diff --git a/db/migrate/20150505023015_add_index_to_homeworkattach_bid_id.rb b/db/migrate/20150505023015_add_index_to_homeworkattach_bid_id.rb
new file mode 100644
index 000000000..ce4d4499c
--- /dev/null
+++ b/db/migrate/20150505023015_add_index_to_homeworkattach_bid_id.rb
@@ -0,0 +1,5 @@
+class AddIndexToHomeworkattachBidId < ActiveRecord::Migration
+  def change
+    add_index(:homework_attaches,:bid_id)
+  end
+end
diff --git a/db/migrate/20150505023127_add_index_to_studentforcourse_student_id.rb b/db/migrate/20150505023127_add_index_to_studentforcourse_student_id.rb
new file mode 100644
index 000000000..d24e2f31e
--- /dev/null
+++ b/db/migrate/20150505023127_add_index_to_studentforcourse_student_id.rb
@@ -0,0 +1,5 @@
+class AddIndexToStudentforcourseStudentId < ActiveRecord::Migration
+  def change
+    add_index(:students_for_courses,:student_id)
+  end
+end
diff --git a/db/migrate/20150505023452_add_index_to_studentforcourse_course_id.rb b/db/migrate/20150505023452_add_index_to_studentforcourse_course_id.rb
new file mode 100644
index 000000000..99c0a640a
--- /dev/null
+++ b/db/migrate/20150505023452_add_index_to_studentforcourse_course_id.rb
@@ -0,0 +1,5 @@
+class AddIndexToStudentforcourseCourseId < ActiveRecord::Migration
+  def change
+    add_index(:students_for_courses,:course_id)
+  end
+end
diff --git a/db/migrate/20150505025003_add_index_to_homeworkforcourse_course_id.rb b/db/migrate/20150505025003_add_index_to_homeworkforcourse_course_id.rb
new file mode 100644
index 000000000..cd60a00af
--- /dev/null
+++ b/db/migrate/20150505025003_add_index_to_homeworkforcourse_course_id.rb
@@ -0,0 +1,5 @@
+class AddIndexToHomeworkattachCourseId < ActiveRecord::Migration
+  def change
+    add_index(:homework_for_courses,:course_id)
+  end
+end
diff --git a/db/migrate/20150505025537_add_index_to_homeworkforcourse_bid_id.rb b/db/migrate/20150505025537_add_index_to_homeworkforcourse_bid_id.rb
new file mode 100644
index 000000000..7504e8421
--- /dev/null
+++ b/db/migrate/20150505025537_add_index_to_homeworkforcourse_bid_id.rb
@@ -0,0 +1,5 @@
+class AddIndexToHomeworkforcourseBidId < ActiveRecord::Migration
+  def change
+    add_index(:homework_for_courses,:bid_id)
+  end
+end