On Thu, Dec 15, 2011 at 8:30 AM, 高增琦 <pgf...@gmail.com> wrote: > I found this several days ago when I try to debug a "fetch" of cursor. > And I have sent a mail to this list, but no one reply... > Maybe this is a very simple problem, please help me, thanks a lot... > > Here is the example: > create table t (a int); > insert into t values (1),(3),(5),(7),(9); > insert into t select a+1 from t; > begin; > declare c cursor for select * from t order by a; > fetch 3 in c; > fetch 3 in c; > fetch 3 in c; > > In 'PortalRun', a fetch stmt will be treated with PORTAL_UTIL_SELECT, > and then a tuplestore will be created in 'FillPortalStore' in the > fetch stmt's portal. > > In 'FillPortalStore', all result will be store at that tuplestore, > Then, go back to 'PortalRun'; next, 'PortalRunSelect' will send this > results to client... > > My problem is: why do we need create that tuplestore as an > middle storeage? why do not we just send these result to clent > at the first time?
Good question. I wouldn't expect it to matter very much for a three-row fetch, but maybe it does for larger ones? What is your motivation for investigating this? -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
