ActiveRecord::RecordNotUnique

ActiveRecord::RecordNotUnique is raised when attempting to insert or update a record that would violate a database-level unique constraint.

Common causes

• Duplicate email or username registration
• Race condition creating duplicate records
• Unique index violation on composite keys
• Missing uniqueness validation in model
• Retry logic creating duplicates

How to fix it

• Add uniqueness validation to model
• Use find_or_create_by for idempotent operations
• Rescue and handle duplicate gracefully
• Use database transactions with proper locking
• Implement retry logic with proper checks

Example

# Error example
User.create!(email: "alice@example.com")
User.create!(email: "alice@example.com")  # => ActiveRecord::RecordNotUnique

# Fix with find_or_create_by
user = User.find_or_create_by(email: "alice@example.com") do |u|
  u.name = "Alice"
end

# Rescue approach
begin
  User.create!(email: email)
rescue ActiveRecord::RecordNotUnique
  User.find_by(email: email)
end

# Model validation (catches before hitting DB)
class User < ApplicationRecord
  validates :email, uniqueness: true
end

Related errors