High CPU usage when postgres_exporter is enabled

CPU usage when postgres_exporter is enabled is pretty high. I've attached a screenshot with metrics after disabling postgres_exporter - cpu usage goes down 

 

after upgrade from 2.25.0 to 2.26.0 is a bit better, but cpu usage is also pretty high

  

I realized that the problem may be also in our environment (or database) but maybe your guidelines will be helpful.