PostgreSQL学习随笔2 clog(xact)损坏

/*
 * Possible transaction statuses --- note that all-zeroes is the initial
 * state.
 *
 * A "subcommitted" transaction is a committed subtransaction whose parent
 * hasn't committed or aborted yet.
 */
typedef int XidStatus;

#define TRANSACTION_STATUS_IN_PROGRESS    0x00
#define TRANSACTION_STATUS_COMMITTED      0x01
#define TRANSACTION_STATUS_ABORTED        0x02
#define TRANSACTION_STATUS_SUB_COMMITTED  0x03
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手工模拟clog损坏
postgres@bogon-> cd opt/pg_root/pg_xact
postgres@bogon-> ll
total 12K
-rw------- 1 postgres postgres 8.1K Jul 19 04:57 0000
postgres@bogon-> cat''>0000
postgres@bogon-> ll
total 0
-rw------- 1 postgres postgres 0 Jul 19 04:57 0000

启动DB,报错无法启动DB
postgres@bogon-> pg_ctl start
waiting for server to start....2021-07-19 05:01:51.774 EDT [56728] LOG:  starting PostgreSQL 12.4 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-39), 64-bit
2021-07-19 05:01:51.774 EDT [56728] LOG:  listening on IPv4 address "0.0.0.0", port 5432
2021-07-19 05:01:51.775 EDT [56728] LOG:  listening on Unix socket "./.s.PGSQL.5432"
...2021-07-19 05:01:54.849 EDT [56728] LOG:  redirecting log output to logging collector process
2021-07-19 05:01:54.849 EDT [56728] HINT:  Future log output will appear in directory "pg_log".
 stopped waiting
pg_ctl: could not start server
Examine the log output.

检查下日志信息：
postgres@bogon-> cat postgresql-2021-07-19_050154.log
2021-07-19 05:01:54.849 EDT [56728] LOG:  ending log output to stderr
2021-07-19 05:01:54.849 EDT [56728] HINT:  Future log output will go to log destination "csvlog".
postgres@bogon-> cat postgresql-2021-07-19_050154.csv
2021-07-19 05:01:54.849 EDT,,,56728,,60f53f7f.dd98,1,,2021-07-19 05:01:51 EDT,,0,LOG,00000,"ending log output to stderr",,"Future log output will go to log destination ""csvlog"".",,,,,,,""
2021-07-19 05:01:54.853 EDT,,,56733,,60f53f82.dd9d,1,,2021-07-19 05:01:54 EDT,,0,LOG,00000,"database system was shut down at 2021-07-19 04:56:09 EDT",,,,,,,,,""
2021-07-19 05:01:54.855 EDT,,,56733,,60f53f82.dd9d,2,,2021-07-19 05:01:54 EDT,,0,FATAL,XX000,"could not access status of transaction 1217","Could not read from file ""pg_xact/0000"" at offset 0: read too few bytes.",,,,,,,,""
2021-07-19 05:01:54.855 EDT,,,56728,,60f53f7f.dd98,2,,2021-07-19 05:01:51 EDT,,0,LOG,00000,"startup process (PID 56733) exited with exit code 1",,,,,,,,,""
2021-07-19 05:01:54.855 EDT,,,56728,,60f53f7f.dd98,3,,2021-07-19 05:01:51 EDT,,0,LOG,00000,"aborting startup due to startup process failure",,,,,,,,,""
2021-07-19 05:01:54.879 EDT,,,56728,,60f53f7f.dd98,4,,2021-07-19 05:01:51 EDT,,0,LOG,00000,"database system is shut down",,,,,,,,,""

错误信息
FATAL,XX000,"could not access status of transaction 1217","Could not read from file ""pg_xact/0000"" at offset 0: read too few bytes.",,,,,,,,""
无法访问事物1217的状态

尝试使用dd工具修复
postgres@bogon-> dd if=/dev/zero of=/opt/pg_root/pg_xact/0000 bs=256K count=1
1+0 records in
1+0 records out
262144 bytes (262 kB) copied, 0.000680516 s, 385 MB/s
postgres@bogon-> ll
total 256K
-rw------- 1 postgres postgres 256K Jul 19 05:12 0000

启动数据库
postgres@bogon-> pg_ctl start
waiting for server to start....2021-07-19 05:13:13.879 EDT [57590] LOG:  starting PostgreSQL 12.4 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-39), 64-bit
2021-07-19 05:13:13.879 EDT [57590] LOG:  listening on IPv4 address "0.0.0.0", port 5432
2021-07-19 05:13:13.881 EDT [57590] LOG:  listening on Unix socket "./.s.PGSQL.5432"
...2021-07-19 05:13:17.483 EDT [57590] LOG:  redirecting log output to logging collector process
2021-07-19 05:13:17.483 EDT [57590] HINT:  Future log output will appear in directory "pg_log".
 done
server started
数据库已经启动

检查数据库日志
2021-07-19 05:13:17.483 EDT,,,57590,,60f54229.e0f6,1,,2021-07-19 05:13:13 EDT,,0,LOG,00000,"ending log output to stderr",,"Future log output will go to log destination ""csvlog"".",,,,,,,""
2021-07-19 05:13:17.495 EDT,,,57595,,60f5422d.e0fb,1,,2021-07-19 05:13:17 EDT,,0,LOG,00000,"database system was shut down at 2021-07-19 04:56:09 EDT",,,,,,,,,""
2021-07-19 05:13:17.536 EDT,,,57590,,60f54229.e0f6,2,,2021-07-19 05:13:13 EDT,,0,LOG,00000,"database system is ready to accept connections",,,,,,,,,""

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