Mongodb_gridfs_ Storing files

Gridfs

MongoDB can save files in addition to saving various documents (JOSN structure). The GRIDFS specification provides a transparent mechanism for splitting a large file into smaller documents, which allows us to effectively save large file objects, especially for huge files such as video, high-definition images, and more.

Gridfs uses two tables to store data:

• Files: Containing metadata objects

The metadata for the file is placed inside this collection, and the default fs.files. Each of these documents represents a file in Gridfs, and the custom metadata associated with the file is also stored in it, in addition to the user-defined key, GRIDFS has some default keys:

1. _ID: The file's unique ID, stored in the block for the value of "files_id" key
2. Length: The total number of bytes in the file contents
3. Chunksize: The size of each block, in bytes. Default 25K, can be adjusted
4. Uploaddate: The time the file was deposited
5. MD5: MD5 checksum of file contents, generated by the server

• Chunks: binary block with some other relevant information

The GRIDFS block has a separate collection. By default, blocks will use the Fs.chunks collection and can be overwritten if necessary. The structure of the document in this block collection is very simple:

1 {  2 "_id": ObjectId ("..."  ),3 "n": 0,  4 "Data" : Bindata ("..."  ),5 "files_id": ObjectId ("...")  6 }  

1. _ID: Logo Unique
2. N: Indicates the number of the block, which is the ordinal number of the block in the original file.
3. Data: Contains binary data that makes up a block of files
4. files_id: "_id" of the file document containing this block metadata

Use Mongofile to manipulate Gridfs:

1   //write "AAAA" to the Foo.txt file2C:\mongodb\mongodb_win32_x86_64_2.2.7\bin>echo "AAAA" >foo.txt3  //save Foo.txt to Gridfs4C:\mongodb\mongodb_win32_x86_64_2.2.7\bin>Mongofiles.exe put Foo.txt5Connected to:127.0.0.16Added file: {_id:objectid (' 53449f0becdebde54ff76105 '), FileName: "Foo.txt", ch7unksize:262144, Uploaddate:NewDate (1397006091696), MD5: "819596956779801cced48fb21379bf023 ", Length:9 }  9done!Ten //View OneC:\mongodb\mongodb_win32_x86_64_2.2.7\bin>Mongofiles.exe List AConnected to:127.0.0.1 -Foo.txt 9 - //Get theC:\mongodb\mongodb_win32_x86_64_2.2.7\bin>Mongofiles.exe Get Foo.txt -Connected to:127.0.0.1 -Done Write To:foo.txt

Command description

Put: Add a file from the file system to the Gridfs

List: Lists all the files added to the Gridfs

Reverse operation of the Get:put

View Gridfs in the MongoDB tool

Mongodb_gridfs_ Storing files