Couch db and_the_web
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- CouchDB is a document-oriented NoSQL database that uses JSON documents and RESTful APIs. It features schema-free design, incremental map-reduce views, and multi-directional replication. - Views in CouchDB allow querying and aggregating documents using JavaScript map/reduce functions. Documents can be indexed and searched by mapping words to document IDs. Results can also be reduced to counts. - Replication in CouchDB allows databases to be copied or continuously synchronized across installations. Replication can be filtered to select specific documents.
![Indexer function(doc) { if (!doc.tweet) return; var clean_text = doc.tweet.replace(/\W/g, ' ').replace(/ /g, ' '); var lower_text = clean_text.toLowerCase(); var text_vector = lower_text.split(/ /); for (var i in text_vector) { var word = text_vector[i]; if (word.length > 2) emit(word, doc._id); } }](https://image.slidesharecdn.com/couchdbandtheweb-100909074802-phpapp01/85/Couch-db-and_the_web-14-320.jpg)
![The mapper output http://localhost:5984/news/_design/parser/_view/index {"total_rows":50,"offset":0,"rows":[ {"id":"123bc00725fc9f83120944079300093e","key":"9xmyxw","value":1}, {"id":"123bc00725fc9f831209440793000f46","key":"a6exod","value":1}, {"id":"123bc00725fc9f831209440793000f46","key":"and","value":1}, {"id":"123bc00725fc9f831209440793001bb6","key":"and","value":1}, {"id":"123bc00725fc9f83120944079300093e","key":"are","value":1}, http://localhost:5984/news/_design/parser/_view/index?key=%22couchdb%22 {"total_rows":50,"offset":11,"rows":[ {"id":"123bc00725fc9f83120944079300093e","key":"couchdb","value":1}, {"id":"123bc00725fc9f831209440793000f46","key":"couchdb","value":1}, {"id":"123bc00725fc9f831209440793001bb6","key":"couchdb","value":1} ]}](https://image.slidesharecdn.com/couchdbandtheweb-100909074802-phpapp01/85/Couch-db-and_the_web-15-320.jpg)
![Add reducer function(keys, values, rereduce) { return sum(values); } http://localhost:5984/news/_design/parser/_view/index {"rows":[ {"key":null,"value":50} ]} http://localhost:5984/news/_design/parser/_view/index?key=%22couchdb%22{"rows":[ {"key":null,"value":3} ]}](https://image.slidesharecdn.com/couchdbandtheweb-100909074802-phpapp01/85/Couch-db-and_the_web-16-320.jpg)
Couch db and_the_web
- 1. CouchDB and the web
- 2. Knut O. Hellan twitter.com/knuthellan knuthellan.com
- 3. NoSQL
- 4. NoSQL Freedom of choice Right tool for the job Use relational databases when appropriate
- 5. Flavor of the week Lightweight key-value: Graph: Document stores: Server spanning: More
- 7. Pros and cons RESTful JSON API Schema free Incremental map reduce views Incremental bi-directional replication
- 8. Pros and cons Robust append-only File backup with cp and tar Scalable?
- 10. Our database
- 11. Our database { "_id": "123bc00725fc9f831209440793001bb6", "_rev": "3-f30fca1f7fb4f387207e4756795aac74", "author": "jchris", "tweet": "This weekend just happened to be a good time for me to hack. Node.js CouchDB and Twitter, makes me feel like I'm part of #nodeko but I'm not", "type": "tweet" }
- 12. View Design
- 13. Default mapper function(doc) { emit(null, doc); }
- 14. Indexer function(doc) { if (!doc.tweet) return; var clean_text = doc.tweet.replace(/\W/g, ' ').replace(/ /g, ' '); var lower_text = clean_text.toLowerCase(); var text_vector = lower_text.split(/ /); for (var i in text_vector) { var word = text_vector[i]; if (word.length > 2) emit(word, doc._id); } }
- 15. The mapper output http://localhost:5984/news/_design/parser/_view/index {"total_rows":50,"offset":0,"rows":[ {"id":"123bc00725fc9f83120944079300093e","key":"9xmyxw","value":1}, {"id":"123bc00725fc9f831209440793000f46","key":"a6exod","value":1}, {"id":"123bc00725fc9f831209440793000f46","key":"and","value":1}, {"id":"123bc00725fc9f831209440793001bb6","key":"and","value":1}, {"id":"123bc00725fc9f83120944079300093e","key":"are","value":1}, http://localhost:5984/news/_design/parser/_view/index?key=%22couchdb%22 {"total_rows":50,"offset":11,"rows":[ {"id":"123bc00725fc9f83120944079300093e","key":"couchdb","value":1}, {"id":"123bc00725fc9f831209440793000f46","key":"couchdb","value":1}, {"id":"123bc00725fc9f831209440793001bb6","key":"couchdb","value":1} ]}
- 16. Add reducer function(keys, values, rereduce) { return sum(values); } http://localhost:5984/news/_design/parser/_view/index {"rows":[ {"key":null,"value":50} ]} http://localhost:5984/news/_design/parser/_view/index?key=%22couchdb%22{"rows":[ {"key":null,"value":3} ]}
- 17. Grouping http://localhost:5984/news/_design/parser/_view/index?group_level=1 {"rows":[ {"key":"9xmyxw","value":1}, {"key":"a6exod","value":1}, {"key":"and","value":2}, {"key":"are","value":1},
- 20. Replication Modes - Copy or replicate once - Continuous replication - Filtered replication
- 21. Multi-Couch
- 22. Offline replication - Mobile phone - Notebook or tablet and the cloud
- 23. Conflicts Multi-master => possible conflicts All masters will agree Conflict information kept in revision history
- 24. Filtered Replication function(doc, req) { if (doc.type && doc.type == "foo") { return true; } else { return false; } }
- 25. Filtered Replication { "_id":"myddoc", "filters": { "myfilter": "function goes here" } }
- 26. Filtered Replication { "source":"http://example.org/example-database", "target":"http://admin:password@127.0.0.1:5984/example-database", "filter":"myddoc/myfilter"}
- 27. CouchDB scaling
- 28. Alternatives - CouchDB lounge - - Pillow
- 29. Pillow - Reuses CouchDB functionality - Transparent for users - Automatic resharding
- 30. Pillow
- 31. Pillow
- 32. Pillow
- 33. Pillow
- 34. Pillow
- 36. CouchDB Experience Map Reduce based views are powerful View experimentation in Futon Three-way multi-master replication Replication monitor
- 37. CouchDB Experience EC2 External middleware still useful Duck typing matches CouchDB's JSON
- 38. Now what? Install and play with CouchDB Visit couchdb.apache.org Visit knuthellan.com
- 39. relax