cursor = db.fs.chunks.find({files_id: myFileID}).sort({n:1});

db.fs.chunks.ensureIndex( { files_id: 1, n: 1 }, { unique: true } );

// returns default GridFS bucket (i.e. "fs" collection)
GridFS myFS = new GridFS(myDatabase);

// saves the file to "fs" GridFS bucket
myFS.createFile(new File("/tmp/largething.mpg"));

// returns GridFS bucket named "contracts"
GridFS myContracts = new GridFS(myDatabase, "contracts");

// retrieve GridFS object "smithco"
GridFSDBFile file = myContracts.findOne("smithco");

// saves the GridFS file to the file system
file.writeTo(new File("/tmp/smithco.pdf"));

출처 - http://docs.mongodb.org/manual/core/gridfs/

When should I use GridFS?

For documents in a MongoDB collection, you should always use GridFS for storing files larger than 16 MB.

In some situations, storing large files may be more efficient in a MongoDB database than on a system-level filesystem.

• If your filesystem limits the number of files in a directory, you can use GridFS to store as many files as needed.
• When you want to keep your files and metadata automatically synced and deployed across a number of systems and facilities. When usinggeographically distributed replica sets MongoDB can distribute files and their metadata automatically to a number of mongod instances and facilities.
• When you want to access information from portions of large files without having to load whole files into memory, you can use GridFS to recall sections of files without reading the entire file into memory.

Do not use GridFS if you need to update the content of the entire file atomically. As an alternative you can store multiple versions of each file and specify the current version of the file in the metadata. You can update the metadata field that indicates “latest” status in an atomic update after uploading the new version of the file, and later remove previous versions if needed.

Furthermore, if your files are all smaller the 16 MB BSON Document Size limit, consider storing the file manually within a single document. You may use the BinData data type to store the binary data. See your drivers documentation for details on using BinData.

For more information on GridFS, see GridFS.

출처 - http://docs.mongodb.org/manual/faq/developers/#faq-developers-when-to-use-gridfs

Data Type Fidelity

JSON does not have the following data types that exist in BSON documents: data_binary, data_date, data_timestamp, data_regex,data_oid and data_ref. As a result using any tool that decodes BSON documents into JSON will suffer some loss of fidelity.

If maintaining type fidelity is important, consider writing a data import and export system that does not force BSON documents into JSON form as part of the process. The following list of types contain examples for how MongoDB will represent how BSON documents render in JSON.

• data_binary

  { "$binary" : "<bindata>", "$type" : "<t>" }
  

  <bindata> is the base64 representation of a binary string. <t> is the hexadecimal representation of a single byte indicating the data type.

• data_date

  Date( <date> )
  

  <date> is the JSON representation of a 64-bit signed integer for milliseconds since epoch.

• data_timestamp

  Timestamp( <t>, <i> )
  

  <t> is the JSON representation of a 32-bit unsigned integer for milliseconds since epoch. <i> is a 32-bit unsigned integer for the increment.

• data_regex

  /<jRegex>/<jOptions>
  

  <jRegex> is a string that may contain valid JSON characters and unescaped double quote (i.e. ") characters, but may not contain unescaped forward slash (i.e. /) characters. <jOptions> is a string that may contain only the characters g, i, m, and s.

• data_oid

  ObjectId( "<id>" )
  

  <id> is a 24 character hexadecimal string. These representations require that data_oid values have an associated field named “_id.”

• data_ref

  DBRef( "<name>", "<id>" )
  

  <name> is a string of valid JSON characters. <id> is a 24 character hexadecimal string.

출처 - http://docs.mongodb.org/manual/core/import-export/#bson-json-type-conversion-fidelity

Should I use GridFS or binary data to store & retrieve images from MongoDB?

6down votefavorite 1	I was wondering which is better/faster: Having a separate collection of documents that just contain the image saved as binary data, and possibly some metadata. Or using GridFS to store the images. mongodb gridfs share|improve this question asked Oct 18 '11 at 11:45 maartencls 984513

출처 - http://stackoverflow.com/questions/7806674/should-i-use-gridfs-or-binary-data-to-store-retrieve-images-from-mongodb

BSON [bee · sahn], short for Bin­ary JSON, is a bin­ary-en­coded seri­al­iz­a­tion of JSON-like doc­u­ments. Like JSON, BSON sup­ports the em­bed­ding of doc­u­ments and ar­rays with­in oth­er doc­u­ments and ar­rays. BSON also con­tains ex­ten­sions that al­low rep­res­ent­a­tion of data types that are not part of the JSON spec. For ex­ample, BSON has a Date type and a BinData type.

출처 - http://bsonspec.org/

See also

The Data Type Fidelity section.

출처 - http://docs.mongodb.org/manual/reference/glossary/