I'm new to mongodb. I wanted to know if I initially code my app using mongodb and later I want to switch to mongodb gridfs, will the switching (of a filled large database) be possible.
So, if I am using mongo db initially and after some time of running the app the database documents exceed the size of 16Mb, I guess I will have to switch to gridfs. I want to know how easy or difficult will it be to switch to gridfs and whether that will be possible?
Thanks.
GridFS is used to store large files. It internally divides data in chunks(By default 255 KB). Let me give you an example of saving a pdf file in MongoDB using both ways. I am assuming the size of pdf as 10 MB so that we can see both normal way and GridFS way.
Normal Way:
Say you want to store it in normal_book collection in testDB database. So, whole pdf is stored in this collection and when you want to fetch it using db.normal_book.find(), whole pdf will be fetched in memory.
GridFS way:
In GridFS, we have two collections, one is for storing data and other is for storing its metadata. It will store data in fs.chunks collection and metadata in fs.filescollection. Now, the beauty of GridFS is that you can find the whole file at once or you can find chunks individually.
Now coming to your question, there is no direct way or property to
tell MongoDB that now I want to switch to GridFS. You need to
reinsert data in GridFS using mongofiles command-line tool or
using MongoDB's drivers.
Related
I'm trying to implement pdf upload with express and save it to mongo db . But it was only saving to localy my pc i can't send it to mongo db. Can any one help me how can i upload or access pdf files using multer or any other library.
As far as I know, you have 2 -maybe 3- ways of using "files" with MongoDB, the approach will depend on your use case (and size of the document):
Store the files directly in the document
As you know you can store anything you want in a JSON/BSON document, you just need to store the bytes and your PDF will be part of the document.
You just need to be careful about the document size limit of 16Mb.
You can add meta-data for the file in the JSON document, and they are stored in the same place.
For example in Java you will just store byte[] in an attribute, look at his test:
https://github.com/mongodb/mongo-java-driver/blob/master/src/test/com/mongodb/ByteTest.java#L188
Use GridFS
GridFS allows you to store files of "any size" into MongoDB. The file you are storing is divided in chunks by the driver and stored into smaller documents into MongoDB, when you read it it will be put back in a single file. With this approach, you do not have any size limit.
In this case, if you want to add metadata, you create a JSON document that you store with all the attributes and a reference to the GridFS file.
You can find information about this here: http://docs.mongodb.org/manual/core/gridfs/
and to this Java test:
https://github.com/mongodb/mongo-java-driver/blob/master/src/test/com/mongodb/gridfs/GridFSTest.java
Create Reference to an external storage
This one is not directly a "MongoDB" use case, but I think it is important to mention it. You can obviously store the files in some special storage and use MongoDB just for the metadata and reference this file. I will take a stupid example but suppose you want to create a Video application, you can store the videos in YouTube and reference this into the document with all your application metadata.
So let's stay on your use case/question, so you can use approaches 1 & 2, and it will depend on the size of the files and how do you access them. If you can give us more information about your application people may have a stronger opinion on the best approach.
If you are looking for people doing this, you can look at this presentation from MongoDB World: http://www.mongodb.com/presentations/translational-medicine-platform-sanofi-0
I have a collection in db which represents mediafiles.
And among other info I shoud store format name. I wonder if there best practices to store info like that. Is it better to create new collection for file formats and use link to that collection or to store format name right in file documents as a plain text? What about perfomance and compression? It supposed to be more than a billion documents in db. What would mongo expers suggest in this situation?
Embedded documents are the preferred approach.
In your case, it means it is better to store file format in the same collection.
Putting the file format into the separate collection means creating a new file on the disk.
It is a slower option and should be used if your document ( any of them ) exceeds 16 MB in size.
See these links for more information
6 Rules of Thumb for MongoDB Schema Design
and
How to Program with MongoDB Using the .NET Driver
I've done some benchmarks and figured out that in my case storing "lookup values" as plaintext is more efficient in terms of disk space than embedded document and than reference to outstanding collection. Sorry for poor terminology.
I am using Mongo-java Driver 2.13. I want to store pdf files of varying size(1mb to 30mb).
Note: I know I can't store a document having size greater than 16mb in
MongoDB. Then, I need to use GridFS.
I want to save pdf files of small size(<16 mb) in BookPDFs collection in normal way. For larger files, I need to store it using GridFS(in fs.chunks and fs.files). When I want to retrieve all PDFs, it need to access BookPDFs collection and fs.chunks, fs.files collections. It will loose atomicity for that find operation and also, it will take much time to get data from different collections.
While fetching data, I don't need it in chunks. So GridFS is not of so much use here. What should be the best way:
Save all of my data in GridFS.(title, author, etc fields in fs.files as
metadata)
Save data in different collections according to size
Any other approach?
Thanks in advance.
I am now using perl script client to store some big data into mongoDB .But now I met a problem ,some document exceeds the size limit of 16M,so ,I have to choose GridFS.From the GridFS document ,I read this:
GridFS is a specification for storing and retrieving files that exceed the BSON-document size limit of 16MB.
Instead of storing a file in a single document, GridFS divides a file into parts, or chunks, [1] and stores each of those chunks as a separate document. By default GridFS limits chunk size to 256k.
It really make me confused.What does it mean by "file"?"Instead of storing a file in a single document",it means , mongoDB stores a file in a single document without using GridFS,right ?But I think it should say:"Instead of storing a document in a single file,...".So ,the relationship and difference between "file" and "document" make me confused.
What does it mean by "file"?
A file. A word document, Excel spreadsheet, HTML file anything that is a file. GridFS is designed for file storage.
it means , mongoDB stores a file in a single document
MongoDB does not do anything, it does not even manage GridFS, the documentation assumes you come to GridFS after encountering the limited size of a single document, as you have.
Instead of storing a document in a single file,...
Nope, that is incorrect. What is a document? MongoDBs own records are called documents, how can you store those within files in the database? You store data within documents in the database.
So ,the relationship and difference between "file" and "document" make me confused.
File is a physical file and a document is basically a row.
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.
If your images are small you can store them as binary data in the documents in your collection. Just consider that you will be retrieving them every time you query your document (unless you exclude the 'image' field from your queries).
However, if your images are larger I would use GridFS. GridFS has some features that make it very good at handling images that you should consider:
For larger images, when they are stored in GridFs they will be split in chunks and you can store very large files. If you try to store images in your document, you are constrained by the 16Mb max size of a document, and you are consuming space that needs to be used for your actual document.
You can add metadata to the image itself and run queries against these attributes, as if you were doing it from a regular document in a collection. So GridFS is as good as a document for metadata about the image.
I really like that I get MD5 hash calculated on the images. (It is very useful for some of my cases).
By storing images in GridFS you save yourself the preprocessing of the image into binary format (not a big deal, but a convenience of GridFS)
In terms of performance, reading/writing against a regular document should be no different than doing it against GridFS. I would not consider performance to be a differentiator in choosing either one.
My personal recommendation is to go with GridFS, but you need to analyze for your particular use case.
Hope this helps.
I use GridFS to store photos and documents. It's so easy and retrieving it from the collection to display or save locally is easy. You can store metadata along w/ the binary data inside the same collection. This way you don't need to create an additional collection to store them.
For example, in one of my project I store user profile photos along with usernames, file type, and date of upload.
GridFS is developed to handle Files in an efficient way.
http://www.mongodb.org/display/DOCS/When+to+use+GridFS
Do not forget that you maybe will have to translate the data
to a file and back.
But to be sure, do a performance test that takes account of your usage pattern.