Skip to main content

MongoDB query optimisation

 Before you read below, make sure MongoDB is the right choice for your application. It's Nonrelational and Document oriented database.

Mongoid::Criteria Let's say you query all user data, @users = User.all while using mongoid. So when you access @users in views, it's Mongoid::Criteria and
ruby methods will not work ex- to_json. When we iterate over @users, say

@users.each do |user| 
  p user
end

For each user entry, query is fired which could easily be avoided by changing the query to @users = User.all.entries or @users = User.all.to_a. Also for single object @user = User.where(email: "bijendra.biju@gmail.com").first.

Index your database: use the specific fields while indexing which will fasten the search. Indexes improve the efficiency of read operations by reducing the amount of data that query operations need to process.
Apart from read operations indexes can support sort operation and allow for a more efficient storage utilization.

For ex: If you need to implement search over user database, index the specific fields which will be used for searching. By default _id will be created and indexed,


class User
  include Mongoid::Document
  field :name, :type => String
  field :email, :type => String
  index({ email: 1 })
end

http://docs.mongodb.org/manual/core/map-reduce/
http://docs.mongodb.org/manual/core/aggregation-pipeline/

Comments

Popular posts from this blog

Starting with Ruby Metaprogamming

Metaprogramming is a programming technique in which computer programs have the ability to treat programs as their data. It means that a program can be designed to read, generate, analyze or transform other programs, and even modify itself while running.(wikipedia)
 Using simple code samples let's give basic start to metaprogramming which helps to relate how code base can be simplified.
 Considering the below class.

Now, using some metaprogramming concepts above code can be modified, notice the assign_attributes method used while the o/p in both the examples is same

Adding some more examples, below simple code helps to generate methods on the fly instead of defining in individually


Metaprogramming should be used with caution and not make the code complicated and difficult to read. It should be easy to understand and modular to change in future.

upload images to AWS::S3 in ruby using aws sdk gem

Using gem aws-sdk for a ROR application for uploading images to s3
Uploading images to a fixed bucket with different folders for each object or application. The s3 keeps a limitation on the number of buckets creation whereas there is no limitation for content inside a bucket. This code will upload image for a user to s3 using aws-sdk gem. The bucket and the image uploaded are made public, so that the images uploaded are directly accessible. The input is takes is the image complete path where it is present, folder in which it should be uploaded and user_id for whom it should be uploaded. def save_screenshot_to_s3(image_location, folder_name,user_id) service = AWS::S3.new(:access_key_id => ACCESS_KEY_ID, :secret_access_key => SECRET_ACCESS_KEY) bucket_name = "app-images" if(service.buckets.include?(bucket_name)) bucket = service.buckets[bucket_name] else bucket = service.buckets.create(bucket_name) …