A little presentation about the basics of MongoDB, for the PIttsburgh Ruby Brigade.

1. Steve Klabnik
Pittsburgh Ruby Brigade
October 7, 2010

2. “The best features of
Document Databases,
Key-Value Stores,
and RDBMSes.”

3. Document Database

5. JSON

6. BSON

7. http://hackety-hack.com/
http://github.com/hacketyhack/hackety-hack.com

8. post = {
"_id" : ObjectId("4c67892ba8d8770eb8000003"),
"title" : "Welcome to the Hackety Site!",
"body" : "This is an intial post, so that you can see how
everything looks. ",
"updated_at" : "Sun Aug 15 2010 02:28:59 GMT-0400 (EDT)"
"created_at" : "Sun Aug 15 2010 02:28:59 GMT-0400 (EDT)",
"comments" : [
{
"body" : "This post is awesome! I've never seen such
insightful writing!!",
"author" : "somebody",
"_id" : ObjectId("4c67892ba8d8770eb8000004"),
"author_email" : "somebody@example.com"
}
],
}

9. post = {
"_id" : ObjectId("4c67892ba8d8770eb8000003"),
"title" : "Welcome to the Hackety Site!",
"body" : "This is an intial post, so that you can see how
everything looks. ",
"updated_at" : "Sun Aug 15 2010 02:28:59 GMT-0400 (EDT)"
"created_at" : "Sun Aug 15 2010 02:28:59 GMT-0400 (EDT)",
"comments" : [
{
"body" : "This post is awesome! I've never seen such
insightful writing!!",
"author" : "somebody",
"_id" : ObjectId("4c67892ba8d8770eb8000004"),
"author_email" : "somebody@example.com"
}
],
}

10. post = {
"_id" : ObjectId("4c67892ba8d8770eb8000003"),
"title" : "Welcome to the Hackety Site!",
"body" : "This is an intial post, so that you can see how
everything looks. ",
"updated_at" : "Sun Aug 15 2010 02:28:59 GMT-0400 (EDT)"
"created_at" : "Sun Aug 15 2010 02:28:59 GMT-0400 (EDT)",
"comments" : [
{
"body" : "This post is awesome! I've never seen such
insightful writing!!",
"author" : "somebody",
"_id" : ObjectId("4c67892ba8d8770eb8000004"),
"author_email" : "somebody@example.com"
}
],
}

11. post = {
"_id" : ObjectId("4c67892ba8d8770eb8000003"),
"title" : "Welcome to the Hackety Site!",
"body" : "This is an intial post, so that you can see how
everything looks. ",
"updated_at" : "Sun Aug 15 2010 02:28:59 GMT-0400 (EDT)"
"created_at" : "Sun Aug 15 2010 02:28:59 GMT-0400 (EDT)",
"comments" : [
{
"body" : "This post is awesome! I've never seen such
insightful writing!!",
"author" : "somebody",
"_id" : ObjectId("4c67892ba8d8770eb8000004"),
"author_email" : "somebody@example.com"
}
],
}

12. Look, Ma! No Schema!

13. post = {
"_id" : ObjectId("4c67892ba8d8770eb8000004"),
"title" : "Here’s a cool update!",
"body" : "This is an explanation of all the new features!",
"updated_at" : "Sun Aug 15 2010 02:29:60 GMT-0400 (EDT)"
"created_at" : "Sun Aug 15 2010 02:29:60 GMT-0400 (EDT)",
}

14. $ mongo
MongoDB shell version: 1.6.3
connecting to: test
> use hackety-development;
switched to db hackety-development
> show collections;
discussions
hackers
messages
posts
programs
system.indexes
users
> db.posts.find();
{ "_id" : ObjectId("...

15. > db.users.find({“username”:”steve”})

16. > db.posts.find({“tags”:{$in:[“ruby”, “rails”]}})

17. JavaScript

18. > f = function(x) { return x + 1; }
function (x) {
return x + 1;
}
> f(2);
3

19. JSON == {}

20. JSON == {}

22. (1.9.x)

23. $ rvm use 1.9.2
info: Using ruby 1.9.2 p0
$ irb
ruby-1.9.2-p0 > {lol: "wut"}
=> {:lol=>"wut"}
ruby-1.9.2-p0 >

24. “Why I think Mongo is to
Databases what Rails was
to Frameworks”
http://railstips.org/blog/archives/2009/12/18/why-i-think-mongo-is-to-databases-what-rails-was-to-frameworks/

26. Map / Reduce

27. Map / Reduce

29. functional programming concepts

30. Map: Enumerable#map

31. map :: (a -> b) -> [a] -> [b]
(transforms one list into another list
via a function)

32. Reduce: Enumerable#inject

33. foldl :: (a -> b -> a) -> a -> [b] -> a
(takes a function with two arguments,
a starting point, and a list, and repeatedly
calls that function until only one value is left)

34. functional programming concepts

35. distributed computing

36. $ ./mongo
> db.things.insert( { _id : 1, tags : ['dog', 'cat'] } );
> db.things.insert( { _id : 2, tags : ['cat'] } );
> db.things.insert( { _id : 3, tags : ['mouse', 'cat',
'dog'] } );
> db.things.insert( { _id : 4, tags : [] } );
> // map function
> m = function(){
... this.tags.forEach(
... function(z){
... emit( z , { count : 1 } );
... }
... );
...};
> // reduce function
> r = function( key , values ){
... var total = 0;
... for ( var i=0; i<values.length; i++ )
... total += values[i].count;
... return { count : total };
...};
> res = db.things.mapReduce(m,r);
> res
{"timeMillis.emit" : 9 , "result" : "mr.things.
1254430454.3" ,
"numObjects" : 4 , "timeMillis" : 9 , "errmsg" : "" , "ok" :
0}
> db[res.result].find()
{"_id" : "cat" , "value" : {"count" : 3}}
{"_id" : "dog" , "value" : {"count" : 2}}
{"_id" : "mouse" , "value" : {"count" : 1}}

39. class Post
include MongoMapper::Document
key :title, String
key :body, String
key :slug, String
many :comments
timestamps!
end

41. “Software Engineering is the art of
choosing
the correct set of tradeoffs”-Me

44. # 1000
mongokit django_mongokit.mongodb
Creating 1000 talks took 0.957674026489
seconds
Editing 1000 talks took 1.60552191734 seconds
Deleting 1000 talks took 1.28869891167
seconds
IN TOTAL 3.8518948555 seconds
sql django.db.backends.postgresql_psycopg2
Creating 1000 talks took 8.57405209541
seconds
Editing 1000 talks took 14.8357069492 seconds
Deleting 1000 talks took 11.9729249477
seconds
http://www.peterbe.com/plog/speed-test-between-django_mongokit-and-postgresql_psycopg2

45. Rich Documents == Less Querying

47. ACID
(Atomicity, Consistency, Isolation, Durability)

48. Durability, Schmerability
(single server)

49. 32 bit?

52. Use the right tool

54. Thanks
@steveklabnik
http://steveklabnik.com/
http://www.slideshare.net/SteveKlabnik