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Django MongoDB BackendUsing Django and Non-relational for Web Development

Flavio Percoco [email protected]

Research & Development, The Net Planet Europe

October 04th, 2010
mailto:[email protected]:[email protected]


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Django MongoDB Backend

Introduction

Disclaimer

Before starting with mongodb specific topics its important to know that we dontdislike relational databases, we know they are good for many things but we also knowthat web applications success is mainly based on their performance and speed sothats what were running after and thats why were all here.


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Existing Technologies

MongoKit (Nicolas Clairon)

mongoengine (Harry Marr)django-mongodb-engine (Flavio Percoco Premoli and Alberto Paro)

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Moving Forward

SQL to MongoDB Query Translation. . .

What matters is who adapts faster to the changing conditions - Charles Darwin

Joins: The best thing you can do here is forget about JOINS

ForeignKeys: We have DBRef but, do we really need them?

M2M?: What about dicionaries/maps and lists/arrays?

And last but not least, If you really need to do a query that joins 2 collectionsbased on a field reference that should handle a many to many relation then youhave map/reduce.



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Moving Forward









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Moving Forward

Keeping things lazy

Yes, because were lazy people so we do lazy things. . .

It is important when getting orms to work with mongodb that we keep things lazy toavoid bottle necks in our web applications. Mongodb doesnt have many to manyrelations but it has lists and dictionaries. For example

class User(models.Model):

nickname = models.CharField(max length=255)

full name = models.CharField(max length=255)

friends = ListField()

groups = ListField()



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Moving Forward

Keeping things lazy

Yes, because were lazy people so we do lazy things. . .

It is important when getting orms to work with mongodb that we keep things lazy toavoid bottle necks in our web applications. Mongodb doesnt have many to manyrelations but it has lists and dictionaries. For example

class User(models.Model):

nickname = models.CharField(max length=255)

full name = models.CharField(max length=255)

friends = ListField()

groups = ListField()



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Moving Forward

Keeping Relations or Embedding?

This is a common question when moving from relational databases to non-rel ones.Should we keep our models related or embed smallest ones into the biggest ones?. The

answer is NO, you shouldnt keep them related. For Example, A common situation (orcommonly used to show how mongodb works) is a blog engine with posts andcomments. Lets see how we could handle comments (not threaded) in our blog engine:



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Moving Forward


Using References

class Comment(models.Model):

post = models.ForeignKey(Post)

user = models.ForeignKey(User)

text = models.CharField(max_length=255)

kwargs = { post : my post,

user : my user,

text : my text,

defaults : {}}

my comment = Comment.objects.get_or_create(**kwargs)[0]



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Moving Forward


Without References

class Post(models.Model):

...

comments = ListField()

post.comments.append({ user : user,text : text }

post.save()

Embedded? Not a good idea.

ForeignKey? If were using RDBMs.Dictionary? Good idea but slow.

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Moving Forward


Without References


...



post.save()



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Without References


...



post.save()



Django MongoDB BackendMoving Forward


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Without References


...



post.save()





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Moving Forward

Taking Advantage from schema-less

Schema-less databases do have a structureDynamicNot typed

Most of then are json-like maps.Great for web development

No Migrations needed.No IntegrityErrors.



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Moving Forward







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Lets improve our Comment model (in case we decided to have some relations).

class Comment(models.Model):post = models.ForeignKey(Post)

user = GenericField()


my user = "FlaPer87" #Known User

my user = { username : FlaPer87,

email : [email protected],url :http://blog.flaper87.org/}#Anonymous


user : my user,

text : my text,

defaults : {}}



T ki Ad f h l


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Lets improve our Comment model (in case we decided to have some relations).

class Comment(models.Model):post = models.ForeignKey(Post)

user = GenericField()


my user = "FlaPer87" #Known User

my user = { username : FlaPer87,

email : [email protected],url :http://blog.flaper87.org/}#Anonymous


user : my user,

text : my text,

defaults : {}}


Django MongoDB BackendSummary

Wh t l d


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What weve learned.. .

Re-model your models

Be Lazy to be faster

Forget about relations, they will slow you down

Remember that dynamism is better than restrictions


What weve learned


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What we ve learned.. .






What weve learned


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What weve learned


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Django MongoDB BackendThe End

A little bit about me


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Full Name: Flavio Percoco Premoli

IRC: FlaPer87 at irc.freenode.net

Twitter: FlaPer87

blog: http://www.flaper87.org

e-mail: [email protected]

Anywhere else: FlaPer87Short Background:

GNOME a11y and Open a11y Contributor (MouseTrap[http://live.gnome.org/MouseTrap]).

Open Source Developer/Contributor (Web and Desktop).

MongoDB Community Member and Contributor.

R&D Developer at The Net Planet Europe.

Knowledge Management SystemsSearch EnginesIndexing EnginesCloud ComputingNoSQL Technologies

Linux Lover/User and Mac user too

Django MongoDB BackendThe End

Interaction
http://www.flaper87.org/mailto:[email protected]:[email protected]://www.flaper87.org/


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Thanks!

Questions?

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