module ActiveRecord::ConnectionAdapters::QueryCache::ConnectionPoolConfiguration

def initialize(...)
  super
  @query_cache_version = Concurrent::AtomicFixnum.new
  @thread_query_caches = QueryCacheRegistry.new
  @query_cache_max_size = \
    case query_cache = db_config&.query_cache
    when 0, false
      nil
    when Integer
      query_cache
    when nil
      DEFAULT_SIZE
    end
end