PostgreSQL插件—数据恢复工具pg_recovery使用详解
说明
pg_recovery 是一款基于PostgreSQL的数据恢复工具。针对表做了 update/delete/rollback/dropcolumn 后的数据恢复。
版本支持
pg_revovery当前支持 PostgreSQL 12/13/14 。
安装
下载插件
墨天轮下载地址：https://www.modb.pro/download/434516
github下载地址：https://github.com/radondb/pg_recovery安装插件
解压
[postgres@lyp ~]$ ls -rlt pg_recovery-master.zip
-rw-r--r--.1 postgres postgres 13023Feb1520:42 pg_recovery-master.zip
[postgres@lyp ~]$ unzip pg_recovery-master.zip
Archive: pg_recovery-master.zip
886fc628534b43eb27344aaa07aabcc85f4d0b0e
creating: pg_recovery-master/
inflating: pg_recovery-master/.gitignore
inflating: pg_recovery-master/License
inflating: pg_recovery-master/Makefile
inflating: pg_recovery-master/README.md
inflating: pg_recovery-master/README_zh_CN.md
creating: pg_recovery-master/expected/
inflating: pg_recovery-master/expected/recovery.out
inflating: pg_recovery-master/pg_recovery--1.0.sql
inflating: pg_recovery-master/pg_recovery.c
inflating: pg_recovery-master/pg_recovery.control
creating: pg_recovery-master/sql/
inflating: pg_recovery-master/sql/recovery.sql
[postgres@lyp ~]$
编译安装
[postgres@lyp ~]$ cd pg_recovery-master/
[postgres@lyp pg_recovery-master]$ make PG_CONFIG=/opt/pgsql14.1/bin/pg_config
gcc -std=gnu99 -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Werror=vla -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -fexcess-precision=standard -O2 -fPIC -I. -I./ -I/opt/pgsql14.1/include/server -I/opt/pgsql14.1/include/internal -D_GNU_SOURCE -c -o pg_recovery.o pg_recovery.c
gcc -std=gnu99 -Wall -Wmissing-prototypes -Wpointer-arith -Wdeclaration-after-statement -Werror=vla -Wendif-labels -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing -fwrapv -fexcess-precision=standard -O2 -fPIC -shared -o pg_recovery.so pg_recovery.o -L/opt/pgsql14.1/lib -Wl,--as-needed -Wl,-rpath,'/opt/pgsql14.1/lib',--enable-new-dtags
[postgres@lyp pg_recovery-master]$
创建extension
[postgres@lyp pg_recovery-master]$ psql
psql (14.1)
Type"help"for help.
postgres=# create extension pg_recovery ;
CREATE EXTENSION
postgres=# \dx pg_recovery
List of installed extensions
Name|Version|Schema|Description
-------------+---------+--------+---------------------------------------------------------------------
pg_recovery |1.0|public| recovery table data of update/delete/rollback rows and drop columns
(1 row)
postgres=#示例
创建测试数据
postgres=# create table lxs(id1 int,id2 int);
CREATE TABLE
postgres=# insert into lxs values (1,11);
INSERT 0 1
postgres=# insert into lxs values (2,22);
INSERT 0 1
postgres=# select * from lxs;
id1 | id2
-----+-----
1 | 11
2 | 22
(2 rows)
postgres=#recovery update
模拟update修改数据
postgres=# update lxs set id1 =3,id2=33where id1=1and id2=11;
UPDATE 1
postgres=# update lxs set id1 =4,id2=44where id1=2and id2=22;
UPDATE 1
postgres=#select*from lxs;
id1 | id2
-----+-----
3|33
4|44
(2 rows)
postgres=#select*from pg_recovery('lxs')as(id1 int,id2 int);
id1 | id2
-----+-----
1|11
2|22
(2 rows)
postgres=#
postgres=#
recovery delete
模拟delete删除数据
postgres=#deletefrom lxs ;
DELETE 2
postgres=#select*from lxs;
id1 | id2
-----+-----
(0 rows)
postgres=#select*from pg_recovery('lxs')as(id1 int,id2 int);
id1 | id2
-----+-----
1|11
2|22
3|33
4|44
(4 rows)
postgres=#
recovery rollback
尝试恢复回滚操作之前的数据。
postgres=#begin;
BEGIN
postgres=*# insert into lxs values(5,55);
INSERT 01
postgres=*# rollback ;
ROLLBACK
postgres=#select*from lxs;
id1 | id2
-----+-----
(0 rows)
postgres=#select*from pg_recovery('lxs')as(id1 int, id2 int);
id1 | id2
-----+-----
1|11
2|22
3|33
4|44
5|55
(5 rows)
postgres=#
postgres=#
recovery drop column
模拟删除的列
postgres=# alter table lxs drop column id2;
ALTER TABLE
postgres=# select attnum from pg_attribute a, pg_class where attrelid = pg_class.oid and pg_class.relname='lxs' and attname ~ 'dropped';
attnum
--------
2
(1 row)
postgres=# select * from lxs;
id1
-----
(0 rows)
postgres=# select * from pg_recovery('lxs') as (id1 int, dropped_attnum_2 int);
id1 | dropped_attnum_2
-----+------------------
1 | 11
2 | 22
3 | 33
4 | 44
5 | 55
(5 rows)
postgres=#
dropped_attnum_2: if the drop attnum is 5, set dropped_attnum_2 to dropped_attnum_5
show all data
显示该表历史上所有写入过的数据。
postgres=# insert into lxs values(6);
INSERT 01
postgres=#select*from lxs;
id1
-----
6
(1 row)
postgres=#select*from pg_recovery('lxs', recoveryrow =>false)as(id1 int, dropped_attnum_2 int, recoveryrow bool);
id1 | dropped_attnum_2 | recoveryrow
-----+------------------+-------------
1|11| t
2|22| t
3|33| t
4|44| t
5|55| t
6|| f
(6 rows)
postgres=#
postgres=#
注意事项
pg_recovery是通过读取postgresql表中的死元组进行数据恢复。
如果表做了vacuum或者vacuum full操作清理了死元组后，pg_recovery无法对表数据进行恢复。
涉及参数
vacuum_defer_cleanup_age (integer)
postgres=# show vacuum_defer_cleanup_age;
vacuum_defer_cleanup_age
--------------------------
0
(1 row)
postgres=#
指定VACUUM和HOT更新在清除死亡行版本之前，应该推迟多久（以事务数量计）。默认值是零个事务，表示死亡行版本将被尽可能快地清除，即当它们不再对任何打开的事务可见时尽快清除。
这个参数只能在postgresql.conf文件中或在服务器命令行上设置。
