MongoDB Tutorial
Table of Content
MongoDb tutorial...................................................................... 1
Audience.................................................................................. 1
Prerequisites............................................................................ 1
MongoDB Overview ................................................................. 6
Database ................................................................................. 6
Collection................................................................................. 6
Document ................................................................................ 6
Sample document .................................................................... 7
MongoDB Advantages ............................................................. 8
Advantages of MongoDB over RDBMS.................................... 8
Why should use MongoDB....................................................... 8
Where should use MongoDB? ................................................. 8
MongoDB Environment............................................................ 9
Install MongoDB On Windows.................................................. 9
Install MongoDB on Ubuntu ................................................... 10
MongoDB Help....................................................................... 11
MongoDB Statistics................................................................ 12
MongoDB Data Modelling ...................................................... 13
Some considerations while designing schema in MongoDB... 13
Example................................................................................. 13
MongoDB Create Database ................................................... 15
The use Command ................................................................ 15
Syntax:................................................................................... 15
Example:................................................................................ 15
MongoDB Drop Database ...................................................... 16
The dropDatabase () Method ................................................. 16
Syntax:................................................................................... 16
Example:................................................................................ 16
MongoDB Create Collection................................................... 17
The createCollection() Method............................................... 17
Syntax:................................................................................... 17
Examples: .............................................................................. 18
MongoDB Drop Collection...................................................... 19
The drop() Method ................................................................. 19
Syntax:................................................................................... 19
Example:................................................................................ 19
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MongoDB Datatypes.............................................................. 20
MongoDB - Insert Document.................................................. 21
The insert() Method................................................................ 21
Syntax.................................................................................... 21
Example................................................................................. 21
Example................................................................................. 21
MongoDB - Query Document................................................. 23
The find() Method................................................................... 23
Syntax.................................................................................... 23
The pretty() Method ............................................................... 23
Syntax:................................................................................... 23
Example................................................................................. 23
RDBMS Where Clause Equivalents in MongoDB................... 24
AND in MongoDB................................................................... 24
Syntax:................................................................................... 24
Example................................................................................. 24
OR in MongoDB..................................................................... 25
Syntax:................................................................................... 25
Example................................................................................. 25
Using AND and OR together.................................................. 26
Example................................................................................. 26
MongoDB Update Document ................................................. 27
MongoDB Update() method ................................................... 27
Syntax:................................................................................... 27
Example................................................................................. 27
MongoDB Save() Method....................................................... 28
Syntax.................................................................................... 28
Example................................................................................. 28
MongoDB Delete Document .................................................. 29
The remove() Method............................................................. 29
Syntax:................................................................................... 29
Example................................................................................. 29
Remove only one ................................................................... 29
Remove All documents .......................................................... 29
MongoDB Projection .............................................................. 30
The find() Method................................................................... 30
Syntax:................................................................................... 30
Example................................................................................. 30
MongoDB Limit Records ........................................................ 31
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The Limit() Method................................................................. 31
Syntax:................................................................................... 31
Example................................................................................. 31
MongoDB Skip() Method........................................................ 31
Syntax:................................................................................... 31
Example:................................................................................ 31
MongoDB Sort Documents .................................................... 32
The sort() Method .................................................................. 32
Syntax:................................................................................... 32
Example................................................................................. 32
MongoDB Indexing ................................................................ 33
The ensureIndex() Method..................................................... 33
Syntax:................................................................................... 33
Example................................................................................. 33
MongoDB Aggregation........................................................... 35
The aggregate() Method ........................................................ 35
Syntax:................................................................................... 35
Example:................................................................................ 35
Pipeline Concept.................................................................... 37
MongoDB Replication ............................................................ 38
Why Replication?................................................................... 38
How replication works in MongoDB........................................ 38
Replica set features ............................................................... 39
Set up a replica set ................................................................ 39
Example................................................................................. 39
Add members to replica set ................................................... 40
Synttax:.................................................................................. 40
Example................................................................................. 40
MongoDB Sharding................................................................ 41
Sharding ................................................................................ 41
Why Sharding? ...................................................................... 41
Sharding in MongoDB............................................................ 41
MongoDB Create Backup ...................................................... 43
Dump MongoDB Data............................................................ 43
Syntax:................................................................................... 43
Example................................................................................. 43
Restore data .......................................................................... 44
Syntax.................................................................................... 44
MongoDB Deployment........................................................... 45
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mongostat.............................................................................. 45
mongotop............................................................................... 46
MongoDB Java ...................................................................... 48
Installation.............................................................................. 48
Connect to database.............................................................. 48
Create a collection ................................................................. 49
Getting/ selecting a collection................................................. 50
Insert a document .................................................................. 51
Retrieve all documents........................................................... 52
Update document................................................................... 53
Delete first document ............................................................. 55
MongoDB PHP....................................................................... 57
Make a connection and Select a database............................. 57
Create a collection ................................................................. 57
Insert a document .................................................................. 58
Find all documents................................................................. 59
Update a document................................................................ 59
Delete a document................................................................. 60
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MongoDB Overview
MongoDB is a cross-platform, document oriented database that provides, high performance, high availability,
and easy scalability. MongoDB works on concept of collection and document.
Database
Database is a physical container for collections. Each database gets its own set of files on the file system. A single
MongoDB server typically has multiple databases.
Collection
Collection is a group of MongoDB documents. It is the equivalent of an RDBMS table. A collection exists within a
single database. Collections do not enforce a schema. Documents within a collection can have different fields.
Typically, all documents in a collection are of similar or related purpose.
Document
A document is a set of key-value pairs. Documents have dynamic schema. Dynamic schema means that documents
in the same collection do not need to have the same set of fields or structure, and common fields in a collection's
documents may hold different types of data.
Below given table shows the relationship of RDBMS terminology with MongoDB
RDBMS MongoDB
Database Database
Table Collection
Tuple/Row Document
column Field
Table Join Embedded Documents
Primary Key Primary Key (Default key _id provided by mongodb
itself)
Database Server and Client
Mysqld/Oracle mongod
mysql/sqlplus mongo
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Sample document
Below given example shows the document structure of a blog site which is simply a comma separated key value pair.
{
_id: ObjectId(7df78ad8902c)
title: 'MongoDB Overview',
description: 'MongoDB is no sql database',
by: 'tutorials point',
url: 'http://www.tutorialspoint.com',
tags: ['mongodb', 'database', 'NoSQL'],
likes: 100,
comments: [
{
user:'user1',
message: 'My first comment',
dateCreated: new Date(2011,1,20,2,15),
like: 0
},
{
user:'user2',
message: 'My second comments',
dateCreated: new Date(2011,1,25,7,45),
like: 5
}
]
}
_id is a 12 bytes hexadecimal number which assures the uniqueness of every document. You can provide _id
while inserting the document. If you didn't provide then MongoDB provide a unique id for every document.
These 12 bytes first 4 bytes for the current timestamp, next 3 bytes for machine id, next 2 bytes for process id
of mongodb server and remaining 3 bytes are simple incremental value.
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MongoDB Advantages
Any relational database has a typical schema design that shows number of tables and the relationship between
these tables. While in MongoDB there is no concept of relationship
Advantages of MongoDB over RDBMS
Schema less : MongoDB is document database in which one collection holds different different documents.
Number of fields, content and size of the document can be differ from one document to another.
Structure of a single object is clear
No complex joins
Deep query-ability. MongoDB supports dynamic queries on documents using a document-based query language
that's nearly as powerful as SQL
Tuning
Ease of scale-out: MongoDB is easy to scale
Conversion / mapping of application objects to database objects not needed
Uses internal memory for storing the (windowed) working set, enabling faster access of data
Why should use MongoDB
Document Oriented Storage : Data is stored in the form of JSON style documents
Index on any attribute
Replication & High Availability
Auto-Sharding
Rich Queries
Fast In-Place Updates
Professional Support By MongoDB
Where should use MongoDB?
Big Data
Content Management and Delivery
Mobile and Social Infrastructure
User Data Management
Data Hub
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MongoDB Environment
Install MongoDB On Windows
To install the MongoDB on windows, first doownload the latest release of MongoDB from
www.mongodb.org/downloads Make sure you get correct version of MongoDB depending upon your windows
version. To get your windows version open command prompt and execute following command
C:\>wmic os get osarchitecture
OSArchitecture
64-bit
C:\>
32-bit versions of MongoDB only support databases smaller than 2GB and suitable only for testing and evaluation
purposes.
Now extract your downloaded file to c:\ drive or any other location. Make sure name of the extracted folder is
mongodb-win32-i386-[version] or mongodb-win32-x86_64-[version]. Here [version] is the version of MongoDB
download.
Now open command prompt and run the following command
C:\>move mongodb-win64-* mongodb
1 dir(s) moved.
C:\>
In case you have extracted the mondodb at different location, then go to that path by using command cd
FOOLDER/DIR and now run the above given process.
MongoDB requires a data folder to store its files. The default location for the MongoDB data directory is c:\data\db. So
you need to create this folder using the Command Prompt. Execute the following command sequence
C:\>md data
C:\md data\db
If you have install the MongoDB at different location, then you need to specify any alternate path for \data\db by
setting the path dbpath in mongod.exe. For the same issue following commands
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In command prompt navigate to the bin directory present into the mongodb installation folder. Suppose my installation
folder is D:\set up\mongodb
C:\Users\XYZ>d:
D:\>cd "set up"
D:\set up>cd mongodb
D:\set up\mongodb>cd bin
D:\set up\mongodb\bin>mongod.exe --dbpath "d:\set up\mongodb\data"
This will show waiting for connections message on the console output indicates that the mongod.exe process is
running successfully.
Now to run the mongodb you need to open another command prompt and issue the following command
D:\set up\mongodb\bin>mongo.exe
MongoDB shell version: 2.4.6
connecting to: test
>db.test.save( { a: 1 } )
>db.test.find()
{ "_id" : ObjectId(5879b0f65a56a454), "a" : 1 }
>
This will show that mongodb is installed and run successfully. Next time when you run mongodb you need to issue
only commands
D:\set up\mongodb\bin>mongod.exe --dbpath "d:\set up\mongodb\data"
D:\set up\mongodb\bin>mongo.exe
Install MongoDB on Ubuntu
Run the following command to import the MongoDB public GPG Key:
sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv 7F0CEB10
Create a /etc/apt/sources.list.d/mongodb.list file using the following command.
echo 'deb downloads-distro.mongodb.org/repo/ubuntu-upstart dist 10gen' | sudo tee
/etc/apt/sources.list.d/mongodb.list
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Now issue the following command to update the repository:
sudo apt-get update
Now install the MongoDB by using following command:
apt-get install mongodb-10gen=2.2.3
In the above installation 2.2.3 is currently released mongodb version. Make sure to install latest version always. Now
mongodb is installed successfully.
Start MongoDB
sudo service mongodb start
Stop MongoDB
sudo service mongodb stop
Restart MongoDB
sudo service mongodb restart
To use mongodb run the following command
mongo
This will connect you to running mongod instance.
MongoDB Help
To get list of commands type db.help() in mongodb client. This will give you list of commands as follows:
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MongoDB Statistics
To get stats about mongodb server type the command db.stats() in mongodb client. This will show the database
name, cumber of collection and documents in the database. Output the command is shown below:
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MongoDB Data Modelling
Data in MongoDB has a flexible schema.documents in the same collection do not need to have the same set of
fields or structure, and common fields in a collection’s documents may hold different types of data.
Some considerations while designing schema in MongoDB
Design your schema according to user requirements.
Combine objects into one document if you will use them together. Otherwise separate them (but make sure there
should not be need of joins).
Duplicate the data (but limited) because disk space is cheap as compare to compute time.
Do joins while write, not on read.
Optimize your schema for most frequent use cases.
Do complex aggregation in the schema
Example
Suppose a client needs a database design for his blog website and see the differences between RDBMS and
MongoDB schema design. Website has the following requirements.
Every post has the unique title, description and url.
Every post can have one or more tags.
Every post has the name of its publisher and total number of likes.
Every Post have comments given by users along with their name, message, data-time and likes.
On each post there can be zero or more comments.
In RDBMS schema design for above requirements will have minimum three tables.
While in MongoDB schema design will have one collection post and has the following structure:
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{
_id: POST_ID
title: TITLE_OF_POST,
description: POST_DESCRIPTION,
by: POST_BY,
url: URL_OF_POST,
tags: [TAG1, TAG2, TAG3],
likes: TOTAL_LIKES,
comments: [
{
user:'COMMENT_BY',
message: TEXT,
dateCreated: DATE_TIME,
like: LIKES
},
{
user:'COMMENT_BY',
message: TEXT,
dateCreated: DATE_TIME,
like: LIKES
}
]
}
So while showing the data, in RDBMS you need to join three tables and in mongodb data will be shown from
one collection only.
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MongoDB Create Database
The use Command
MongoDB use DATABASE_NAME is used to create database. The command will create a new database, if it
doesn't exist otherwise it will return the existing database.
Syntax:
Basic syntax of use DATABASE statement is as follows:
use DATABASE_NAME
Example:
If you want to create a database with name
>use mydb
switched to db mydb
To check your currently selected database use the command db
>db
mydb
If you want to check your databases list, then use the command show dbs.
>show dbs
local 0.78125GB
test 0.23012GB
Your created database (mydb) is not present in list. To display database you need to insert atleast one document into
it.
>db.movie.insert({"name":"tutorials point"})
>show dbs
local 0.78125GB
mydb 0.23012GB
test 0.23012GB
In mongodb default database is test. If you didn't create any database then collections will be stored in test database.
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MongoDB Drop Database
The dropDatabase () Method
MongoDB db.dropDatabase () command is used to drop a existing database.
Syntax:
Basic syn tax of dropDatabase () command is as follows:
db.dropDatabase()
This will delete the selected database. If you have not selected any database, then it will delete default 'test' database
Example:
First, check the list available databases by using the command show dbs
>show dbs
local 0.78125GB
mydb 0.23012GB
test 0.23012GB
>
If you want to delete new database
>use mydb
switched to db mydb
>db.dropDatabase()
>{ "dropped" : "mydb", "ok" : 1 }
>
Now check list of databases
>show dbs
local 0.78125GB
test 0.23012GB
>
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MongoDB Create Collection
The createCollection() Method
MongoDB db.createCollection(name, options) is used to create collection.
Syntax:
Basic syntax of createCollection() command is as follows
db.createCollection(name, options)
In the command, name is name of collection to be created. Options is a document and used to specify configuration
of collection
Parameter Type Description
Name String Name of the collection to be created
Options Document (Optional) Specify options about memory size and
indexing
Options parameter is optional, so you need to specify only name of the collection. Following is the list of options you
can use:
Field Type Description
capped Boolean
(Optional) If true, enables a capped collection. Capped
collection is a collection fixed size collecction that
automatically overwrites its oldest entries when it reaches
its maximum size. If you specify true, you need to
specify size parameter also.
autoIndexID Boolean (Optional) If true, automatically create index on _id field.s
Default value is false.
size number
(Optional) Specifies a maximum size in bytes for a capped
collection. If If capped is true, then you need to specify
this field also.
max number (Optional) Specifies the maximum number of documents
allowed in the capped collection.
While inserting the document, MongoDB first checks size field of capped collection, then it checks max field.
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Examples:
Basic syntax of createCollection() method without options is as follows
>use test
switched to db test
>db.createCollection("mycollection")
{ "ok" : 1 }
>
You can check the created collection by using the command show collections
>show collections
mycollection
system.indexes
Following example shows the syntax of createCollection() method with few important options:
>db.createCollection("mycol", { capped : true, autoIndexID : true, size : 6142800, max : 10000 } )
{ "ok" : 1 }
>
In mongodb you don't need to create collection. MongoDB creates collection automatically, when you insert some
document.
>db.tutorialspoint.insert({"name" : "tutorialspoint"})
>show collections
mycol
mycollection
system.indexes
tutorialspoint
>
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MongoDB Drop Collection
The drop() Method
MongoDB's db.collection.drop() is used to drop a collection from the database.
Syntax:
Basic syntax of drop() command is as follows
db.COLLECTION_NAME.drop()
Example:
First, check the available collections into your database mydb
>use mydb
switched to db mydb
>show collections
mycol
mycollection
system.indexes
tutorialspoint
>
Now drop the collection with the name mycollection
>db.mycollection.drop()
true
>
Again check the list of collections into database
>show collections
mycol
system.indexes
tutorialspoint
>
drop() method will return true, if the selected collection is dropped successfully otherwise it will return false
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MongoDB Datatypes
MongoDB supports many datatypes whose list is given below:
String : This is most commonly used datatype to store the data. String in mongodb must be UTF-8 valid.
Integer : This type is used to store a numerical value. Integer can be 32 bit or 64 bit depending upon your server.
Boolean : This type is used to store a boolean (true/ false) value.
Double : This type is used to store floating point values.
Min/ Max keys : This type is used to compare a value against the lowest and highest BSON elements.
Arrays : This type is used to store arrays or list or multiple values into one key.
Timestamp : ctimestamp. This can be handy for recording when a document has been modified or added.
Object : This datatype is used for embedded documents.
Null : This type is used to store a Null value.
Symbol : This datatype is used identically to a string however, it's generally reserved for languages that use a
specific symbol type.
Date : This datatype is used to store the current date or time in UNIX time format. You can specify your own date
time by creating object of Date and passing day, month, year into it.
Object ID : This datatype is used to store the document’s ID.
Binary data : This datatype is used to store binay data.
Code : This datatype is used to store javascript code into document.
Regular expression : This datatype is used to store regular expression
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MongoDB - Insert Document
The insert() Method
To insert data into MongoDB collection, you need to use MongoDB's insert() or save()method.
Syntax
Basic syntax of insert() command is as follows:
>db.COLLECTION_NAME.insert(document)
Example
>db.mycol.insert({
_id: ObjectId(7df78ad8902c),
title: 'MongoDB Overview',
description: 'MongoDB is no sql database',
by: 'tutorials point',
url: 'http://www.tutorialspoint.com',
tags: ['mongodb', 'database', 'NoSQL'],
likes: 100
})
Here mycol is our collection name, as created in previous tutorial. If the collection doesn't exist in the database, then
MongoDB will create this collection and then insert document into it.
In the inserted document if we don't specify the _id parameter, then MongoDB assigns an unique ObjectId for this
document.
_id is 12 bytes hexadecimal number unique for every document in a collection. 12 bytes are divided as follows:
_id: ObjectId(4 bytes timestamp, 3 bytes machine id, 2 bytes process id, 3 bytes incrementer)
To insert multiple documents in single query, you can pass an array of documents in insert() command.
Example
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>db.post.insert([
{
title: 'MongoDB Overview',
description: 'MongoDB is no sql database',
by: 'tutorials point',
url: 'http://www.tutorialspoint.com',
tags: ['mongodb', 'database', 'NoSQL'],
likes: 100
},
{
title: 'NoSQL Database',
description: 'NoSQL database doesn't have tables',
by: 'tutorials point',
url: 'http://www.tutorialspoint.com',
tags: ['mongodb', 'database', 'NoSQL'],
likes: 20,
comments: [
{
user:'user1',
message: 'My first comment',
dateCreated: new Date(2013,11,10,2,35),
like: 0
}
]
}
])
To insert the document you can use db.post.save(document) also. If you don't specify _id in the document
then save() method will work same as insert() method. If you specify _id then it will replace whole data of
document containing _id as specified in save() method.
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MongoDB - Query Document
The find() Method
To query data from MongoDB collection, you need to use MongoDB's find() method.
Syntax
Basic syntax of find() method is as follows
>db.COLLECTION_NAME.find()
find() method will display all the documents in a non structured way.
The pretty() Method
To display the results in a formatted way, you can use pretty() method.
Syntax:
>db.mycol.find().pretty()
Example
>db.mycol.find().pretty()
{
"_id": ObjectId(7df78ad8902c),
"title": "MongoDB Overview",
"description": "MongoDB is no sql database",
"by": "tutorials point",
"url": "http://www.tutorialspoint.com",
"tags": ["mongodb", "database", "NoSQL"],
"likes": "100"
} >
Apart from find() method there is findOne() method, that reruns only one document.
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RDBMS Where Clause Equivalents in MongoDB
To query the document on the basis of some condition, you can use following operations
Operation Syntax Example RDBMS
Equivalent
Equality {
rials point"}).pretty()
where by =
'tutorials point'
Less Than {
t:50}}).pretty() where likes < 50
Less Than
Equals
{
te:50}}).pretty()
where likes <=
50
Greater Than {
gt:50}}).pretty() where likes > 50
Greater Than
Equals
{
gte:50}}).pretty()
where likes >=
50
Not Equals {
ne:50}}).pretty()
where likes !=
50
AND in MongoDB
Syntax:
In the find() method if you pass multiple keys by separating them by ',' then MongoDB treats it AND condition. Basic
syntax of AND is shown below:
>db.mycol.find({key1:value1, key2:value2}).pretty()
Example
Below given example will show all the tutorials written by 'tutorials point' and whose title is 'MongoDB Overview'
>db.mycol.find({"by":"tutorials point","title": "MongoDB Overview"}).pretty()
{
"_id": ObjectId(7df78ad8902c),
"title": "MongoDB Overview",
"description": "MongoDB is no sql database",
"by": "tutorials point",
"url": "http://www.tutorialspoint.com",
"tags": ["mongodb", "database", "NoSQL"],
"likes": "100"
} >
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For the above given example equivalent where clause will be ' where by='tutorials point' AND title='MongoDB
Overview' '. You can pass any number of key, value pairs in find clause.
OR in MongoDB
Syntax:
To query documents based on the OR condition, you need to use $or keyword. Basic syntax of OR is shown below:
>db.mycol.find(
{
$or: [
{key1: value1}, {key2:value2}
]
}
).pretty()
Example
Below given example will show all the tutorials written by 'tutorials point' or whose title is 'MongoDB Overview'
>db.mycol.find({$or:[{"by":"tutorials point"},{"title": "MongoDB Overview"}]}).pretty()
{
"_id": ObjectId(7df78ad8902c),
"title": "MongoDB Overview",
"description": "MongoDB is no sql database",
"by": "tutorials point",
"url": "http://www.tutorialspoint.com",
"tags": ["mongodb", "database", "NoSQL"],
"likes": "100"
} >
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Using AND and OR together
Example
Below given example will show the documents that have likes greater than 100 and whose title is either 'MongoDB
Overview' or by is 'tutorials point'. Equivalent sql where clause is 'where likes>10 AND (by = 'tutorials point' OR title
= 'MongoDB Overview')'
>db.mycol.find("likes": {$gt:10}, $or: [{"by": "tutorials point"}, {"title": "MongoDB Overview"}] }).pretty()
{
"_id": ObjectId(7df78ad8902c),
"title": "MongoDB Overview",
"description": "MongoDB is no sql database",
"by": "tutorials point",
"url": "http://www.tutorialspoint.com",
"tags": ["mongodb", "database", "NoSQL"],
"likes": "100"
} >
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MongoDB Update Document
MongoDB's update() and save() methods are used to update document into a collection. The update() method
update values in the existing document while the save() method replaces the existing document with the document
passed in save() method.
MongoDB Update() method
The update() method updates values in the existing document.
Syntax:
Basic syntax of update() method is as follows
>db.COLLECTION_NAME.update(SELECTIOIN_CRITERIA, UPDATED_DATA)
Example
Consider the mycol collectioin has following data.
{ "_id" : ObjectId(5983548781331adf45ec5), "title":"MongoDB Overview"}
{ "_id" : ObjectId(5983548781331adf45ec6), "title":"NoSQL Overview"}
{ "_id" : ObjectId(5983548781331adf45ec7), "title":"Tutorials Point Overview"}
Following example will set the new title 'New MongoDB Tutorial' of the documents whose title is 'MongoDB Overview'
>db.mycol.update({'title':'MongoDB Overview'},{$set:{'title':'New MongoDB Tutorial'}})
>db.mycol.find()
{ "_id" : ObjectId(5983548781331adf45ec5), "title":"New MongoDB Tutorial"}
{ "_id" : ObjectId(5983548781331adf45ec6), "title":"NoSQL Overview"}
{ "_id" : ObjectId(5983548781331adf45ec7), "title":"Tutorials Point Overview"}
>
By default mongodb will update only single document, to update multiple you need to set a paramter 'multi' to true.
>db.mycol.update({'title':'MongoDB Overview'},{$set:{'title':'New MongoDB Tutorial'}},{multi:true})
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MongoDB Save() Method
The save() method replaces the existing document with the new document passed in save() method
Syntax
Basic syntax of mongodb save() method is shown below:
>db.COLLECTION_NAME.save({_id:ObjectId(),NEW_DATA})
Example
Following example will replace the document with the _id '5983548781331adf45ec7'
>db.mycol.save(
{
"_id" : ObjectId(5983548781331adf45ec7), "title":"Tutorials Point New Topic", "by":"Tutorials
Point"
}
)
>db.mycol.find()
{ "_id" : ObjectId(5983548781331adf45ec5), "title":"Tutorials Point New Topic", "by":"Tutorials
Point"}
{ "_id" : ObjectId(5983548781331adf45ec6), "title":"NoSQL Overview"}
{ "_id" : ObjectId(5983548781331adf45ec7), "title":"Tutorials Point Overview"}
>
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MongoDB Delete Document
The remove() Method
MongoDB's remove() method is used to remove document from the collection. remove() method accepts two
parameters. One is deletion criteria and second is justOne flag
1. deletion criteria : (Optional) deletion criteria according to documents will be removed.
2. justOne : (Optional) if set to true or 1, then remove only one document.
Syntax:
Basic syntax of remove() method is as follows
>db.COLLECTION_NAME.remove(DELLETION_CRITTERIA)
Example
Consider the mycol collectioin has following data.
{ "_id" : ObjectId(5983548781331adf45ec5), "title":"MongoDB Overview"}
{ "_id" : ObjectId(5983548781331adf45ec6), "title":"NoSQL Overview"}
{ "_id" : ObjectId(5983548781331adf45ec7), "title":"Tutorials Point Overview"}
Following example will remove all the documents whose title is 'MongoDB Overview'
>db.mycol.remove({'title':'MongoDB Overview'})
>db.mycol.find()
{ "_id" : ObjectId(5983548781331adf45ec6), "title":"NoSQL Overview"}
{ "_id" : ObjectId(5983548781331adf45ec7), "title":"Tutorials Point Overview"}
>
Remove only one
If there are multiple records and you want to delete only first record, then set justOne parameter in remove() method
>db.COLLECTION_NAME.remove(DELETION_CRITERIA,1)
Remove All documents
If you don't specify deletion criteria, then mongodb will delete whole documents from the collection. This is equivalent
of SQL's truncate command.
>db.mycol.remove()
>db.mycol.find()
>
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MongoDB Projection
In mongodb projection meaning is selecting only necessary data rather than selecting whole of the data of a
document. If a document has 5 fields and you need to show only 3, then select only 3 fields from them.
The find() Method
MongoDB's find() method, explained in MongoDB Query Document accepts second optional parameter that is list of
fields that you want to retrieve. In MongoDB when you execute find() method, then it displays all fields of a document.
To limit this you need to set list of fields with value 1 or 0. 1 is used to show the filed while 0 is used to hide the field.
Syntax:
Basic syntax of find() method with projection is as follows
>db.COLLECTION_NAME.find({},{KEY:1})
Example
Consider the collection myycol has the following data
{ "_id" : ObjectId(5983548781331adf45ec5), "title":"MongoDB Overview"}
{ "_id" : ObjectId(5983548781331adf45ec6), "title":"NoSQL Overview"}
{ "_id" : ObjectId(5983548781331adf45ec7), "title":"Tutorials Point Overview"}
Following example will display the title of the document while quering the document.
>db.mycol.find({},{"title":1,_id:0})
{"title":"MongoDB Overview"}
{"title":"NoSQL Overview"}
{"title":"Tutorials Point Overview"}
>
Please note _id field is always displayed while executing find() method, if you don't want this field, then you need to
set it as 0
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MongoDB Limit Records
The Limit() Method
To limit the records in MongoDB, you need to use limit() method. limit() method accepts one number type argument,
which is number of documents that you want to displayed.
Syntax:
Basic syntax of limit() method is as follows
>db.COLLECTION_NAME.find().limit(NUMBER)
Example
Consider the collection myycol has the following data
{ "_id" : ObjectId(5983548781331adf45ec5), "title":"MongoDB Overview"}
{ "_id" : ObjectId(5983548781331adf45ec6), "title":"NoSQL Overview"}
{ "_id" : ObjectId(5983548781331adf45ec7), "title":"Tutorials Point Overview"}
Following example will display only 2 documents while quering the document.
>db.mycol.find({},{"title":1,_id:0}).limit(2)
{"title":"MongoDB Overview"}
{"title":"NoSQL Overview"}
>
If you don't specify number argument in limit() method then it will display all documents from the collection.
MongoDB Skip() Method
Apart from limit() method there is one more method skip() which also accepts number type argument and used to
skip number of documents.
Syntax:
Basic syntax of skip() method is as follows
>db.COLLECTION_NAME.find().limit(NUMBER).skip(NUMBER)
Example:
Following example will only display only second document.
>db.mycol.find({},{"title":1,_id:0}).limit(1).skip(1)
{"title":"NoSQL Overview"}
>
Please note default value in skip() method is 0
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MongoDB Sort Documents
The sort() Method
To sort documents in MongoDB, you need to use sort() method. sort() method accepts a document containing list of
fields along with their sorting order. To specify sorting order 1 and -1 are used. 1 is used for ascending order while -1
is used for descending order.
Syntax:
Basic syntax of sort() method is as follows
>db.COLLECTION_NAME.find().sort({KEY:1})
Example
Consider the collection myycol has the following data
{ "_id" : ObjectId(5983548781331adf45ec5), "title":"MongoDB Overview"}
{ "_id" : ObjectId(5983548781331adf45ec6), "title":"NoSQL Overview"}
{ "_id" : ObjectId(5983548781331adf45ec7), "title":"Tutorials Point Overview"}
Following example will display the documents sorted by title in descending order.
>db.mycol.find({},{"title":1,_id:0}).sort({"title":-1})
{"title":"Tutorials Point Overview"}
{"title":"NoSQL Overview"}
{"title":"MongoDB Overview"}
>
Please note if you don't specify the sorting preference, then sort() method will display documents in ascending order.
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MongoDB Indexing
Indexes support the efficient resolution of queries. Without indexes, MongoDB must scan every document of a
collection to select those documents that match the query statement. This scan is highly inefficient and require the
mongod to process a large volume of data.
Indexes are special data structures, that store a small portion of the data set in an easy to traverse form. The index
stores the value of a specific field or set of fields, ordered by the value of the field as specified in index.
The ensureIndex() Method
To create an index you need to use ensureIndex() method of mongodb.
Syntax:
Basic syntax of ensureIndex() method is as follows()
>db.COLLECTION_NAME.ensureIndex({KEY:1})
Here key is the name of filed on which you want to create index and 1 is for ascending order. To create index in
descending order you need to use -1.
Example
>db.mycol.ensureIndex({"title":1})
>
In ensureIndex() method you can pass multiple fields, to create index on multiple fields.
>db.mycol.ensureIndex({"title":1,"description":-1})
>
ensureIndex() method also accepts list of options (which are optional), whose list is given below:
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Parameter Type Description
background Boolean
Builds the index in the background so that building an index
does not block other database activities. Specify true to build
in the background. The default value is false.
unique Boolean
Creates a unique index so that the collection will not accept
insertion of documents where the index key or keys match
an existing value in the index. Specify true to create a unique
index. The default value is false.
name string
The name of the index. If unspecified, MongoDB generates
an index name by concatenating the names of the indexed
fields and the sort order.
dropDups Boolean
Creates a unique index on a field that may have duplicates.
MongoDB indexes only the first occurrence of a key and
removes all documents from the collection that contain
subsequent occurrences of that key. Specify true to create
unique index. The default value is false.
sparse Boolean
If true, the index only references documents with the
specified field. These indexes use less space but behave
differently in some situations (particularly sorts). The default
value is false.
expireAfterSeconds integer Specifies a value, in seconds, as a TTL to control how long
MongoDB retains documents in this collection.
v
index
version
The index version number. The default index version
depends on the version of mongod running when creating
the index.
weights document
The weight is a number ranging from 1 to 99,999 and
denotes the significance of the field relative to the other
indexed fields in terms of the score.
default_language string
For a text index, the language that determines the list of stop
words and the rules for the stemmer and tokenizer. The
default value is english.
language_override string
For a text index, specify the name of the field in the
document that contains, the language to override the default
language. The default value is language.
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MongoDB Aggregation
Aggregations operations process data records and return computed results. Aggregation operations group
values from multiple documents together, and can perform a variety of operations on the grouped data to return a
single result. In sql count(*) and with group by is an equivalent of mongodb aggregation.
The aggregate() Method
For the aggregation in mongodb you should use aggregate() method.
Syntax:
Basic syntax of aggregate() method is as follows
>db.COLLECTION_NAME.aggregate(AGGREGATE_OPERATION)
Example:
In the collection you have the following data:
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{
_id: ObjectId(7df78ad8902c)
title: 'MongoDB Overview',
description: 'MongoDB is no sql database',
by_user: 'tutorials point',
url: 'http://www.tutorialspoint.com',
tags: ['mongodb', 'database', 'NoSQL'],
likes: 100
},
{
_id: ObjectId(7df78ad8902d)
title: 'NoSQL Overview',
description: 'No sql database is very fast',
by_user: 'tutorials point',
url: 'http://www.tutorialspoint.com',
tags: ['mongodb', 'database', 'NoSQL'],
likes: 10
},
{
_id: ObjectId(7df78ad8902e)
title: 'Neo4j Overview',
description: 'Neo4j is no sql database',
by_user: 'Neo4j',
url: 'http://www.neo4j.com',
tags: ['neo4j', 'database', 'NoSQL'],
likes: 750
},
Now from the above collection if you want to display a list that how many tutorials are written by each user then you
will use aggregate() method as shown below:
> db.mycol.aggregate([{$group : {_id : "$by_user", num_tutorial : {$sum : 1}}}])
{
"result" : [
{
"_id" : "tutorials point",
"num_tutorial" : 2
},
{
"_id" : "tutorials point",
"num_tutorial" : 1
}
],
"ok" : 1
} >
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Sql equivalent query for the above use case will be select by_user, count(*) from mycol group by by_user
In the above example we have grouped documents by field by_user and on each occurance of by_user previous
value of sum is incremented. There is a list available aggregation expressions .
Expression Description Example
$sum Sums up the defined value from all documents in the
collection.
db.mycol.aggregate([{$group : {_id
: "$by_user", num_tutorial : {$sum :
"$likes"}}}])
$avg Calculates the average of all given values from all
documents in the collection.
db.mycol.aggregate([{$group : {_id
: "$by_user", num_tutorial : {$avg :
"$likes"}}}])
$min Gets the minimum of the corresponding values from all
documents in the collection.
db.mycol.aggregate([{$group : {_id
: "$by_user", num_tutorial : {$min :
"$likes"}}}])
$max Gets the maximum of the corresponding values from all
documents in the collection.
db.mycol.aggregate([{$group : {_id
: "$by_user", num_tutorial : {$max :
"$likes"}}}])
$push Inserts the value to an array in the resulting document. db.mycol.aggregate([{$group : {_id
: "$by_user", url : {$push: "$url"}}}])
$addToSet Inserts the value to an array in the resulting document
but does not create duplicates.
db.mycol.aggregate([{$group : {_id
: "$by_user", url : {$addToSet :
"$url"}}}])
$first
Gets the first document from the source documents
according to the grouping. Typically this makes only
sense together with some previously applied “$sort”-
stage.
db.mycol.aggregate([{$group : {_id
: "$by_user", first_url : {$first :
"$url"}}}])
$last
Gets the last document from the source documents
according to the grouping. Typically this makes only
sense together with some previously applied “$sort”-
stage.
db.mycol.aggregate([{$group : {_id
: "$by_user", last_url : {$last :
"$url"}}}])
Pipeline Concept
In UNIX command shell pipeline means the possibility to execute an operation on some input and use the output as
the input for the next command and so on. MongoDB also support same concept in aggregation framework. There is
a set of possible stages and each of those is taken a set of documents as an input and is producing a resulting set of
documents (or the final resulting JSON document at the end of the pipeline). This can then in turn again be used for
the next stage an so on.
Possible stages in aggregation framework are following:
$project: Used to select some specific fields from a collection.
$match: This is a filtering operation and thus this can reduce the amount of documents that are given as input to
the next stage.
$group: This does the actual aggregation as discussed above.
$sort: Sorts the documents.
$skip: With this it is possible to skip forward in the list of documents for a given amount of documents.
$limit: This limits the amount of documents to look at by the given number starting from the current position.s
$unwind: This is used to unwind document that are using arrays. when using an array the data is kind of prejoinded and this operation will be undone with this to have individual documents again. Thus with this stage we
will increase the amount of documents for the next stage.
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MongoDB Replication
Replication is the process of synchronizing data across multiple servers. Replication provides redundancy and
increases data availability with multiple copies of data on different database servers, replication protects a database
from the loss of a single server. Replication also allows you to recover from hardware failure and service interruptions.
With additional copies of the data, you can dedicate one to disaster recovery, reporting, or backup.
Why Replication?
To keep your data safe
High (24*7) availability of data
Disaster Recovery
No downtime for maintenance (like backups, index rebuilds, compaction)
Read scaling (extra copies to read from)
Replica set is transparent to the application
How replication works in MongoDB
MongoDB achieves replication by the use of replica set. A replica set is a group of mongod instances that host the
same data set. In a replica one node is primary node that receives all write operations. All other instances,
secondaries, apply operations from the primary so that they have the same data set. Replica set can have only one
primary node.
1. Replica set is a group of two or more nodes (generally minimum 3 nodes are required).
2. In a replica set one node is primary node and remaining nodes are secondary.
3. All data replicates from primary to secondary node.
4. At the time of automatic failover or maintenance, election establishes for primary and a new primary node is
elected.
5. After the recovery of failed node, it again join the replica set and works as a secondary node.
A typical diagram of mongodb replication is shown in which client application always interact with primary node and
primary node then replicate the data to the secondary nodes.
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Replica set features
A cluster of N nodess
Anyone node can be primary
All write operations goes to primary
Automatic failover
Automatic Recovery
Consensus election of primary
Set up a replica set
In this tutorial we will convert standalone mongod instance to a replica set. To convert to replica set follow the below
given steps:
Shutdown already running mongodb server.
Now start the mongodb server by specifying --replSet option. Basic syntax of --replSet is given below:
mongod --port "PORT" --dbpath "YOUR_DB_DATA_PATH" --replSet "REPLICA_SET_INSTANCE_NAME"
Example
mongod --port 27017 --dbpath "D:\set up\mongodb\data" --replSet rs0
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It will start a mongod instance with the name rs0, on port 27017. Now start the command prompt and connect to this
mongod instance. In mongo client issue the command rs.initiate() to initiate a new replica set. To check the replica
set configuration issue the command rs.conf(). To check the status of replica sete issue the command rs.status().
Add members to replica set
To add members to replica set, start mongod instances on multiple machines. Now start a mongo client and issue a
command rs.add().
Synttax:
Basic syntax of rs.add() command is as follows:
>rs.add(HOST_NAME:PORT)
Example
Suppose your mongod instance name is mongod1.net and it is running on port 27017. To add this instance to replica
set issue the command rs.add() in mongo client.
>rs.add("mongod1.net:27017")
>
You can add mongod instance to replica set only when you are connected to primary node. To check whether
you are connected to primary or not issue the command db.isMaster() in mongo client.
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MongoDB Sharding
Sharding
Sharding is the process of storing data records across multiple machines and it is MongoDB's approach to meeting
the demands of data growth. As the size of the data increases, a single machine may not be sufficient to store the
data nor provide an acceptable read and write throughput. Sharding solves the problem with horizontal scaling. With
sharding, you add more machines to support data growth and the demands of read and write operations.
Why Sharding?
In replication all writes go to master node
Latency sensitive queries still go to master
Single replica set has limitation of 12 nodes
Memory can't be large enough when active dataset is big
Local Disk is not big enough
Vertical scaling is too expensive
Sharding in MongoDB
Below given diagram shows the sharding in MongoDB using sharded cluster.
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In the above given diagram there are three main components which are described below:
Shards: Shards are used to store data. They provide high availability and data consistency. In production
environment each shard is a separate replica set.
Config Servers: Config servers store the cluster's metadata. This data contains a mapping of the cluster's data
set to the shards. The query router uses this metadata to target operations to specific shards. In production
environment sharded clusters have exactly 3 config servers.
Query Routers: Query Routers are basically mongos instances, interface with client applications and direct
operations to the appropriate shard. The query router processes and targets operations to shards and then
returns results to the clients. A sharded cluster can contain more than one query router to divide the client request
load. A client sends requests to one query router. Generally a sharded cluster have many query routers.
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MongoDB Create Backup
Dump MongoDB Data
To create backup of database in mongodb you should use mongodump command. This command will dump all data
of your server into dump directory. There are many options available by which you can limit the amount of data or
create backup of your remote server.
Syntax:
Basic syntax of mongodump command is as follows
>mongodump
Example
Start your mongod server. Assuming that your mongod server is running on localhost and port 27017. Now open a
command prompt and go to bin directory of your mongodb instance and type the command mongodump
Consider the mycol collectioin has following data.
>mongodump
The command will connect to the server running at 127.0.0.1 and port 27017 and back all data of the server to
directory /bin/dump/. Output of the command is shown below:
There are a list of available options that can be used with the mongodump command.
This command will backup only specified database at specified path
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Syntax Description Example
mongodump --host HOST_NAME –port
PORT_NUMBER
This commmand will
backup all databases of
specified mongod instance.
mongodump --host
tutorialspoint.com –
port 27017
mongodump --dbpath DB_PATH --out
BACKUP_DIRECTORY
mongodump --dbpath
/data/db/ --out
/data/backup/
mongodump --collection COLLECTION
--db DB_NAME
This command will backup
only specified collection of
specified database.
mongodump --collection
mycol --db test
Restore data
To restore backup data mongodb's mongorerstore command is used. This command restore all of the data from the
back up directory.
Syntax
Basic syntax of mongorestore command is
>mongorestore
Output of the command is shown below:
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MongoDB Deployment
When you are preparing a MongoDB deployment, you should try to understand how your application is going
to hold up in production. It’s a good idea to develop a consistent, repeatable approach to managing your deployment
environment so that you can minimize any surprises once you’re in production.
The best approach incorporates prototyping your set up, conducting load testing, monitoring key metrics, and using
that information to scale your set up. The key part of the approach is to proactively monitor your entire system - this
will help you understand how your production system will hold up before deploying, and determine where you will
need to add capacity. Having insight into potential spikes in your memory usage, for example, could help put out a
write-lock fire before it starts.
To monitor your deployment MongoDB provides some commands that are shown below:
mongostat
This command checks the status of all running mongod instances and return counters of database operations. These
counters include inserts, queries, updates, deletes, and cursors. Command also shows when you’re hitting page
faults, and showcase your lock percentage. This means that you're running low on memory, hitting write capacity or
have some performance issue.
To run the command start your mongod instance. In another command prompt go to bin directory of your mongodb
installation and type mongostat.
D:\set up\mongodb\bin>mongostat
Output of the command is shown below:
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mongotop
This command track and report the read and write activity of MongoDB instance on a collection basis. By default
mongotop returns information in each second, by you can change it accordingly. You should check that this read
and write activity matches your application intention, and you’re not firing too many writes to the database at a time,
reading too frequently from disk, or are exceeding your working set size.
To run the command start your mongod instance. In another command prompt go to bin directory of your mongodb
installation and type mongotop.
D:\set up\mongodb\bin>mongotop
Output of the command is shown below:
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To change mongotop command to return information less frequently specify a specific number after the mongotop
command.
D:\set up\mongodb\bin>mongotop 30
The above example will return values every 30 seconds.
Apart from the mongodb tools, 10gen provides a free, hosted monitoring service MongoDB Management Service
(MMS), that provides a dashboard and gives you a view of the metrics from your entire cluster.
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MongoDB Java
Installation
Before we start using MongoDB in our Java programs, we need to make sure that we have MongoDB JDBC Driver
and Java set up on the machine. You can check Java tutorial for Java installation on your machine. Now, let us check
how to set up MongoDB JDBC driver.
You need to download the jar from the path Download mongo.jar. Make sure to download latest release of it.
You need to include the mongo.jar into your classpath.
Connect to database
To connect database, you need to specify database name, if database doesn't exist then mongodb creates it
automatically.
Code snippets to connect to database would be as follows:
import com.mongodb.MongoClient;
import com.mongodb.MongoException;
import com.mongodb.WriteConcern;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import com.mongodb.DBCursor;
import com.mongodb.ServerAddress;
import java.util.Arrays;
public class MongoDBJDBC{
public static void main( String args[] ){
try{
// To connect to mongodb server
MongoClient mongoClient = new MongoClient( "localhost" , 27017 );
// Now connect to your databases
DB db = mongoClient.getDB( "test" );
System.out.println("Connect to database successfully");
boolean auth = db.authenticate(myUserName, myPassword);
System.out.println("Authentication: "+auth);
}catch(Exception e){
System.err.println( e.getClass().getName() + ": " + e.getMessage() );
}
}
}
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Now, let's compile and run above program to create our database test. You can change your path as per your
requirement. We are assuming current version of JDBC driver mongo-2.10.1.jar is available in the current path
$javac MongoDBJDBC.java
$java -classpath ".:mongo-2.10.1.jar" MongoDBJDBC
Connect to database successfully
Authentication: true
If you are going to use Windows machine, then you can compile and run your code as follows:
$javac MongoDBJDBC.java
$java -classpath ".;mongo-2.10.1.jar" MongoDBJDBC
Connect to database successfully
Authentication: true
Value of auth will be true, if the user name and password are valid for the selected database.
Create a collection
To create a collection, createCollection() method of com.mongodb.DB class is used.
Code snippets to create a collection:
import com.mongodb.MongoClient;
import com.mongodb.MongoException;
import com.mongodb.WriteConcern;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import com.mongodb.DBCursor;
import com.mongodb.ServerAddress;
import java.util.Arrays;
public class MongoDBJDBC{
public static void main( String args[] ){
try{
// To connect to mongodb server
MongoClient mongoClient = new MongoClient( "localhost" , 27017 );
// Now connect to your databases
DB db = mongoClient.getDB( "test" );
System.out.println("Connect to database successfully");
boolean auth = db.authenticate(myUserName, myPassword);
System.out.println("Authentication: "+auth);
DBCollection coll = db.createCollection("mycol");
System.out.println("Collection created successfully");
}catch(Exception e){
System.err.println( e.getClass().getName() + ": " + e.getMessage() );
}
}
}
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When program is compiled and executed, it will produce the following result::
Connect to database successfully
Authentication: true
Collection created successfully
Getting/ selecting a collection
To get/select a collection from the database, getCollection() method of com.mongodb.DBCollection class is used.
Code snippets to get/select a collection:
import com.mongodb.MongoClient;
import com.mongodb.MongoException;
import com.mongodb.WriteConcern;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import com.mongodb.DBCursor;
import com.mongodb.ServerAddress;
import java.util.Arrays;
public class MongoDBJDBC{
public static void main( String args[] ){
try{
// To connect to mongodb server
MongoClient mongoClient = new MongoClient( "localhost" , 27017 );
// Now connect to your databases
DB db = mongoClient.getDB( "test" );
System.out.println("Connect to database successfully");
boolean auth = db.authenticate(myUserName, myPassword);
System.out.println("Authentication: "+auth);
DBCollection coll = db.createCollection("mycol");
System.out.println("Collection created successfully");
DBCollection coll = db.getCollection("mycol");
System.out.println("Collection mycol selected successfully");
}catch(Exception e){
System.err.println( e.getClass().getName() + ": " + e.getMessage() );
}
}
}
TUTORIALS POINT
Simply Easy Learning Page 51
When program is compiled and executed, it will produce the following result::
Connect to database successfully
Authentication: true
Collection created successfully
Collection mycol selected successfully
Insert a document
To insert a document into mongodb, insert() method of com.mongodb.DBCollection class is used.
Code snippets to insert a documents :
import com.mongodb.MongoClient;
import com.mongodb.MongoException;
import com.mongodb.WriteConcern;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObject;
import com.mongodb.DBCursor;
import com.mongodb.ServerAddress;
import java.util.Arrays;
public class MongoDBJDBC{
public static void main( String args[] ){
try{
// To connect to mongodb server
MongoClient mongoClient = new MongoClient( "localhost" , 27017 );
// Now connect to your databases
DB db = mongoClient.getDB( "test" );
System.out.println("Connect to database successfully");
boolean auth = db.authenticate(myUserName, myPassword);
System.out.println("Authentication: "+auth);
DBCollection coll = db.getCollection("mycol");
System.out.println("Collection mycol selected successfully");
BasicDBObject doc = new BasicDBObject("title", "MongoDB").
append("description", "database").
append("likes", 100).
append("url", "http://www.tutorialspoint.com/mongodb/").
append("by", "tutorials point");
coll.insert(doc);
System.out.println("Document inserted successfully");
}catch(Exception e){
System.err.println( e.getClass().getName() + ": " + e.getMessage() );
}
}
}
When program is compiled and executed, it will produce the following result: :
TUTORIALS POINT
Simply Easy Learning Page 52
Connect to database successfully
Authentication: true
Collection mycol selected successfully
Document inserted successfully
Retrieve all documents
To select all documents from the collection, find() method of com.mongodb.DBCollection class is used. This
method returns a cursor, so you need to iterate this cursor.
Code snippets to select all documents:
import com.mongodb.MongoClient;
import com.mongodb.MongoException;
import com.mongodb.WriteConcern;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.BasicDBObject;
import com.mongodb.DBObj
