分类目录归档：PostgreSQL恢复

PostgreSQL恢复系列:pg_filedump恢复字典构造

发表于 2024 年 4 月 15 日 由 惜分飞

pg_filedump是在pg数据库极端情况下直接解析数据库文件的利器,但是由于是开源软件,本身难以实现批量处理,通过对底层基表分析,可以实现批量处理功能
分析PostgreSQL库中数据库信息

--数据库查询结果
postgres=# select oid,datname,datdba,dattablespace from pg_database;
  oid  |   datname   | datdba | dattablespace 
-------+-------------+--------+---------------
 14187 | postgres    |     10 |          1663
 16403 | db_xff      |     10 |          1663
     1 | template1   |     10 |          1663
 14186 | template0   |     10 |          1663
 16407 | db_xifenfei |  16405 |         16406
(5 rows)

--通过dump 该文件解析数据
<Data> -----
 Item   1 -- Length:    0  Offset:    5 (0x0005)  Flags: REDIRECT
 Item   2 -- Length:    0  Offset:    6 (0x0006)  Flags: REDIRECT
 Item   3 -- Length:  260  Offset: 7320 (0x1c98)  Flags: NORMAL
COPY: 14187     postgres
 Item   4 -- Length:  260  Offset: 7056 (0x1b90)  Flags: NORMAL
COPY: 16403     db_xff
 Item   5 -- Length:  297  Offset: 7888 (0x1ed0)  Flags: NORMAL
COPY: 1 template1
 Item   6 -- Length:  297  Offset: 7584 (0x1da0)  Flags: NORMAL
COPY: 14186     template0
 Item   7 -- Length:  260  Offset: 6792 (0x1a88)  Flags: NORMAL
COPY: 16407     db_xifenfei

分析PostgreSQL 表空间信息

--sql查询表空间信息
postgres=# select * from pg_tablespace;
  oid  |   spcname    | spcowner | spcacl | spcoptions 
-------+--------------+----------+--------+------------
  1663 | pg_default   |       10 |        | 
  1664 | pg_global    |       10 |        | 
 16406 | tbs_xifenfei |    16405 |        | 
(3 rows)


--通过dump 该文件解析数据
<Data> -----
 Item   1 -- Length:   96  Offset: 8096 (0x1fa0)  Flags: NORMAL
COPY: 1663      pg_default
 Item   2 -- Length:   96  Offset: 8000 (0x1f40)  Flags: NORMAL
COPY: 1664      pg_global
 Item   3 -- Length:   96  Offset: 7904 (0x1ee0)  Flags: NORMAL
COPY: 16406     tbs_xifenfei

分析PostgreSQL 对象id、name、path对应关系

--对象信息查询
postgres=# select oid ,relname,relnamespace,reltype,reloftype,relowner,relam,relfilenode,
           reltablespace from pg_class where relname like 't_t%' or relname like 't_x%';
  oid  |  relname   | relnamespace | reltype | reloftype | relowner | relam | relfilenode | reltablespace 
-------+------------+--------------+---------+-----------+----------+-------+-------------+---------------
 16387 | t_xifenfei |         2200 |   16389 |         0 |       10 |     2 |       16390 |             0
 16391 | t_xff      |         2200 |   16393 |         0 |       10 |     2 |       16391 |             0
 16394 | t_xff2     |         2200 |   16396 |         0 |       10 |     2 |       16394 |             0
 16397 | t_xff3     |         2200 |   16399 |         0 |       10 |     2 |       16397 |             0
 16400 | t_xff4     |         2200 |   16402 |         0 |       10 |     2 |       16400 |             0
 16408 | t_tbs      |         2200 |   16410 |         0 |       10 |     2 |       16408 |         16406
(6 rows)

--通过dump 该文件解析数据（显示部分）
COPY: 16394     t_xff2  2200    16396   0       10      2       16394   0       0       0.000000000000  0       0       f       f       p       r
 Item  29 -- Length:    0  Offset:   31 (0x001f)  Flags: REDIRECT
 Item  30 -- Length:  172  Offset: 2592 (0x0a20)  Flags: NORMAL
COPY: 16397     t_xff3  2200    16399   0       10      2       16397   0       0       0.000000000000  0       0       f       f       p       r
 Item  31 -- Length:  205  Offset: 3376 (0x0d30)  Flags: NORMAL
COPY: 12093     pg_shadow       11      12094   0       10      0       0       0       0       0.000000000000  0       0       f       f       p       v
 Item  32 -- Length:  172  Offset: 2416 (0x0970)  Flags: NORMAL
COPY: 16400     t_xff4  2200    16402   0       10      2       16400   0       0       0.000000000000  0       0       f       f       p       r

这个里面获取到pg_class.reltablespace是表空间的id值,根据自定义表空间的规则:在pgdata/pg_tblspc创建link指向创建表空间时候的文件夹路径

-bash-4.2$ pwd
/var/lib/pgsql/12/data/pg_tblspc
-bash-4.2$ ls -ltr
total 0
lrwxrwxrwx 1 postgres postgres 30 Apr 15 20:13 16406 -> /var/lib/pgsql/12/data/tbs_xff

结合上述的pg_database,pg_tablespace,pg_class信息,可以获取到每个表对应实际的存储路径
分析PostgreSQL 模式信息

--sql查询模式信息
postgres=# select * from pg_namespace;
  oid  |      nspname       | nspowner |               nspacl                
-------+--------------------+----------+-------------------------------------
    99 | pg_toast           |       10 | 
 12314 | pg_temp_1          |       10 | 
 12315 | pg_toast_temp_1    |       10 | 
    11 | pg_catalog         |       10 | {postgres=UC/postgres,=U/postgres}
  2200 | public             |       10 | {postgres=UC/postgres,=UC/postgres}
 13887 | information_schema |       10 | {postgres=UC/postgres,=U/postgres}
 16404 | u_xifenfei         |       10 | 
(7 rows)


--通过dump 该文件解析数据
<Data> -----
 Item   1 -- Length:    0  Offset:    6 (0x0006)  Flags: REDIRECT
 Item   2 -- Length:   96  Offset: 8096 (0x1fa0)  Flags: NORMAL
COPY: 99        pg_toast
 Item   3 -- Length:    0  Offset:    7 (0x0007)  Flags: REDIRECT
 Item   4 -- Length:   96  Offset: 8000 (0x1f40)  Flags: NORMAL
COPY: 12314     pg_temp_1
 Item   5 -- Length:   96  Offset: 7904 (0x1ee0)  Flags: NORMAL
COPY: 12315     pg_toast_temp_1
 Item   6 -- Length:  141  Offset: 7760 (0x1e50)  Flags: NORMAL
COPY: 11        pg_catalog
 Item   7 -- Length:  141  Offset: 7616 (0x1dc0)  Flags: NORMAL
COPY: 2200      public
 Item   8 -- Length:    0  Offset:    9 (0x0009)  Flags: REDIRECT
 Item   9 -- Length:  141  Offset: 7472 (0x1d30)  Flags: NORMAL
COPY: 13887     information_schema
 Item  10 -- Length:   96  Offset: 7376 (0x1cd0)  Flags: NORMAL
COPY: 16404     u_xifenfei

通过pg_namespace，pg_class信息，可以获取到对象所属的模式关系，基于上述汇总,可以获取到某个模式下面,所有表id和实际存储路径,现在使用pg_filedump进行恢复,还缺少表的列类型信息,通过pg_type和pg_attribute来获取。

获取PostgreSQL表的列名称和类型[编号]信息

--sql查询列信息
postgres=# \d t_tbs
               Table "public.t_tbs"
  Column  | Type | Collation | Nullable | Default 
----------+------+-----------+----------+---------
 oid      | oid  |           |          | 
 spcname  | name |           |          | 
 spcowner | oid  |           |          | 
Tablespace: "tbs_xifenfei"

postgres=# select attrelid,attname,atttypid,attstattarget,attlen,attnum from pg_attribute where attrelid=16408;
 attrelid | attname  | atttypid | attstattarget | attlen | attnum 
----------+----------+----------+---------------+--------+--------
    16408 | tableoid |       26 |             0 |      4 |     -6
    16408 | cmax     |       29 |             0 |      4 |     -5
    16408 | xmax     |       28 |             0 |      4 |     -4
    16408 | cmin     |       29 |             0 |      4 |     -3
    16408 | xmin     |       28 |             0 |      4 |     -2
    16408 | ctid     |       27 |             0 |      6 |     -1
    16408 | oid      |       26 |            -1 |      4 |      1
    16408 | spcname  |       19 |            -1 |     64 |      2
    16408 | spcowner |       26 |            -1 |      4 |      3
(9 rows)

--dump 内容（截取部分）
 Item  11 -- Length:  144  Offset: 1424 (0x0590)  Flags: NORMAL
COPY: 16408     oid     26      -1      4       1
 Item  12 -- Length:  144  Offset: 1280 (0x0500)  Flags: NORMAL
COPY: 16408     spcname 19      -1      64      2
 Item  13 -- Length:  144  Offset: 1136 (0x0470)  Flags: NORMAL
COPY: 16408     spcowner        26      -1      4       3
 Item  14 -- Length:  144  Offset:  992 (0x03e0)  Flags: NORMAL
COPY: 16408     ctid    27      0       6       -1
 Item  15 -- Length:  144  Offset:  848 (0x0350)  Flags: NORMAL
COPY: 16408     xmin    28      0       4       -2
 Item  16 -- Length:  144  Offset:  704 (0x02c0)  Flags: NORMAL
COPY: 16408     cmin    29      0       4       -3
 Item  17 -- Length:  144  Offset:  560 (0x0230)  Flags: NORMAL
COPY: 16408     xmax    28      0       4       -4
 Item  18 -- Length:  144  Offset:  416 (0x01a0)  Flags: NORMAL
COPY: 16408     cmax    29      0       4       -5

PostgreSQL获取类型编号和实际类型名称对应关系

--查询类型编号和实际类型关系
postgres=# select oid,typname from pg_type;
  oid  |                typname                
-------+---------------------------------------
    16 | bool
    17 | bytea
    18 | char
    19 | name
    20 | int8
    21 | int2
    22 | int2vector
    23 | int4
    24 | regproc
    25 | text
    26 | oid
    27 | tid
    28 | xid
    29 | cid
……

--dump 内容（截取部分）
 Item   1 -- Length:  176  Offset: 8016 (0x1f50)  Flags: NORMAL
COPY: 16        bool
 Item   2 -- Length:  176  Offset: 7840 (0x1ea0)  Flags: NORMAL
COPY: 17        bytea
 Item   3 -- Length:  176  Offset: 7664 (0x1df0)  Flags: NORMAL
COPY: 18        char
 Item   4 -- Length:  176  Offset: 7488 (0x1d40)  Flags: NORMAL
COPY: 19        name
 Item   5 -- Length:  176  Offset: 7312 (0x1c90)  Flags: NORMAL
COPY: 20        int8
 Item   6 -- Length:  176  Offset: 7136 (0x1be0)  Flags: NORMAL
COPY: 21        int2
 Item   7 -- Length:  176  Offset: 6960 (0x1b30)  Flags: NORMAL
COPY: 22        int2vector
 Item   8 -- Length:  176  Offset: 6784 (0x1a80)  Flags: NORMAL
COPY: 23        int4
 Item   9 -- Length:  176  Offset: 6608 (0x19d0)  Flags: NORMAL
COPY: 24        regproc
 Item  10 -- Length:  176  Offset: 6432 (0x1920)  Flags: NORMAL
COPY: 25        text
 Item  11 -- Length:  176  Offset: 6256 (0x1870)  Flags: NORMAL
COPY: 26        oid
 Item  12 -- Length:  176  Offset: 6080 (0x17c0)  Flags: NORMAL
COPY: 27        tid
 Item  13 -- Length:  176  Offset: 5904 (0x1710)  Flags: NORMAL
COPY: 28        xid
 Item  14 -- Length:  176  Offset: 5728 (0x1660)  Flags: NORMAL
COPY: 29        cid
 Item  15 -- Length:  176  Offset: 5552 (0x15b0)  Flags: NORMAL
COPY: 30        oidvector

通过pg_class、pg_type和pg_attribute可以获取对象的表的列名称，数据类型等信息。通过以上几个对象，即可获取到pg_filedmp处理所需要的所有信息,然后可以实现批量处理

发表在 PostgreSQL恢复 | 标签为 , , | 评论关闭

PostgreSQL恢复系列:pg_filedump基本使用

发表于 2022 年 6 月 3 日 由 惜分飞

当PostgreSQL遇到重大故障,使用各种方法都无法直接启动数据库，可以考虑使用类似oracle dul工具,直接离线方式读取文件进行恢复.这个工具为pg_filedump
pg_filedump安装

[root@xifenfei ~]# yum install pg_filedump_14.x86_64
Loaded plugins: langpacks, ulninfo
Resolving Dependencies
--> Running transaction check
---> Package pg_filedump_14.x86_64 0:14.1-1.rhel7 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

======================================================================================================================
 Package                            Arch      Version                 Repository                                 Size
======================================================================================================================
Installing:                                 
 pg_filedump_14                     x86_64    14.1-1.rhel7            pgdg14                                     43 k
                                            
Transaction Summary                         
======================================================================================================================
Install  1 Package

Total download size: 43 k
Installed size: 81 k
Is this ok [y/d/N]: y
Downloading packages:
pg_filedump_14-14.1-1.rhel7.x86_64.rpm                                              |  43 kB  00:00:02     
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : pg_filedump_14-14.1-1.rhel7.x86_64                                                      1/1 
  Verifying  : pg_filedump_14-14.1-1.rhel7.x86_64                                                      1/1 

Installed:
  pg_filedump_14.x86_64 0:14.1-1.rhel7                                                                     

Complete!
-bash-4.2$ pg_filedump 

Version 14.1 (for PostgreSQL 8.x .. 14.x)
Copyright (c) 2002-2010 Red Hat, Inc.
Copyright (c) 2011-2022, PostgreSQL Global Development Group

Usage: pg_filedump [-abcdfhikxy] [-R startblock [endblock]] [-D attrlist] [-S blocksize] [-s segsize] [-n segnumber] file

Display formatted contents of a PostgreSQL heap/index/control file
Defaults are: relative addressing, range of the entire file, block
               size as listed on block 0 in the file

The following options are valid for heap and index files:
  -a  Display absolute addresses when formatting (Block header
      information is always block relative)
  -b  Display binary block images within a range (Option will turn
      off all formatting options)
  -d  Display formatted block content dump (Option will turn off
      all other formatting options)
  -D  Decode tuples using given comma separated list of types
      Supported types:
        bigint bigserial bool char charN date float float4 float8 int
        json macaddr name numeric oid real serial smallint smallserial text
        time timestamp timestamptz timetz uuid varchar varcharN xid xml
      ~ ignores all attributes left in a tuple
  -f  Display formatted block content dump along with interpretation
  -h  Display this information
  -i  Display interpreted item details
  -k  Verify block checksums
  -o  Do not dump old values.
  -R  Display specific block ranges within the file (Blocks are
      indexed from 0)
        [startblock]: block to start at
        [endblock]: block to end at
      A startblock without an endblock will format the single block
  -s  Force segment size to [segsize]
  -t  Dump TOAST files
  -v  Ouput additional information about TOAST relations
  -n  Force segment number to [segnumber]
  -S  Force block size to [blocksize]
  -x  Force interpreted formatting of block items as index items
  -y  Force interpreted formatting of block items as heap items

The following options are valid for control files:
  -c  Interpret the file listed as a control file
  -f  Display formatted content dump along with interpretation
  -S  Force block size to [blocksize]
Additional functions:
  -m  Interpret file as pg_filenode.map file and print contents (all
      other options will be ignored)

Report bugs to <pgsql-bugs@postgresql.org>

创建测试表

-bash-4.2$ psql
psql (14.3)
Type "help" for help.

postgres=# create table pg_xifenfei(id int,name varchar(100));
CREATE TABLE
postgres=# insert into pg_xifenfei values(1,'www.xifenfei.com');
INSERT 0 1
postgres=# insert into pg_xifenfei values(2,'xienfei_pg_recovery');
INSERT 0 1
postgres=# select * from pg_xifenfei;
 id |        name         
----+---------------------
  1 | www.xifenfei.com
  2 | xienfei_pg_recovery
(2 rows)

postgres=#

pg_filedump恢复数据

-bash-4.2$ pg_filedump /var/lib/pgsql/14/data/base/14487/16384

*******************************************************************
* PostgreSQL File/Block Formatted Dump Utility
*
* File: /var/lib/pgsql/14/data/base/14487/16384
* Options used: None
*******************************************************************

Block    0 ********************************************************
<Header> -----
 Block Offset: 0x00000000         Offsets: Lower      32 (0x0020)
 Block: Size 8192  Version    4            Upper    8096 (0x1fa0)
 LSN:  logid      0 recoff 0x16299cf0      Special  8192 (0x2000)
 Items:    2                      Free Space: 8064
 Checksum: 0x0000  Prune XID: 0x00000000  Flags: 0x0000 ()
 Length (including item array): 32

<Data> -----
 Item   1 -- Length:   45  Offset: 8144 (0x1fd0)  Flags: NORMAL
 Item   2 -- Length:   48  Offset: 8096 (0x1fa0)  Flags: NORMAL


*** End of File Encountered. Last Block Read: 0 ***

-bash-4.2$ pg_filedump -D int,charn /var/lib/pgsql/14/data/base/14487/16384|grep COPY
COPY: 1 www.xifenfei.com
COPY: 2 xienfei_pg_recovery
-bash-4.2$ pg_filedump -D int,charn /var/lib/pgsql/14/data/base/14487/16384|grep COPY
> |awk '{$1=null;print $0}'>/tmp/pg_xifenfei_rec
-bash-4.2$ sed -i 's/^[ ]*//g' /tmp/pg_xifenfei_rec

导入数据验证

postgres=# truncate table pg_xifenfei;
TRUNCATE TABLE
postgres=# select * from pg_xifenfei;
 id | name 
----+------
(0 rows)
postgres=# copy pg_xifenfei from '/tmp/pg_xifenfei_rec'(DELIMITER ' ');
COPY 2
postgres=# select * from pg_xifenfei;
 id |        name         
----+---------------------
  1 | www.xifenfei.com
  2 | xienfei_pg_recovery
(2 rows)

通过上述简单测试证明,在PG数据库出现极端情况下，可以使用该方法进行最后的数据恢复,减少因为数据丢失带来的损失.

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PostgreSQL恢复系列:pg_control异常恢复

发表于 2022 年 5 月 30 日 由 惜分飞

在PG中pg_control文件类似oracle数据库的control文件(控制文件),在Oracle中如果该文件丢失/损坏,可以通过alter database create controlfile命令进行创建,对于PG数据库来说也可以通过pg_resetwal命令来实现创建,由于pg_control文件损坏,需要人工指定一些参数完成pg_resetwal相关操作
pg_resetwal 使用说明

-bash-4.2$ pg_resetwal --help
pg_resetwal resets the PostgreSQL write-ahead log.

Usage:
  pg_resetwal [OPTION]... DATADIR

Options:
  -c, --commit-timestamp-ids=XID,XID
                                   set oldest and newest transactions bearing
                                   commit timestamp (zero means no change)
 [-D, --pgdata=]DATADIR            data directory
  -e, --epoch=XIDEPOCH             set next transaction ID epoch
  -f, --force                      force update to be done
  -l, --next-wal-file=WALFILE      set minimum starting location for new WAL
  -m, --multixact-ids=MXID,MXID    set next and oldest multitransaction ID
  -n, --dry-run                    no update, just show what would be done
  -o, --next-oid=OID               set next OID
  -O, --multixact-offset=OFFSET    set next multitransaction offset
  -u, --oldest-transaction-id=XID  set oldest transaction ID
  -V, --version                    output version information, then exit
  -x, --next-transaction-id=XID    set next transaction ID
      --wal-segsize=SIZE           size of WAL segments, in megabytes
  -?, --help                       show this help, then exit

Report bugs to <pgsql-bugs@lists.postgresql.org>.
PostgreSQL home page: <https://www.postgresql.org/>

确认现在业务表记录情况

-bash-4.2$ psql
psql (14.3)
Type "help" for help.

postgres=# select count(1) from ac_event;
 count  
--------
 246266
(1 row)

模拟pg_control文件异常

-bash-4.2$ ps -ef|grep postgres
postgres  37178      1  0 09:58 ?        00:00:00 /usr/pgsql-14/bin/postgres -D /var/lib/pgsql/14/data
postgres  37179  37178  0 09:58 ?        00:00:00 postgres: logger 
postgres  37181  37178  0 09:58 ?        00:00:00 postgres: checkpointer 
postgres  37182  37178  0 09:58 ?        00:00:00 postgres: background writer 
postgres  37183  37178  0 09:58 ?        00:00:00 postgres: walwriter 
postgres  37184  37178  0 09:58 ?        00:00:00 postgres: autovacuum launcher 
postgres  37185  37178  0 09:58 ?        00:00:00 postgres: stats collector 
postgres  37186  37178  0 09:58 ?        00:00:00 postgres: logical replication launcher 
root      41368  41314  0 11:06 pts/1    00:00:00 su - postgres
postgres  41369  41368  0 11:06 pts/1    00:00:00 -bash
postgres  45071  41369  0 12:07 pts/1    00:00:00 ps -ef
postgres  45072  41369  0 12:07 pts/1    00:00:00 grep --color=auto postgres
-bash-4.2$ kill -9 37178
-bash-4.2$ ps -ef|grep postgres
root      41368  41314  0 11:06 pts/1    00:00:00 su - postgres
postgres  41369  41368  0 11:06 pts/1    00:00:00 -bash
postgres  45095  41369  0 12:08 pts/1    00:00:00 ps -ef
postgres  45096  41369  0 12:08 pts/1    00:00:00 grep --color=auto postgres
-bash-4.2$ pwd
/var/lib/pgsql/14/data/global
-bash-4.2$ ls -l pg_control 
-rw-------. 1 postgres postgres 8192 May 30 12:04 pg_control
-bash-4.2$ rm -rf pg_control 
-bash-4.2$ ls -l pg_control 
ls: cannot access pg_control: No such file or directory

PG启动失败

-bash-4.2$ pg_ctl start 
pg_ctl: another server might be running; trying to start server anyway
waiting for server to start....postgres: could not find the database system
Expected to find it in the directory "/var/lib/pgsql/14/data",
but could not open file "/var/lib/pgsql/14/data/global/pg_control": No such file or directory
 stopped waiting
pg_ctl: could not start server
Examine the log output.

创建空pg_control文件启动依旧失败

-bash-4.2$ touch /var/lib/pgsql/14/data/global/pg_control
-bash-4.2$ pg_ctl start 
pg_ctl: another server might be running; trying to start server anyway
waiting for server to start....2022-05-30 12:09:43.953 CST [45215] PANIC:  
   could not read file "global/pg_control": read 0 of 296
 stopped waiting
pg_ctl: could not start server
Examine the log output.

设置next-wal-file
-l, –next-wal-file=WALFILE,这个参数设置下一个新的WAL文件的最小值，这个值可以从$PGDATA/pg_wal目录下去看最后一个WAL 文件，这个文件的id+1即可

-bash-4.2$ pwd
/var/lib/pgsql/14/data/pg_wal
-bash-4.2$ ls -l
total 16384
-rw-------. 1 postgres postgres 16777216 May 30 12:04 000000010000000000000014
drwx------. 2 postgres postgres        6 May 24 02:20 archive_status
-bash-4.2$

这个文件+1，-l 000000010000000000000015
设置next-transaction
-x, –next-transaction-id=XID,这个参数设置pg_control中的下一个XID的值，这个值可以从pg_xact目录下的文件中查询

-bash-4.2$ pwd
/var/lib/pgsql/14/data/pg_xact
-bash-4.2$ ls -ltr
total 8
-rw-------. 1 postgres postgres 8192 May 30 12:03 0000

最后一个是0000，那么下一个XID就是0001，然后乘以 1048576 (0×100000)，实际上后面直接加5个0就行了。注意，这个值是16进制的。-x 0×000100000
multixact-ids设置
-m, –multixact-ids=MXID1,MXID2，这个参数包含两个部分，MXID1和MXID2，都可以从$PGDATA/pg_multixact/offsets目录下获得。MXID1的值，首先找到最大值，+1，再乘以 65536 (0×10000，相当于后面加4个0)作为这个参数的前半部分。找到最小的值，后面加4个0，作为MXID2的值

-bash-4.2$ pwd
/var/lib/pgsql/14/data/pg_multixact/offsets
-bash-4.2$ ls -ltr
total 8
-rw-------. 1 postgres postgres 8192 May 29 22:06 0000
-bash-4.2$

-m 0×00010000, 0×00000000（由于oldest multitransaction ID不能为0,因此后续这个值需要适当调整）
multixact-offset设置
-O, –multixact-offset=OFFSET,这个参数可以从$PGDATA/pg_multixact/members目录下获得。找到最大值，+1，乘以 52352 (0xCC80)

-bash-4.2$ pwd
/var/lib/pgsql/14/data/pg_multixact/members
-bash-4.2$ ls -ltr
total 8
-rw-------. 1 postgres postgres 8192 May 24 02:20 0000

-O 0xCC80
尝试执行pg_resetwal 

-bash-4.2$ pg_resetwal -l 000000010000000000000015 -x 0x000100000 -m 0x00010000,0x00000000 -O 0xCC80 $PGDATA
pg_resetwal: error: oldest multitransaction ID (-m) must not be 0

multixact-ids值不对,进行调整后处理
postmaster.pid文件需要清理
由于PG库异常关闭,需要人工清理掉该文件

-bash-4.2$ pg_resetwal -l 000000010000000000000015 -x 0x000100000 -m 0x00020000,0x00010000 -O 0xCC80 $PGDATA
pg_resetwal: error: lock file "postmaster.pid" exists
-bash-4.2$ rm -rf postmaster.pid

pg_resetwal结果预览

-bash-4.2$ pg_resetwal -l 000000010000000000000015 -x 0x000100000 -m 0x00020000,0x00010000 -O 0xCC80 $PGDATA
pg_resetwal: warning: pg_control exists but is broken or wrong version; ignoring it
Guessed pg_control values:

pg_control version number:            1300
Catalog version number:               202107181
Database system identifier:           7103392535324046312
Latest checkpoint's TimeLineID:       1
Latest checkpoint's full_page_writes: off
Latest checkpoint's NextXID:          0:3
Latest checkpoint's NextOID:          12000
Latest checkpoint's NextMultiXactId:  1
Latest checkpoint's NextMultiOffset:  0
Latest checkpoint's oldestXID:        3
Latest checkpoint's oldestXID's DB:   0
Latest checkpoint's oldestActiveXID:  0
Latest checkpoint's oldestMultiXid:   1
Latest checkpoint's oldestMulti's DB: 0
Latest checkpoint's oldestCommitTsXid:0
Latest checkpoint's newestCommitTsXid:0
Maximum data alignment:               8
Database block size:                  8192
Blocks per segment of large relation: 131072
WAL block size:                       8192
Bytes per WAL segment:                16777216
Maximum length of identifiers:        64
Maximum columns in an index:          32
Maximum size of a TOAST chunk:        1996
Size of a large-object chunk:         2048
Date/time type storage:               64-bit integers
Float8 argument passing:              by value
Data page checksum version:           0


Values to be changed:

First log segment after reset:        000000010000000000000015
NextMultiXactId:                      131072
OldestMultiXid:                       65536
OldestMulti's DB:                     0
NextMultiOffset:                      52352
NextXID:                              1048576
OldestXID:                            3
OldestXID's DB:                       0

If these values seem acceptable, use -f to force reset.

pg_resetwal进行创建pg_control并启动PG

-bash-4.2$ pg_resetwal -l 000000010000000000000015 -x 0x000100000 -m 0x00020000,0x00010000 -O 0xCC80 -f $PGDATA
pg_resetwal: warning: pg_control exists but is broken or wrong version; ignoring it
Write-ahead log reset
-bash-4.2$ pg_ctl start
waiting for server to start....2022-05-30 13:33:28.266 CST [51437] LOG:  
redirecting log output to logging collector process
2022-05-30 13:33:28.266 CST [51437] HINT:  Future log output will appear in directory "log".
 done
server started

验证数据

-bash-4.2$ psql
psql (14.3)
Type "help" for help.

postgres=#  select count(1) from ac_event;
 count  
--------
 245275
(1 row)

这种方法恢复之后,建议理解dump数据,然后导入到新库中

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