Question

I am trying to retrieve 100000 docouments from MongoDb like below and its taking very long to return collection.

var query = Query.EQ("Status", "E");
var items = collection.Find(query).SetLimit(100000).ToList();

Or

var query = Query.GT("_id", idValue);
var items = collection.Find(query).SetLimit(100000).ToList();

Explain:

{
    "cursor" : "BtreeCursor _id_", 
    "nscanned" : 1, 
    "nscannedObjects" :1, 
    "n" : 1, 
    "millis" : 0, 
    "nYields" : 0, 
    "nChunkSkips" : 0,
    "isMultiKey" : false, 
    "indexOnly" : false, 
    "indexBounds" : 
        {
            "_id" :[[ObjectId("4f79a64eca98b5fc0e5ae35a"),
                ObjectId("4f79a64eca98b5fc0e5ae35a")]]
        } 
}

Any suggestions to improve query performance. My table having 2 million documents.

-Venkat

Answer 1

This question was also asked on Google Groups:

https://groups.google.com/forum/?fromgroups#!topicsearchin/mongodb-user/100000/mongodb-user/a6FHFp5aOnA

As I responded on the Google Groups question I tried to reproduce this and was unable to observe any slowness. I was able to read 100,000 documents in 2-3 seconds, depending on whether the documents were near the beginning or near the end of the collection (because I didn’t create an index).

My answer to the Google groups question has more details and a link to the test program I used to try and reproduce this.