postgresql wal文件誤刪恢復

2021-09-10 17:22:42.417183T  @  startup  00000 [2021-09-10 17:22:42 CST] 0 [9298] LOCATION:  StartupXLOG, xlog.c:6347
2021-09-10 17:22:42.417206T  @  startup  XX000 [2021-09-10 17:22:42 CST] 0 [9298] FATAL:  XX000: required WAL directory "pg_wal" does not exist
2021-09-10 17:22:42.417206T  @  startup  XX000 [2021-09-10 17:22:42 CST] 0 [9298] LOCATION:  ValidateXLOGDirectoryStructure, xlog.c:4262
2021-09-10 17:22:42.417407T  @  postmaster  00000 [2021-09-10 17:22:42 CST] 0 [9296] LOG:  00000: startup process (PID 9298) exited with exit code 1
2021-09-10 17:22:42.417407T  @  postmaster  00000 [2021-09-10 17:22:42 CST] 0 [9296] LOCATION:  LogChildExit, postmaster.c:3714
2021-09-10 17:22:42.417417T  @  postmaster  00000 [2021-09-10 17:22:42 CST] 0 [9296] LOG:  00000: aborting startup due to startup process failure
2021-09-10 17:22:42.417417T  @  postmaster  00000 [2021-09-10 17:22:42 CST] 0 [9296] LOCATION:  reaper, postmaster.c:2969
2021-09-10 17:22:42.427171T  @  postmaster  00000 [2021-09-10 17:22:42 CST] 0 [9296] LOG:  00000: database system is shut down
2021-09-10 17:22:42.427171T  @  postmaster  00000 [2021-09-10 17:22:42 CST] 0 [9296] LOCATION:  UnlinkLockFiles, miscinit.c:928

　　執行pg_resetwal -f PGDATA可以重新初始化wal文件，但是會丟失事務日志以及數據不一致，因為可能有full checkpoint之前的數據丟失，極端情況下某些數據塊丟失。此時初始化WAL文件如下：

[zjh@lightdb1 pgsql13.2]$ cd data/pg_wal/
[zjh@lightdb1 pg_wal]$ ll
total 1048576
-rw------- 1 zjh zjh 1073741824 Sep 10 21:44 00000001000000BB00000001
drwx------ 2 zjh zjh          6 Sep 10 21:42 archive_status

　　再啟動PG，備份、重建。

　　具體會丟失多少數據，可以通過pg_controldata輸出中的latest checkpoint確認。

 

 

　　如果因為wal_size設置的比較大，希望刪除歷史wal的話，可以通過pg_archivecleanup清理latest checkpoint之前的wal日志，如下：

　　pg_archivecleanup /data1/zjh/coordinator/pg_wal/ 000000010000000900000023

　　清理000000010000000900000023之前的wal文件。

 

 　　確實，比他小的沒有了，但是問題在於之前的日志都還沒刪除。