ActiveTree

This gem implements a denormalized database model for tree data backed up by the Postgres LTREE extension.

Installation

This gem is at home within a Rails 6+ console-only, API or full fledged application on top of a Postgres database.

Add this line to your application's Gemfile:

gem 'active_tree'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install active_tree

Upon installing the gem you must run the install process in your Rails application's root:

$ rails g active_tree:install

This will generate a config/active_tree.yml which you may customize to your needs, an initializer and a migration file which you can also customize to add any database columns your models will require.

Usage

Include the ActiveTreeAble concern into one of your models which will own lifecycle trees (owner model):

    class User < ApplicationRecord
        include ActiveTree::ActiveTreeAble
        # ...
    end

This will extend your model and enable the following functionality:

# query with ActiveRecord syntax
User.last.active_trees
User.find_by(name: "Acme").active_trees.select("product_name, sum(product_price) as total_price").group(:product_name)
User.last.active_trees.where(...)
User.last.active_trees.where(...).group(...)
User.last.active_trees.where(...).limit(...).offset(...)

# AR query with ltree syntax
User.last.active_trees.disabled.match_path("*.ProductName.*")
User.last.active_trees.match_path("*{5,10}.CategoryName.*.ProductName.*")
User.last.active_trees.active.match_path("*.CategoryName.*.SubcategoryName.*.ProductName.*").where( product_price: [100..150]).sum(:product_price)

ActiveTree::Model.match_path("Top.Category.*").products.match_path("*.Scooter*").where( product_price: [ 1000..10000 ]).average(:product_price)
ActiveTree::Model.where(name: "RC Airplane").products.match_path("*.Battery.*").sum(:product_price)
ActiveTree::Model.where(owner: User.last).match_path("*{10,20}.*Category.*")
ActiveTree::Model.match_path("*.Product.*")

# pg_ltree queries
User.last.active_trees.last.parent
ActiveTree::Model.match_path("*.Category.*").children

# pg_ltree combined with AR syntax
User.last.active_trees(type: "Sellable::Product").children.match_path("*.Battery").children

# all queries can be directed to a specific partition:
ActiveTree::Model.owned_by( owner_id ).match_path("*.Category.*").where(currency: "USD").products.sum(:product_price)

To see what syntax to use for path traversal please check out the following resources:

• pg_ltree gem https://github.com/sjke/pg_ltree
• Postgres ltree extension documentation https://www.postgresql.org/docs/9.1/ltree.html

The ActiveTree gem is designed to be compatible with PostgREST. PostgREST is an amazing tool that generates a CRUD REST API for your Postgres database, read more about it here: https://postgrest.org

If the create_postgrest_roles setting is on each new owner will be assigned a Postgres role allowing them to access data within their partition using PostgREST. Your owner model will be extended with a .generate_jwt method you can use to generate the PostgREST authentication token.

Metadata

The ActiveTree::Model comes with a JSONB column where you can store random information structured in any required way. Subclasses of the Model can implement methods to store/retrieve JSONB data as well as validations.

The ActiveTree::Metadata model can store key-value pairs queryable through ActiveRecord simple queries or joins:

ActiveTree::Model.match_path("*.Battery.*").metadata.where(key: "Shipping weight").sum(:value)

Partitioning

All data is partitioned for each owner using the owner_id as partition index. Through the yml configuration you can choose how the gem behaves when deleting an owner record - either delete the partition and all the data, or detach the partition and keep the data for later use.

Through subsequent ActiveRecord migrations the data can be federated from a separate Postgres server.

The main table as well as its partitions can be queried through PostgREST using the role attached to the owner model.

Caveats

pg_ltree .child / .parent queries do not work across different models due to an ActiveRecord limitation that requires results to be related via inheritance.

Roadmap

• postgres RECURSIVE queries
• builders
• seeds/fixtures

Contributing

Bug reports, pull requests and feature suggestions are welcome on GitHub at https://github.com/nicksterious/active_tree

License

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