Use normal associations instead of polymorphic.

We can't properly use foreign keys on columns that are configured for
polymorphic associations which has disadvantages related to data
integrity and storage. Given we only use time tracking for Issues and
Merge Requests we're moving to the usage of regular associations.

1 files changed, 45 insertions, 0 deletions

diff --git a/db/migrate/20170124174637_add_foreign_keys_to_timelogs.rb b/db/migrate/20170124174637_add_foreign_keys_to_timelogs.rb
new file mode 100644
index 00000000000..7956463e12c
--- /dev/null
+++ b/db/migrate/20170124174637_add_foreign_keys_to_timelogs.rb
@@ -0,0 +1,45 @@
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class AddForeignKeysToTimelogs < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  # Set this constant to true if this migration requires downtime.
+  DOWNTIME = true
+  # 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'
+
+  # 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
+    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 }
+    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'")
+
+    remove_columns :timelogs, :issue_id, :merge_request_id
+  end
+end