Generate consistent names for foreign keys

activerecord/CHANGELOG.md

@@ -1,3 +1,12 @@
+*   Foreign keys added by migrations were given random, generated names. This
+    meant a different `structure.sql` would be generated every time a developer
+    ran migrations on their machine.
+
+    The generated part of foreign key names is now a hash of the table name and
+    column name, which is consistent every time you run the migration.
+
+    *Chris Sinjakli*
+
 *   Validation errors would be raised for parent records when an association
     was saved when the parent had `validate: false`. It should not be the
     responsibility of the model to validate an associated object unless the

activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb

@@ -1,4 +1,6 @@
 require 'active_record/migration/join_table'
+require 'active_support/core_ext/string/access'
+require 'digest'
 
 module ActiveRecord
   module ConnectionAdapters # :nodoc:
@@ -990,8 +992,10 @@ def create_alter_table(name)
       end
 
       def foreign_key_name(table_name, options) # :nodoc:
+        identifier = "#{table_name}_#{options.fetch(:column)}_fk"
+        hashed_identifier = Digest::SHA256.hexdigest(identifier).first(10)
         options.fetch(:name) do
-          "fk_rails_#{SecureRandom.hex(5)}"
+          "fk_rails_#{hashed_identifier}"
         end
       end
 

activerecord/test/cases/migration/foreign_key_test.rb

@@ -57,7 +57,7 @@ def test_add_foreign_key_inferes_column
         assert_equal "rockets", fk.to_table
         assert_equal "rocket_id", fk.column
         assert_equal "id", fk.primary_key
-        assert_match(/^fk_rails_.{10}$/, fk.name)
+        assert_equal("fk_rails_78146ddd2e", fk.name)
       end
 
       def test_add_foreign_key_with_column
@@ -71,7 +71,7 @@ def test_add_foreign_key_with_column
         assert_equal "rockets", fk.to_table
         assert_equal "rocket_id", fk.column
         assert_equal "id", fk.primary_key
-        assert_match(/^fk_rails_.{10}$/, fk.name)
+        assert_equal("fk_rails_78146ddd2e", fk.name)
       end
 
       def test_add_foreign_key_with_non_standard_primary_key