Hi, On 2018-08-16 17:27:45 +0300, Surafel Temesgen wrote: > FETCH FIRST with PERCENT option is SQL standard that state limit count to > be specified in a percentage in addition to specify it in exact count and > listed as one of Major features simply not implemented yet in recent wiki > page [1]. > > I implemented it by executing the query plan twice. One without limit > filter to find the total number of row that will be feed to limit node so > the exact limit count can be calculated and the query plan execute again > with limit filter with newly calculated exact count .
Won't that have rather massive issues with multiple evaluations of clauses in the query? Besides being really expensive? I think you'd have to instead spill the query results into a tuplestore (like we do for FOR HOLD queries at end of xact), and then do the computations based on that. - Andres
