Refactor migration to not require downtime

db/migrate/20170124174637_add_foreign_keys_to_timelogs.rb

@@ -5,11 +5,11 @@ class AddForeignKeysToTimelogs < ActiveRecord::Migration
   include Gitlab::Database::MigrationHelpers
 
   # Set this constant to true if this migration requires downtime.
-  DOWNTIME = true
+  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 = 'Adding foreign keys'
+  DOWNTIME_REASON = ''
 
   # When using the methods "add_concurrent_index" or "add_column_with_default"
   # you must disable the use of transactions as these methods can not run in an
@@ -20,23 +20,32 @@ class AddForeignKeysToTimelogs < ActiveRecord::Migration
   #
   # To disable transactions uncomment the following line and remove these
   # comments:
-  # disable_ddl_transaction!
+  disable_ddl_transaction!
 
   def up
     change_table :timelogs do |t|
-      t.references :issue, index: true, foreign_key: { on_delete: :cascade }
-      t.references :merge_request, index: true, foreign_key: { on_delete: :cascade }
+      t.column :issue_id, :integer
+      t.column :merge_request_id, :integer
+    end
+
+    add_concurrent_index :timelogs, :issue_id
+    add_concurrent_index :timelogs, :merge_request_id
+
+    if Gitlab::Database.postgresql?
+      execute <<-EOF
+        ALTER TABLE timelogs ADD CONSTRAINT "fk_timelogs_issues_issue_id" FOREIGN KEY (issue_id) REFERENCES "issues" (id) ON DELETE CASCADE NOT VALID;
+        ALTER TABLE timelogs ADD CONSTRAINT "fk_timelogs_merge_requests_merge_request_id" FOREIGN KEY (merge_request_id) REFERENCES "merge_requests" (id) ON DELETE CASCADE NOT VALID;
+      EOF
+    else
+      execute "ALTER TABLE timelogs ADD CONSTRAINT fk_timelogs_issues_issue_id FOREIGN KEY (issue_id) REFERENCES issues(id) ON DELETE CASCADE;"
+      execute "ALTER TABLE timelogs ADD CONSTRAINT fk_timelogs_merge_requests_merge_request_id FOREIGN KEY (merge_request_id) REFERENCES merge_requests(id) ON DELETE CASCADE;"
     end
 
     Timelog.where(trackable_type: 'Issue').update_all("issue_id = trackable_id")
     Timelog.where(trackable_type: 'MergeRequest').update_all("merge_request_id = trackable_id")
-
-    remove_columns :timelogs, :trackable_id, :trackable_type
   end
 
   def down
-    add_reference :timelogs, :trackable, polymorphic: true, index: true
-
     Timelog.where('issue_id IS NOT NULL').update_all("trackable_id = issue_id, trackable_type = 'Issue'")
     Timelog.where('merge_request_id IS NOT NULL').update_all("trackable_id = merge_request_id, trackable_type = 'MergeRequest'")
 

db/post_migrate/20170206101007_remove_trackable_columns_from_timelogs.rb

@@ -0,0 +1,23 @@
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class RemoveTrackableColumnsFromTimelogs < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  # When using the methods "add_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" make sure that this
+  # method 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 fails and can be retried or reverted easily.
+  #
+  # To disable transactions uncomment the following line and remove these
+  # comments:
+  # disable_ddl_transaction!
+
+  def change
+    remove_columns :timelogs, :trackable_id, :trackable_type
+  end
+end

db/post_migrate/20170206101030_validate_foreign_keys_on_timelogs.rb

@@ -0,0 +1,32 @@
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class ValidateForeignKeysOnTimelogs < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  # When using the methods "add_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" make sure that this
+  # method 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 fails and can be retried or reverted easily.
+  #
+  # To disable transactions uncomment the following line and remove these
+  # comments:
+  disable_ddl_transaction!
+
+  def up
+    if Gitlab::Database.postgresql?
+      execute <<-EOF
+        ALTER TABLE timelogs VALIDATE CONSTRAINT "fk_timelogs_issues_issue_id";
+        ALTER TABLE timelogs VALIDATE CONSTRAINT "fk_timelogs_merge_requests_merge_request_id";
+      EOF
+    end
+  end
+
+  def down
+    # noop
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20170206071414) do
+ActiveRecord::Schema.define(version: 20170206101030) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -1341,8 +1341,8 @@ ActiveRecord::Schema.define(version: 20170206071414) do
   add_foreign_key "protected_branch_merge_access_levels", "protected_branches"
   add_foreign_key "protected_branch_push_access_levels", "protected_branches"
   add_foreign_key "subscriptions", "projects", on_delete: :cascade
-  add_foreign_key "timelogs", "issues", on_delete: :cascade
-  add_foreign_key "timelogs", "merge_requests", on_delete: :cascade
+  add_foreign_key "timelogs", "issues", name: "fk_timelogs_issues_issue_id", on_delete: :cascade
+  add_foreign_key "timelogs", "merge_requests", name: "fk_timelogs_merge_requests_merge_request_id", on_delete: :cascade
   add_foreign_key "trending_projects", "projects", on_delete: :cascade
   add_foreign_key "u2f_registrations", "users"
 end