Get the count of the number of documents in a Collection Mongodb

Question

Is there a way to list all the collection names and the document count for each collection in a single query?

The one that I could find only gives the count for a particular collection. For example, if Users was a collection then

db.Users.count()

Would give me the count of the number of documents in the collection Users.

Answer 1

In the shell all you need to do is this:

db.getCollectionNames().map(function(name) { 
    return { "name": name, "count": db[name].count() } 
})

There is no "command" and there is not "singular" collection query ( it is technically still multiple queries made for each collection, and a "source" query ) to do this since that is not how MongoDB stores the data. But there is a simple programitic method, and this is basically available to all drivers as well.

Answer 2

If you just want to print the numbers and count, then you can use forEach.

db.getCollectionNames().forEach(function(colName){
  print(colName+": "+db.collection(colName).count());
});

If you want to use it for any other operations, then you can use map function.

db.getCollectionNames().map(function(colName){
  return {
    "columnName":colName,
    "count":db.getCollection(colName).count()
  }
});