blank? vs empty? - ActiveRecord

README.md

blank? will load the entire array, then check to see if the array is empty.

On the other hand, empty? asks the database for a count, and checks to see if that count is zero or not. This might not make a difference in small datasets (like development), but it can make a big difference in databases with large datasets (like production).

It will also make a huge difference in memory consumption when thousands of records are loaded vs a single integer.

Reference:

http://hashrocket.com/blog/posts/rails-quick-tips-easy-activerecord-optimizations

blank.rb

User.where(screen_name: ['user1','user2']).blank?

# 1. Queries database for all user data
#   SELECT "users".* FROM "users" WHERE "users"."screen_name" IN ('user1','user2')

# 2. Loads users into an array
#   [<#User:0x007fbf6413c510>,<#User:0x007fbf65ab1c70>]

# 3. Checks to see if the array size is zero
#   => true

empty.rb

# Using `empty?`
User.where(screen_name: ['user1','user2').empty?

# 1. Queries database for ONLY a count
#   SELECT COUNT(*) FROM "users" WHERE "users"."screen_name" IN ('user1','user2')

# 2. Checks to see if the count is zero
# => true