module Foreigner::ConnectionAdapters::AbstractAdapter
Public Instance Methods
Adds a new foreign key to the from_table
, referencing the
primary key of to_table
The foreign key will be named after the from and to tables unless you pass
:name
as an option.
Examples¶ ↑
Creating a foreign key¶ ↑
add_foreign_key(:comments, :posts)
generates
ALTER TABLE `comments` ADD CONSTRAINT `comments_post_id_fk` FOREIGN KEY (`post_id`) REFERENCES `posts` (`id`)
Creating a named foreign key¶ ↑
add_foreign_key(:comments, :posts, name: 'comments_belongs_to_posts')
generates
ALTER TABLE `comments` ADD CONSTRAINT `comments_belongs_to_posts` FOREIGN KEY (`post_id`) REFERENCES `posts` (`id`)
Creating a cascading foreign_key on a custom column¶ ↑
add_foreign_key(:people, :people, column: 'best_friend_id', dependent: :nullify)
generates
ALTER TABLE `people` ADD CONSTRAINT `people_best_friend_id_fk` FOREIGN KEY (`best_friend_id`) REFERENCES `people` (`id`) ON DELETE SET NULL
Supported options¶ ↑
- :column
-
Specify the column name on the from_table that references the to_table. By default this is guessed to be the singular name of the to_table with “_id” suffixed. So a to_table of :posts will use “post_id” as the default
:column
. - :primary_key
-
Specify the column name on the to_table that is referenced by this foreign key. By default this is assumed to be “id”.
- :name
-
Specify the name of the foreign key constraint. This defaults to use from_table and foreign key column.
- :dependent
-
If set to
:delete
, the associated records in from_table are deleted when records in to_table table are deleted. If set to:nullify
, the foreign key column is set toNULL
. - :options
-
Any extra options you want appended to the foreign key definition.
# File lib/foreigner/connection_adapters/abstract/schema_statements.rb, line 83 def add_foreign_key(from_table, to_table, options = {}) end
# File lib/foreigner/connection_adapters/abstract/schema_statements.rb, line 12 def create_table(table_name, *args, &block) definition = nil super do |td| definition = td # This is my trick to get the definition block.call(td) unless block.nil? end definition.foreign_keys.each do |to_table, options_list| options_list.each do |options| add_foreign_key(table_name, to_table, options) end end end
Checks to see if a foreign key exists on a table for a given constraint.
# Check a foreign key exists foreign_key_exists?(:suppliers, :companies) # Check a foreign key with a custom name exists foreign_key_exists?(:suppliers, name: "fk_company_id") # Check a foreign key on a column foreign_key_exists?(:suppliers, column: "company_id")
# File lib/foreigner/connection_adapters/abstract/schema_statements.rb, line 40 def foreign_key_exists?(table_name, options) end
Return the foreign keys for the schema_dumper
# File lib/foreigner/connection_adapters/abstract/schema_statements.rb, line 99 def foreign_keys(table_name) [] end
Remove the given foreign key from the table.
Examples¶ ↑
Remove the suppliers_company_id_fk in the suppliers table.¶ ↑
remove_foreign_key :suppliers, :companies
Remove the foreign key named accounts_branch_id_fk in the accounts table.¶ ↑
remove_foreign_key :accounts, column: :branch_id
Remove the foreign key named party_foreign_key in the accounts table.¶ ↑
remove_foreign_key :accounts, name: :party_foreign_key
# File lib/foreigner/connection_adapters/abstract/schema_statements.rb, line 95 def remove_foreign_key(from_table, options) end
# File lib/foreigner/connection_adapters/abstract/schema_statements.rb, line 25 def supports_foreign_keys? false end