class TableMigrationHelper def self.read_only_table(table_name) ActiveRecord::Base.exec_sql <<-SQL CREATE OR REPLACE FUNCTION raise_read_only() RETURNS trigger AS $rro$ BEGIN RAISE EXCEPTION 'Discourse: Table is read only'; RETURN null; END $rro$ LANGUAGE plpgsql; SQL ActiveRecord::Base.exec_sql <<-SQL CREATE TRIGGER #{table_name}_read_only BEFORE INSERT OR UPDATE OR DELETE OR TRUNCATE ON #{table_name} FOR EACH STATEMENT EXECUTE PROCEDURE raise_read_only(); SQL end def self.delayed_drop(old_name:, new_name:, after_migration:, delay: nil, on_drop: nil) delay ||= Rails.env.production? ? 300 : 0 sql = <<SQL SELECT 1 FROM INFORMATION_SCHEMA.TABLES WHERE table_schema = 'public' AND table_name = :old_name AND EXISTS ( SELECT 1 FROM schema_migration_details WHERE name = :after_migration AND created_at <= (current_timestamp at time zone 'UTC' - interval :delay) ) AND EXISTS ( SELECT 1 FROM INFORMATION_SCHEMA.TABLES WHERE table_schema = 'public' AND table_name = :new_name ) LIMIT 1 SQL if ActiveRecord::Base.exec_sql(sql, old_name: old_name, new_name: new_name, delay: "#{delay.to_i || 0} seconds", after_migration: after_migration).to_a.length > 0 on_drop&.call ActiveRecord::Base.exec_sql("DROP TABLE #{old_name}") end end end