FileStorage

To avoid too memoy consume, LiteDB has a limit document size in 1Mb. To text documents, this is a huge size. But for store files, 1Mb is too small. So, LiteDB implements FileStorage, a custom colleciton to store files and streams.

LiteDB use 2 special collections to split files in 1Mb each chunck.

_files collection store file reference and metadata only

{
    _id: "my-photo",
    filename: "my-photo.jpg",
    mimeType: "image/jpg",
    length: { $numberLong: "2340000" },
    uploadDate: { $date: "2015-01-01T00:00:00Z" },
    metadata: { key: "value" }
}

_chunks collection stores binary data in 1MB each chunck.

{
    _id: "my-photo\00001",
    data: { $binary: "VHlwZSAob3Igc ... GUpIGhlcmUuLi4" }
}
{
    _id: "my-photo\00002",
    data: { $binary: "pGaGhlcmUuLi4 ... VHlwZSAob3Igc" }
}
...

How use FileStorage

Each file in FileStorage are identified by an _id. This _id must be a string value, with folling rules:

• Starts with a letter, number, _, -, $, @, !, +, %, ; or .
• If contains a /, must be sequence with chars above

To better organize many files, you can use _id as a directory/file_id. This will be a great solution to quick find all files in a directory using Find method.

$/photos/2014/picture-01.jpg

FileStorage API

To access files, FileStorage collection contains simple methods like:

• Upload: Send file or stream to database. Can be used with file or Stream
• SetMetadata: Update a stored file metadata. This method doesn't change data bytes, affect only _files.metadata
• Download: Get your file from database.
• Delete: Delete a file reference and data chunks
• Find: Find one or many files in _files collection. Returns LiteFileInfo class, that can be download data after.

// Upload a file from file system
db.FileStorage.Upload("$/photos/2014/picture-01.jpg", @"C:\Temp\picture-01.jpg");

// Upload a file from a Stream
db.FileStorage.Upload("$/photos/2014/picture-01.jpg", strem);

// Find file reference only (no binary data yet) - returns null if not found
var file = db.FileStoage.FindById("$/photos/2014/picture-01.jpg");

// Now, load data and save to file system
file.SaveAs(@"C:\Temp\new-picture.jpg");

// Or get data as Stream and copy to another Stream
using(var stream = file.OpenRead())
{
    stream.CopyTo(Response.OutputStream);
}

// Find all files references in a "directory"
var files = db.FileStoage.Find("$/photos/2014/");