Alex Jesipow discusses the importance of monitoring SQL statements in Postgres, focusing on how even SELECT queries can lead to data being written to disk. The article delves into the inner workings of Postgres, explaining concepts such as multi-version concurrency control and the organization of table data. Surprisingly, the author highlights how row updates in Postgres create new versions of data rather than updating the existing one, leading to potential performance implications. The discussion also covers mechanisms like hint bits and page pruning that can cause writes by read-only statements, shedding light on the complexities of database management.
https://jesipow.com/blog/postgres-reads-cause-writes/