Skip to main content

GridFS in MongoDB

GridFS

GridFS is responsible for storing and retrieving files, GridFS store file in single document and divides a file into parts, or chunks and stores each or those chunks as a separates document. By default chunk size limit is 255k. GridFS uses two collections to store files, one collection stores the file chunks and other stores file metadata.   
  
Driver or client can reassemble the chunks as needed when you query a GridFS store for a file. We can execute range queries on files stored during GridFS. We can also access information from arbitrary sections of files, which allows you to “skip” into the middle of a video or audio file.

Note:  GridFS retrieving files that exceed the BSON-document size limit of 16MB.

GridFS Collections

GridFS stores files in two collections:

1.       chunks stores the binary chunks.
2.       files stores the file’s metadata. 

GridFS places the collections in a common bucket by prefixing each with the bucket name. By default, GridFS uses two collections with names prefixed by fs bucket:

1.       fs.files
2.       fs.chunks

Note: We can choose a different bucket name than fs, and create multiple buckets in a single database.

Each document in the chunks collection represents a distinct chunk of a file as represented in the GridFS store. Each chunk is identified by its unique ObjectId stored in its _id field.

Popular posts from this blog

Add day to ISODate in MongoDB

We can use $add operator to add days in ISODate in mongodb, $add is the Arithmetic Aggregation Operator which adds number and date in mongodb.
Syntax:

{ $add: [ <expression1>, <expression2>, ... ] }

Note:  If one of the argument is date $add operator treats to other arguments as milliseconds to add to the date.
Example: Suppose we have a Test collection as below.

{"Title" : "Add day to ISODate in MongoBD","CreatedDate" : ISODate("2016-07-07T08:00:00.000Z")}

Query to add 2 days in CreatedDate

db.Test.aggregate([      { $project: { Title: 1, AddedDate: { $add: [ "$CreatedDate", 2*24*60*60000 ] } } }    ])

Result:

{ "_id" : ObjectId("579a1567ac1b3f3732483de0"), "Title" : "Add day to ISODate in MongoBD", "AddedDate" : ISODate("2016-07-09T08:00:00.000Z") }

Note: As mentioned in above note we have to convert days in millisecond because $add operator treat to other arg…

Remove special character from string in MongoDB

Problem: Suppose wehave a collection and one field is type string contains some special character (like !@#$%) and we don’t want these special character.
Solution: We can easily remove the special character from field using script “replace(/[^a-zA-Z 0-9 ]/g, '')” in our query.  How can we remove special character from string using this script please see following example.
Example: Suppose we have a collection “EduSurvey “where we are collecting information from institutions.

{Name:"JB institute”, About:"This is good one collage for MBA", Information:"This $%%institute ##has good faculty etc$$"}
{Name:"MK institute”, About:"This is good one collage for MCA", Information:"This$$%# is the dummy text12"}
{Name:"MG institute”, About:"This is good one collage for B,Tech", Information:"This# institute@ has&* good infrastructure"}

Did you notice Information fields contains some special character so we…