https://github.com/delonnewman/activerecord-setops

Union, Intersect, and Difference set operations for ActiveRecord (also, SQL's UnionAll).
https://github.com/delonnewman/activerecord-setops

activerecord activerecord-extension activerecord-queries arel query relational-algebra relational-database relational-databases ruby ruby-gem ruby-on-rails set set-operations set-theory sets sql sql-except sql-intersect sql-union sql-unionall

Last synced: 12 days ago
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Union, Intersect, and Difference set operations for ActiveRecord (also, SQL's UnionAll).

• Host: GitHub
• URL: https://github.com/delonnewman/activerecord-setops
• Owner: delonnewman
• License: mit
• Created: 2020-01-30T21:15:06.000Z (almost 5 years ago)
• Default Branch: master
• Last Pushed: 2022-12-14T20:48:49.000Z (about 2 years ago)
• Last Synced: 2024-11-15T01:42:37.799Z (about 1 month ago)
• Topics: activerecord, activerecord-extension, activerecord-queries, arel, query, relational-algebra, relational-database, relational-databases, ruby, ruby-gem, ruby-on-rails, set, set-operations, set-theory, sets, sql, sql-except, sql-intersect, sql-union, sql-unionall
• Language: Ruby
• Size: 656 KB
• Stars: 21
• Watchers: 3
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • Changelog: CHANGELOG.md
  • License: LICENSE.txt

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# ActiveRecord::Setops

Union, Intersect, and Difference set operations for ActiveRecord (also, SQL's UnionAll).

Has only been tested with Rails 5.

# Synopsis

```ruby

class Student < ActiveRecord::Base; end

class Employee < ActiveRecord::Base; end

(Student.select(:name, :birth_date) | Employee.select(:name, :birth_date)).where("name like John%")

```

# Why?

Joins can be difficult to reason about in Arel (and SQL for that matter). Many joins can be replaced

with set operations which are much simpler beasts, may offer performance gains, and have consistent

mathematical properties. But these operations while present in Arel are missing in ActiveRecord. This

module attempts to correct this lack.

# Installation

Add this line to your application's Gemfile:

```ruby

gem 'activerecord-setops'

```

And then execute:

    $ bundle

Or install it yourself as:

    $ gem install activerecord-setops

# Non-Installation

If you'd like the functionality, but would prefer to avoid yet another dependency, please fill free to paste the following code into your nearest lib directory, I'm certain it's not perfect but it has been [tested](spec/active_record/setops_spec.rb) with Rails 5, and is being used in production.

```ruby

module ActiveRecord

  class Relation

    def union(other)

      binary_operation(Arel::Nodes::Union, other)

    end

    alias | union

    def union_all(other)

      binary_operation(Arel::Nodes::UnionAll, other)

    end

    alias + union_all

    def intersect(other)

      binary_operation(Arel::Nodes::Intersect, other)

    end

    alias & intersect

    def difference(other)

      binary_operation(Arel::Nodes::Except, other)

    end

    alias - difference

    private

    def binary_operation(op_class, other)

      @klass.unscoped.from(Arel::Nodes::TableAlias.new(op_class.new(self.arel.ast, other.arel.ast), @klass.arel_table.name))

    end

  end

end

```

# See Also

- [Sequel](http://sequel.jeremyevans.net)

- [SQL Set Operations](https://en.wikipedia.org/wiki/Set_operations_(SQL))

- [active_record_union](https://github.com/brianhempel/active_record_union)