Remove issues.assignee_id column

db/migrate/20170523073948_remove_assignee_id_from_issue.rb

+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class RemoveAssigneeIdFromIssue < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = false
+
+  # When a migration requires downtime you **must** uncomment the following
+  # constant and define a short and easy to understand explanation as to why the
+  # migration requires downtime.
+  # DOWNTIME_REASON = ''
+
+  # When using the methods "add_concurrent_index", "remove_concurrent_index" or
+  # "add_column_with_default" you must disable the use of transactions
+  # as these methods can not run in an existing transaction.
+  # When using "add_concurrent_index" or "remove_concurrent_index" methods make sure
+  # that either of them is the _only_ method called in the migration,
+  # any other changes should go in a separate migration.
+  # This ensures that upon failure _only_ the index creation or removing fails
+  # and can be retried or reverted easily.
+  #
+  # To disable transactions uncomment the following line and remove these
+  # comments:
+  disable_ddl_transaction!
+
+  def up
+    remove_column :issues, :assignee_id
+  end
+
+  def down
+    add_column :issues, :assignee_id, :integer
+    add_concurrent_index :issues, :assignee_id
+  end
+end

db/schema.rb

@@ -841,7 +841,6 @@ ActiveRecord::Schema.define(version: 20171206221519) do
 
   create_table "issues", force: :cascade do |t|
     t.string "title"
-    t.integer "assignee_id"
     t.integer "author_id"
     t.integer "project_id"
     t.datetime "created_at"
@@ -867,7 +866,6 @@ ActiveRecord::Schema.define(version: 20171206221519) do
     t.datetime_with_timezone "closed_at"
   end
 
-  add_index "issues", ["assignee_id"], name: "index_issues_on_assignee_id", using: :btree
   add_index "issues", ["author_id"], name: "index_issues_on_author_id", using: :btree
   add_index "issues", ["confidential"], name: "index_issues_on_confidential", using: :btree
   add_index "issues", ["deleted_at"], name: "index_issues_on_deleted_at", using: :btree