Bug/Slow: Truncation very slow in case of many tables (PG)

[zealot128]

We have about 150 tables and are using PostgreSQL. After switching to a cloud development VM with probable slower Hard Drive access, we noticed a delay for starting the test suite each time.

We saw the TRUNCATE table statements in Test log:

And found, that factory_bot-preload will truncate all table every time. In sum, that took us 3 extra seconds boot time.

Environment

• Ruby 3.3.0
• Rails 7.1.3.2
• PG 16.2
• Ubuntu 22 Cloud VM - 8 core, 32 GB RAM - PgTune config applied.

Workaround

We only use 3 preload factories that touches only 4 tables, so we overrode the tables that FactoryBot::Preload truncates:

# spec_helper / test_helper
module FactoryBot
  module Preload
    def self.active_record_names
      %w[organisations domains users memberships]
    end
  end
end

Ideas for a full fix

• Maybe make the tables configurable
• Faster SSD / No CoudVM but local or Bare Metal needed
• Maybe better to batch all truncations into one call?