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= 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 Farmer
has n, :pigs #equivalent to: has n, :pigs, :constraint => :protect
end
# M:M Example
class Articles
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 Farmer
has 1, :beloved_sheep, :constraint => :protect
end
Version data entries
11 entries across 11 versions & 1 rubygems