Extract foreign key action from `information_schema`

Fixes #25300.

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -516,18 +516,20 @@ def foreign_keys(table_name)
         schema, name = extract_schema_qualified_name(table_name)
 
         fk_info = select_all(<<-SQL.strip_heredoc, 'SCHEMA')
-          SELECT fk.referenced_table_name as 'to_table'
-                ,fk.referenced_column_name as 'primary_key'
-                ,fk.column_name as 'column'
-                ,fk.constraint_name as 'name'
+          SELECT fk.referenced_table_name AS 'to_table',
+                 fk.referenced_column_name AS 'primary_key',
+                 fk.column_name AS 'column',
+                 fk.constraint_name AS 'name',
+                 rc.update_rule AS 'on_update',
+                 rc.delete_rule AS 'on_delete'
           FROM information_schema.key_column_usage fk
-          WHERE fk.referenced_column_name is not null
+          JOIN information_schema.referential_constraints rc
+          USING (constraint_schema, constraint_name)
+          WHERE fk.referenced_column_name IS NOT NULL
             AND fk.table_schema = #{quote(schema)}
             AND fk.table_name = #{quote(name)}
         SQL
 
-        create_table_info = create_table_info(table_name)
-
         fk_info.map do |row|
           options = {
             column: row['column'],
@@ -535,8 +537,8 @@ def foreign_keys(table_name)
             primary_key: row['primary_key']
           }
 
-          options[:on_update] = extract_foreign_key_action(create_table_info, row['name'], "UPDATE")
-          options[:on_delete] = extract_foreign_key_action(create_table_info, row['name'], "DELETE")
+          options[:on_update] = extract_foreign_key_action(row['on_update'])
+          options[:on_delete] = extract_foreign_key_action(row['on_delete'])
 
           ForeignKeyDefinition.new(table_name, row['to_table'], options)
         end
@@ -891,12 +893,10 @@ def column_definitions(table_name) # :nodoc:
         end
       end
 
-      def extract_foreign_key_action(structure, name, action) # :nodoc:
-        if structure =~ /CONSTRAINT #{quote_column_name(name)} FOREIGN KEY .* REFERENCES .* ON #{action} (CASCADE|SET NULL|RESTRICT)/
-          case $1
-          when 'CASCADE'; :cascade
-          when 'SET NULL'; :nullify
-          end
+      def extract_foreign_key_action(specifier) # :nodoc:
+        case specifier
+        when 'CASCADE'; :cascade
+        when 'SET NULL'; :nullify
         end
       end
 

activerecord/test/cases/adapters/mysql2/schema_test.rb

@@ -103,3 +103,24 @@ def test_drop_temporary_table
     end
   end
 end
+
+class Mysql2AnsiQuotesTest < ActiveRecord::Mysql2TestCase
+  def setup
+    @connection = ActiveRecord::Base.connection
+    @connection.execute("SET SESSION sql_mode='ANSI_QUOTES'")
+  end
+
+  def teardown
+    @connection.reconnect!
+  end
+
+  def test_primary_key_method_with_ansi_quotes
+    assert_equal "id", @connection.primary_key("topics")
+  end
+
+  def test_foreign_keys_method_with_ansi_quotes
+    fks = @connection.foreign_keys("lessons_students")
+    assert_equal([["lessons_students", "students", :cascade]],
+                 fks.map {|fk| [fk.from_table, fk.to_table, fk.on_delete] })
+  end
+end

activerecord/test/cases/primary_keys_test.rb

@@ -275,18 +275,6 @@ def test_collectly_dump_composite_primary_key
 end
 
 if current_adapter?(:Mysql2Adapter)
-  class PrimaryKeyWithAnsiQuotesTest < ActiveRecord::TestCase
-    self.use_transactional_tests = false
-
-    def test_primary_key_method_with_ansi_quotes
-      con = ActiveRecord::Base.connection
-      con.execute("SET SESSION sql_mode='ANSI_QUOTES'")
-      assert_equal "id", con.primary_key("topics")
-    ensure
-      con.reconnect!
-    end
-  end
-
   class PrimaryKeyBigintNilDefaultTest < ActiveRecord::TestCase
     include SchemaDumpingHelper
 

activerecord/test/schema/schema.rb

@@ -409,6 +409,14 @@
     t.references :student
   end
 
+  create_table :students, force: true do |t|
+    t.string :name
+    t.boolean :active
+    t.integer :college_id
+  end
+
+  add_foreign_key :lessons_students, :students, on_delete: :cascade
+
   create_table :lint_models, force: true
 
   create_table :line_items, force: true do |t|
@@ -777,12 +785,6 @@
     t.integer    :lock_version, null: false, default: 0
   end
 
-  create_table :students, force: true do |t|
-    t.string :name
-    t.boolean :active
-    t.integer :college_id
-  end
-
   create_table :subscribers, force: true, id: false do |t|
     t.string :nick, null: false
     t.string :name
@@ -1002,7 +1004,6 @@
     end
 
     add_foreign_key :fk_test_has_fk, :fk_test_has_pk, column: "fk_id", name: "fk_name", primary_key: "pk_id"
-    add_foreign_key :lessons_students, :students
   end
 
   create_table :overloaded_types, force: true do |t|