dm-constraints

Plugin that adds foreign key constraints to associations. Currently supports only PostgreSQL and MySQL

All constraints are added to the underlying database, but constraining is implemented in pure ruby.

Constraints

 - :protect     returns false on destroy if there are child records
 - :destroy     deletes children if present
 - :destroy!    deletes children directly without instantiating the resource, bypassing any hooks
                Does not support 1:1 Relationships as #destroy! is not supported on Resource in dm-master
 - :set_nil     sets parent id to nil in child associations
                Not valid for M:M relationships as duplicate records could be created (see explanation in specs)
 - :skip        Does nothing with children, results in orphaned records

By default a relationship will PROTECT its children.

Cardinality Notes

 * 1:1
  * Applicable constraints: [:set_nil, :skip, :protect, :destroy]

 * 1:M
  * Applicable constraints: [:set_nil, :skip, :protect, :destroy, :destroy!]

 * M:M
  * Applicable constraints: [:skip, :protect, :destroy, :destroy!]

Examples

  # 1:M Example
  class Post
    has n, :comments
    # equivalent to:
    # has n, :comments, :constraint => :protect
  end

  # M:M Example
  class Article
    has n, :tags, :through => Resource, :constraint => :destroy
  end

  class Tags
    has n, :articles, :through => Resource, :constraint => :destroy
  end

  # Intermediary constraints for relationships using :through => Resource
  # are automatically inherited from the M:M relationship.

  # 1:1 Example
  class User
    has 1, :address, :constraint => :protect
  end