fk: `add_foreign_key` and `remove_foreign_key` for PostgreSQL adapter.

4 files changed, 85 insertions, 0 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index cc494a7f40..294ed6d7bf 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -233,6 +233,11 @@ module ActiveRecord
         false
       end
 
+      # Does this adapter support creating foreign key constraints?
+      def supports_foreign_keys?
+        false
+      end
+
       # This is meant to be implemented by the adapters that support extensions
       def disable_extension(name)
       end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
index b2aeb3a058..f09ce113d6 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb
@@ -448,6 +448,33 @@ module ActiveRecord
           execute "ALTER INDEX #{quote_column_name(old_name)} RENAME TO #{quote_table_name(new_name)}"
         end
 
+        def add_foreign_key(from_table, to_table, options = {})
+          foreign_key_column = options.fetch(:column)
+          referenced_column = "id"
+          foreign_key_name = foreign_key_name(from_table, options)
+          execute <<-SQL
+ALTER TABLE #{quote_table_name(from_table)}
+ADD CONSTRAINT #{foreign_key_name}
+  FOREIGN KEY (#{quote_column_name(foreign_key_column)})
+  REFERENCES #{quote_table_name(to_table)} (#{quote_column_name(referenced_column)})
+          SQL
+        end
+
+        def remove_foreign_key(from_table, options = {})
+          foreign_key_name = foreign_key_name(from_table, options)
+          execute <<-SQL
+ALTER TABLE #{quote_table_name(from_table)}
+DROP CONSTRAINT #{foreign_key_name}
+          SQL
+        end
+
+        def foreign_key_name(table_name, options)
+          options.fetch(:name) do
+            column_name = options.fetch(:column)
+            "#{table_name}_#{column_name}_fk"
+          end
+        end
+
         def index_name_length
           63
         end
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index be4ae47d09..34262cf91d 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -159,6 +159,10 @@ module ActiveRecord
         true
       end
 
+      def supports_foreign_keys?
+        true
+      end
+
       def index_algorithms
         { concurrently: 'CONCURRENTLY' }
       end
diff --git a/activerecord/test/cases/migration/foreign_key_test.rb b/activerecord/test/cases/migration/foreign_key_test.rb
new file mode 100644
index 0000000000..978d1a8cf1
--- /dev/null
+++ b/activerecord/test/cases/migration/foreign_key_test.rb
@@ -0,0 +1,49 @@
+require 'cases/helper'
+
+if ActiveRecord::Base.connection.supports_foreign_keys?
+module ActiveRecord
+  class Migration
+    class ForeignKeyTest < ActiveRecord::TestCase
+      class Rocket < ActiveRecord::Base
+      end
+
+      class Astronaut < ActiveRecord::Base
+      end
+
+      setup do
+        @connection = ActiveRecord::Base.connection
+        @connection.create_table "rockets" do |t|
+          t.string :name
+        end
+
+        @connection.create_table "astronauts" do |t|
+          t.string :name
+          t.references :rocket
+        end
+      end
+
+      def test_add_foreign_key
+        @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id"
+
+        assert_raises ActiveRecord::InvalidForeignKey do
+          Astronaut.create rocket_id: 33
+        end
+      end
+
+      def test_remove_foreign_key
+        @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id"
+        @connection.remove_foreign_key :astronauts, column: "rocket_id"
+
+        Astronaut.create rocket_id: 33
+      end
+
+      def test_remove_foreign_key_by_name
+        @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", name: "fancy_named_fk"
+        @connection.remove_foreign_key :astronauts, name: "fancy_named_fk"
+
+        Astronaut.create rocket_id: 33
+      end
+    end
+  end
+end
+end