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Round pegs and square holes

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Round pegs and square holes

  1. Round Pegs and Square Holes Django and MongoDB by Daniel Greenfeld and Audrey Roy
  2. Audrey / Danny • Principals at Cartwheel Web Photo credit: Christopher Neugebauer • Co-founders of consumer.io • Met at PyCon 2010 • Now affianced @pydanny / @audreyr cartwheelweb.com
  3. What is MongoDB? • NoSQL • Fast, Scalable, Indexable, Shardable • Schema-less @pydanny / @audreyr cartwheelweb.com
  4. What is MongoDB? • Written in C++ • Stores data in BSON (kinda like JSON) • Uses JavaScript internally for scripting • Has Python, Ruby, PHP, C, other drivers • Huge community @pydanny / @audreyr cartwheelweb.com
  5. MongoDB: SQL Analogy • Collections are like tables • Documents are like records (rows) @pydanny / @audreyr cartwheelweb.com
  6. What is a MongoDB queryset? As served by pymongo Minimalist view @pydanny / @audreyr cartwheelweb.com
  7. What is a MongoDB queryset? As served by pymongo A list of dictionaries Minimalist view @pydanny / @audreyr cartwheelweb.com
  8. What it looks like list Minimalist view collection = [] document = { '_objectId': ObjectId('4f844e916c97c1000c000003'), 'username': 'pydanny', 'fiancee': { 'username': 'audreyr', 'location': 'Zurich' } } collection = [document, ] @pydanny / @audreyr cartwheelweb.com
  9. What it looks like list Minimalist view dictiona collection = [] document = { '_objectId': ObjectId('4f844e916c97c1000c000003'), 'username': 'pydanny', 'fiancee': { 'username': 'audreyr', 'location': 'Zurich' } } collection = [document, ] @pydanny / @audreyr cartwheelweb.com
  10. What it looks like list Minimalist view dictiona collection = [] document = { '_objectId': ObjectId('4f844e916c97c1000c000003'), 'username': 'pydanny', 'fiancee': { 'username': 'audreyr', 'location': 'Zurich' } } collection = [document, ] list of dictionaries! @pydanny / @audreyr cartwheelweb.com
  11. Tools for using MongoDB with Django (actually, most of these are not Django-
  12. “MongoDB connectors” • pymongo • mongoengine • mongokit • Django-nonrel • the only one here requiring Django @pydanny / @audreyr cartwheelweb.com
  13. Option 1 pymongo
  14. pymongo http://api.mongodb.org/python/current/ Official Python binding for MongoDB >>> from pymongo import Connection >>> connection = Connection() >>> my_data = {'rating': 3, 'title': 'I like ice cream'} >>> connection.reviews.insert(my_data) >>> your_data = {'rating': 3, 'subject': 'You like ice cream'} >>> connection.reviews.insert(your_data) @pydanny / @audreyr cartwheelweb.com
  15. pymongo http://api.mongodb.org/python/current/ Official Python binding for MongoDB my_data with title >>> from pymongo import Connection >>> connection = Connection() >>> my_data = {'rating': 3, 'title': 'I like ice cream'} >>> connection.reviews.insert(my_data) >>> your_data = {'rating': 3, 'subject': 'You like ice cream'} >>> connection.reviews.insert(your_data) @pydanny / @audreyr cartwheelweb.com
  16. pymongo http://api.mongodb.org/python/current/ Official Python binding for MongoDB my_data with title >>> from pymongo import Connection >>> connection = Connection() >>> my_data = {'rating': 3, 'title': 'I like ice cream'} >>> connection.reviews.insert(my_data) >>> your_data = {'rating': 3, 'subject': 'You like ice cream'} >>> connection.reviews.insert(your_data) your_data with subject @pydanny / @audreyr cartwheelweb.com
  17. pymongo [ {'rating': 3,'title': 'I like ice cream'}, {'rating': 3, 'subject': 'You like ice cream'} ] >>> connection = pymongo.Connection() >>> db = connection.db >>> for review in db.reviews.find({'rating': 3}): ... review['title'] >>> for review in db.reviews.find( ... {"title": {"$regex": "ice cream"} } ... ): ... review['title'] @pydanny / @audreyr cartwheelweb.com
  18. pymongo [ {'rating': 3,'title': 'I like ice cream'}, {'rating': 3, 'subject': 'You like ice cream'} ] >>> connection = pymongo.Connection() >>> db = connection.db >>> for review in db.reviews.find({'rating': 3}): ... review['title'] >>> for review in db.reviews.find( ... {"title": {"$regex": "ice cream"} } ... ): ... review['title'] Finds all reviews with a rating of 3 @pydanny / @audreyr cartwheelweb.com
  19. pymongo [ {'rating': 3,'title': 'I like ice cream'}, {'rating': 3, 'subject': 'You like ice cream'} ] >>> connection = pymongo.Connection() >>> db = connection.db >>> for review in db.reviews.find({'rating': 3}): ... review['title'] >>> for review in db.reviews.find( ... {"title": {"$regex": "ice cream"} } ... ): ... review['title'] @pydanny / @audreyr cartwheelweb.com
  20. pymongo [ {'rating': 3,'title': 'I like ice cream'}, {'rating': 3, 'subject': 'You like ice cream'} ] >>> connection = pymongo.Connection() >>> db = connection.db >>> for review in db.reviews.find({'rating': 3}): ... review['title'] >>> for review in db.reviews.find( ... {"title": {"$regex": "ice cream"} } ... ): ... review['title'] Only finds the document with ‘title’ in it. @pydanny / @audreyr cartwheelweb.com
  21. pymongo Pros • Really fast, bare metal • Lets you go schema-crazy • Supported directly by 10gen • They say “PyMongo to work with recommended way is the MongoDB from Python.” @pydanny / @audreyr cartwheelweb.com
  22. pymongo Cons • “PyMongo introspection” is an oxymoron • Very low-level • Lose out on ModelForms, Auth, Admin, etc • Syntax mapperclean as with an object not as @pydanny / @audreyr cartwheelweb.com
  23. Option 2 MongoEngine
  24. MongoEngine http://mongoengine.org/ Doesn’t this look import mongoengine as me like the Django class Review(me.Document): ORM? title = me.StringField() body = me.StringField() author = me.StringField() created = me.DateTimeField(default=datetime.utcnow) rating = me.IntField() @pydanny / @audreyr cartwheelweb.com
  25. MongoEngine Doesn’t this look like a Django query? >>> from reviews.models import Review >>> for review in Review.objects.all(): ... review.title @pydanny / @audreyr cartwheelweb.com
  26. MongoEngine Pros • Looks similar to Django ORM code • You can develop SUPER-QUICKLY • Can use with django-mongonaut for introspection • Light schema, unenforced by the db • Supports some inter-document connections @pydanny / @audreyr cartwheelweb.com
  27. MongoEngine Cons • Some feel there’s too much structure • Validation messages sometimes unclear • Using it with Django,introspection*on the Django Admin’s you lose out and ModelForms * django-mongonaut addresses this. @pydanny / @audreyr cartwheelweb.com
  28. mongoengine and django-mongonaut http://bit.ly/django-mongonaut @pydanny / @audreyr cartwheelweb.com
  29. Option 3 MongoKit
  30. MongoKit http://namlook.github.com/mongokit/ from mongokit import Document, Connection connection = Connection() @connection.register class Review(Document): structure = { 'title':unicode, 'body':unicode, 'author':unicode, 'created':datetime.datetime, 'rating':int } required_fields = ['title', 'author', 'created'] default_values = {'rating': 0, 'created': datetime.utcnow} @pydanny / @audreyr cartwheelweb.com
  31. MongoKit http://namlook.github.com/mongokit/ from mongokit import Document, Connection connection = Connection() @connection.register class Review(Document): Review model structure = { representing 'title':unicode, MongoDB 'body':unicode, 'author':unicode, collection 'created':datetime.datetime, 'rating':int } required_fields = ['title', 'author', 'created'] default_values = {'rating': 0, 'created': datetime.utcnow} @pydanny / @audreyr cartwheelweb.com
  32. MongoKit http://namlook.github.com/mongokit/ from mongokit import Document, Connection connection = Connection() @connection.register class Review(Document): Review model structure = { representing 'title':unicode, MongoDB 'body':unicode, Expected 'author':unicode, collection fields 'created':datetime.datetime, 'rating':int } required_fields = ['title', 'author', 'created'] default_values = {'rating': 0, 'created': datetime.utcnow} @pydanny / @audreyr cartwheelweb.com
  33. MongoKit http://namlook.github.com/mongokit/ Connect to from mongokit import Document, Connection reviews collectio connection = Connection() n @connection.register class Review(Document): Review model structure = { representing 'title':unicode, MongoDB 'body':unicode, Expected 'author':unicode, collection fields 'created':datetime.datetime, 'rating':int } required_fields = ['title', 'author', 'created'] default_values = {'rating': 0, 'created': datetime.utcnow} @pydanny / @audreyr cartwheelweb.com
  34. MongoKit http://namlook.github.com/mongokit/ >>> from mongokit import Connection >>> connection = Connection() >>> for review in connection.Review.find({'rating': 3}): ... review['title'] Identical to pymongo queries @pydanny / @audreyr cartwheelweb.com
  35. MongoKit Pros • Light schema, unenforced by the db • Or can go all out schemaless! • Speed • Types are a mix of Python & MongoDB • Uses pymongo-style queries @pydanny / @audreyr cartwheelweb.com
  36. MongoKit Cons • Using itDjango Admin’s lose out on the with Django, you introspection, ModelForms, auth, etc • Introspection is hard @pydanny / @audreyr cartwheelweb.com
  37. Option 4 Django-nonrel + mongodb-engine
  38. Django-nonrel + mongodb-engine http://docs.django-nonrel.org • A patch to Django thatORM NoSQL support to the Django adds • Works with GAE, MongoDB, even SQL DBs @pydanny / @audreyr cartwheelweb.com
  39. Django-nonrel + mongodb-engine Pros • Can use Django as you normally would • Mirrors the ORM functionality • Introspection via djangotoolbox @pydanny / @audreyr cartwheelweb.com
  40. Django-nonrel + mongodb-engine Cons • Fork of the whole Django project. • Dependent Django core (still on parity with on others to maintain Django 1.3). • Multi-db usage is confusing @pydanny / @audreyr cartwheelweb.com
  41. Summary • pymongo is low-level and well-supported by 10gen. • MongoEngine is like schemaless Django models. • MongoKit is like pymongo with extra structure. • Django-nonrel is a fork of Django 1.3. @pydanny / @audreyr cartwheelweb.com
  42. The Take Away?
  43. Danny’s Thoughts Can we build a “simple” bridge? What about a single third-party app that lets you combine critical Django apps and MongoDB? • django.contrib.auth • django.forms • django-social-auth / registration • others... @pydanny / @audreyr cartwheelweb.com
  44. Danny’s Thoughts I wonder, why add schemas to schema-less when: Relational Databases South High level Caching tools* allow you to develop fast moving datastores with transactions and built- in Djangoorsupport? * cache-machine johnny-cache @pydanny / @audreyr cartwheelweb.com
  45. Danny’s Thoughts Introspection Tool Idea Treat introspection like MongoDB Queries Immediate introspection tool (no ‘title’ then don’t show title) @pydanny / @audreyr cartwheelweb.com
  46. Audrey’s Thoughts • Schemaless dbs promise performance advantages • Especially for distributed systems • Tradeoff: ACID compliance http://stackoverflow.com/questions/3856222/whats-the-attraction-of-schemaless- database-systems @pydanny / @audreyr cartwheelweb.com
  47. Audrey’s Thoughts “Schemaless database” == ACID-noncompliant database OK when performance is more important than being consistent 100% of the time. @pydanny / @audreyr cartwheelweb.com
  48. Audrey’s Thoughts Schemaless Python models != Schemaless MongoDB collections I think MongoEngine is best unless your use case calls for schema anarchy. @pydanny / @audreyr cartwheelweb.com
  49. Going Forward
  50. Using Django With MongoDB • Big hurdles: ORM, Admin, ModelForms, Auth • Were built for relational data • But the situation is improving rapidly @pydanny / @audreyr cartwheelweb.com
  51. What needs to be done • New introspection tools (working on it) • django.forms bridge. • django.contrib.admin bridge. • Drop-in 1.5?) (Django replacement for Django Auth • Creation of best practices document for use of MongoDB with Django. @pydanny / @audreyr cartwheelweb.com
  52. Django Mongonaut • Introspection tool for MongoEngine • Works well so far • Integrate graphing tools • Make independent from mongoengine • Contributors wanted: • https://github.com/pydanny/django- mongonaut @pydanny / @audreyr cartwheelweb.com
  53. Django Mongonaut Based off of immediate introspection - not definition @pydanny / @audreyr Mockup cartwheelweb.com
  54. Django Mongonaut Based off of immediate introspection - not definition SVG w/links for examining nested structures @pydanny / @audreyr Mockup cartwheelweb.com
  55. Final Summary { pymongo mongoengine Python/ mongokit MongoDB tools django-nonrel to consider django-mongodb django- mongonaut @pydanny / @audreyr cartwheelweb.com

Notas del editor

  • A: We have a specific time we have to present in, so please hold your questions and comments to the end.\n
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  • A: Which is why we’re presenting here today rather than at LA Django - this is useful info for any Python developer.\n
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  • D - Using a review system...\n
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  • D: MongoDB queries are meant for schema-less data.\n
  • D: MongoDB queries are meant for schema-less data.\n
  • D: You can do crazy things like have every document in a collection have a completely different schema. \n
  • D: No introspection tools, just the shell. Certainly no admin. \n
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  • A: If you use ReferenceFields all the time, you might as well be using SQL\n
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  • A: According to posts on the mailing list, you should be able to use multiple databases. But I pored over the docs/mailing list and couldn’t find an example of, say, using Postgres for auth and MongoDB for a custom app\n
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  • D I’m in discussion with some other Python/MongoDB aficionados.\n
  • D I love normalization. I love what you can do with a schema. I love what you can do without a schema\n
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  • A: Atomicity, consistency, isolation, durability. Properties that guarantee that a db transaction has been processed reliably.\n
  • A: Atomicity, consistency, isolation, durability. Properties that guarantee that a db transaction has been processed reliably.\nThere’s the very small risk that data you retrieve could be in a temporary inconsistent state.\n
  • A: NYT, Heroku, Intuit, IGN, Posterous, and others use Ruby’s MongoMapper\nIn the Ruby world, Mongo object mappers are much more prevalent.\n
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