po 31. 8. 2020 v 13:29 odesílatel Thomas Kellerer <sham...@gmx.net> napsal:
> Thorsten Schöning schrieb am 31.08.2020 um 12:37: > > So for what query size or number of IDs to compare in IN would you > > consider a different approach at all? > > > In my experience "hundreds" of IDs tend to be quite slow if used with an > IN clause. > > Rewriting the IN to a JOIN against a VALUES clause is very often faster: > > So instead of: > > select * > from t > where id in (1,2,3, .... ,500); > > using this: > > select * > from t > join ( > values (1),(2),(3),...(500) > ) as x(id) on x.id = t.id > > produces more often than not a more efficient execution plan (assuming no > values are duplicated in the IN list) > > Obviously I don't know if such a re-write is even feasible though. > yes - this query probably will have a slow start, but the execution will be fast. Unfortunately, there are not available statistics. > Thomas > > > >
