DELETE 1

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

2013-03-29 11:04:08.148 PDT,,,5554,,514933a6.15b2,42,,2013-03-19 20:57:26 PDT,,0,LOG,00000,"received SIGHUP, reloading configuration files",,,,,,,,,""

2013-03-29 11:04:08.151 PDT,,,5554,,514933a6.15b2,43,,2013-03-19 20:57:26 PDT,,0,LOG,00000,"parameter ""log_statement"" changed to ""mod""",,,,,,,,,""

2013-03-29 11:05:33.346 PDT,"postgres","postgres",2324,"[local]",5155d681.914,6,"idle",2013-03-29 10:59:29 PDT,2/11952,0,LOG,00000,"statement: insert into t_ken_yon values(1),(2);",,,,,,,,,"psql"

2013-03-29 11:05:52.033 PDT,"postgres","postgres",2324,"[local]",5155d681.914,7,"idle",2013-03-29 10:59:29 PDT,2/11953,0,LOG,00000,"statement: delete from t_ken_yon where id =1;",,,,,,,,,"psql"

--修改为all级别，并reload

postgres=# show log_statement;

log_statement

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

all

(1 row)

postgres=# select * from t_ken_yon;

id

----

2

(1 row)

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

2013-03-29 11:07:14.820 PDT,,,5554,,514933a6.15b2,44,,2013-03-19 20:57:26 PDT,,0,LOG,00000,"received SIGHUP, reloading configuration files",,,,,,,,,""

2013-03-29 11:07:14.821 PDT,,,5554,,514933a6.15b2,45,,2013-03-19 20:57:26 PDT,,0,LOG,00000,"parameter ""log_statement"" changed to ""all""",,,,,,,,,""

2013-03-29 11:07:19.784 PDT,"postgres","postgres",2324,"[local]",5155d681.914,8,"idle",2013-03-29 10:59:29 PDT,2/11954,0,LOG,00000,"statement: show log_statement;",,,,,,,,,"psql"

2013-03-29 11:07:28.631 PDT,"postgres","postgres",2324,"[local]",5155d681.914,9,"idle",2013-03-29 10:59:29 PDT,2/11955,0,LOG,00000,"statement: select * from t_ken_yon;",,,,,,,,,"psql"

一般的OLTP系统审计级别设置为ddl就够了，因为记录输出各种SQL对性能的影响还是蛮大的，安全级别高一点的也可以设置mod模式，有条件也可以不在数据库层面做，而是购买设备放在网络层监控解析。

2.定位慢查询SQL

可以设置一定时长的参数(log_min_duration_statement)，来记录超过该时长的所有SQL，对找出当前数据库的慢查询很有效。 比如log_min_duration_statement = 2s,记录超过2秒的SQL，改完需要reload

示例:

postgres=# show log_min_duration_statement ;

log_min_duration_statement

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

2s

(1 row)

postgres=# \timing

Timing is on.

postgres=# select now(),pg_sleep(1);

now | pg_sleep

------------------------------+----------

2013-03-29 12:36:48.13353-07 |

(1 row)

Time: 1001.844 ms

postgres=# select now(),pg_sleep(4);

now | pg_sleep

-------------------------------+----------

2013-03-29 12:36:28.309595-07 |

(1 row)

Time: 4002.273 ms

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

2013-03-29 12:36:19.265 PDT,"postgres","postgres",2324,"[local]",5155d681.914,10,"SELECT",2013-03-29 10:59:29 PDT,2/0,0,LOG,00000,"duration: 4027.183 ms statement: select now(),pg_sleep(4);",,,,,,,,,"psql"

可以看到只记录了4秒的那个SQL，而没有记录1秒的SQL。

3.监控数据库的checkpoint

当数据库进行一项大更新操作时，如果参数设置不当，会在日志里留下大量的告警信息，频繁的做checkpoint会导致系统变慢，如: