Mongo Db Overview

Front 1

Features

Back 1

1.Document based Db

2.BSON

3.High Performance and Scalability(esp.horizontal Scaling via sharding)

4.DbServer->Databases->Collections->Documents

5.Stored in files.

6.No joins or Transactions.

7.Indexing

Front 2

Database

Back 2

1.Has its own set of files.

2.Equivalent to database in sql.

Front 3

Collection

Back 3

1.Equivalent to table in sql

2.Contains multiple documents.

3.Schemaless - documents do not need to have same keys(columns), datatype of key in one document need not be the same as in another document etc.

Front 4

Document

Back 4

1.JSON format

2.Stored as BSON- has more datatypes compared to json

3.Must not exceed 16MB.

Front 5

_id

Back 5

1.Primary Key.

2.Unique Identifier.

3.Required

4.Immutable - cannot be changed.

5.If user does not provide _d while inserting a document, an ObjectID will be automatically created and inserted as _id by mongo db.

Front 6

ObjectId

Back 6

1.12 bytes hexadecimal number

2.4 bytes for the current timestamp(representing the seconds since the Unix epoch), next 3 bytes for machine id, next 2 bytes for process id of MongoDB server and remaining 3 bytes are simple incremental VALUE.

Front 7

No Joins

Back 7

Embedding documents should help in most cases

Front 8

No Transactions

Back 8

Operations at document level are atomic.

Embedded documents help upto some extent.

If not iImplement Transaction Logic in Code

Front 9

Horizontal Scaling

Back 9

Distributing data across multiple servers

Front 10

Vertical Scaling

Back 10

Increasing the server configuration -processing power, RAM etc.

Front 11

mongod.exe --dbpath "d:\set up\mongodb\data" --logpath "d:\set up\mongodb\log"

Back 11

mongod server installation

Front 12

mongo

Back 12

1.mongodb client- mongo shell.

2.uses javascript.

Front 13

db.help()

Front 14

db.stats()

Back 14

{

"db" : "test",

"collections" : 15,

"objects" : 730,

"avgObjSize" : 108.05479452054794,

"dataSize" : 78880,

"storageSize" : 282624,

"numExtents" : 17,

"indexes" : 14,

"indexSize" : 138992,

"fileSize" : 67108864,

"nsSizeMB" : 16,

"extentFreeList" : { "num" : 0, "totalSize" : 0 }, "dataFileVersion" : { "major" : 4, "minor" : 22 }, "ok" : 1

}

Front 15

ObjectId.getTimestamp()

Back 15

Returns the timestamp portion of the object as a Date.

Front 16

x = ObjectId()

Back 16

In this example, the value of x would be:ObjectId("507f1f77bcf86cd799439011")