preloading associations with dynamic condition in rails
N+1 queries issue The N+1 query issue is common performance problem in Rails applications. To better understand it let’s consider typical e-commerce application where we’re dealing with products with prices in multiple currencies. class Product < ActiveRecord::Base has_many :prices end class Price < ActiveRecord::Base belongs_to :product validates :currency_code, presence: true end When we want to
Really fast CSV imports with Rails and PostgreSQL
Let’s say that we have to import data from some social network. We will be provided with CSV file generated every 5 minutes containing list of posts that were added/liked/commented since the beginning of the day together with likes’ and comments’ counts for each post. As you can imagine the file will grow in size during the day; also we are looking at not only inserting new posts but also updating
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