Query planners are like compilers: sophisticated and sometimes surprising but not perfect. Writing sql is just like writing any other code: optimize for an easy

Query planners are like compilers: sophisticated and sometimes surprising but not perfect. Writing sql is just like writing any other code: optimize for an easy to understand query first, performance if needed (and always comment your performance optimizations)! They are also like just-in-time hotspot optimizations: the query planner keeps statistics and the second run of a query can be 10x or more faster than the first run. (Side note: most analytics queries in my experience are run against cold data so it’s usually worth optimizing for first-query performance.) This stuff is also my day job, and fun!