fk: raise when identifiers are longer than `allowed_index_name_length`.

2 files changed, 14 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
index 18e73b0200..5a863717e5 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
@@ -682,7 +682,11 @@ module ActiveRecord
 
       def foreign_key_name(table_name, options) # :nodoc:
         options.fetch(:name) do
-          "#{table_name}_#{options.fetch(:column)}_fk"
+          identifier = "#{table_name}_#{options.fetch(:column)}_fk"
+          if identifier.length > allowed_index_name_length
+            raise ArgumentError, "Foreign key name '#{identifier}' is too long; the limit is #{allowed_index_name_length} characters"
+          end
+          identifier
         end
       end
 
diff --git a/activerecord/test/cases/migration/foreign_key_test.rb b/activerecord/test/cases/migration/foreign_key_test.rb
index c69fc18d82..815c6b2955 100644
--- a/activerecord/test/cases/migration/foreign_key_test.rb
+++ b/activerecord/test/cases/migration/foreign_key_test.rb
@@ -136,6 +136,15 @@ module ActiveRecord
         assert_equal :nullify, fk.on_update
       end
 
+      def test_add_foreign_key_with_too_long_identifier
+        with_example_table @connection, "long_table_name_will_result_in_a_long_foreign_key_name", "rocket_id integer" do
+          e = assert_raises(ArgumentError) do
+            @connection.add_foreign_key "long_table_name_will_result_in_a_long_foreign_key_name", "rockets"
+          end
+          assert_match(/^Foreign key name 'long_table_name_will_result_in_a_long_foreign_key_name_rocket_id_fk' is too long;/, e.message)
+        end
+      end
+
       def test_remove_foreign_key_inferes_column
         @connection.add_foreign_key :astronauts, :rockets