I recommend the book "SQL Performance Explained" by Markus Winand: https://sql-performance-explained.com/ https://sql-performance-explained.com/ It covers all

I recommend the book "SQL Performance Explained" by Markus Winand: https://sql-performance-explained.com/ https://sql-performance-explained.com/ It covers all major databases and is a good start to dive into database interna and how to interpret output from query analyzers. Other than that, I highly recommend joining the mailing list and IRC (#postgresql on libera.chat). Lots of valuable tricks being shared there by people with decades of experience.