wiki pages: convert other_names to array (#3987).

db/migrate/20181113174914_change_strings_to_arrays_on_wiki_pages.rb

@@ -0,0 +1,26 @@
+class ChangeStringsToArraysOnWikiPages < ActiveRecord::Migration[5.2]
+  def up
+    WikiPage.without_timeout do
+      change_column :wiki_pages, :other_names, "text[]", using: "string_to_array(other_names, ' ')::text[]", default: "{}"
+      change_column :wiki_page_versions, :other_names, "text[]", using: "string_to_array(other_names, ' ')::text[]", default: "{}"
+
+      remove_column :wiki_pages, :other_names_index
+      execute "DROP TRIGGER trigger_wiki_pages_on_update_for_other_names ON wiki_pages"
+
+      add_index :wiki_pages, :other_names, using: :gin
+    end
+  end
+
+  def down
+    WikiPage.without_timeout do
+      remove_index :wiki_pages, :other_names
+
+      add_column :wiki_pages, :other_names_index, :tsvector
+      add_index :wiki_pages, :other_names_index, using: :gin
+      execute "CREATE TRIGGER trigger_wiki_pages_on_update_for_other_names BEFORE INSERT OR UPDATE ON wiki_pages FOR EACH ROW EXECUTE PROCEDURE tsvector_update_trigger('other_names_index', 'public.danbooru', 'other_names')"
+
+      change_column :wiki_pages, :other_names, "text", using: "array_to_string(other_names, ' ')", default: nil
+      change_column :wiki_page_versions, :other_names, "text", using: "array_to_string(other_names, ' ')", default: nil
+    end
+  end
+end