PG重建控制文件

1. 工具
	a. pg10版本以前使用pg_resetxlog工具
	b. pg10及以后版本pg_resetwal工具
2. 命令语法
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
3. 重建控制具体操作
	a. 模拟pg_control文件丢失
	[postgres@pg15tar global]$ mv pg_control pg_control.bak
	[postgres@pg15tar global]$ pg_ctl start
	waiting for server to start....postgres: could not find the database system
	Expected to find it in the directory "/u01/app/postgresql/pgdata",
	but could not open file "/u01/app/postgresql/pgdata/global/pg_control": No such file or directory
	 stopped waiting
	pg_ctl: could not start server
	Examine the log output.
	b. 获取-l参数
	-l XLOGFILE：  force minimum WAL starting location for new transaction log(XLOGFILE强制新事务日志的最小WAL起始位置）
	定位办法：pg_wal下面创建的最大的日志文件，编号+1
	
	[postgres@pg15tar pgdata]$ ll pg_wal
	total 114712
	-rw------- 1 postgres postgres       41 Aug  4 12:46 00000002.history
	-rw------- 1 postgres postgres       93 Aug  4 12:46 00000003.history
	-rw------- 1 postgres postgres      348 Aug  4 12:46 0000000400000000000000AF.00000028.backup
	-rw------- 1 postgres postgres      145 Aug  5 08:27 00000004.history
	-rw------- 1 postgres postgres 16777216 Aug  5 12:09 0000000500000000000000B1
	-rw------- 1 postgres postgres 16777216 Aug  4 12:46 0000000500000000000000B2
	-rw------- 1 postgres postgres 16777216 Aug  4 12:46 0000000500000000000000B3
	-rw------- 1 postgres postgres 16777216 Aug  4 12:46 0000000500000000000000B4
	-rw------- 1 postgres postgres 16777216 Aug  4 12:46 0000000500000000000000B5
	-rw------- 1 postgres postgres 16777216 Aug  4 12:46 0000000500000000000000B6
	-rw------- 1 postgres postgres 16777216 Aug  5 08:27 0000000500000000000000B7
	-rw------- 1 postgres postgres      197 Aug  5 11:02 00000005.history
	drwx------ 2 postgres postgres     4096 Aug  5 12:09 archive_status
	
	那么这里的-l=0000000500000000000000B8 （编号+1）
	c. 获取-O参数
	-O OFFSET： set next multitransaction offset
	在pg_multixact/members下面，取最大值加1然后乘以65536， 转换成16进制，然后在末尾添加4个0
	
	#步骤
	*进入相应目录
	cd $PGDATA/pg_multixact/memebers/
	
	*查看文件
	[postgres@pg15tar members]$ ll
	-rwx------ 1 postgres postgres 8192 Aug  4 12:46 0000
	
	*计算
	(0+1)*65536=65536
	65536转换成16进制为10000
	
	那么-O =0x100000000
	d. 获取-m
	-m=MXID：MXID set next and oldest multitransaction ID
	zai pg_multixact/offsets下面，找到最大的文件编号，+1(文件编号+1） 后面跟上4个0
	
	#步骤
	*进入相应目录
	cd $PGDATA/pg_multixact/offsets
	
	*查看文件
	[postgres@pg15tar offsets]$ ll
	-rwx------ 1 postgres postgres 8192 Aug  5 11:02 0000
	
	*计算结果
	-m=0x00010000
	e. 获取-x
	-x XID ：set next transaction ID
	在pg_xact下面，找到最大的文件编号，+1后面跟上5个0
	
	步骤
	*进入相应目录
	cd $PGDATA/pg_xact
	
	*查看当前文件
	[postgres@pg15tar pg_xact]$ ll
	-rwx------ 1 postgres postgres 8192 Aug  5 11:02 0000
	
	*计算-x值
	-x=0x000100000
	f. 重建控制文件
	cd $PGDATA/global
	touch pg_control
	
	[postgres@pg15tar global]$ pg_resetwal -l 0000000500000000000000B8 -O 0x100000000 -m 0x00010000,0x00010000 -x 0x000100000 -f $PGDATA
	pg_resetwal: warning: pg_control exists but is broken or wrong version; ignoring it
	Write-ahead log reset
	g. 启动数据库
	pg_ctl start
	
	[postgres@pg15tar global]$ pg_controldata
	pg_control version number:            1300
	Catalog version number:               202209061
	Database system identifier:           7399511071694827642
	Database cluster state:               in production
	pg_control last modified:             Mon 05 Aug 2024 12:45:14 PM CST
	Latest checkpoint location:           0/B8000028
	Latest checkpoint's REDO location:    0/B8000028
	Latest checkpoint's REDO WAL file:    0000000500000000000000B8
	Latest checkpoint's TimeLineID:       5
	Latest checkpoint's PrevTimeLineID:   5
	Latest checkpoint's full_page_writes: off
	Latest checkpoint's NextXID:          0:1048576
	Latest checkpoint's NextOID:          10000
	Latest checkpoint's NextMultiXactId:  65536
	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:   65536
	Latest checkpoint's oldestMulti's DB: 0
	Latest checkpoint's oldestCommitTsXid:0
	Latest checkpoint's newestCommitTsXid:0
	Time of latest checkpoint:            Mon 05 Aug 2024 12:42:05 PM CST
	Fake LSN counter for unlogged rels:   0/3E8
	Minimum recovery ending location:     0/0
	Min recovery ending loc's timeline:   0
	Backup start location:                0/0
	Backup end location:                  0/0
	End-of-backup record required:        no
	wal_level setting:                    replica
	wal_log_hints setting:                off
	max_connections setting:              100
	max_worker_processes setting:         8
	max_wal_senders setting:              10
	max_prepared_xacts setting:           0
	max_locks_per_xact setting:           64
	track_commit_timestamp setting:       on
	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
	Mock authentication nonce:            0000000000000000000000000000000000000000000000000000000000000000