relax your project with couchdb

Relax your project with CouchDB

Benoît Chesneau26/05/2010 - djangocon berlin

Wednesday, May 26, 2010

• Why using a “NoSQL” solution ?

• CouchDB ?

• CouchDBKit: CouchDB & Django


• CouchDB developer• Maintainer of CouchDBkit,

Couchbeam, Couchapp , couchdbproxy, ...

• [email protected]

Why i’m here


• We don’t need “scalability” sometimes• Most of DB size < 300 GB (2 GB)• All my data could be on a machine

(comcast)• Often, DB requests are fast enough

Why NOSQL ?


Agile

• Different kinds of data• Easy denormalisation• Migrate your data easily• Keep your data safe• Flexibility, Simplicity


KEEP YOUR DATA SAFE


Order Customer Delivery

Item Item

Ex. Shop


• Oriented Document Database• REST• Map/Reduce (M/R)• Append-Only• Javascript/Erlang• Replication

CouchDB


Document Oriented?

• Schema-less• JSON• Attachments


JSON DOCUMENT

{ "_id": "foo", "_rev": "1-....", "url": "http://apache.couchdb.org", "vote": 1}


FutonWednesday, May 26, 2010

Map/Reduce ?

• Map (M) : Collect a list of values associated to a key

• Return a K-V list• Reduce (R) : Reduce a list of K-V in one

list of values• Rereduce


MAP.JS

function(doc) { if (doc.url && doc.vote) emit(doc.url, doc.vote);}


{ "total_rows": 3, "offset": 0, "rows": [{ "id": "15c92051cc81d564db4337a05087bc8d", "key": "http://apache.couchdb.org", "value": 1 }, { "id": "fa9658810d25cac893748e4ff15e7253", "key": "http://apache.couchdb.org", "value": 1 }, { "id": "1fa0c68d8455196507b8b01645e65186", "key": "http://mysql.com", "value": -1 }]}


REDUCE.JS

function(keys, values, rereduce) { return sum(values);}

{ "rows": [ { "key": "http://mysql.com", "value": -1 }, { "key": "http://apache.couchdb.org", "value": 2 } ]}


Réplicatuon

• Incremental• Master-Master• Continue or when needed


More

• Sharding: yes• couchdb-lounge, cloudant, yours• Geocouch. Full r-tree


couchdbkit


CouchDBKit

• CouchDB Python framework• support CouchDB 0.10.2 & 0.11.0• Simple client• Object Document Mapping (“ODM”)• Django extension• Couchapp compatible


client

from couchdbkit import Server

s = Server("http://127.0.0.1:5984")db = s["mydb"]doc = { "a": 1 }db.save_doc(doc)doc["b"] = 2db.save(doc)

doc1 = db.get(doc['_id'])


Other features

• db.views• from couchdbkit.loaders import

FileSystemDocsLoader


from couchdbkit.loaders import FileSystemDocsLoader

loader = FileSystemDocsLoader('/path/to/example/_design')loader.sync(db, verbose=True)


Object Document Mapping

from couchdbkit.schema import *

class MyDoc(Document): a = IntegerProperty() contain(db, MyDoc)

doc = MyDoc()doc.a = 1doc.save()

doc.b = 2doc.save()

doc1 = MyDoc.get(doc._id)


Django Extension

• from couchdbkt.ext.django import *• Django helper• manage.py syncdb• DocumentForm


settings.py

...

COUCHDB_DATABASES = ( ('djangoapp.greeting', 'http://127.0.0.1:5984/greeting'), )

...

INSTALLED_APPS = ( ... 'couchdbkit.ext.django', 'djangoapp.greeting', ... )


models.py

from datetime import datetimefrom couchdbkit.ext.django.schema import *

class Greeting(Document): author = StringProperty() content = StringProperty(required=True) date = DateTimeProperty(default=datetime.utcnow)


forms.py

class GreetingForm(DocumentForm): class Meta: document = Greeting


views.py

def home(request): greet = None if request.POST: form = GreetingForm(request.POST) if form.is_valid(): greet = form.save() else: form = GreetingForm() greetings = Greeting.view("greeting/all") return render("home.html", { "form": form, "greet": greet, "greetings": greetings }, context_instance=RequestContext(request))


0.5

• New mapping (Objects with annotations)

• Admin integration• Possibility to attach design doc to some

objects• MultiDB & DB backend in extension• Eventlet support


Liens

• http://apache.couchdb.org• http://couchdbkit.org


http://apache.couchdb.org

http://apache.couchdb.org

http://couchdbkit.org

http://couchdbkit.org

Questions


@benoitc


Cette création est mise à disposition selon le Contrat Paternité 2.0 France disponible en ligne http://

creativecommons.org/licenses/by/2.0/fr/ ou par courrier postal à Creative Commons, 171 Second Street, Suite

300, San Francisco, California 94105, USA.


http://creativecommons.org/licenses/by/2.0/fr/




relax your project with couchdb

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