Add creator_id column to custom_emoji table

To keep track of who added a the custom emoji add a foreign key to the
user id.

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/284641

changelogs/unreleased/tc-add-custom-emoji-creator.yml

+---
+title: Add creator to custom emoji
+merge_request: 53879
+author:
+type: changed

db/migrate/20210205134213_add_creator_id_to_custom_emoji.rb

+# frozen_string_literal: true
+
+class AddCreatorIdToCustomEmoji < ActiveRecord::Migration[6.0]
+  DOWNTIME = false
+
+  def up
+    # Custom Emoji is at the moment behind a default-disabled feature flag. It
+    # will be unlikely there are any records in this table, but to able to
+    # ensure a not-null constraint delete any existing rows.
+    # Roll-out issue: https://gitlab.com/gitlab-org/gitlab/-/issues/231317
+    execute 'DELETE FROM custom_emoji'
+
+    add_reference :custom_emoji, # rubocop:disable Migration/AddReference
+                  :creator,
+                  index: true,
+                  null: false, # rubocop:disable Rails/NotNullColumn
+                  foreign_key: false # FK is added in 20210219100137
+  end
+
+  def down
+    remove_reference :custom_emoji, :creator
+  end
+end

db/migrate/20210219100137_add_creator_foreign_key_to_custom_emoji.rb

+# frozen_string_literal: true
+
+class AddCreatorForeignKeyToCustomEmoji < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  FK_NAME = 'fk_custom_emoji_creator_id'
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_foreign_key :custom_emoji, :users,
+                               on_delete: :cascade,
+                               column: :creator_id,
+                               name: FK_NAME
+  end
+
+  def down
+    with_lock_retries do
+      remove_foreign_key :custom_emoji, name: FK_NAME
+    end
+  end
+end

db/schema_migrations/20210205134213

+7c368cad497ccfd86c6a92e2edfec1d2a16879eb749184b1d20c5ab4c702b974
\ No newline at end of file

db/schema_migrations/20210219100137

+be2ddc15e16d7d59bd050a60faaa0b6941d94ba7c47a88be473bcf3a17bb2763
\ No newline at end of file

db/structure.sql

@@ -11607,6 +11607,7 @@ CREATE TABLE custom_emoji (
     name text NOT NULL,
     file text NOT NULL,
     external boolean DEFAULT true NOT NULL,
+    creator_id bigint NOT NULL,
     CONSTRAINT check_8c586dd507 CHECK ((char_length(name) <= 36)),
     CONSTRAINT check_dd5d60f1fb CHECK ((char_length(file) <= 255))
 );
@@ -21967,6 +21968,8 @@ CREATE INDEX index_csv_issue_imports_on_project_id ON csv_issue_imports USING bt
 
 CREATE INDEX index_csv_issue_imports_on_user_id ON csv_issue_imports USING btree (user_id);
 
+CREATE INDEX index_custom_emoji_on_creator_id ON custom_emoji USING btree (creator_id);
+
 CREATE UNIQUE INDEX index_custom_emoji_on_namespace_id_and_name ON custom_emoji USING btree (namespace_id, name);
 
 CREATE UNIQUE INDEX index_daily_build_group_report_results_unique_columns ON ci_daily_build_group_report_results USING btree (project_id, ref_path, date, group_name);
@@ -24686,6 +24689,9 @@ ALTER TABLE ONLY todos
 ALTER TABLE ONLY geo_event_log
     ADD CONSTRAINT fk_cff7185ad2 FOREIGN KEY (reset_checksum_event_id) REFERENCES geo_reset_checksum_events(id) ON DELETE CASCADE;
 
+ALTER TABLE ONLY custom_emoji
+    ADD CONSTRAINT fk_custom_emoji_creator_id FOREIGN KEY (creator_id) REFERENCES users(id) ON DELETE CASCADE;
+
 ALTER TABLE ONLY bulk_import_entities
     ADD CONSTRAINT fk_d06d023c30 FOREIGN KEY (project_id) REFERENCES projects(id) ON DELETE CASCADE;