I don't know if this will help. In my days with Oracle and Sybase, it use to work for both. Just give PG a hint like this select count(*) from test where id > 0;
You can try it while you wait for other on the list with more knowledge for a different idea. Mel On Sun, Oct 11, 2009 at 4:26 AM, 旭斌 裴 <peixu...@yahoo.com.cn> wrote: > > I have a 30,000,000 records table, counts the record number to need for 40 > seconds. > The table has a primary key on column id; > > perf=# explain select count(*) from test; > ... > ----------------------------------------- > Aggregate (cost=603702.80..603702.81 rows=1 width=0) > -> Seq scan on test (cost=0.00..527681.04 rows=30408704 width=0) > ... > perf=# select count(*) from test; > count > ------------ > 30408704 > > perf=# > > > The postgresql database uses the table full scan.but in oracle, the similar > SQL uses the index full scanning,speed quickly many than postgresql. > > postgresql's optimizer whether to have the necessity to make the > adjustment? > > > > ------------------------------ > 好玩贺卡等你发，邮箱贺卡全新上线！<http://cn.rd.yahoo.com/mail_cn/tagline/card/*http://card.mail.cn.yahoo.com/>
