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CS-695 NoSQL DatabaseCouchDB (part 1 of 2)

Dr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck CartledgeDr. Chuck Cartledge

22 Oct. 201522 Oct. 201522 Oct. 201522 Oct. 201522 Oct. 201522 Oct. 201522 Oct. 201522 Oct. 201522 Oct. 201522 Oct. 201522 Oct. 201522 Oct. 201522 Oct. 201522 Oct. 201522 Oct. 201522 Oct. 201522 Oct. 201522 Oct. 201522 Oct. 201522 Oct. 201522 Oct. 2015

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Table of contents I

1 Miscellanea

2 Mid-term

3 DB comparisons

4 Assgn. #5

5 Origins and history

6 Data model

7 CRUDy stuff

8 Conclusion

9 References

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Corrections and additions since last lecture.

Assignment #05 is available

Mid-term

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How different DBs compare to a RDBMS

We have some terms to compare now[4]

RDBMS K/V Columnar Doc.

DB. instance cluster cluster instancedatabase — namespace —table bucket table collectionrow key-value row documentrowid key — idcol. — col. fam. —schema — — databasejoin — — DBRef

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Words of explanation.

The full text is available at:http://www.cs.odu.edu/~ccartled/Teaching/2015-Fall/NoSQL/Assignments/05/

In general terms:

1 Parse data

2 Create document database(possibly two, or three)

3 Update documents based onnumber of movies filmed per year,and number of trivia facts permovie

4 Query database

5 Create list of movies per year(two different types of lists)

6 Plot graphic

7 Create a list of number of triviafacts by movie

8 Plot graphic

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Where it came from and why.

Cluster of unreliable commodity hardware DataBase(CouchDB)1

Started in April 2005

Became an ApacheIncubator project in 2008

Overview

Document StorageACID Semantics (at thedocument level)Map/Reduce Views andIndexesDistributed Architecturewith ReplicationREST APIEventual ConsistencyBuilt for Offline

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What is in the backend?

JSON is our friend.

Document databases storedocuments in the value part of akey-value store

Document databases havekey-value stores where the valuepart is examinable

Each document has unique fields:

1 id: a unique ID for thedocument

2 rev: a unique revisionnumber for the document

id and rev are required toupdate a document

The JSON attributes are wherethe data lives.

Image from [2].

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Pre-CRUDy stuff

The mongoDB already exists

The database is static andavailable at all times

The collection is a group ofidentifiers

Anyone can create anddelete a collection

Database administrators canbe created andauthenticated

Lots of simularities to MongoDB.

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CouchDB Futon

Futon is a web UI for CouchDB

Futon alows total access to theCouchDB.

Create and delete databases

Create and deletedocuments

Create and edit JavascriptMap and Reduce functions

Image from [1].

Futon is available on cs695-nosql. Hooking a browser to it couldbe a challenge.

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CouchDB Futon

Making sure that CouchDB is alive and well (1 of 2)

Checking CouchDB’s health

Is it alive:curl http://127.0.0.1:5984/

Which databases are defined:curl -X GET http://127.0.0.1:5984/ all dbs

Information about a database:curl -X GET http://127.0.0.1:5984/ users

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CouchDB Futon

Making sure that CouchDB is alive and well (2 of 2)

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CRUDy nuts and bolts

Drivers and other things2

CouchDB is available via curlcommands, or drivers for

Java, JavaScript, C#,python, ruby,

And others.

Image from [3].

Too many choices. All use HTTP ReST communications backend.2https://cwiki.apache.org/confluence/display/COUCHDB/CouchDB+clients

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CRUDy nuts and bolts

Create a database (1 of 2)

The database is created when the PUT command is executed:

curl -X PUT http://127.0.0.1:5984/<database name >

curl -X PUT http://127.0.0.1:5984/test db

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CRUDy nuts and bolts

Create a database (2 of 2)

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CRUDy nuts and bolts

Create data3 (1 of 2)

curl -X POST URLtoDataBase -H ’Content-Type:application/json’ -d ’JSON’

curl -X POST http://couchhost:5984/test db -H’Content-Type: application/json’ -d ’{”FirstName”:”Isabella”,”FamilyName”:”Huegdon”, ”Age”:2, ”Likes”:[”noise”,”animals”, ”chocolate”, ”kicking Milly”, ”throwingtantrums”]}’

3Data taken from:http://nefariousdesigns.co.uk/couchdbs-restful-api.html

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CRUDy nuts and bolts

Create data (2 of 2)

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CRUDy nuts and bolts

Find data (1 of 2)

Seehttp://couchdb-13.readthedocs.org/en/latest/api/database/

for complete list of database methods.

curl -X GET URLtoCouchHost/databse/ all docs

curl -X GET http://127.0.0.1:5984/test db/ all docs

curl -X GET URLtoCouchHost/databse/id

curl -X GET http://127.0.0.1:5984/test db/19124749379a656b309520811100020a

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CRUDy nuts and bolts

Find data (2 of 2)

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CRUDy nuts and bolts

Update data (1 of 2)

Partial document updates are not supported. An update willreplace the previous document in its entirety.

Find the document based on id and rev

Update the JSON data locally

Add the id and rev fields to the JSON data

POST the update JSON to the database

CouchDB is a key-value database. The id and rev fields are thekey, and the JSON is the value.

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CRUDy nuts and bolts

Update data (2 of 2)

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CRUDy nuts and bolts

Remove a document (1 of 3)

Its not as obvious as you might think[6].

curl -X DELETEURLtoCouchHost/id?rev=REVISION-STRING

curl -X DELETE http://127.0.0.1:5984/test db/19124749379a656b309520811100020a?rev=2-c5c854b1d41d5ed00a2039400b4950d8

Alternative way is to UPDATE the document with a newJSON containing the “ deleted” attribute set to “true”

Alternative way is to POST document information theCouchDB’s purge API

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CRUDy nuts and bolts

Remove a document (2 of 3)

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CRUDy nuts and bolts

Remove a document (3 of 3)

“Note: Deleted documents remain in the databaseforever, even after compaction, to allow eventualconsistency when replicating. If you delete using theDELETE method above, only the id, rev and a deletedflag are preserved. If you deleted a document by adding“ deleted”:true then all the fields of the document arepreserved. This is to allow, for example, recording thetime you deleted a document, or the reason you deletedit.”

Couchdb Wiki Staff [5]

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Special fields

CouchDB has special fields4

Name Description

id The unique identifier of the document (mandatory and im-mutable)

rev The current MVCC-token/revision of this document (manda-tory and immutable)

attachments If the document has attachments, attachments holds a(meta-)data structure

deleted Indicates that this document has been deleted and previousrevisions will be removed on next compaction run

revisions Revision history of the documentrevs info A list of revisions of the document, and their availabilityconflicts Information about conflictsdeleted conflicts Information about conflictslocal seq Sequence number of the revision in the database (as found

in the changes feed)

4https://wiki.apache.org/couchdb/HTTP_Document_API

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What have we covered?

Had mid-termReviewed assignment #05Covered some of theCouchDB CRUDy stuffRemember Assignment #05due before next class

Next time: continued CRUDy exploration

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References I

[1] J Chris Anderson, Jan Lehnardt, and Noah Slater, Couchdb: The definitiveguide, O’Reilly Media, Inc., 2010.

[2] Bradley Holt, Learning couchdb,http://www.slideshare.net/bradley.holt/oscon-2011-learning-couchdb,2011.

[3] Tim Juravich, Getting started with couchdb and futon,https://www.packtpub.com/books/content/getting-started-couchdb-and-futon

2012.

[4] Eric Redmond and Jim R Wilson, Seven databases in seven weeks,Pragmatic Bookshelf, 2012.

[5] CouchDB Wiki Staff, Http document api,https://wiki.apache.org/couchdb/HTTP_Document_API, 2015.

[6] Nate Vanderwilt, The three ways to remove a document from couchdb,http://n.exts.ch/2012/11/baleting, 2012.