An introduction to CouchDB

An introduction to #CouchDB Sit back and relax @davidcoallier, University Limerick 2010

WTF IS COUCH? - Highly concurrent database server - Schema free, document based database - RESTFul API - Map/Reduce Views generation - EASY replication (like... really)

... AGAIN.. WTF?!

HISTORY CLASS TIME!

32 CouchDB servers 2 datacenters SSL based user auth, sharding, etc. This is the only BBC transparent logo I found and it’s not BBC World News using CouchDB but BBC. See: http://www.erlang-factory.com/conference/London2009/speakers/endafarrell

Ubuntu One

mozilla.org IBM Apple myspace.com ebay meebo oh so many more.

DOCUMENT BASED KEY/VALUE STORE...

key value name david email e@e.com phones Array createdAt timetsamp

DOCUMENT BASED WHAT? - Dictionary of data - JSON Objects - A doc can have attachments - Auto generated IDs (CLAP NOW) - Revisions (THAT’S RIGHT..)

DOCUMENT { "_id": "3fc3b3bf3c101e15fa7d08e2ecf9c900", "_rev": "1-34c5c7adcf1fdb8898498d1e6b64ebdd", "firstname": "David", "email": "david@echolibre.com" }

DOCUMENT { "_id": "3fc3b3bf3c101e15fa7d08e2ecf9c900", "_rev": "1-34c5c7adcf1fdb8898498d1e6b64ebdd", "firstname": "David", "email": "david@echolibre.com", "phones": { "mobile": "086x209x69", "home": "none" }, "createdAt": "2009-09-16T22:12:43Z" }

key value name david email e@e.com phones Array createdAt timetsamp

WHAT ABOUT MY CRUD? - Create PUT /db/docid - Retrieve GET /db/docid - Update POST /db/docid - Delete DELETE /db/docid

VIEWS - Persistent representation of docs - Prod is solid. No _temp shit. - Javascript, Erlang, Python, wtf ever.

MAP/REDUCE ...

JAVASCRIPT

MAP map: function(doc) { if (doc.firstname) { emit(doc.firstname, doc); } }

MAP %% Map Function fun({Doc}) -> case {proplists:get_value(<<"firstname">>, Doc)} of {undefined} -> false; {Name} -> Emit(Name, Doc); _ -> ok end end.

fun({Doc}) -> Emitter = fun(Doc) -> Name = proplists:get_value(<<"name">>, Doc, null), Emit(Name, Doc) end, HasRequiredFields = fun(Doc) -> case {proplists:is_defined(<<"firstname">>, Doc)} of {true} -> Emitter(Doc); _-> false end end, HasRequiredFields(Doc) end.

MAP/REDUCE EXAMPLE

MAP { "_id": "3fc3b3bf3c101e15fa7d08e2ecf9c900", "_rev": "1-34c5c7adcf1fdb8898498d1e6b64ebdd", "firstname": "David", "email": "david@echolibre.com", "phones": { "mobile": "086x209x69", "home": "none" }, "createdAt": "2009-09-16T22:12:43Z", "tags": ["cool", "php", "couchdb", "skynet"] }

MAP map: function(doc) { if (doc.tags && docs.tags.length > 0) { for (var i = 0; i < doc.tags.length; i++) { emit(doc.tags[i], 1); } } }

REDUCE map: function(doc) { if (doc.tags && docs.tags.length > 0) { for (var i = 0; i < doc.tags.length; i++) { emit(doc.tags[i], 1); } } }, reduce: function(tag, counts) { int sum = 0; for(var i = 0; i < counts.length; i++) { sum += counts[i]; } return sum; }

REDUCE function(tag, counts) { int sum = 0; for(var i = 0; i < counts.length; i++) { sum += counts[i]; } return sum; }

REDUCE { "total_rows":4, "rows":[ { "key":"cool", "value":1}, { "key":"php", "value":1}, { "key":"couchdb", "value":1}, { "key":"skynet", "value":1}, ] }

REDUCE TRICKS map: function(doc) { if (doc.tags && docs.tags.length > 0) { for (var i = 0; i < doc.tags.length; i++) { emit(doc.tags[i], 1); } } } reduce: "_count"

REDUCE { "total_rows":4, "rows":[ { "key":"cool", "value":1}, { "key":"php", "value":1}, { "key":"couchdb", "value":1}, { "key":"skynet", "value":1}, ] }

REDUCE map: function(doc) { if (doc.tags && docs.tags.length > 0) { for (var i = 0; i < doc.tags.length; i++) { emit(doc.tags[i], "yer ma"); } } }, reduce: function (tag, count) { return sum(tag); }

THEN...

BEWARE OF REDUCE VALUES

REPLICATION It fuckin’ rules.

REPLICATION Easy (See later futon ;-)) Continuous... or not :P Replicates your views Replicate only what you need (ﬁlter?)

REPLICATION curl -X POST http://localhost:5984/_replicate '{"source":"/dbname", "target": "http://localhost:5555/otherdb", "continuous": true}'

REPLICATION Source The boss Target changes? watcha need?? target needs x, y, z save them

REPLICATION MASTER / SLAVES

REPLICATION MULTI MASTER

REPLICATION USE CASE Automated job to validate and test data and do bunch of shits

NOTE TO SELF. Show them. Open up CouchDBX

COOL THINGS Authorization CouchDB Lucene Lounge CouchDBX Couchio Cloudant A bunch of random bits and pieces

COMPLETE SHITE COMING UP eas r e id sha W le! NO p s peo cus Dis

CONCEPTS AND IDEAS Graph Theory ... ss ion u a disc t d star tr y an

CONCEPTS AND IDEAS Ghost Replication ... ss ion u a disc t d star tr y an

CONCEPTS AND IDEAS Shared Index Replication ... ss ion u a disc t d star tr y an

QUESTIONS?

ME! MEEE!!! @davidcoallier david@echolibre.com

THANKS

LINKS - https://nosqleast.com/2009/slides/miller-couchdb.pdf - http://couch.io - http://cloudant.com - http://wiki.apache.org/couchdb/CouchDB_in_the_wild - irc://couchdb@freenode.net (Bug jan___ ;-))

http://nosql.mypopescu.com	2880
http://www.mostofreddy.com.ar	85
http://www.slideshare.net	72
http://varga-multimedia.com	51
http://youthvoices.dev	5
http://sphere.lithify.me	4
http://translate.googleusercontent.com	4
http://localhost	4
https://abs.twimg.com	3
http://bender	3
http://webcache.googleusercontent.com	3
http://flexbuddha.wordpress.com	3
http://127.0.0.1	2
http://francisvarga.posterous.com	2
http://www.thehouseofblogs.com	2
http://bender.radada.gruik.org	1
app://nl.ditnet.couchdb	1
https://twitter.com	1

An introduction to CouchDB

by David Coallier

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