SimpleQuery

SimpleQuery is a lightweight and efficient query builder for ActiveRecord, designed to provide a flexible and performant way to construct complex database queries in Ruby on Rails applications.

Installation

Add this line to your application's Gemfile:

gem 'simple_query'

And then execute:

bundle install

Or install it yourself as:

gem install simple_query

Configuration

By default, SimpleQuery does not automatically patch ActiveRecord::Base. You can manually include the module in individual models or in a global initializer:

# Manual include (per model)
class User < ActiveRecord::Base
  include SimpleQuery
end

# or do it globally
ActiveRecord::Base.include(SimpleQuery)

If you prefer a “just works” approach (i.e., every model has .simple_query), you can opt in:

# config/initializers/simple_query.rb
SimpleQuery.configure do |config|
  config.auto_include_ar = true
end

This tells SimpleQuery to automatically do ActiveRecord::Base.include(SimpleQuery) for you.

Usage

SimpleQuery offers an intuitive interface for building queries with joins, conditions, and aggregations. Here are some examples:

Basic query

User.simple_query.select(:name, :email).where(active: true).execute

Query with join

SimpleQuery now supports all major SQL join types — including LEFT, RIGHT, and FULL — through the following DSL methods:

User.simple_query
    .left_join(:users, :companies, foreign_key: :user_id, primary_key: :id)
    .select("users.name", "companies.name")
    .execute

Complex query with multiple joins and conditions

User.simple_query
    .select(:name)
    .join(:users, :companies, foreign_key: :user_id, primary_key: :id)
    .join(:companies, :projects, foreign_key: :company_id, primary_key: :id)
    .where(Company.arel_table[:industry].eq("Technology"))
    .where(Project.arel_table[:status].eq("active"))
    .where(User.arel_table[:admin].eq(true))
    .execute

Lazy execution

User.simple_query
    .select(:name)
    .where(active: true)
    .lazy_execute

Placeholder-Based Conditions

SimpleQuery now supports ActiveRecord-style placeholders, letting you pass arrays with ? or :named placeholders to your .where clauses:

# Positional placeholders:
User.simple_query
    .where(["name LIKE ?", "%Alice%"])
    .execute

# Named placeholders:
User.simple_query
    .where(["email = :email", { email: "alice@example.com" }])
    .execute

# Multiple placeholders in one condition:
User.simple_query
    .where(["age >= :min_age AND age <= :max_age", { min_age: 18, max_age: 35 }])
    .execute

Custom Read Models

By default, SimpleQuery returns results as Struct objects for maximum speed. However, you can also define a lightweight model class for more explicit attribute handling or custom logic.

Create a read model inheriting from SimpleQuery::ReadModel:

class MyUserReadModel < SimpleQuery::ReadModel
  attribute :identifier, column: :id
  attribute :full_name,  column: :name
end

Map query results to your read model:

results = User.simple_query
              .select("users.id AS id", "users.name AS name")
              .where(active: true)
              .map_to(MyUserReadModel)
              .execute

results.each do |user|
  puts user.identifier    # => user.id from the DB
  puts user.full_name     # => user.name from the DB
end

This custom read model approach provides more clarity or domain-specific logic while still being faster than typical ActiveRecord instantiation.

Named Scopes

SimpleQuery now supports named scopes, allowing you to reuse common query logic in a style similar to ActiveRecord’s built-in scopes. To define a scope, use the simple_scope class method in your model:

class User < ActiveRecord::Base
  include SimpleQuery

  simple_scope :active do
    where(active: true)
  end

  simple_scope :admins do
    where(admin: true)
  end

  # Block-based scope with parameter
  simple_scope :by_name do |name|
    where(name: name)
  end

  # Lambda-based scope with parameter
  simple_scope :by_name, ->(name) { where(name: name) }
end

You can then chain these scopes seamlessly with the normal SimpleQuery DSL:

# Parameterless scopes
results = User.simple_query.active.admins.execute

# Parameterized scope
results = User.simple_query.by_name("Jane Doe").execute

# Mixing scopes with other DSL calls
results = User.simple_query
              .by_name("John")
              .active
              .select(:id, :name)
              .order(name: :asc)
              .execute

How It Works

Each scope block (e.g. by_name) is evaluated in the context of the SimpleQuery builder, so you can call any DSL method (where, order, etc.) inside it. Parameterized scopes accept arguments — passed directly to the block (e.g. |name| above). Scopes return self, so you can chain multiple scopes or mix them with standard query methods.

Streaming Large Datasets

For massive queries (millions of rows), SimpleQuery offers a .stream_each method to avoid loading the entire result set into memory. It automatically picks a streaming approach depending on your database adapter:

• PostgreSQL: Uses a server-side cursor via DECLARE ... FETCH.
• MySQL: Uses mysql2 gem’s streaming (stream: true, cache_rows: false, as: :hash).

# Example usage:
User.simple_query
    .where(active: true)
    .stream_each(batch_size: 10_000) do |row|
  # row is a struct or read-model instance
  puts row.name
end

Performance

SimpleQuery aims to outperform standard ActiveRecord queries at scale. We’ve benchmarked 1,000,000 records on both PostgreSQL and MySQL, with the following results:

PostgreSQL (1,000,000 records)

🚀 Performance Results (1000,000 records):
ActiveRecord Query:                  10.36932 seconds
SimpleQuery Execution (Struct):      3.46136 seconds
SimpleQuery Execution (Read model):  2.20905 seconds

----------------------------------------------------
ActiveRecord find_each:              6.10077 seconds
SimpleQuery stream_each:             2.75639 seconds

--- AR find_each Memory Report ---
Total allocated: 1.98 GB (16,001,659 objects)
Retained:        ~2 KB

--- SimpleQuery stream_each Memory Report ---
Total allocated: 1.38 GB (8,000,211 objects)
Retained:        ~3 KB

• Struct-based approach remains the fastest, skipping model overhead.
• Read model approach is still significantly faster than standard ActiveRecord while allowing domain-specific logic.

MySQL (1,000,000 records)

🚀 Performance Results (1000,000 records):
ActiveRecord Query:                  10.45833 seconds
SimpleQuery Execution (Struct):      3.04655 seconds
SimpleQuery Execution (Read model):  3.69052 seconds

----------------------------------------------------
ActiveRecord find_each:              5.04671 seconds
SimpleQuery stream_each:             2.96602 seconds

--- AR find_each Memory Report ---
Total allocated: 1.32 GB (11,001,445 objects)
Retained:        ~2.7 KB

--- SimpleQuery stream_each Memory Report ---
Total allocated: 1.22 GB (8,000,068 objects)
Retained:        ~3.9 KB

• Even in MySQL, Struct was roughly three times faster than ActiveRecord’s overhead.
• Read models still outperform AR, though by a narrower margin in this scenario.

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/kholdrex/simple_query. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the code of conduct.

License

The gem is available as open source under the terms of the MIT License.

Code of Conduct

Everyone interacting in the SimpleQuery project's codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.