GridFS - The Definitive Guide to MongoDB - page 86

> db.fs.files.find()
{ "_id" : ObjectId("51cb61b26487b3d8ce7af440"), "filename" : "/tmp/dictionary",
"chunkSize" : 262144, "uploadDate" : ISODate("2013-06-26T21:48:34.621Z"), "md5" :
"40c0825855792bd20e8a2d515fe9c3e3", "length" : 4953699 }
>

The output should look familiar—after all, it's the same data that you saw earlier in this chapter. Now you can see
that the information printed by mongofiles was taken from the file's entry in the fs.files collection.
Next, let's take a look at the chunks collection (we have to add a filter; otherwise, it will show us all of the raw
binary data as well):

$ mongo test
MongoDB shell version: 2.5.1-pre
connecting to: test
> db.fs.chunks.find({},{"data":0});
{ "_id" : ObjectId("51cb61b29b2daad9857ca205"), "files_id" : ObjectId("51cb61b26487b3d8ce7af440"), "n" : 4 }
{ "_id" : ObjectId("51cb61b29b2daad9857ca206"), "files_id" : ObjectId("51cb61b26487b3d8ce7af440"), "n" : 5 }
{ "_id" : ObjectId("51cb61b29b2daad9857ca207"), "files_id" : ObjectId("51cb61b26487b3d8ce7af440"), "n" : 6 }
{ "_id" : ObjectId("51cb61b29b2daad9857ca208"), "files_id" : ObjectId("51cb61b26487b3d8ce7af440"), "n" : 7 }
{ "_id" : ObjectId("51cb61b29b2daad9857ca209"), "files_id" : ObjectId("51cb61b26487b3d8ce7af440"), "n" : 8 }
{ "_id" : ObjectId("51cb61b29b2daad9857ca20a"), "files_id" : ObjectId("51cb61b26487b3d8ce7af440"), "n" : 9 }
{ "_id" : ObjectId("51cb61b29b2daad9857ca20b"), "files_id" : ObjectId("51cb61b26487b3d8ce7af440"), "n" : 10 }
{ "_id" : ObjectId("51cb61b29b2daad9857ca20c"), "files_id" : ObjectId("51cb61b26487b3d8ce7af440"), "n" : 11 }
{ "_id" : ObjectId("51cb61b29b2daad9857ca20d"), "files_id" : ObjectId("51cb61b26487b3d8ce7af440"), "n" : 12 }
{ "_id" : ObjectId("51cb61b29b2daad9857ca20e"), "files_id" : ObjectId("51cb61b26487b3d8ce7af440"), "n" : 13 }
{ "_id" : ObjectId("51cb61b29b2daad9857ca20f"), "files_id" : ObjectId("51cb61b26487b3d8ce7af440"), "n" : 14 }
{ "_id" : ObjectId("51cb61b29b2daad9857ca210"), "files_id" : ObjectId("51cb61b26487b3d8ce7af440"), "n" : 15 }
{ "_id" : ObjectId("51cb61b29b2daad9857ca211"), "files_id" : ObjectId("51cb61b26487b3d8ce7af440"), "n" : 16 }
{ "_id" : ObjectId("51cb61b29b2daad9857ca212"), "files_id" : ObjectId("51cb61b26487b3d8ce7af440"), "n" : 17 }
{ "_id" : ObjectId("51cb61b29b2daad9857ca201"), "files_id" : ObjectId("51cb61b26487b3d8ce7af440"), "n" : 0 }
{ "_id" : ObjectId("51cb61b29b2daad9857ca202"), "files_id" : ObjectId("51cb61b26487b3d8ce7af440"), "n" : 1 }
{ "_id" : ObjectId("51cb61b29b2daad9857ca203"), "files_id" : ObjectId("51cb61b26487b3d8ce7af440"), "n" : 2 }
{ "_id" : ObjectId("51cb61b29b2daad9857ca204"), "files_id" : ObjectId("51cb61b26487b3d8ce7af440"), "n" : 3 }
{ "_id" : ObjectId("51cb61b29b2daad9857ca213"), "files_id" : ObjectId("51cb61b26487b3d8ce7af440"), "n" : 18 }>

You might wonder why the output here has so many entries. As noted previously, GridFS is just a specification.
That is, it uses what MongoDB already provides. While we were testing the commands for the topic, the dictionary
file was added a couple of times. Later, this file was deleted when we emptied the fs.files collection. You can see for
yourself what happened next! The fact that some documents were removed from a collection has no bearing on what
happens in another collection. Remember: MongoDB doesn't treat these documents or collections in any special way.
If the file had been deleted properly through a driver or the mongofiles tool, that tool would also have cleaned up the
chunks collection.

■ accessing documents and collections directly is a powerful feature, but you need to be careful. This feature
also makes it much easier to shoot yourself in both feet at the same time. Make sure you know what you're doing and
that you perform a great deal of testing if you decide to edit these documents and collections manually. also, keep in
mind that the GridFS support in MongoDB's drivers won't know anything about any customizations that you've made.

Warning