Re: insert/update performance

And I also found the pg_stat_all_tables may be not so accurate.

testdb=# truncate test;
testdb=# select pg_stat_reset_single_table_counters(42515);
testdb=# select
n_tup_ins,n_tup_upd,n_tup_hot_upd,n_tup_del,n_live_tup,n_dead_tup from
pg_stat_all_tables where relid=42515;
n_tup_ins | n_tup_upd | n_tup_hot_upd | n_tup_del | n_live_tup | n_dead_tup
-----------+-----------+---------------+-----------+------------+------------
0 | 0 | 0 | 0 | 0 | 0
(1 row)

##### run application a while

testdb=# select
n_tup_ins,n_tup_upd,n_tup_hot_upd,n_tup_del,n_live_tup,n_dead_tup from
pg_stat_all_tables where relid=42515;
n_tup_ins | n_tup_upd | n_tup_hot_upd | n_tup_del | n_live_tup | n_dead_tup
-----------+-----------+---------------+-----------+------------+------------
24829 | 24839 | 0 | 0 | 24829 | 24839
(1 row)

testdb=# select count(*) from test;
count
-------
24780
(1 row)

testdb=# vacuum verbose test;
...
DETAIL: 24780 index row versions were removed.
...
INFO: "test": found 863 removable, 24780 nonremovable row versions in
3148 out of 3148 pages

The n_tup_ins is bigger than actual rows, and the n_tup_upd is even
bigger than n_tup_ins!

Regards,
Jinhua Luo