PostgreSQL恢复误删数据

时间 2020-06-03

原文原文链接

　　在Oracle中；删除表或者误删表记录；有个闪回特性，不须要停机操做，能够完美找回记录。固然也有一些其余的恢复工具；例如odu工具，gdul工具。均可以找回数据。而PostgreSQL目前没有闪回特性。如何在不停机状况下恢复误删数据。还好是有完整的热备份。sql

　　本文描述的方法是：利用热备份在另外一台服务器进行数据恢复；再导入正式环境；这样不影响数据库操做。这方法也适用在Oracle恢复。必须知足几个条件数据库

有完整的基础数据文件备份和归档文件备份.因此备份是很重要的。
有一台装好同款Postgres软件的服务器

实例模拟讲解

　　过程模拟误删表tbl_lottu_drop后；后续进行dml/ddl操做；代表正式数据库仍是进行正常工做。在另一台数据库基于数据库PITR恢复。恢复表tbl_lottu_drop的数据。缓存

Postgres201 ：线上数据库服务器
Postgres202 ：操做服务器

1. 建立一个有效的备份

postgres=# select pg_start_backup(now()::text); pg_start_backup -----------------
 0/F000060 (1 row) [postgres@Postgres201 ~]$ rsync -acvz -L --exclude "pg_xlog" --exclude "pg_log" $PGDATA /data/backup/20180428
 postgres=# select pg_stop_backup(); NOTICE: pg_stop_backup complete, all required WAL segments have been archived pg_stop_backup ----------------
 0/F000168 (1 row)

2. 模拟误操做

　　2.1 建立一个须要恢复对象表tbl_lottu_drop。并插入1000记录。也保证数据从数据缓存写入磁盘中。bash

lottu=> create table tbl_lottu_drop (id int); CREATE TABLE lottu=> insert into tbl_lottu_drop select generate_series(1,1000); INSERT 0 1000 lottu=> \c lottu postgres You are now connected to database "lottu" as user "postgres".

　　2.2 这个获取一个时间：用于后面基于数据库PITR恢复(固然现实操做后只能记住一个大概的时间；还每每是不许；可能记住的时间是误操做以后。后面有讲解如何获取须要恢复到那个时间点)服务器

lottu=# select now(); now -------------------------------
 2018-04-28 20:47:31.617808+08 (1 row) lottu=# checkpoint; CHECKPOINT lottu=# select pg_xlogfile_name(pg_switch_xlog()); pg_xlogfile_name --------------------------
 000000030000000000000010 (1 row)

　　2.3 进行drop表工具

lottu=# drop table tbl_lottu_drop; DROP TABLE

　　2.4 后续进行dml/ddl操做；代表正式数据库仍是进行正常工做post

lottu=# create table tbl_lottu_log (id int); CREATE TABLE lottu=# insert into  tbl_lottu_log values (1),(2); INSERT 0 2 lottu=# checkpoint; CHECKPOINT lottu=# select pg_xlogfile_name(pg_switch_xlog()); pg_xlogfile_name --------------------------
 000000030000000000000011 (1 row)

3. 恢复操做

　　3.1 将备份拷贝到Postgres202数据库上ui

[postgres@Postgres201 20180428]$ cd /data/backup/20180428 [postgres@Postgres201 20180428]$ ll total 4 drwx------. 18 postgres postgres 4096 Apr 28 20:42 data [postgres@Postgres201 20180428]$ rsync -acvz -L data postgres@192.168.1.202:/data/postgres

　　3.2 删除没必要要的文件spa

[postgres@Postgres202 data]$ cd $PGDATA [postgres@Postgres202 data]$ rm backup_label.old postmaster.pid tablespace_map.old

　　3.3 还原备份表空间软连接rest

[postgres@Postgres202 data]$ cat tablespace_map 16385 /data/pg_data/lottu [postgres@Postgres202 data]$ mkdir -p /data/pg_data [postgres@Postgres202 data]$ cd pg_tblspc/ [postgres@Postgres202 pg_tblspc]$ mv 16385/  /data/pg_data/lottu [postgres@Postgres202 pg_tblspc]$ ln -s /data/pg_data/lottu ./16385 [postgres@Postgres202 pg_tblspc]$ ll total 0 lrwxrwxrwx. 1 postgres postgres 19 Apr 28 23:12 16385 -> /data/pg_data/lottu

　　3.4 将wal日志拷贝到Postgres202数据库上pg_xlog目录下；从哪一个日志开始拷贝？

[postgres@Postgres202 data]$ mkdir -p pg_xlog/archive_status [postgres@Postgres202 data]$ cat backup_label START WAL LOCATION: 0/F000060 (file 00000003000000000000000F) CHECKPOINT LOCATION: 0/F000098 BACKUP METHOD: pg_start_backup BACKUP FROM: master START TIME: 2018-04-28 20:42:15 CST LABEL: 2018-04-28 20:42:13.244358+08

　　查看backup_label；知道00000003000000000000000F开始到正在写入的wal日志。

[postgres@Postgres202 pg_xlog]$ ll total 65540
-rw-------. 1 postgres postgres 16777216 Apr 28 20:42 00000003000000000000000F -rw-------. 1 postgres postgres      313 Apr 28 20:42 00000003000000000000000F.00000060.backup -rw-------. 1 postgres postgres 16777216 Apr 28 20:48 000000030000000000000010
-rw-------. 1 postgres postgres 16777216 Apr 28 20:50 000000030000000000000011
-rw-------. 1 postgres postgres 16777216 Apr 28 20:55 000000030000000000000012

　　3.5 编辑recovery.conf文件

[postgres@Postgres202 data]$ vi recovery.conf restore_command = 'cp /data/arch/%f %p'            # e.g. 'cp /mnt/server/archivedir/%f %p'
recovery_target_time = '2018-04-28 20:47:31.617808+08' recovery_target_inclusive = false recovery_target_timeline = 'latest'

　　3.6 启动数据库；并验证数据

[postgres@Postgres202 data]$ pg_start server starting [postgres@Postgres202 data]$ ps -ef | grep postgres root 1098  1083  0 22:32 pts/0    00:00:00 su - postgres postgres 1099  1098  0 22:32 pts/0    00:00:00 -bash root 1210  1195  0 22:55 pts/1    00:00:00 su - postgres postgres 1211  1210  0 22:55 pts/1    00:00:00 -bash postgres 1442     1  1 23:16 pts/0    00:00:00 /opt/pgsql96/bin/postgres postgres 1450  1442  0 23:16 ?        00:00:00 postgres: checkpointer process postgres 1451  1442  0 23:16 ?        00:00:00 postgres: writer process postgres 1459  1442  0 23:16 ?        00:00:00 postgres: wal writer process postgres 1460  1442  0 23:16 ?        00:00:00 postgres: autovacuum launcher process postgres 1461  1442  0 23:16 ?        00:00:00 postgres: archiver process   last was 00000005.history postgres 1462  1442  0 23:16 ?        00:00:00 postgres: stats collector process postgres 1464  1099  0 23:16 pts/0    00:00:00 ps -ef postgres 1465  1099  0 23:16 pts/0    00:00:00 grep postgres [postgres@Postgres202 data]$ psql psql (9.6.0) Type "help" for help. postgres=# \c lottu lottu
You are now connected to database "lottu" as user "lottu". lottu=> \dt List of relations Schema |      Name      | Type  | Owner --------+----------------+-------+------- public | pitr_test      | table | lottu public | tbl_lottu_drop | table | lottu lottu=> select count(1) from tbl_lottu_drop; count -------
  1000 (1 row)

　　从这看数据是恢复了；copy到线上数据库操做略。

延伸点

下面讲解下如何找到误操做的时间。即recovery_target_time = '2018-04-28 20:47:31.617808+08'的时间点。上文是前面已经获取的；

　　1. 用pg_xlogdump解析这段日志。

[postgres@Postgres201 pg_xlog]$ pg_xlogdump -b 00000003000000000000000F 000000030000000000000012 > lottu.log pg_xlogdump: FATAL: error in WAL record at 0/12000648: invalid record length at 0/12000680: wanted 24, got 0

　　2. 从lottu.log中能够找到这段日志

rmgr: Transaction len (rec/tot):      8/    34, tx:       1689, lsn: 0/100244A0, prev 0/10024460, desc: COMMIT 2018-04-28 20:45:49.736013 CST rmgr: Standby len (rec/tot):     24/    50, tx:          0, lsn: 0/100244C8, prev 0/100244A0, desc: RUNNING_XACTS nextXid 1690 latestCompletedXid 1689 oldestRunningXid 1690 rmgr: Heap len (rec/tot):      3/  3130, tx:       1690, lsn: 0/10024500, prev 0/100244C8, desc: INSERT off 9 blkref #0: rel 16385/16386/2619 fork main blk 15 (FPW); hole: offset: 60, length: 5116
 rmgr: Btree len (rec/tot):      2/  7793, tx:       1690, lsn: 0/10025140, prev 0/10024500, desc: INSERT_LEAF off 385 blkref #0: rel 16385/16386/2696 fork main blk 1 (FPW); hole: offset: 1564, length: 452
 rmgr: Heap len (rec/tot):      2/   184, tx:       1690, lsn: 0/10026FD0, prev 0/10025140, desc: INPLACE off 16 blkref #0: rel 16385/16386/1259 fork main blk 0
rmgr: Transaction len (rec/tot):     88/   114, tx:       1690, lsn: 0/10027088, prev 0/10026FD0, desc: COMMIT 2018-04-28 20:46:37.718442 CST; inval msgs: catcache 49 catcache 45 catcache 44 relcache 32784 rmgr: Standby len (rec/tot):     24/    50, tx:          0, lsn: 0/10027100, prev 0/10027088, desc: RUNNING_XACTS nextXid 1691 latestCompletedXid 1690 oldestRunningXid 1691 rmgr: Standby len (rec/tot):     24/    50, tx:          0, lsn: 0/10027138, prev 0/10027100, desc: RUNNING_XACTS nextXid 1691 latestCompletedXid 1690 oldestRunningXid 1691 rmgr: XLOG len (rec/tot):     80/   106, tx:          0, lsn: 0/10027170, prev 0/10027138, desc: CHECKPOINT_ONLINE redo 0/10027138; tli 3; prev tli 3; fpw true; xid 0:1691; oid 40976; multi 1; offset 0; oldest xid 1668 in DB 1; oldest multi 1 in DB 1; oldest/newest commit timestamp xid: 0/0; oldest running xid 1691; online rmgr: Standby len (rec/tot):     24/    50, tx:          0, lsn: 0/100271E0, prev 0/10027170, desc: RUNNING_XACTS nextXid 1691 latestCompletedXid 1690 oldestRunningXid 1691 rmgr: Standby len (rec/tot):     24/    50, tx:          0, lsn: 0/10027218, prev 0/100271E0, desc: RUNNING_XACTS nextXid 1691 latestCompletedXid 1690 oldestRunningXid 1691 rmgr: XLOG len (rec/tot):     80/   106, tx:          0, lsn: 0/10027250, prev 0/10027218, desc: CHECKPOINT_ONLINE redo 0/10027218; tli 3; prev tli 3; fpw true; xid 0:1691; oid 40976; multi 1; offset 0; oldest xid 1668 in DB 1; oldest multi 1 in DB 1; oldest/newest commit timestamp xid: 0/0; oldest running xid 1691; online rmgr: XLOG len (rec/tot):      0/    24, tx:          0, lsn: 0/100272C0, prev 0/10027250, desc: SWITCH rmgr: Standby len (rec/tot):     24/    50, tx:          0, lsn: 0/11000028, prev 0/100272C0, desc: RUNNING_XACTS nextXid 1691 latestCompletedXid 1690 oldestRunningXid 1691 rmgr: Standby len (rec/tot):     16/    42, tx:       1691, lsn: 0/11000060, prev 0/11000028, desc: LOCK xid 1691 db 16386 rel 32784 rmgr: Heap len (rec/tot):      8/  2963, tx:       1691, lsn: 0/11000090, prev 0/11000060, desc: DELETE off 16 KEYS_UPDATED blkref #0: rel 16385/16386/1247 fork main blk 8 (FPW); hole: offset: 88, length: 5288

根据“32784”日志能够看到是表tbl_lottu_drop在2018-04-28 20:46:37.718442插入1000条记录(因此恢复时间点选2018-04-28 20:47:31.617808+08没毛病)；即也是在事务id为1690操做的。并在事务id为1691进行删除操做。

因此上面的recovery.conf 也能够改写为：

restore_command = 'cp /data/arch/%f %p'            # e.g. 'cp /mnt/server/archivedir/%f %p'
recovery_target_xid = '1690' recovery_target_inclusive = false recovery_target_timeline = 'latest'