2013-03-28 17:01:50.427 CST,,,10350,,50bd676b.286e,2,,2012-12-04 11:00:59 CST,,0,LOG,00000,"checkpoints are occurring too frequently (11 seconds apart)",,"Consider increasing the configuration parameter ""checkpoint_segments"".",,,,,,,""

但是不会记录系统正常的checkpoint，如果你想看系统一天之类发生了多少次checkpoint，以及每次checkpoint的一些详细信息，比如buffer,sync等，就可以通过设置log_checkpoints，该参数默认值是off，修改log_checkpoints = on 示例：

postgres=# show log_checkpoints ;

log_checkpoints

-----------------

on

(1 row)

postgres=# checkpoint;

CHECKPOINT

postgres=#

[postgres@localhost pg_log]$ tail -f postgresql-2013-03-29_000000.csv

2013-03-29 12:43:38.900 PDT,,,5557,,514933a7.15b5,45,,2013-03-19 20:57:27 PDT,,0,LOG,00000,"checkpoint starting: immediate force wait",,,,,,,,,""

2013-03-29 12:43:38.941 PDT,,,5557,,514933a7.15b5,46,,2013-03-19 20:57:27 PDT,,0,LOG,00000,"checkpoint complete: wrote 0 buffers (0.0%); 0 transaction log file(s) added, 0 removed, 0 recycled; write=0.009 s, sync=0.000 s, total=0.040 s; sync files=0, longest=0.000 s, average=0.000 s",,,,,,,,,""

4.监控数据库的锁

数据库的锁通常可以在pg_locks这个系统表里找，但这只是当前的锁表/行信息，如果你想看一天内有多少个超过死锁时间的锁发生，可以在日志里设置并查看，log_lock_waits 默认是off，可以设置开启。这个可以区分SQL慢是资源紧张还是锁等待的问题。 示例:

postgres=# show log_lock_waits ;

log_lock_waits

----------------

on

(1 row)

postgres=# show deadlock_timeout ;

deadlock_timeout

------------------

1s

(1 row)

--模拟锁

postgres=# begin;

BEGIN

postgres=# SELECT * FROM t_ken_yon ;

id

----

11

(1 row)

postgres=# delete from t_ken_yon ;

DELETE 1

--另一个session

postgres=# begin;

BEGIN

postgres=# delete from t_ken_yon;

--查看日志

[postgres@localhost pg_log]$ tail -f postgresql-2013-03-29_000000.csv

2013-03-29 14:01:02.673 PDT,"postgres","postgres",3056,"[local]",5155f4d9.bf0,6,"DELETE waiting",2013-03-29 13:08:57 PDT,5/12502,2659,LOG,00000,"process 3056 still waiting for ShareLock on transaction 2658 after 1000.398 ms",,,,,,"delete from t_ken_yon;",,,"psql"

2013-03-29 14:02:06.208 PDT,"postgres","postgres",3056,"[local]",5155f4d9.bf0,7,"DELETE waiting",2013-03-29 13:08:57 PDT,5/12502,2659,LOG,00000,"process 3056 acquired ShareLock on transaction 2658 after 64535.339 ms",,,,,,"delete from t_ken_yon;",,,"psql"

2013-03-29 14:02:06.209 PDT,"postgres","postgres",3056,"[local]",5155f4d9.bf0,8,"DELETE",2013-03-29 13:08:57 PDT,5/12502,2659,LOG,00000,"duration: 64536.118 ms statement: delete from t_ken_yon;",,,,,,,,,"psql"

还有一些Debug功能，适合修改 源码调试，一般的的 系统上并不需要，暂时比较关注的就这些。