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MongoDB: How to delete all the documents from a collection ?

+2 votes
MongoDB: How to delete all the documents from a collection ?
posted Jun 23, 2015 by Vikram Singh

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Do you want to delete all the documents one by one or in one shot ?

1 Answer

0 votes

Single command to delete all the documents from a collection is db.collection_name.remove({}) .
I have verified this command. Please let me know If you are still facing any problem.

answer Jun 24, 2015 by Harshita
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+3 votes

Here I would like to explain my query a bit more.

I inserted multiple documents within a collection. Few documents have same set of keys and few of them have some extra key:value pairs . For example:
document 1 : key1 : "key1"
document 2: key1 : "key1", key2: "key2"
document 3: key1 : "key1", key2: "key2", key3 : "key3"
document 4: key1 : "key1", key3 : "key3"

Now I want to delete the documents which have key1 and key2.
What will be the command to do so ?

+1 vote

I have a project, which has 1000 images. From each image, I get 1 million documents that I currently store in a mongoDB collection.

I have 2 alternatives,
1. Create a separate collection for each image, over multiple projects, say 10 projects, and each image(collection) would have 1 million documents that will be indexed. OR
2. Have a single collection and have 1000x1,000,000 documents in one collection, which again will be indexed.

My research and reading suggests that it is not a very good idea to create 1000 collections (for each image) and create an index for each one of 1000, and go with adding a billion documents to a single collection, to which mongoDB caters with no major issue.
My main aim is to enhance performance for reading. There would be no updates and deletes. Only reads and writes. I can afford writes to be slow, but not reads. So am I right in choosing the 2nd alternative?

Any guidance is highly appreciated.

+1 vote

I am trying to get all the collection names from MongoDb server using C# code using db.GetCollectionNames() method.

I have 12 collections in my database, but the above method returns an empty list. I have verified that I am referring to the correct database. What am I doing wrong? Or if there is an alternate way?