openGauss每日一练第 21 天 | 数据库例行维护

学习目标
学习检查数据库运行状态、锁信息、维护表、重建索引等数据库维护操作技术

课程作业
1、使用操作系统命令和数据库工具检查实例状态

root@modb:~# su - omm
omm@modb:~$ ps -ef|grep gaussdb
omm          1     0  0 10:01 ?        00:00:01 gaussdb
omm        410   406  0 10:05 pts/0    00:00:00 grep gaussdb
omm@modb:~$ ps -Tp 1
  PID  SPID TTY          TIME CMD
    1     1 ?        00:00:00 gaussdb
    1   296 ?        00:00:00 alarm
    1   297 ?        00:00:00 reaper
    1   294 ?        00:00:00 syslogger
    1   295 ?        00:00:00 jemalloc_bg_thd
    1   298 ?        00:00:00 jemalloc_bg_thd
    1   299 ?        00:00:00 jemalloc_bg_thd
    1   287 ?        00:00:00 jemalloc_bg_thd
    1   293 ?        00:00:00 gaussdb
    1   343 ?        00:00:00 checkpointer
    1   344 ?        00:00:00 Spbgwriter
    1   345 ?        00:00:00 pagewriter
    1   346 ?        00:00:00 pagewriter
    1   350 ?        00:00:00 WALwriter
    1   351 ?        00:00:00 WALwriteraux
    1   352 ?        00:00:00 AVClauncher
    1   347 ?        00:00:00 pagewriter
    1   348 ?        00:00:00 pagewriter
    1   349 ?        00:00:00 pagewriter
    1   353 ?        00:00:00 Jobscheduler
    1   354 ?        00:00:00 asyncundolaunch
    1   355 ?        00:00:00 globalstats
    1   356 ?        00:00:00 applylauncher
    1   357 ?        00:00:00 statscollector
    1   358 ?        00:00:00 percentworker
    1   359 ?        00:00:00 ashworker
    1   360 ?        00:00:00 TrackStmtWorker
    1   361 ?        00:00:00 auditor
    1   362 ?        00:00:00 2pccleaner
    1   363 ?        00:00:00 faultmonitor
    1   364 ?        00:00:00 WLMworker
    1   365 ?        00:00:00 WLMmonitor
    1   366 ?        00:00:00 WLMarbiter
    1   367 ?        00:00:00 undorecycler

omm@modb:~$ gs_ctl status -D /var/lib/opengauss/data
[2022-12-14 10:07:34.345][438][][gs_ctl]: gs_ctl status,datadir is /var/lib/opengauss/data 
gs_ctl: server is running (PID: 1)
/usr/local/opengauss/bin/gaussdb

omm@modb:~$ gsql -r
gsql ((openGauss 3.0.0 build 02c14696) compiled at 2022-04-01 18:12:00 commit 0 last mr  )
Non-SSL connection (SSL connection is recommended when requiring high-security)
Type "help" for help.

omm=# show data_directory;
     data_directory      
-------------------------
 /var/lib/opengauss/data
(1 row)

2、检查锁信息

–查询数据库中的锁信息

SELECT * FROM pg_locks;

–查询等待锁的线程状态信息

SELECT * FROM pg_thread_wait_status WHERE wait_status = ‘acquire lock’;

omm=#  SELECT * FROM pg_locks;
  locktype  | database | relation | page | tuple | bucket | virtualxid | transactionid | classid | objid | objsubid | virtualt
ransaction |       pid       |    sessionid    |      mode       | granted | fastpath |      locktag      | global_sessionid 
------------+----------+----------+------+-------+--------+------------+---------------+---------+-------+----------+---------
-----------+-----------------+-----------------+-----------------+---------+----------+-------------------+------------------
 relation   |    16384 |    12010 |      |       |        |            |               |         |       |          | 11/8    
           | 281471523519728 | 281471523519728 | AccessShareLock | t       | t        | 4000:2eea:0:0:0:0 | 0:0#0
 virtualxid |          |          |      |       |        | 11/8       |               |         |       |          | 11/8    
           | 281471523519728 | 281471523519728 | ExclusiveLock   | t       | t        | b:8:0:0:0:7       | 0:0#0
 virtualxid |          |          |      |       |        | 8/13       |               |         |       |          | 8/13    
           | 281471693913328 | 281471693913328 | ExclusiveLock   | t       | t        | 8:d:0:0:0:7       | 0:0#0
(3 rows)

omm=#
omm=# omm=#
omm=# --查询等待锁的线程状态信息
SELECT * FROM pg_thread_wait_status WHERE wait_status = ‘acquire lock’;

node_name | db_name | thread_name | query_id | tid | sessionid | lwtid | psessionid | tlevel | smpid | wait_status | wait_eve
nt | locktag | lockmode | block_sessionid | global_sessionid

-----------±--------±------------±---------±----±----------±------±-----------±-------±------±------------±--------
—±--------±---------±----------------±-----------------

3、查看数据库版本、日志信息
–数据库版本
SELECT version();

–在gsql中
! ls /var/lib/opengauss/data/pg_log
\q

–数据库日志位置
cd /var/lib/opengauss/data/pg_log
ls /var/lib/opengauss/data/pg_log

4、检查应用连接数、查看现有最大连接数
–执行如下SQL语句查看连接数。
gsql -r

SELECT count(*) FROM (SELECT pg_stat_get_backend_idset() AS backendid) AS s;

–查看现有最大连接数。
SHOW max_connections;

omm=# SELECT count(*) FROM (SELECT pg_stat_get_backend_idset() AS backendid) AS s;
 count 
-------
    21
(1 row)

omm=# 
omm=# --查看现有最大连接数。
omm=# SHOW max_connections;
 max_connections 
-----------------
 200
(1 row)

5、对表进行VACUUM、VACUUM FULL和ANALYZE操作

为了保证数据库的有效运行，数据库必须在插入/删除操作后，基于客户场景，定期做VACUUM FULL和ANALYZE，更新统计信息，以便获得更优的性能。
VACUUM和ANALYZE会导致I/O流量的大幅增加，这可能会影响其他活动会话的性能。

omm=# create table t2(id int,name varchar(10));
CREATE TABLE
omm=# insert into t2 values(10,'aa'),(20,'bb'),(30,'cc');
INSERT 0 3
omm=# vacuum t2;
VACUUM
omm=# vacuum full t2;
VACUUM
omm=# analyze t2;
ANALYZE
omm=# analyze verbose t2;
INFO:  analyzing "public.t2"(gaussdb pid=1)
INFO:  ANALYZE INFO : "t2": scanned 1 of 1 pages, containing 3 live rows and 0 dead rows; 3 rows in sample, 3 estimated total rows(gaussdb pid=1)
ANALYZE
omm=# vacuum analyze t2;
VACUUM

维护建议：

定期对部分大表做VACUUM FULL，在性能下降后为全库做VACUUM FULL，目前暂定每月做一次VACUUM FULL。

定期对系统表做VACUUM FULL，主要是PG_ATTRIBUTE。

启用系统自动清理线程（AUTOVACUUM）自动执行VACUUM和ANALYZE，回收被标识为删除状态的记录空间，并更新表的统计数据。

6、建表、索引，进行重建索引操作

root@modb:~# su - omm
omm@modb:~$ gsql -r
gsql ((openGauss 3.0.0 build 02c14696) compiled at 2022-04-01 18:12:00 commit 0 last mr  )
Non-SSL connection (SSL connection is recommended when requiring high-security)
Type "help" for help.

omm=# create table t1(id int,name varchar(10));
CREATE TABLE
omm=# create index t1_id on t1(id);
CREATE INDEX
omm=# reindex table t1;
REINDEX