MongoDB count and get limited data

mongodb

I'm trying to get the count all the data for the query and as well as get the limited data (for pagination) but both the console output gives me the count. What is that I'm doing wrong. Pls help

const curFind = fbUser.find(find, 'firstName gender age birthday facebookId profileURL email imageUrl preferences blocked flames likes rejects location reported')

  curFind.count(function(e, count) {
    console.log(count);
    curFind.skip(0).limit(10).hint( { $natural : 1 } ).exec(function(err, data) {
      console.log(data);
    });
  });

Best Answer

As per MongoDB BLOG Here In certain situations, count can be avoided for better performance Counting things can be hard on a database. The obvious things to count, number of items in a collection or index, are easy to keep track of, but as soon as you start trying to count records based on a query, things get slower and slower. This is because the database has to do more work scanning practically every item in the database to see if it matches.

MongoDB does have an optimisation for a fast count where all the queried fields are indexed and the query is based around equivalence, but only in that circumstance.

Related Solutions

MongoDB: Should I combine fields for performance in limited circumstances

Without combining the fields in your data set you could just create a compound index using both. No changes to your data necessary. To do so, just create the index like so:

db.collection.ensureIndex({"user" : 1, "domain" : 1})

Docs are here:

http://www.mongodb.org/display/DOCS/Indexes#Indexes-CompoundKeys

Once you have created such a compound key it essentially makes an index on the leftmost element (user in my example above) redundant, and so an index on user (if it exists) could be removed.

Don't forget that the query optimizer only runs every ~1000 queries, so you will have to hint() the index to make sure it is used if you are testing it out.

MongoDB: how to get the all the embedded data

If you had multiple documents containing products, you could retrieve all as follows by capturing the query cursor and iterating over the set:

replset:PRIMARY> var cur = db.Category.find( {}, {products:1} );
replset:PRIMARY> while (cur.hasNext()) {
... var doc = cur.next();
... printjson(doc);
... }
{
    "_id" : ObjectId("542450a928db034349fb3bf2"),
    "products" : [
        {
            "_id" : ObjectId("542450a928db034349fb3bf3"),
            "name" : "Producto de categoria",
            "price" : 11.11
        }
    ]
}

If you have multiple products within the "products" array then you would iterate over the array contained in each result document.

Best Answer

Related Solutions

MongoDB: Should I combine fields for performance in limited circumstances

MongoDB: how to get the all the embedded data

Related Question