Jerry Brenner <jbrenner@xxxxxxxxxxxxx> writes: > We are currently on 13. We are capturing the explain plans for query > executions taking 1 second or longer and storing the json files. We are > most of the way through implementing a home grown solution to generate a > consistent hash value for a query plan, so we can find queries with > multiple plans. I've attached 2 query plans that we've captured that > differ in a seemingly strange way. (All executions are from the same exact > code path.) One of the plans has parameter markers in the predicates in > the values for "Recheck Cond" and "Index Cond", while the other does not. > Any insight into why we are seeing parameter markers in the body of the > query plan? The one with parameter markers is a "generic" plan for a parameterized query. When you get a plan without parameter markers for the same input query, that's a "custom" plan in which concrete values of the parameters have been substituted, possibly allowing const-simplification and more accurate rowcount estimates. The backend will generally try custom plans a few times and then try a generic plan to see if that's meaningfully slower -- if not, replanning each time is deemed to be wasteful. regards, tom lane
