DynamicRecord Presentation

DynamicRecord Jonathan Linowes Parkerhill Technology Group NH Ruby Group, January 15, 2009 Extending Rails' ActiveRecord with on-the-fly virtual attributes

Overview Built on Rails' ActiveRecord Dynamic attributes look and behave like standard ActiveRecord attributes Extends any attributes with meta properties Runtime add, modify, delete attributes A single AR model class can have multiple sets of dynamic attributes (e.g. per account)

acts_as_dynamic_record enables dynamic attributes in an ActiveRecord model supports active record magic including all flavors of find dynamic accessors (eg find_by_name)

Example class Submission < ActiveRecord::Base acts_as_dynamic_record --- Submission.dynamic_attributes.create :name => 'title' Submission.create :title => 'The title' @s = Submission.find_by_title( 'The title' )

DynamicAttribute Attribute definition name storage value_type Meta description of attribute default_value null_allowed validators description value_options choices calculations

Storage types Active actual AR attributes (table columns) Dynamic add, modify, delete at runtime Delegation attributes in an association appear here e.g. @submission.user_email Attachment built-in association to an attachments table presently implemented with Paperclip

Value types string text integer float decimal datetime boolean

value options choices for selection lists notation: ['MA, 'ME', 'NH'] or [['Mass','MA'],['NewHamp','NH']] reports math: sum, average, min, max counting: count, %complete, completed type: in-record: calculated on save (set of operands) summary: calculated on load (one operand, across records) datetime date only, time only, date and time

Validators null_allowed injected Rails validators [['numericality', { :only_integer => true }], ['inclusion', {:in => 1..5} ]] # => validates_numericality_of :attr_name, :only_integer => true # => validates_inclusion_of :attr_name, :in => 1..5

Associations also supports: has_one, has_many, belongs_to has_one_of_many http://www.vaporbase.com/postings/has_one_of_many eager loading, nesting

Architecture DynamicModel model DynamicAttribute model DynamicRow model DynamicRecord module

Storage schema tried EVA, didn't like it http://www.vaporbase.com/postings/Choosing_a_Schema_for_Dynamic_Records using fixed width rows

Migrations required tables for dynamic_models dynamic_attributes dynamic_rows

App-wide dynamic model Create in a migration create_table :things do |t| t.string :title end Thing.dynamic_model = DynamicModel.create :resource => :thing Thing.activate_attributes # add a dynamic attribute Thing.dynamic_attributes.create :name => 'color', :value_type => 'string' Load in initializer Thing.dynamic_model = DynamicModel.find_by_name( 'thing' )

Multiple Dynamic Models Multiple sets of attributes for a given model A parent model maintains the dynamic attributes of a child one # each project has its own set of submission attributes project < ActiveRecord::Base has_many :submissions contains_dynamic_model :submission Add [child]_model_id to the parent model (aka belongs_to) Add dynamic_model_id to the child model

acts_as_dynamic_record class methods - configuration dynamic_model accessor dynamicable: names, descriptions, read_only dynamic_belongs_to dynamic_delegations_for class methods dynamic_attributes accessor dynamic_attributes_by_name find_with_dynamics

DynamicAttribute dynamic_storage, active_storage?, delegation_storage?, attachment_storage? resource, resource_class value_options: choices, choices_for_select, choices_for_edit, choices_to_s, choices_to_a report, math?, counting?, summary_report?, operands, operands=, operation, operation=, all_required, all_required?, validate_operands, calculate datetime attachment_for confirmation_required?

contains_dynamic_model activate_dynamic_attributes to create initial dattr's for a model initialize_dynamic_record_classes per request (not thread safe)

nested, eager associations To reference, load dynamic attributes in an association, nested Review < ActiveRecord::Base acts_as_dynamic_record belongs_to :submission dynamic_belongs_to :submission ... Review.find :all, :include => { :submission => :user }

On the rails/ Off the rails Internal models also built on ActiveRecord Use of class variables @@dynamic_model Injects SQL translation between AR and connectors Tons of rspecs

“SQL injection” hackery re-process sql queries before they're issued solves: supports any (most) AR plugins supports all variants of AR#find including sort order, pagination, etc

Performance Issues of course! havent benchmarked, production env eager loading query caching key indexing etc.

Disclaimers Still in R&D, not a release API definition tuned for this presentation (i.e. dont use this as documentation) Learning curves developed while learning Ruby, i'm not a database/sql guru, and I dont mind breaking conventions to learn later that wasnt necessary... Not open sourced (yet), because not proven in production api still in flux need to pluginize (gemize) needs performance tuning not thread safe (uses class variables) it's still Rails 2.02 lack of time

DynamicRecord Presentation

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