node-and-mongodb',
body: '...',
published: true,
created: new Date('09/01/2011'),
updated: new Date('09/16/2011'),
comments: [
{
author: 'bob',
email: 'bob@bob.me',
body: '...',
created: new Date('09/17/2011')
}
],
tags: ['MongoDB', 'database']
}

9. Overview of MongoDB
Get c ollec t ion
MongoDB shell
posts = db.posts
NodeJS
var mongodb = require('mongodb');
var db = new Db('test', new Server(host, port, {}),
{native_parser:true});
db.open(function(err, db){
db.collection('posts', function(err, posts){
// use posts collection here
});
});

10. Overview of MongoDB
I n ser t
MongoDB shell
var doc = {title: 'test posts', ...};
posts.insert(doc);
NodeJS
posts.insert(doc, function(err, reply){
// error or done
});

11. Overview of MongoDB
Q u er y
MongoDB shell
posts.find({"comments.author", "bob"})
NodeJS
posts.find({"comments.author", "bob"}, function(err, cursor){
cursor.toArray(function(err, docs){
// found docs here
});
});

12. Overview of MongoDB
Q u er y op er at or
{<field>:{<operator>:<value>}}
db.things.find({j:{$in: [2,4,6]}});
$gt, $lt, $gte, $lte
$all, $exists
$mod, $ne
$in, $nin
$nor, $or, $and
$size, $type, …

13. Overview of MongoDB
Up d at e
MongoDB shell
posts.update({_id: doc.id}, {$inc: {votes: 1}})
NodeJS
posts.update({_id: doc.id}, {$inc: {votes: 1}}, function(err, count){
});

14. Overview of MongoDB
M od if ier op er at ion s
$set – set a particular value
$unset – delete a particular field (v1.3+)
$inc – increment a particular value by a certain amount
$push – append a value to an array
$pushAll – append several values to an array
$pull – remove a value(s) from an existing array
$pullAll – remove several value(s) from an existing array
$bit – bitwise operations

15. Overview of MongoDB
R em ove
MongoDB shell
posts.remove({author: 'bob'})
NodeJS
posts.remove({author: 'bob'}, function(err, reply){})

16. Overview of MongoDB
I n d ex
MongoDB shell
posts.ensureIndex({author:1})
posts.ensureIndex({slug: 1 }, {unique: true});
db.things.ensureIndex(
{firstname: 1, lastname: 1},
{unique: true, background:true});
NodeJS
posts.ensureIndex({author:1}, function(err, reply){})
posts.ensureIndex({slug: 1 }, {unique: true}, function(err, reply){});
db.things.ensureIndex(
{firstname: 1, lastname: 1},
{unique: true, background:true}, function(err, reply){});

17. Overview of MongoDB
Geosp at ial
{ loc : [ 50 , 30 ] } //SUGGESTED OPTION
{ loc : { x : 50 , y : 30 } }
{ loc : { foo : 50 , y : 30 } }
{ loc : { lon : 40.739037, lat: 73.992964 } }
db.places.ensureIndex( { loc : "2d" } )
db.places.find( { loc : { $near : [50,50] , $maxDistance : 5 } } )
box = [[40.73083, -73.99756], [40.741404, -73.988135]]
db.places.find({"loc" : {"$within" : {"$box" : box}}})
center = [50, 50]
radius = 10
db.places.find({"loc" : {"$within" : {"$center" : [center, radius]}}})

18. Overview of MongoDB
O p t im izat ion
Don’t create index for every field
Be careful about single-key indexes with low selectivity.
Only one index could be used per query.
Use compound-key index.
db.places.ensureIndex( { location : “2d” , category : 1 } );
db.places.find( { location : { $near : [50,50] }, category : ‘coffee’ } );
Use hint. Use explain. Use the profiler.
Pay attention to the read/write ratio of your application.
See docs for more information

19. Overview of MongoDB
Ag g r eg at ion
posts.count( {author: 'bob'} )
posts.distinct("author")
SQL group
select a,b,sum(c) csum from coll where active=1 group by a,b
MongoDB group
db.coll.group(
{key: { a:true, b:true },
cond: { active:1 },
reduce: function(obj, out) { out.csum += obj.c; },
initial: { csum: 0 }
});

20. Overview of MongoDB
M ap R ed u c e
map = function() {
for (var i in this.tags) {
emit(this.tags[i], 1);
}
}
reduce = function(key, values) {
var count = 0;
for (var i in values) {
count += current[i];
}
return count;
}
// 1.8+ must set out collection
db.posts.mapReduce(map, reduce, {out: 'tags_count'})

21. Overview of MongoDB
M ap R ed u c e
> db.tags_count.find()
{"_id" : "MongoDB", "value" : 4}
{"_id" : "Map/Reduce", "value" : 2}
{"_id" : "Recipe", "value" : 7}
{"_id" : "Group", "value" : 1}

22. Overview of MongoDB
Gr id F S
Upload image
var gridStore = new GridStore(db, filename, "w");
gridStore.open(function(err, gridStore) {
gridStore.write(imageData, function(err, gridStore) {
gridStore.close(function(err, result) {
console.log(result._id);
users.update({_id: userId}, {$set: {avatarId: result._id}});
});
});
});
HTML
<img src="http://asset.url/gridfs/{{ user.avatarId }}" />
Use nginx-gridfs

23. Overview of MongoDB
R ep lic at ion and S h ar d in g

24. Nice

25. Nice ,but node

26. Nest ed c allb ac k s, an d n ot D R Y ?
var database = new mongo.Db('testdb', new mongo.Server('localhost',
27017));
database.open(function(err, db) {
if(err) return handle(err);
db.collection('user', function(err, collection) {
if(err) return handle(err);
collection.find({}, function(err, cursor) {
if(err) return handle(err);
cursor.toArray(function(err, users) {
if(err) return handle(err);
doSomething(users);
});
});
});
});

27. How t o exp or t c ollec t ion
var database = new mongo.Db('testdb', new mongo.Server('localhost',
27017));
database.open(function(err, db){
db.collection('posts', function(err, posts) {
// can't export here?
});
});
exports.posts = ?

28. How t o sh ar e c ollec t ion ob jec t
controllers/user.js
var database = new mongo.Db('testdb', new mongo.Server('localhost',
27017));
//...
database.open(function(err, db){
db.collection('user', function(err, userColl){
userColl.find({}, function(err, cursor){
if(err) return handle(err);
cursor.toArray(function(err, users){
res.render('/user.html', {users: users});
})
});
});
});

29. How t o sh ar e c ollec t ion ob jec t
controllers/book.js
var database = new mongo.Db('testdb', new mongo.Server('localhost',
27017));
//...
database.open(function(err, db){
db.collection('user', function(err, userColl){
userColl.findOne({_id: book.author_id}, function(err, author){
res.render('/book.html', {book: book, author: author});
});
});
});

30. Redsign the API

31. How ab ou t t h is
config.js
exports.db = mongo.db('mongo://localhost:27017/testdb')

32. An d t h is
controllers/user.js
var db = require('../config').db;
db.collection('user').find({}).toArray(function(err, users){
if(err) return handle(err);
res.render('/user.html', {users: users});
});

33. An d t h is
controllers/book.js
var db = require('../config').db;
db.collection('user').findOne({_id, book.author_id}, function(err,
author){
if(err) return handle(err);
res.render('/book.html', {book: book, author: author});
});

34. It’s MongoSkin

35. Patterns of mongoskin
var mongoskin = require('mongoskin');
var db = mongoskin.db('mongo://localhost:27017/testdb');
db.bind('users');
db.bind('books');
db.users.find({}).limit(10).sort({name:-1}).toArray(function(err,
users){
});
db.books.update({_id: bookId}, {$inc: {votes: 1}}, function(err,
reply){
});

36. Patterns of mongoskin
Pr oxy all m et h od s
node-mongoskin
var skindb = mongoskin.db('mongo://localhost:27017/testdb')
function callback(err, reply){}
skindb.addUser('foo', 'bar', callback);
node-mongodb-native
var db = new mongodb.Db('testdb',
new mongodb.Server('localhost', 27017));
function callback(err, reply){}
db.open(function(err, db){
if(err) return callback(err);
db.addUser('foo', 'bar', callback);
});

37. Patterns of mongoskin
SkinClass hold all parameters to open it
var SkinDb = exports.SkinDb = function(db, username, password) {
this.db = db;
this.username = username;
this.password = password;
this.state = STATE_CLOSE;
this.emitter = new events.EventEmitter();
this._collections = {};
};

38. Patterns of mongoskin
Proxy all methods inside open
for (var name in Db.prototype) {
SkinDb.prototype[name] = function() {
var args = Array.prototype.slice.call(arguments);
this.open(function(err, db) {
if (err) {
return args[args.length - 1](err);//callback(err)
} else {
return Db.prototype[name].apply(db, args);
}
});
};
}

39. Patterns of mongoskin
Open only on c e (pseudo-code)
SkinDb.prototype.open = function(fn) {
switch (this.state) {
case STATE_OPEN:
return fn(null, this.db);
case STATE_OPENNING:
// if call 'open' method multi times before opened
return this.emitter.addListener('open', fn);
case STATE_CLOSE:
this.state = STATE_OPENNING;
var that = this;
this.db.open(function(err, db){
that.db = db;
fn(err, db);
that.state = STATE_OPEN;
that.emitter.emit('open', err, db);
});
}

40. }
};
Patterns of mongoskin
R et u r n s S k in Collec t ion
SkinDb.prototype.collection = function(name) {
var collection = this._collections[name];
if (!collection) {
this._collections[name] = collection = new SkinCollection(this,
name);
}
return collection;
};

41. Patterns of mongoskin
S k in Collec t ion
var SkinCollection = exports.SkinCollection = function(skinDb,
collectionName) {
this.skinDb = skinDb;
this.collectionName = collectionName;
this.collection;
this.state = STATE_CLOSE;
this.internalHint;
var that = this;
this.__defineGetter__('hint', function() { return this.internalHint;
});
this.__defineSetter__('hint', function(value) {
this.internalHint = value;
this.open(function(err, collection) {
collection.hint = value;
that.internalHint = collection.hint;
});
});
this.emitter = new events.EventEmitter();
}

42. }
Patterns of mongoskin
Pr oxy all m et h od s in sid e S k in Collec t ion . op en
for (var name in Collection.prototype) {
SkinCollection.prototype[name] = function() {
var args = Array.prototype.slice.call(arguments);
this.open(function(err, collection) {
if (err) {
args[args.length - 1](err);// callback(err)
} else {
Collection.prototype[name].apply(collection, args);
}
});
};
}

43. Patterns of mongoskin
S k in Collec t ion . op en
SkinCollection.prototype.open = function(callback) {
//...
var that = this;
this.skinDb.open(function(err, db){
db.collection(that.collectionName, function(err, collection){
this.nativeCollection = collection;
callback(err, collection);
}
});
}

44. Patterns of mongoskin
R et u r n s S k in Cu r sor if n o c allb ac k
SkinCollection.prototype.find = function() {
var args = Array.prototype.slice.call(arguments);
if (args.length > 0 && typeof(args[args.length - 1]) === 'function')
{
this._find.apply(this, args);
}else {
return new SkinCursor(null, this, args);
}
};
An d so d o w it h S k in Cu r sor

45. Patterns of mongoskin
Pat t er n s of m on g osk in
SkinClass contains all parameters to get NativeObject
Proxy all method inside callback of op en ( )
Make open() method cache result
Return SkinClass object to chain execution

46. Reference
MongoDB The Definitive Guide
MongoDB Docs http://www.mongodb.org/display/DOCS/Home
MongoDB Cookbook http://cookbook.mongodb.org/
Node mongodb https://github.com/christkv/node-mongodb-native
Mongoskin https://github.com/guileen/node-mongoskin

47. Thank you
桂糊涂@weibo
guileen@gmail.com