POSTGRESQL WAL 日志问题合集之WAL 如何解析
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最近经常有同学会问关于WAL 的问题，问能不能总结一下，这里我们总结关于WAL write ahead log 的问题的一个系列
在PostgreSQL write ahead log 的解析部分，pg_waldump 是必须被提起的工具，并且这个工具在不同的版本中都有变化， pg_waldump工具最早是产生于 PG9.3作为一个 contrib module 模块中的部分出现的，经历了9.4.9.5 的功能的添加，在PG10 将原来 pg_xlogdump 名字改为pg_waldump 截止到当前 postgresql 16(非正式) 版本中 pg_waldump还在进行各种的随着数据库的升级后的版本更新。
pg_waldump 中获取日志信息的来源可以通过 pg_waldump --rmgr-list来获得可以获得事务信息来源。
在使用pg_waldump的命令读取日志，可能会出现错误，一般产生这个问题主要是数据库处理数据的时候在 idel 的状态，因为PG 有相关的参数在没有数据库的活动的情况下，也可以产生日志，在读取这样的部分的情况下就会产生问题。
pg_waldump /pgdata/data/pg_wal/00000001000000070000000Drmgr: Standby len (rec/tot): 50/ 50, tx: 0, lsn: 7/34000028, prev 7/331903C8, desc: RUNNING_XACTS nextXid 1061 latestCompletedXid 1060 oldestRunningXid 1061rmgr: Standby len (rec/tot): 50/ 50, tx: 0, lsn: 7/34000060, prev 7/34000028, desc: RUNNING_XACTS nextXid 1061 latestCompletedXid 1060 oldestRunningXid 1061rmgr: XLOG len (rec/tot): 114/ 114, tx: 0, lsn: 7/34000098, prev 7/34000060, desc: CHECKPOINT_ONLINE redo 7/34000060; tli 1; prev tli 1; fpw true; xid 0:1061; oid 32873; multi 4; offset 9; oldest xid 726 in DB 1; oldest multi 1 in DB 1; oldest/newest commit timestamp xid: 0/0; oldest running xid 1061; onlinermgr: Standby len (rec/tot): 50/ 50, tx: 0, lsn: 7/34000110, prev 7/34000098, desc: RUNNING_XACTS nextXid 1061 latestCompletedXid 1060 oldestRunningXid 1061pg_waldump: fatal: error in WAL record at 7/34000110: invalid record length at 7/34000148: wanted 24, got 0
我们做如下的操作，然后通过pg_waldump 来查看相关的记录
cache 7 catcache 6 catcache 7 catcache 6 catcache 7 catcache 6 catcache 7 catcache 6 snapshot 2608 relcache 24778
rmgr: Standby len (rec/tot): 50/ 50, tx: 0, lsn: 7/34021D88, prev 7/34021BF0, desc: RUNNING_XACTS nextXid 1062 latestCompletedXid 1061 oldestRunningXid 1062
rmgr: Heap len (rec/tot): 59/ 59, tx: 1062, lsn: 7/34021DC0, prev 7/34021D88, desc: INSERT+INIT off 1 flags 0x00, blkref #0: rel 1663/24760/24778 blk 0
rmgr: Transaction len (rec/tot): 34/ 34, tx: 1062, lsn: 7/34021E00, prev 7/34021DC0, desc: COMMIT 2023-03-26 08:16:06.160522 EDT
rmgr: Standby len (rec/tot): 50/ 50, tx: 0, lsn: 7/34021E28, prev 7/34021E00, desc: RUNNING_XACTS nextXid 1063 latestCompletedXid 1062 oldestRunningXid 1063
rmgr: Heap len (rec/tot): 69/ 69, tx: 1063, lsn: 7/34021E60, prev 7/34021E28, desc: HOT_UPDATE off 1 xmax 1063 flags 0x40 ; new off 2 xmax 0, blkref #0: rel 1663/24760/24778 blk 0
rmgr: Transaction len (rec/tot): 34/ 34, tx: 1063, lsn: 7/34021EA8, prev 7/34021E60, desc: COMMIT 2023-03-26 08:16:19.239652 EDT
rmgr: Standby len (rec/tot): 50/ 50, tx: 0, lsn: 7/34021ED0, prev 7/34021EA8, desc: RUNNING_XACTS nextXid 1064 latestCompletedXid 1063 oldestRunningXid 1064
rmgr: Heap len (rec/tot): 54/ 54, tx: 1064, lsn: 7/34021F08, prev 7/34021ED0, desc: DELETE off 2 flags 0x00 KEYS_UPDATED , blkref #0: rel 1663/24760/24778 blk 0
rmgr: Transaction len (rec/tot): 34/ 34, tx: 1064, lsn: 7/34021F40, prev 7/34021F08, desc: COMMIT 2023-03-26 08:16:32.959424 EDT
rmgr: Standby len (rec/tot): 50/ 50, tx: 0, lsn: 7/34021F68, prev 7/34021F40, desc: RUNNING_XACTS nextXid 1065 latestCompletedXid 1064 oldestRunningXid 1065
rmgr: XLOG len (rec/tot): 114/ 114, tx: 0, lsn: 7/34021FA0, prev 7/34021F68, desc: CHECKPOINT_ONLINE redo 7/34021F68; tli 1; prev tli 1; fpw true; xid 0:1065; oid 32873; multi 4; offset 9; oldest xid 726 in DB 1; oldest multi 1 in DB 1; oldest/newest commit timestamp xid: 0/0; oldest running xid 1065; online
rmgr: Standby len (rec/tot): 50/ 50, tx: 0, lsn: 7/34022030, prev 7/34021FA0, desc: RUNNING_XACTS nextXid 1065 latestCompletedXid 1064 oldestRunningXid 1065
从上面的pg_wal 日志里，我们可以清晰的看出来相关的操作， standby , heap ,transaction 为组成的整体操作。
从这里我们搞清楚了进行一个操作如 INSERT UPDATE DELETE ，在wal 日志中均会产生
1 具体的操作 2 commit 3 更新 XACTS ID
在分析中，我们可以针对要分析的位置和日志进行定位，在需要分析的操作前我们先查看当前的 wal lsn 通过 select pg_current_wal_lsn(); 来进行定位
通过语句我们定位到当前的LSN 号，日志文件号信息等。通过pg_waldump 命令的参数，-s -e
下面我们做一个实验
日志的初始lsn 7/34022068 操作结束时lsn 7/3403C748
日志的名字为 00000001000000070000000D
pg_waldump pgdata/data/pg_wal/00000001000000070000000D -s 7/34022068 -e 7/3403C748 在我们确认日志，开始，结束点后，我们得到如下的解析后的日志信息
rmgr: Storage len (rec/tot): 42/ 42, tx: 0, lsn: 7/34022068, prev 7/34022030, desc: CREATE base/24760/24781
rmgr: Heap len (rec/tot): 54/ 1582, tx: 1065, lsn: 7/34022098, prev 7/34022068, desc: INSERT off 8 flags 0x00, blkref #0: rel 1663/24760/1247 blk 14 FPW
rmgr: Btree len (rec/tot): 53/ 4973, tx: 1065, lsn: 7/340226C8, prev 7/34022098, desc: INSERT_LEAF off 244, blkref #0: rel 1663/24760/2703 blk 2 FPW
rmgr: Btree len (rec/tot): 53/ 6165, tx: 1065, lsn: 7/34023A38, prev 7/340226C8, desc: INSERT_LEAF off 172, blkref #0: rel 1663/24760/2704 blk 2 FPW
rmgr: Heap2 len (rec/tot): 57/ 261, tx: 1065, lsn: 7/34025268, prev 7/34023A38, desc: MULTI_INSERT 1 tuples flags 0x02, blkref #0: rel 1663/24760/2608 blk 65 FPW
rmgr: Btree len (rec/tot): 53/ 4929, tx: 1065, lsn: 7/34025370, prev 7/34025268, desc: INSERT_LEAF off 113, blkref #0: rel 1663/24760/2673 blk 37 FPW
rmgr: Btree len (rec/tot): 53/ 5657, tx: 1065, lsn: 7/340266D0, prev 7/34025370, desc: INSERT_LEAF off 199, blkref #0: rel 1663/24760/2674 blk 52 FPW
rmgr: Heap len (rec/tot): 211/ 211, tx: 1065, lsn: 7/34027CF0, prev 7/340266D0, desc: INSERT off 9 flags 0x00, blkref #0: rel 1663/24760/1247 blk 14
rmgr: Btree len (rec/tot): 64/ 64, tx: 1065, lsn: 7/34027DC8, prev 7/34027CF0, desc: INSERT_LEAF off 244, blkref #0: rel 1663/24760/2703 blk 2
rmgr: Btree len (rec/tot): 53/ 7097, tx: 1065, lsn: 7/34027E08, prev 7/34027DC8, desc: INSERT_LEAF off 68, blkref #0: rel 1663/24760/2704 blk 4 FPW
rmgr: Heap2 len (rec/tot): 85/ 85, tx: 1065, lsn: 7/340299E0, prev 7/34027E08, desc: MULTI_INSERT 1 tuples flags 0x02, blkref #0: rel 1663/24760/2608 blk 65
rmgr: Btree len (rec/tot): 72/ 72, tx: 1065, lsn: 7/34029A38, prev 7/340299E0, desc: INSERT_LEAF off 113, blkref #0: rel 1663/24760/2673 blk 37
rmgr: Btree len (rec/tot): 53/ 4229, tx: 1065, lsn: 7/34029A80, prev 7/34029A38, desc: INSERT_LEAF off 148, blkref #0: rel 1663/24760/2674 blk 50 FPW
rmgr: Heap len (rec/tot): 54/ 5218, tx: 1065, lsn: 7/3402AB20, prev 7/34029A80, desc: INSERT off 25 flags 0x01, blkref #0: rel 1663/24760/1259 blk 5 FPW
rmgr: Btree len (rec/tot): 53/ 2553, tx: 1065, lsn: 7/3402BF88, prev 7/3402AB20, desc: INSERT_LEAF off 123, blkref #0: rel 1663/24760/2662 blk 2 FPW
rmgr: Btree len (rec/tot): 53/ 4085, tx: 1065, lsn: 7/3402C9A0, prev 7/3402BF88, desc: INSERT_LEAF off 108, blkref #0: rel 1663/24760/2663 blk 2 FPW
rmgr: Btree len (rec/tot): 53/ 3853, tx: 1065, lsn: 7/3402D998, prev 7/3402C9A0, desc: INSERT_LEAF off 188, blkref #0: rel 1663/24760/3455 blk 4 FPW
rmgr: Heap2 len (rec/tot): 57/ 1117, tx: 1065, lsn: 7/3402E8C0, prev 7/3402D998, desc: MULTI_INSERT 1 tuples flags 0x02, blkref #0: rel 1663/24760/1249 blk 55 FPW
rmgr: Btree len (rec/tot): 53/ 5689, tx: 1065, lsn: 7/3402ED20, prev 7/3402E8C0, desc: INSERT_LEAF off 165, blkref #0: rel 1663/24760/2658 blk 14 FPW
rmgr: Btree len (rec/tot): 53/ 1553, tx: 1065, lsn: 7/34030378, prev 7/3402ED20, desc: INSERT_LEAF off 73, blkref #0: rel 1663/24760/2659 blk 10 FPW
rmgr: Heap2 len (rec/tot): 830/ 830, tx: 1065, lsn: 7/34030990, prev 7/34030378, desc: MULTI_INSERT 6 tuples flags 0x02, blkref #0: rel 1663/24760/1249 blk 55
rmgr: Btree len (rec/tot): 72/ 72, tx: 1065, lsn: 7/34030CD0, prev 7/34030990, desc: INSERT_LEAF off 165, blkref #0: rel 1663/24760/2658 blk 14
rmgr: Btree len (rec/tot): 64/ 64, tx: 1065, lsn: 7/34030D18, prev 7/34030CD0, desc: INSERT_LEAF off 73, blkref #0: rel 1663/24760/2659 blk 10
rmgr: Btree len (rec/tot): 72/ 72, tx: 1065, lsn: 7/34030D58, prev 7/34030D18, desc: INSERT_LEAF off 167, blkref #0: rel 1663/24760/2658 blk 14
rmgr: Btree len (rec/tot): 64/ 64, tx: 1065, lsn: 7/34030DA0, prev 7/34030D58, desc: INSERT_LEAF off 73, blkref #0: rel 1663/24760/2659 blk 10
rmgr: Btree len (rec/tot): 72/ 72, tx: 1065, lsn: 7/34030DE0, prev 7/34030DA0, desc: INSERT_LEAF off 165, blkref #0: rel 1663/24760/2658 blk 14
rmgr: Btree len (rec/tot): 64/ 64, tx: 1065, lsn: 7/34030E28, prev 7/34030DE0, desc: INSERT_LEAF off 73, blkref #0: rel 1663/24760/2659 blk 10
rmgr: Btree len (rec/tot): 72/ 72, tx: 1065, lsn: 7/34030E68, prev 7/34030E28, desc: INSERT_LEAF off 168, blkref #0: rel 1663/24760/2658 blk 14
rmgr: Btree len (rec/tot): 64/ 64, tx: 1065, lsn: 7/34030EB0, prev 7/34030E68, desc: INSERT_LEAF off 73, blkref #0: rel 1663/24760/2659 blk 10
rmgr: Btree len (rec/tot): 72/ 72, tx: 1065, lsn: 7/34030EF0, prev 7/34030EB0, desc: INSERT_LEAF off 165, blkref #0: rel 1663/24760/2658 blk 14
rmgr: Btree len (rec/tot): 64/ 64, tx: 1065, lsn: 7/34030F38, prev 7/34030EF0, desc: INSERT_LEAF off 73, blkref #0: rel 1663/24760/2659 blk 10
rmgr: Btree len (rec/tot): 72/ 72, tx: 1065, lsn: 7/34030F78, prev 7/34030F38, desc: INSERT_LEAF off 169, blkref #0: rel 1663/24760/2658 blk 14
rmgr: Btree len (rec/tot): 64/ 64, tx: 1065, lsn: 7/34030FC0, prev 7/34030F78, desc: INSERT_LEAF off 73, blkref #0: rel 1663/24760/2659 blk 10
rmgr: Heap2 len (rec/tot): 85/ 85, tx: 1065, lsn: 7/34031000, prev 7/34030FC0, desc: MULTI_INSERT 1 tuples flags 0x02, blkref #0: rel 1663/24760/2608 blk 65
rmgr: Btree len (rec/tot): 53/ 6161, tx: 1065, lsn: 7/34031058, prev 7/34031000, desc: INSERT_LEAF off 208, blkref #0: rel 1663/24760/2673 blk 41 FPW
rmgr: Btree len (rec/tot): 53/ 6133, tx: 1065, lsn: 7/34032888, prev 7/34031058, desc: INSERT_LEAF off 102, blkref #0: rel 1663/24760/2674 blk 48 FPW
rmgr: Standby len (rec/tot): 42/ 42, tx: 1065, lsn: 7/34034098, prev 7/34032888, desc: LOCK xid 1065 db 24760 rel 24781
rmgr: Transaction len (rec/tot): 405/ 405, tx: 1065, lsn: 7/340340C8, prev 7/34034098, desc: COMMIT 2023-03-26 11:45:21.364693 EDT; inval msgs: catcache 76 catcache 75 catcache 76 catcache 75 catcache 51 catcache 50 catcache 7 catcache 6 catcache 7 catcache 6 catcache 7 catcache 6 catcache 7 catcache 6 catcache 7 catcache 6 catcache 7 catcache 6 catcache 7 catcache 6 snapshot 2608 relcache 24781
rmgr: Standby len (rec/tot): 50/ 50, tx: 0, lsn: 7/34034260, prev 7/340340C8, desc: RUNNING_XACTS nextXid 1066 latestCompletedXid 1065 oldestRunningXid 1066
rmgr: Heap len (rec/tot): 59/ 59, tx: 1066, lsn: 7/34034298, prev 7/34034260, desc: INSERT+INIT off 1 flags 0x00, blkref #0: rel 1663/24760/24781 blk 0
rmgr: Transaction len (rec/tot): 34/ 34, tx: 1066, lsn: 7/340342D8, prev 7/34034298, desc: COMMIT 2023-03-26 11:45:32.308997 EDT
rmgr: Heap len (rec/tot): 59/ 59, tx: 1067, lsn: 7/34034300, prev 7/340342D8, desc: INSERT off 2 flags 0x00, blkref #0: rel 1663/24760/24781 blk 0
rmgr: Transaction len (rec/tot): 34/ 34, tx: 1067, lsn: 7/34034340, prev 7/34034300, desc: COMMIT 2023-03-26 11:45:41.511395 EDT
rmgr: Standby len (rec/tot): 50/ 50, tx: 0, lsn: 7/34034368, prev 7/34034340, desc: RUNNING_XACTS nextXid 1068 latestCompletedXid 1067 oldestRunningXid 1068
rmgr: Heap len (rec/tot): 54/ 54, tx: 1068, lsn: 7/340343A0, prev 7/34034368, desc: DELETE off 2 flags 0x00 KEYS_UPDATED , blkref #0: rel 1663/24760/24781 blk 0
rmgr: Transaction len (rec/tot): 34/ 34, tx: 1068, lsn: 7/340343D8, prev 7/340343A0, desc: COMMIT 2023-03-26 11:45:56.431164 EDT
rmgr: Standby len (rec/tot): 50/ 50, tx: 0, lsn: 7/34034400, prev 7/340343D8, desc: RUNNING_XACTS nextXid 1069 latestCompletedXid 1068 oldestRunningXid 1069
rmgr: Storage len (rec/tot): 42/ 42, tx: 0, lsn: 7/34034438, prev 7/34034400, desc: CREATE base/24760/24784
rmgr: Standby len (rec/tot): 42/ 42, tx: 1069, lsn: 7/34034468, prev 7/34034438, desc: LOCK xid 1069 db 24760 rel 24784
rmgr: Heap len (rec/tot): 203/ 203, tx: 1069, lsn: 7/34034498, prev 7/34034468, desc: INSERT off 27 flags 0x00, blkref #0: rel 1663/24760/1259 blk 5
rmgr: Btree len (rec/tot): 64/ 64, tx: 1069, lsn: 7/34034568, prev 7/34034498, desc: INSERT_LEAF off 124, blkref #0: rel 1663/24760/2662 blk 2
rmgr: Btree len (rec/tot): 53/ 5905, tx: 1069, lsn: 7/340345A8, prev 7/34034568, desc: INSERT_LEAF off 40, blkref #0: rel 1663/24760/2663 blk 1 FPW
rmgr: Btree len (rec/tot): 64/ 64, tx: 1069, lsn: 7/34035CC0, prev 7/340345A8, desc: INSERT_LEAF off 189, blkref #0: rel 1663/24760/3455 blk 4
rmgr: Heap2 len (rec/tot): 180/ 180, tx: 1069, lsn: 7/34035D00, prev 7/34035CC0, desc: MULTI_INSERT 1 tuples flags 0x02, blkref #0: rel 1663/24760/1249 blk 55
rmgr: Btree len (rec/tot): 64/ 64, tx: 1069, lsn: 7/34035DB8, prev 7/34035D00, desc: INSERT_LEAF off 172, blkref #0: rel 1663/24760/2658 blk 14
rmgr: Btree len (rec/tot): 64/ 64, tx: 1069, lsn: 7/34035DF8, prev 7/34035DB8, desc: INSERT_LEAF off 80, blkref #0: rel 1663/24760/2659 blk 10
rmgr: Heap len (rec/tot): 54/ 8042, tx: 1069, lsn: 7/34035E38, prev 7/34035DF8, desc: INSERT off 4 flags 0x01, blkref #0: rel 1663/24760/2610 blk 1 FPW
rmgr: Btree len (rec/tot): 53/ 3253, tx: 1069, lsn: 7/34037DC0, prev 7/34035E38, desc: INSERT_LEAF off 158, blkref #0: rel 1663/24760/2678 blk 1 FPW
rmgr: Btree len (rec/tot): 53/ 3253, tx: 1069, lsn: 7/34038A90, prev 7/34037DC0, desc: INSERT_LEAF off 158, blkref #0: rel 1663/24760/2679 blk 1 FPW
rmgr: Heap2 len (rec/tot): 85/ 85, tx: 1069, lsn: 7/34039748, prev 7/34038A90, desc: MULTI_INSERT 1 tuples flags 0x02, blkref #0: rel 1663/24760/2608 blk 65
rmgr: Btree len (rec/tot): 72/ 72, tx: 1069, lsn: 7/340397A0, prev 7/34039748, desc: INSERT_LEAF off 209, blkref #0: rel 1663/24760/2673 blk 41
rmgr: Btree len (rec/tot): 72/ 72, tx: 1069, lsn: 7/340397E8, prev 7/340397A0, desc: INSERT_LEAF off 200, blkref #0: rel 1663/24760/2674 blk 52
rmgr: XLOG len (rec/tot): 49/ 109, tx: 1069, lsn: 7/34039830, prev 7/340397E8, desc: FPI , blkref #0: rel 1663/24760/24784 blk 1 FPW
rmgr: XLOG len (rec/tot): 49/ 137, tx: 1069, lsn: 7/340398A0, prev 7/34039830, desc: FPI , blkref #0: rel 1663/24760/24784 blk 0 FPW
rmgr: Heap len (rec/tot): 188/ 188, tx: 1069, lsn: 7/34039930, prev 7/340398A0, desc: INPLACE off 25, blkref #0: rel 1663/24760/1259 blk 5
rmgr: Heap len (rec/tot): 188/ 188, tx: 1069, lsn: 7/340399F0, prev 7/34039930, desc: INPLACE off 27, blkref #0: rel 1663/24760/1259 blk 5
rmgr: Transaction len (rec/tot): 274/ 274, tx: 1069, lsn: 7/34039AB0, prev 7/340399F0, desc: COMMIT 2023-03-26 11:46:15.154540 EDT; inval msgs: catcache 51 catcache 50 catcache 51 catcache 50 catcache 51 catcache 50 catcache 7 catcache 6 catcache 32 relcache 24781 relcache 24784 relcache 24784 relcache 24781 snapshot 2608
rmgr: Standby len (rec/tot): 50/ 50, tx: 0, lsn: 7/34039BC8, prev 7/34039AB0, desc: RUNNING_XACTS nextXid 1070 latestCompletedXid 1069 oldestRunningXid 1070
rmgr: XLOG len (rec/tot): 49/ 8037, tx: 0, lsn: 7/34039C00, prev 7/34039BC8, desc: FPI_FOR_HINT , blkref #0: rel 1663/24760/2610 blk 1 FPW
rmgr: XLOG len (rec/tot): 49/ 2145, tx: 0, lsn: 7/3403BB80, prev 7/34039C00, desc: FPI_FOR_HINT , blkref #0: rel 1663/24760/1249 blk 55 FPW
rmgr: Standby len (rec/tot): 50/ 50, tx: 0, lsn: 7/3403C400, prev 7/3403BB80, desc: RUNNING_XACTS nextXid 1070 latestCompletedXid 1069 oldestRunningXid 1070
rmgr: Heap len (rec/tot): 65/ 197, tx: 1070, lsn: 7/3403C438, prev 7/3403C400, desc: UPDATE off 1 xmax 1070 flags 0x00 ; new off 3 xmax 0, blkref #0: rel 1663/24760/24781 blk 0 FPW
rmgr: Btree len (rec/tot): 53/ 133, tx: 1070, lsn: 7/3403C500, prev 7/3403C438, desc: INSERT_LEAF off 2, blkref #0: rel 1663/24760/24784 blk 1 FPW
rmgr: Transaction len (rec/tot): 34/ 34, tx: 1070, lsn: 7/3403C588, prev 7/3403C500, desc: COMMIT 2023-03-26 11:46:50.660698 EDT
rmgr: Standby len (rec/tot): 50/ 50, tx: 0, lsn: 7/3403C5B0, prev 7/3403C588, desc: RUNNING_XACTS nextXid 1071 latestCompletedXid 1070 oldestRunningXid 1071
rmgr: XLOG len (rec/tot): 114/ 114, tx: 0, lsn: 7/3403C5E8, prev 7/3403C5B0, desc: CHECKPOINT_ONLINE redo 7/34039C00; tli 1; prev tli 1; fpw true; xid 0:1070; oid 32873; multi 4; offset 9; oldest xid 726 in DB 1; oldest multi 1 in DB 1; oldest/newest commit timestamp xid: 0/0; oldest running xid 1070; online
rmgr: Standby len (rec/tot): 50/ 50, tx: 0, lsn: 7/3403C660, prev 7/3403C5E8, desc: RUNNING_XACTS nextXid 1071 latestCompletedXid 1070 oldestRunningXid 1071
rmgr: Standby len (rec/tot): 50/ 50, tx: 0, lsn: 7/3403C698, prev 7/3403C660, desc: RUNNING_XACTS nextXid 1071 latestCompletedXid 1070 oldestRunningXid 1071
rmgr: XLOG len (rec/tot): 114/ 114, tx: 0, lsn: 7/3403C6D0, prev 7/3403C698, desc: CHECKPOINT_ONLINE redo 7/3403C698; tli 1; prev tli 1; fpw true; xid 0:1071; oid 32873; multi 4; offset 9; oldest xid 726 in DB 1; oldest multi 1 in DB 1; oldest/newest commit timestamp xid: 0/0; oldest running xid 1071; online
那么这里需要说明通过pg_waldump 本身是无法给你解析出类似 mysqlbinlog 那样的解析出实际操作的数据的，pg_waldump 本身是在告诉你pg_wal 中的日志本身操作后写入的方式和数据类型，同时pg_wal 本身另一个功能更是将日志中的数据统计信息进行输出，如下方截图中的部分。
从下图可以看到，FPI ，full page write 所在日志中占据的比重，通过pg_waldump 中的 -z 参数
pg_waldump /pgdata/data/pg_wal/00000001000000070000000D -s 7/34022068 -e 7/3403C748 -z
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