Orm N Plus One Query (ARCH6079)

Key ruby.performance.orm-n-plus-one · Severity error · Category performance

Retired

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Looping over a query result and accessing each item’s relationship fires a separate query per record (N+1). Eager-load the relationship with includes.

Incorrect

def author_names(posts)
  Post.where(published: true).map do |post|
    post.author.name
  end
end

Correct

def author_names(posts)
  Post.where(published: true).includes(:author).map do |post|
    post.author.name
  end
end

Fix

Eager-load related records with includes/preload when you access them inside a loop.