Rails order by association field

Reducing redundancy and resolving edge cases

Include related records in the result set, for this apply includes:

@users = User.includes(:user_extension).order("user_extensions.company asc")


Looks akin to using joins, yet includes is different, it aims to curb N+1 queries loading the associated records in a unique query.

Complex sorting scenarios

Standard order isn't all, we often deal with custom requisites throwing off Rails innate setup. Here, merge comes as our white knight:

# Sorting like a boss now 👇
@users = User.joins(:user_extension).merge(UserExtension.order(company: :desc))


merge aids to blend scopes of the associated model, pretty handy for complex queries and befitting for clean and readable code.

Case-insensitive sorting & managing performance

Tackling case-sensitive databases needing case-insensitive order, we utilize Arel:

# Lowercase party 🎉 Let's go!
@users = User.joins(:user_extension)
             .order(UserExtension.arel_table[:company].lower.asc)


High volumes of data? Remember to benchmark your queries. Indexed columns significantly improve performance.

Ensuring database health

Get your database schema and indexes right before query implementations. Database integrity is a vital gearwheel in preventing disruptions during ordering operations.

Encapsulating in scopes

Conceal your order logic within a scope in the model:

class User < ApplicationRecord
  # Keeping it tidy, one scope at a time. 
  scope :ordered_by_company, -> { 
    joins(:user_extension).order("user_extensions.company ASC") 
  }
end


It keeps controller code tidy as well as encourages reusable query logic across the application.

Dealing with outliers

Off-the-peg solutions might fall short, which means tailoring ActiveRecord queries or resorting to straight-up SQL. Remember: Rails is flexible, but always prioritize clean code and maintainability.

Exploiting database-specific features

Some ordering techniques might lean on database-specific merits. For example, PostgreSQL has a pack of query functions that outmanoeuvre others like MySQL or SQLite.

Breezing through deeper associations

To order by a field from a model associated at more than one step away, chain includes:

# Tiptoeing through the association maze
@posts = Post.includes(author: :agency).order('agencies.name ASC')


This sorts posts by agency name given an author belongs to an agency and a post belongs to an author.

Watch out for potholes

Though Rails offers a flexible querying paradigm, beware of traps like N+1 queries, memory glut, or weakened database performance due to unindexed columns or hastily composed queries.

A helping hand from PostgreSQL

Use PostgreSQL's advanced weaponry like CTE (Common Table Expressions) or window functions for winding association ordering too gnarly for plain ActiveRecord queries.

Choosing between joins and includes

Mastering when to use joins vs includes is pivotal. Choose joins for filtering and conditions applied to the associated models, and includes to sidestep N+1 queries.