On Fri, 2006-02-17 at 11:06, Emi Lu wrote: > >>>>In another way, whenever we "delete/truncate and then insert" data into > >>>>a table, it is better to "vacuum anaylze"? > >>>> > >>>> > >>>> > >>>> > >>>You shouldn't need a VACUUM if you haven't yet done any updates or > >>>deletes since the TRUNCATE. An ANALYZE seems like a good idea, though. > >>>(You could get away without ANALYZE if the new data has essentially the > >>>same statistics as the old, but if you're making only minor changes, why > >>>are you using this technique at all ...) > >>> > >>> > >>> > >>> > >>After truncate table A, around 60,000 will be inserted. Then a > >>comparision will be done between table A and table B. After that, table > >>B will be updated according to the comparision result. Records inserted > >>into table A is increasing everyday. > >> > >>So, your suggestion is that after the population of table A, the query > >>planner should be able to find the most efficient query plan because we > >>do truncate but not delete, and we do not need to do vacuum analyze at > >>all, right? > >> > >> > > > >no. the suggestion was that a VACUUM is not needed, but > >that an ANALYZE might be. > > > > > > Thank you gnari for your answer. But I am a bit confused about not running vacuum but only "analyze". Can I seperate these two operations? I guess "vacuum analyze" do both vacuum and analyze. Or "EXPLAIN ANALYZE" can do it for me? Yeah, vacuum analyze is kind of a leftover from the olden days when you could only run an analyze as part of a vacuum command. analyze has been it's own command for quite some time now.
