Postgres数据库维护

1.全自动备份

需要在备份机上也安装postgres(最好同一个版本)

在postgres目录下建立密码保存文件(明码保存,所以保密很重要),如果不建立,则因为每次备份都要输入密码,不能进行自动备份

#创建.pgpass文件
touch .pgpass
#在文件中写入以下内容,可多行
#127.0.0.1:5432:dbName:dbUser:dbPassword
#127.0.0.1:5432:dbName2:dbUser2:dbPassword2

创建自动脚本,自动按月分文件夹

#!/bin/sh
. /etc/profile
. ~/.bash_profile
dirname=$(date +%Y%m)
filename=$(date +%Y%m%d%H%M%S)
mkdir -p /home/postgres/backup/$dirname/
pg_dump -h [ipAddr] -U [dbUser] [dbName]| gzip>/home/postgres/backup/$dirname/bk_$filename.gz

创建crontab自动执行即可

#去除限制导出
#--no-tablespaces 代表去除表空间限制(不导出表空间信息)
#-O 代表不导出对象/库的所有者信息
#-x 代表不导出ACL权限信息和表的权限信息
pg_dump -h 127.0.0.1 -U postgres --no-tablespaces -O -x -f sqlname.sql  dbname
pg_dump -h 127.0.0.1 -U postgres --no-tablespaces -O -x dbname | gzip>dbname.gz

2.恢复数据库

解压gz

#直接解压,不保留原gz文件
gunzip xxx.gz
#解压保留源gz文件
gunzip -c xxx.gz > xxx.sql

进去pgsql控制台

psql -U dbUser

#切换到待导入的数据库
c dbName;
#导入sql文件
i xxx.sql
#退出控制台
q

3.PG查看当前进程 

#查看连接数和详情
select * from pg_stat_activity;
#查看最大连接数
show max_connections;

4.批量删除空闲进程

#使用PG账户在数据库客户端上删除
SELECT pg_terminate_backend(p.pid) FROM (
SELECT pid FROM pg_stat_activity WHERE pid <> pg_backend_pid() AND state = 'idle'
UNION ALL
SELECT pid FROM pg_stat_activity WHERE pid <> pg_backend_pid() AND state = 'idle in transaction' AND backend_xid IS NULL
) p

#直接到服务器上删除
ps -ef|grep postgres|grep idle |awk '{print $2}' | xargs kill

kill有两种方式，第一种是：
SELECT pg_cancel_backend(PID);
这种方式只能kill select查询，对update、delete 及DML不生效)

第二种是：
SELECT pg_terminate_backend(PID);
这种可以kill掉各种操作(select、update、delete、drop等)操作

5.系统表结构

PG_TABLES 查看所有表

查看表结构

SELECT a.attnum,
a.attname AS field,
t.typname AS type,
a.attlen AS length,
a.atttypmod AS lengthvar,
a.attnotnull AS notnull,
b.description AS comment
FROM pg_class c,
pg_attribute a
LEFT OUTER JOIN pg_description b ON a.attrelid=b.objoid AND a.attnum = b.objsubid,
pg_type t
WHERE c.relname = 'udoc_saldiscount'
and a.attnum > 0
and a.attrelid = c.oid
and a.atttypid = t.oid
ORDER BY a.attnum;

 查看索引

SELECT
A.SCHEMANAME,
A.TABLENAME,
A.INDEXNAME,
A.TABLESPACE,
A.INDEXDEF,
B.AMNAME,
C.INDEXRELID,
C.INDNATTS,
C.INDISUNIQUE,
C.INDISPRIMARY,
C.INDISCLUSTERED,
D.DESCRIPTION
FROM
PG_AM B
LEFT JOIN PG_CLASS F ON B.OID = F.RELAM
LEFT JOIN PG_STAT_ALL_INDEXES E ON F.OID = E.INDEXRELID
LEFT JOIN PG_INDEX C ON E.INDEXRELID = C.INDEXRELID
LEFT OUTER JOIN PG_DESCRIPTION D ON C.INDEXRELID = D.OBJOID,
PG_INDEXES A
WHERE
A.SCHEMANAME = E.SCHEMANAME AND A.TABLENAME = E.RELNAME AND A.INDEXNAME = E.INDEXRELNAME
AND E.SCHEMANAME = 'public'

XX .在线热备份（归档） -- 待研究

（一）备份
1，配置归档模式
配置归档需要编辑postgresql.conf文件，默认为与/usr/local/pgsql/data/目录下
vim /usr/local/pgsql/data/postgesql.conf
archive_mode = on
archive_command = ‘cp %p /usr/local/pgsql/backup/archived_log/%f’
注：%p要被归档的日志文件的路径，%f是要被归档的日志文件的文件名
2，启动数据库
pg_ctl –D /usr/local/pgsql/data start
3，创建数据库arch
createdb arch
4，创建表并插入记录
psql arch
arch=# create table tb(a int);
arch=# insert into tb(a) values(1);
5，创建备份
arch=# select pg_start_backup(‘baseline’);
6，备份整个data目录
tar –jcv –f /usr/local/pgsql/backup/baseline.tar.bz2 /usr/local/pgsql/data/
7，停止备份
psql arch
arch=# select pg_stop_backup();
8，插入新记录，然后切换日志，重复3次
arch=# insert into tb(a) values(2);
arch=# select pg_switch_xlog();
arch=# insert into tb(a) values(3);
arch=# select pg_switch_xlog();
arch=# insert into tb(a) values(4);
arch=# select pg_switch_xlog();
9，把/data/pg_xlog/下的WAL日志文件复制到预设的归档目录下，保证产生的WAL日志都已归档。
（二）恢复
1，停止数据库
pg_ctl –D /usr/local/pgsql/data/ stop
2，删除/data/
rm –r /usr/local/pgsql/data/
3，恢复备份
tar –jxv –f /usr/local/pgsql/backup/baseline.tar.bz2 –C /
4，清空/data/pg_xlog/目录下所有文件
rm –r /usr/local/pgsql/data/pg_xlog/
5，创建/pg_xlog/及其下面的archive_status目录
mkdir /usr/local/pgsql/data/pg_xlog/
mkdir /usr/local/pgsql/data/pg_xlog/archive_status
6，在/data/目录下创建recovery.conf
vim /usr/local/pgsql/data/recovery.conf
restore_command = ‘cp /usr/local/pgsql/backup/archived_log/%f “%p”’
7，启动数据库
pg_ctl –D /usr/local/pgsql/data/ start
一切正常的话数据库就会自动应用WAL日志进行恢复
8，查看数据库arch是否恢复
psql arch
arch=# select * from tb;
a
---
1
2
3
4
(4 rows)
至此，数据已经成功恢复！