On Thu, Mar 27, 2025 at 6:12 AM Ilia Evdokimov <ilya.evdoki...@tantorlabs.com> wrote: > I understand the concerns raised about the risk of opening the door to more > diagnostic detail across various plan nodes. However, in Hash Join, Merge > Join, and Nested Loop, EXPLAIN typically reveals at least some of the > planner’s expectations. For example, Hash Join shows the number of batches > and originally expected buckets, giving insight into whether the hash table > fit in memory. Merge Join shows unexpected Sort nodes when presorted inputs > were assumed. Nested Loop reflects planner assumptions via loops and row > estimates. In other words, these nodes expose at least some information about > what the planner thought would happen. > > Memoize is unique in that it shows runtime statistics (hits, misses, > evictions), but reveals nothing about the planner’s expectations. We don’t > see how many distinct keys were estimated or how many entries the planner > thought would fit in memory. This makes it very difficult to understand > whether Memoize was a good choice or not, or how to fix it when it performs > poorly.
Right. Without taking a strong position on this particular patch, I think it's entirely reasonable, as a concept, to think of making Memoize work similarly to what other nodes already do. -- Robert Haas EDB: http://www.enterprisedb.com
