Relational databases are central to web applications, but they have also been the primary source of pain when it comes to scale and performance. Recently, non-relational databases (also referred to as NoSQL) have arrived on the scene. This session explains not only what MongoDB is and how it works, but when and how to gain the most benefit.

1. Building Apps With
Nate Abele
IPC — 1 June 2010
Berlin

3. X

4. Me
Former lead developer, CakePHP
Lead developer, Lithium
Twitter: @nateabele

5. “Alternative” databases?
What’s the point?
Relational databases » relational algebra » set theory
ORM “impedance mismatch”
Failed alternatives reinforced the status quo

6. What’s a document database?
Composed of documents ...duh
Each document is heterogenous, and may have a
completely unique structure compared to other
documents
...That’s pretty much it

7. Why Mongo?
.org :
“The best features of document databases,
key-value stores, and relational databases.”

8. Mongo is...
Fast
Smart
Scalable

9. Terminology
Database » Database
Table » Collection
Row » Document

10. Common Tasks
tags
id
MySQL
name
posts_tags
id posts comments
post_id id id
tag_id title post_id
slug author
body email
published body
created created
updated

11. Common Tasks id
posts
title
slug
MongoDB body
published
created
updated
comments
author
email
body
created
tags

12. Common Tasks
MongoDB
{
"_id" : ObjectId("4c03e856e258c2701930c091"),
"title" : "Welcome to MongoDB",
"slug" : "welcome-to-mongodb",
"body" : "Today, we're gonna totally rock your world...",
"published" : true,
"created" : "Mon May 31 2010 12:48:22 GMT-0400 (EDT)",
"updated" : "Mon May 31 2010 12:48:22 GMT-0400 (EDT)",
"comments" : [
{
"author" : "Bob",
"email" : "bob@example.com",
"body" : "My mind has been totally blown!",
"created" : "Mon May 31 2010 12:48:22 GMT-0400 (EDT)"
}
],
"tags" : [
"databases", "MongoDB", "awesome"
]
}

13. [...frantic hand-wringing ensues...]

14. [...pause, deep breath...]

15. Doing the “normal db” stuff
How do I...
...do pattern-matching?
db.posts.find({ "title" : /mongodb/i })
...find all posts tagged ‘MongoDB’?
db.posts.find({ "tags" : "MongoDB" })
...find all Bob’s comments?
db.posts.find({ "comments.email" : "bob@example.com" })

16. Doing the “normal db” stuff
How do I...
...change Bob’s email?
db.posts.update(
{ "comments.email": "bob@example.com" },
{ $set : { "comments.$.email" : "robert@example.com" }}
)

17. $set?

18. Querying
$gt $all
$gte $size
$lt $exists
$lte $type
$ne $elemMatch
$in $not
$nin $where
$mod

19. Querying
dontTrust = db.people.find({
“age”: { $gt : 30 }
})
awesome = db.posts.find({ “tags” : {
$in : [‘MongoDB’, ‘awesome’]
}})
todo = db.tasks.find({
“status” : { $nin : [
‘In Progress’, ‘Completed‘
]}
})

20. Querying
By arbitrary function:
db.posts.find({ $where: function() {
return this.hits % 2 == 0;
}})
By grouping key:
db.posts.group({
"key": { "hits": true },
"initial": { count: 0 },
"reduce": function(obj, prev) {
prev.count++;
}
});

21. Querying
By grouping function:
db.photos.group({
keyf: function(o) {
return {
hits: Math.round(o.hits / 1000)
};
},
"initial": { count: 0 },
"reduce": function(obj, prev) {
prev.count++;
}
});

22. Grouping results
[
{ 'hits' => 0, 'count' => 5 },
{ 'hits' => 1, 'count' => 4 },
{ 'hits' => 2, 'count' => 7 },
...
]

23. Map/reduce
...with apologies to John Nunemaker.

24. Map/reduce
> db.items.insert({tags: ['dog', 'cat']})
> db.items.insert({tags: ['dog']})
> db.items.insert({tags: ['dog', 'mouse']})
> db.items.insert({tags: ['dog', 'mouse', 'hippo']})
> db.items.insert({tags: ['dog', 'mouse', 'hippo']})
> db.items.insert({tags: ['dog', 'hippo']})

25. Map/reduce
> var map = function() {
this.tags.forEach(function(t) {
emit(t, {count: 1});
});
}

26. Map/reduce
> var reduce = function(key, val) {
var count = 0;
for(var i = 0, len = val.length; i < len; i++) {
count += val[i].count;
}
return { count: count };
}

27. Map/reduce
> var result = db.items.mapReduce(map, reduce);

28. Map/reduce
{
"ok" : 1,
"timeMillis" : 86,
"result" : "tmp.mr.mapreduce_1273861517_683",
"counts" : {
"input" : 6,
"emit" : 13,
"output" : 4
}
}

29. Map/reduce
db["tmp.mr.mapreduce_1273861517_683"].find()
{ "_id" : "cat", "value" : { "count" : 1 } }
{ "_id" : "dog", "value" : { "count" : 6 } }
{ "_id" : "hippo", "value" : { "count" : 3 } }
{ "_id" : "mouse", "value" : { "count" : 3 } }

30. Atomic Operations
Incrementing & decrementing: $inc:
db.posts.update(
{ _id : new ObjectId("4c041e...30c093") },
{ $inc : { "hits" : 1 }}
)
db.posts.update(
{ _id : new ObjectId("4c041e...30c093") },
{ $inc : { "hits" : -1 }}
)

31. Atomic Operations
Adding, updating & removing: $set & $unset:
db.posts.update({}, { $set : { "hits" : 0 }})
db.posts.update({}, { $unset : { "hits" : 1 }})

32. Atomic Operations
Array operations: $push[All], $pull[All],
$addToSet & $pop:
db.posts.update({ "tags": "MongoDB" }, {
$push: { "tags" : "awesome" }
})
db.posts.update({ "tags": "MySQL" }, {
$pull: { "tags" : "awesome" }
})

33. Atomic Operations
Array operations: $push[All], $pull[All],
$addToSet & $pop:
db.queues.update(
{ _id : new ObjectId("4c041e...30c093") },
{ $pop: { "operations" : 1 }}
)
db.todos.update(
{ _id : new ObjectId("4c041e...30c093") },
{ $pop: { "listItems" : -1 }}
)

34. Indexes
Slows write performance, but greatly improves reads
For best results, index on what you query on
Mongo likes to fit its indexes in memory

35. Indexes
db.users.ensureIndex({ “email”: 1 })
db.posts.ensureIndex({ “tags”: 1 })
db.posts.ensureIndex({ “created”: -1 })
db.posts.ensureIndex({
“tags”: 1,
“created”: -1
})

36. Indexes
“unique” / “dropDups”: ensure uniqueness
“safe”: Make sure it worked. Else, panic.
“name”: Mostly for troubleshooting
“background”:
Best. Performance. Panic. Button. Ever.

37. Indexes
When in doubt, explain()
{ "cursor" : "BtreeCursor hits_1 multi",
"indexBounds" : [
[{ "hits" : 0 }, { "hits" : 0 }],
[{ "hits" : 1 }, { "hits" : 1 }]
],
"nscanned" : 1,
"nscannedObjects" : 1,
"n" : 1,
"millis" : 35,
"allPlans" : [
{
"cursor" : "BtreeCursor hits_1 multi",
"indexBounds" : [
[{ "hits" : 0 }, { "hits" : 0 }],
[{ "hits" : 1 }, { "hits" : 1 }]
]
}
]
}

38. Location, location, location

39. Location
MongoDB makes location-aware apps stupid-simple
First, add an index:
db.places.ensureIndex({ location: “2d” })
Go to town:
db.places.find({
location: { $near : [
40.79870933724115, -73.7656099560547
]}
})

40. Location

41. Location
db.places.find({
location: { $within : { $box : {
[
[40.800788494123154,
-73.85556051757814],
[40.68008976560161,
-74.04232809570314]
]
});

42. Easy to get started
Up and running on most systems in a half-dozen
commands or less fewer
http://try.mongodb.org/

43. Coming to a platform near you

44. Drupal for MongoDB
http://drupal.org/project/mongodb
D7: mongodb_cache: Store cache items in mongodb
D7: mongodb_field_storage: Store the fields in mongodb
D7: mongodb_session: Store sessions in mongodb
D6/D7: mongodb_watchdog: Store the watchdog messages in mongodb
D6/D7: mongodb: support library for the other modules
D7: mongodb_block: Store block information in mongodb. Very close to the core
block API
D7: mongodb_queue: DrupalQueueInterface implementation using mongodb
http://sf2010.drupal.org/conference/sessions/mongodb-humongous-drupal

45. Even MORE Drupal
Work to get listing API into core:
http://drupal.org/node/780154
Experimental goodies to play with:
http://drupalcode.org/viewvc/drupal/contributions/
sandbox/chx/dbtng_mongo_experimental/

46. Joomla!
MongoDB helper library for Joomla!
Branch of 1.6 development for alternative query builder
Full MongoDB support most likely in 2.0

47. Lithium PHP framework
MongoDB native support since 0.2
http://rad-dev.org/lithium/wiki
Projects demonstrating MongoDB support:
http://rad-dev.org/lithium_mongo/source
http://rad-dev.org/lithium_blog/source

48. CakePHP framework
MongoDB datasource
http://github.com/ichikaway/mongoDB-Datasource
Example article
http://mark-story.com/posts/view/using-mongodb-
with-cakephp

49. MongoDB Language Center
http://www.mongodb.org/display/DOCS/Drivers

50. Community Resources
http://www.mongodb.org/display/DOCS/
Community

51. Development Tracker
http://jira.mongodb.org

52. MongoDB Cookbook
http://cookbook.mongodb.org/

53. Thanks!
{
email: “nate.abele@gmail.com”,
twitter: “@nateabele”,
web: “http://lithify.me/”,
slides: “http://www.slideshare.net/nateabele”
}