Rails N+1 because of .joins?

Question

I got a simple search for posts in my rails app. It searches through taggings of the post and the content (body) of the post. Everything works finde, but bullet moans about a N+1 query.

N+1 Query detected Post => [:tags] Add to your finder: :includes => [:tags]

How can I avoid that in my situation? Code looks like that:

model

  def self.search(search)

    Post.joins(:tags).where("name LIKE ? or body LIKE ?", "%#{search}%", "%#{search}%").uniq

  end

controller

  def index

    if params[:search]

      @posts = Post.includes(:author).search(params[:search])

    else

      @posts = Post.includes(:author, :tags).all

    end

  end

If i use .includes instead of .joins, I get the following:

SQLite3::SQLException: no such column: name:

so, as a beginner, how to deal with that? Are there better solutions? Thank you in advance!

Answer 1

You need to tell ActiveRecord which table you are using in the WHERE clause.

In most cases you would use a hash like this to target the associated table:

Post.includes(:tags).where(tags: { name: 'foo' })

When using LIKE however you need to create a string condition and in that case you would simply specify the table:

class Post
  # don't use an argument with the same name as the method.
  # its confusing and can lead to strange edge cases.
  def self.search(query)
    # Note that we use a named placeholder instead of ?
    self.includes(:tags)
        .where("tags.name LIKE %:q% OR posts.content LIKE %:q%", q: query)
        .uniq
  end
end

Rails N+1 because of .joins?

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