Drop forked_project_links table

changelogs/unreleased/drop_forked_project_links_table.yml

+---
+title: Drop forked_project_links table
+merge_request: 20771
+author: Lee Tickett
+type: other

db/migrate/20200215222507_drop_forked_project_links_fk.rb

+# frozen_string_literal: true
+
+class DropForkedProjectLinksFk < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    with_lock_retries do
+      remove_foreign_key_if_exists :forked_project_links, column: :forked_to_project_id
+    end
+  end
+
+  def down
+    unless foreign_key_exists?(:forked_project_links, :projects, column: :forked_to_project_id)
+      with_lock_retries do
+        # rubocop: disable Migration/AddConcurrentForeignKey
+        add_foreign_key :forked_project_links, :projects, column: :forked_to_project_id, on_delete: :cascade, validate: false
+      end
+    end
+
+    fk_name = concurrent_foreign_key_name(:forked_project_links, :forked_to_project_id, prefix: 'fk_rails_')
+    validate_foreign_key(:forked_project_links, :forked_to_project_id, name: fk_name)
+  end
+end

db/migrate/20200215225103_drop_forked_project_links_table.rb

+# frozen_string_literal: true
+
+class DropForkedProjectLinksTable < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  def change
+    drop_table "forked_project_links", id: :serial do |t|
+      t.integer "forked_to_project_id", null: false
+      t.integer "forked_from_project_id", null: false
+      t.datetime "created_at"
+      t.datetime "updated_at"
+      t.index ["forked_to_project_id"], name: "index_forked_project_links_on_forked_to_project_id", unique: true
+    end
+  end
+end

db/schema.rb

@@ -1654,14 +1654,6 @@ ActiveRecord::Schema.define(version: 2020_02_20_180944) do
     t.index ["root_project_id"], name: "index_fork_networks_on_root_project_id", unique: true
   end
 
-  create_table "forked_project_links", id: :serial, force: :cascade do |t|
-    t.integer "forked_to_project_id", null: false
-    t.integer "forked_from_project_id", null: false
-    t.datetime "created_at"
-    t.datetime "updated_at"
-    t.index ["forked_to_project_id"], name: "index_forked_project_links_on_forked_to_project_id", unique: true
-  end
-
   create_table "geo_cache_invalidation_events", force: :cascade do |t|
     t.string "key", null: false
   end
@@ -4747,7 +4739,6 @@ ActiveRecord::Schema.define(version: 2020_02_20_180944) do
   add_foreign_key "fork_network_members", "projects", column: "forked_from_project_id", name: "fk_b01280dae4", on_delete: :nullify
   add_foreign_key "fork_network_members", "projects", on_delete: :cascade
   add_foreign_key "fork_networks", "projects", column: "root_project_id", name: "fk_e7b436b2b5", on_delete: :nullify
-  add_foreign_key "forked_project_links", "projects", column: "forked_to_project_id", name: "fk_434510edb0", on_delete: :cascade
   add_foreign_key "geo_container_repository_updated_events", "container_repositories", name: "fk_212c89c706", on_delete: :cascade
   add_foreign_key "geo_event_log", "geo_cache_invalidation_events", column: "cache_invalidation_event_id", name: "fk_42c3b54bed", on_delete: :cascade
   add_foreign_key "geo_event_log", "geo_container_repository_updated_events", column: "container_repository_updated_event_id", name: "fk_6ada82d42a", on_delete: :cascade

lib/gitlab/database/migration_helpers.rb

@@ -235,11 +235,17 @@ module Gitlab
       # PostgreSQL constraint names have a limit of 63 bytes. The logic used
       # here is based on Rails' foreign_key_name() method, which unfortunately
       # is private so we can't rely on it directly.
-      def concurrent_foreign_key_name(table, column)
+      #
+      # prefix:
+      # - The default prefix is `fk_` for backward compatibility with the existing
+      # concurrent foreign key helpers.
+      # - For standard rails foreign keys the prefix is `fk_rails_`
+      #
+      def concurrent_foreign_key_name(table, column, prefix: 'fk_')
         identifier = "#{table}_#{column}_fk"
         hashed_identifier = Digest::SHA256.hexdigest(identifier).first(10)
 
-        "fk_#{hashed_identifier}"
+        "#{prefix}#{hashed_identifier}"
       end
 
       # Long-running migrations may take more than the timeout allowed by