Why count(*) can be very slow in PostgreSQL?

The article I read discusses the performance of systems and explains why counting can be slow in calculations. The author begins by introducing basic concepts related to computational complexity, illustrating how algorithm complexity impacts computation time. Specifically, the problems with counters in different data types and their influence on the extensiveness of calculations are emphasized. Furthermore, the article provides concrete examples to illustrate these theoretical concepts, demonstrating how appropriate approaches can enhance performance significantly. In conclusion, the author highlights the importance of optimizing algorithm performance and the need for continuous improvement in solutions regarding efficiency.