Simple MongoDB tutorial

MongoDB has become one of the popular NoSQL db engines. It is considered as a NoSQL db and uses some concepts and names that are different from these used in relational database systems.

Alongside MongoDB there are many others NoSQL dbs. An short summary of available db options and theirs features can be found here.

Below are some of my notes how to start with MongoDB.

How to install MongoDB

• Create a cloud instance
• Download the software into your cloud  http://www.mongodb.org/downloads
• Install and start your mongod server process http://docs.mongodb.org/manual/tutorial/install-mongodb-on-ubuntu/

How to create your first table in the NoSQL data base

It is important to note that data bases will be created dynamically after you insert a first data into a collection (e.i insert a row into your table in the db - collection is a name for table in mongo).

http://docs.mongodb.org/manual/reference/sql-comparison/
http://docs.mongodb.org/manual/tutorial/getting-started/
http://www.mkyong.com/mongodb/how-to-create-database-or-collection-in-mongodb/

How to insert data into table

http://docs.mongodb.org/manual/tutorial/getting-started/

# start the shell interpreter
$ mongo
> show dbs
help    (empty)
local   0.078125GB
test    (empty)

> use rado
switched to db rado

> j = { name : "hello  word" }
{ "name" : "hello  word" }
> k = { x : 3 }
{ "x" : 3 }

> db.mycollection1.insert(j)
> db.mycollection1.insert(k)

> show dbs
help    (empty)
local   0.078125GB
rado    0.203125GB  <<<
test    (empty)

> use rado
> show collections
mycollection1  <<<<< 
system.indexes

> db.mycollection1.find()
{ "_id" : ObjectId("52767264795748b715336b87"), "x" : 3 }
{ "_id" : ObjectId("5276726a795748b715336b88"), "name" : "hello  word" }

Mongo shell commands 

http://docs.mongodb.org/manual/reference/method/

Install python API library for MongoDB

• Install the library 

http://docs.mongodb.org/manual/applications/drivers/
http://docs.mongodb.org/ecosystem/drivers/python/

apt-get install python-pymongo

• Customize the bash environment and install ipython 

http://rtomaszewski.blogspot.co.uk/2013/10/home-directory-and-dotfiles-management.html

 apt-get install ipython

Your first Python script that connects to MongoDB 

http://api.mongodb.org/python/current/tutorial.html
http://docs.mongodb.org/manual/reference/method/db.collection.insert/

Example Python code to insert data to our Mongo collection:

 
# rado-hello-world.py

import pymongo
from pymongo import MongoClien

client = MongoClient()
db = client['rado']

db.collection_names()
[u'system.indexes', u'mycollection1']

collection = db['mycollection1']

for doc in collection.find():
   ....:     print doc
   ....:
{u'x': 3.0, u'_id': ObjectId('52767264795748b715336b87')}
{u'_id': ObjectId('5276726a795748b715336b88'), u'name': u'hello  word'}

l = { "from" : "python", "mytext" : "hello from python" }
collection.insert(l)
ObjectId('52767d071d011c22eb1a7de5')

for doc in collection.find():
    print doc
   ....:
{u'x': 3.0, u'_id': ObjectId('52767264795748b715336b87')}
{u'_id': ObjectId('5276726a795748b715336b88'), u'name': u'hello  word'}
{u'_id': ObjectId('52767d071d011c22eb1a7de5'), u'from': u'python', u'mytext': u'hello from python'}

Further info about write operations 

Once of the big differences when working with NoSQL is that they are an implement of CRUD instead of ACID operation.

http://rsmith.co/opinion/technology/2012/11/05/mongodb-gotchas-and-how-to-avoid-them/
http://docs.mongodb.org/manual/core/write-operations/
http://docs.mongodb.org/manual/core/write-concern/
http://api.mongodb.org/python/current/api/pymongo/mongo_client.html#module-pymongo.mongo_client

We could say than that the performance increase is at the cost of security and integrity. If you don't want to lost any data and see errors as you type the commands you can use the options below when connecting to mongo DB. Please keep in mind that this trade off will have some performance implication in busy production systems although

 
# default 
>>> client = MongoClient()
>>> client2 = MongoClient( j=True, fsync=True )

>>> client2.write_concern
 {'fsync': True, 'j': True}

>>> client.write_concern
 {}