MogDB/openGauss 壞塊測試-對啟動的影響-測試筆記1

openGaussbaby發表於2024-03-30
筆記

MogDB/openGauss 壞塊測試-對啟動的影響-測試筆記 1
在 UPDATE 操作提交後，髒塊落盤前 kill 掉 mogdb 資料庫，然後對 UPDATE 修改的壞進行以下破壞操作，仍然能夠啟動資料庫，資料未丟失。

1、用舊資料檔案替換，可以啟動 2、修改成錯誤的 checksum，可以啟動 3、資料塊修改成錯誤的 lsn,可以啟動 4、dd 一個資料塊為 0,可以啟動

full_page_writes 開啟時，每次 checkpoint 後第一次修改的塊，會在 wal 中記錄完整副本，recover 時直接使用該副本重寫資料檔案中的塊。

[omm2@og01 ~]$ gsql
gsql ((MogDB 2.1.0 build 56189e20) compiled at 2022-01-07 18:47:53 commit 0 last mr )
Non-SSL connection (SSL connection is recommended when requiring high-security)
Type "help" for help.

omm2=# drop table t;
DROP TABLE

omm2=# create table t(id numeric,c varchar(100)) with (fillfactor=50);
CREATE TABLE
omm2=# insert into t select i,'test'||i from generate_series(1,1000)i;
INSERT 0 100
omm2=# checkpoint;
CHECKPOINT

select (select setting from pg_settings where name='data_directory')||'/'||pg_relation_filepath('t');

omm2=# select (select setting from pg_settings where name='data_directory')||'/'||pg_relation_filepath('t');
?column?

/home/omm2/data/base/16385/73775
(1 row)

[omm2@og01 ~]$ cp /home/omm2/data/base/16385/73775 /home/omm2/data/base/16385/73775_old
[omm2@og01 ~]$

omm2=# select ctid,id from t;
ctid | id
--------+-----
(0,1) | 1
(0,2) | 2
(0,3) | 3
(0,4) | 4
(0,5) | 5
(0,6) | 6
(0,7) | 7
(0,8) | 8
(0,9) | 9
(0,10) | 10
(0,11) | 11
(0,12) | 12
(0,13) | 13
(0,14) | 14
(0,15) | 15

omm2=# update t set c='a' where id<3;
UPDATE 2
omm2=#
omm2=# checkpoint;
CHECKPOINT

[omm2@og01 ~]$ ps -ef |grep mogdb
omm2 25231 1 3 15:17 pts/0 00:00:04 /home/omm2/mogdb210/bin/mogdb
omm2 26265 20027 0 15:19 pts/1 00:00:00 grep --color=auto mogdb

omm2=# update t set c='b' where id<500;
UPDATE 499

[omm2@og01 ~]$ kill -9 25231

---用舊資料檔案替換，可以啟動

cp /home/omm2/data/base/16385/73775 /home/omm2/data/base/16385/73775_bak

cp /home/omm2/data/base/16385/73775_old /home/omm2/data/base/16385/73775

gs_ctl start

2022-04-26 15:21:26.028 [unknown] [unknown] localhost 139810735888128 0[0:0#0] 0 [BACKEND] LOG: undo launcher started
2022-04-26 15:21:26.066 omm2 postgres localhost 139810614208256 0[0:0#0] 0 [BACKEND] LOG: instrumention percentile started
2022-04-26 15:21:26.067 [unknown] [unknown] localhost 139810414786304 0[0:0#0] 0 [UNDO] LOG: [UndoRecycleMain:362]undo recycle started.
2022-04-26 15:21:26.069 omm2 postgres localhost 139810580645632 0[0:0#0] 0 [BACKEND] LOG: statement flush thread start
2022-04-26 15:21:26.069 omm2 postgres localhost 139810479863552 0[0:0#0] 0 [BACKEND] LOG: process wlm thread starting up.
2022-04-26 15:21:26.069 omm2 postgres localhost 139810479863552 0[0:0#0] 0 [BACKEND] LOG: build user data finished
2022-04-26 15:21:26.070 omm2 postgres localhost 139810463082240 0[0:0#0] 0 [BACKEND] LOG: WLMmonitor thread is starting up.
2022-04-26 15:21:26.070 omm2 postgres localhost 139810446300928 0[0:0#0] 0 [BACKEND] LOG: WLMarbiter thread is starting up.
2022-04-26 15:21:26.076 omm2 postgres localhost 139810597426944 0[0:0#0] 0 [BACKEND] LOG: ASP thread start
2022-04-26 15:21:40.996 [unknown] [unknown] localhost 139810836576000 0[0:0#0] 0 [BACKEND] LOG: database first startup and recovery finish,so do checkpointer
2022-04-26 15:21:40.997 [MOT] TID:27119/----- SID:-----/----- [INFO] Creating MOT checkpoint snapshot: id: 1650957700
2022-04-26 15:21:40.997 [MOT] TID:27119/----- SID:-----/----- [INFO] MOT snapshot ready. id: 1650957700, lsn: 0
2022-04-26 15:21:40.997 [unknown] [unknown] localhost 139810836576000 0[0:0#0] 0 [SLRU] LOG: remove old segments(<0) under pg_csnlog
2022-04-26 15:21:40.997 [unknown] [unknown] localhost 139810836576000 0[0:0#0] 0 [BACKEND] LOG: truncate CSN log oldestXact 46536, next xid 46539
2022-04-26 15:21:41.000 [unknown] [unknown] localhost 139810836576000 0[0:0#0] 0 [SLRU] LOG: remove old segments(<0) under pg_multixact/offsets
2022-04-26 15:21:41.000 [unknown] [unknown] localhost 139810836576000 0[0:0#0] 0 [SLRU] LOG: remove old segments(<0) under pg_multixact/members
2022-04-26 15:21:41.005 [unknown] [unknown] localhost 139810836576000 0[0:0#0] 0 [UNDO] LOG: [CheckPointUndoSystemMeta:353]undo metadata checkPointRedo = 349161880.
2022-04-26 15:21:41.009 [MOT] TID:27119/----- SID:-----/----- [INFO] MOT begin checkpoint capture. id: 1650957700, lsn: 349161880
2022-04-26 15:21:41.010 [MOT] TID:27257/00000 SID:00004/00000 [INFO] GC PARAMS: isGcEnabled = true, limboSizeLimit = 524288, limboSizeLimitHigh = 8388608, rcuFreeCount = 8192
2022-04-26 15:21:41.011 [MOT] TID:27258/00000 SID:00006/00000 [INFO] GC PARAMS: isGcEnabled = true, limboSizeLimit = 524288, limboSizeLimitHigh = 8388608, rcuFreeCount = 8192
2022-04-26 15:21:41.113 [MOT] TID:27119/----- SID:-----/----- [INFO] Checkpoint [1650957700] completed
2022-04-26 15:21:41.112 [unknown] [unknown] localhost 139810836576000 0[0:0#0] 0 [BACKEND] WARNING: replicationSlotMinLSN is InvalidXLogRecPtr!!!
2022-04-26 15:21:41.112 [unknown] [unknown] localhost 139810836576000 0[0:0#0] 0 [BACKEND] WARNING: replicationSlotMaxLSN is InvalidXLogRecPtr!!!
2022-04-26 15:21:41.113 [unknown] [unknown] localhost 139810836576000 0[0:0#0] 0 [BACKEND] LOG: CreateCheckPoint PrintCkpXctlControlFile: [checkPoint] oldCkpLoc:0/14CA2AC8, oldRedo:0/14CA2A48, newCkpLoc:0/14CFCA18, newRedo:0/14CFC998, preCkpLoc:0/14CA2AC8
2022-04-26 15:21:41.113 [unknown] [unknown] localhost 139810836576000 0[0:0#0] 0 [BACKEND] LOG: will update control file (create checkpoint), shutdown:0
2022-04-26 15:21:41.115 [unknown] [unknown] localhost 139810836576000 0[0:0#0] 0 [BACKEND] LOG: attempting to remove WAL segments older than log file 000000010000000000000002
2022-04-26 15:22:29.772 omm2 postgres localhost 139810250028800 0[0:0#0] 0 [BACKEND] LOG: clean statement thread start

omm2=# select * from t where id<10;
id | c
----+---
3 | b
4 | b
5 | b
6 | b
7 | b
8 | b
9 | b
1 | b
2 | b
(9 rows)

omm2=# vacuum t;
VACUUM

omm2=# checkpoint;
CHECKPOINT

---修改成錯誤的checksum，可以啟動

[omm2@og01 dump]$ ./dump -file /home/omm2/data/base/16385/73775 -bs 8192 -n 0 -decoder pg_header
{0 [] 24 map[Pd_checksum:0xc0000682d0 Pd_flags:0xc000068330 Pd_lower:0xc000068390 Pd_lsn:0xc000068240 Pd_pagesize_version:0xc0000684b0 Pd_prune_xid:0xc000068510 Pd_special:0xc000068450 Pd_upper:0xc0000683f0] [0xc000068240 0xc0000682d0 0xc000068330 0xc000068390 0xc0000683f0 0xc000068450 0xc0000684b0 0xc000068510]}
read and dump block 0=
@0 Pd_lsn size:8 hex:0x14d4834000000000 val:1500968886722363392
@8 Pd_checksum size:2 hex:0x4263 val:16995
@10 Pd_flags size:2 hex:0x45 val:69
@12 Pd_lower size:2 hex:0x310 val:784
@14 Pd_upper size:2 hex:0x1480 val:5248
@16 Pd_special size:2 hex:0x2000 val:8192
@18 Pd_pagesize_version size:2 hex:0x2006 val:8198
@20 Pd_prune_xid size:4 hex:0x0 val:0
[omm2@og01 dump]$

omm2=# update t set c='c' where id<500;
UPDATE 499

[omm2@og01 dump]$ kill -9 27074

./dump -file /home/omm2/data/base/16385/73775 -bs 8192 -n 0 -decoder pg_header
{0 [] 24 map[Pd_checksum:0xc00008c2d0 Pd_flags:0xc00008c330 Pd_lower:0xc00008c390 Pd_lsn:0xc00008c240 Pd_pagesize_version:0xc00008c4b0 Pd_prune_xid:0xc00008c510 Pd_special:0xc00008c450 Pd_upper:0xc00008c3f0] [0xc00008c240 0xc00008c2d0 0xc00008c330 0xc00008c390 0xc00008c3f0 0xc00008c450 0xc00008c4b0 0xc00008c510]}
read and dump block 0=
@0 Pd_lsn size:8 hex:0x14d4834000000000 val:1500968886722363392
@8 Pd_checksum size:2 hex:0x4263 val:16995
@10 Pd_flags size:2 hex:0x45 val:69
@12 Pd_lower size:2 hex:0x310 val:784
@14 Pd_upper size:2 hex:0x1480 val:5248
@16 Pd_special size:2 hex:0x2000 val:8192
@18 Pd_pagesize_version size:2 hex:0x2006 val:8198
@20 Pd_prune_xid size:4 hex:0x0 val:0
[omm2@og01 dump]$

./dump -file /home/omm2/data/base/16385/73775 -bs 8192 -n 0 -decoder pg_header -setname Pd_checksum -setval uint16#10

[omm2@og01 dump]$ ./dump -file /home/omm2/data/base/16385/73775 -bs 8192 -n 0 -decoder pg_header -setname Pd_checksum -setval uint16#10
{0 [] 24 map[Pd_checksum:0xc00008e2d0 Pd_flags:0xc00008e330 Pd_lower:0xc00008e390 Pd_lsn:0xc00008e240 Pd_pagesize_version:0xc00008e4b0 Pd_prune_xid:0xc00008e510 Pd_special:0xc00008e450 Pd_upper:0xc00008e3f0] [0xc00008e240 0xc00008e2d0 0xc00008e330 0xc00008e390 0xc00008e3f0 0xc00008e450 0xc00008e4b0 0xc00008e510]}
read and dump block 0=
@0 Pd_lsn size:8 hex:0x14d4834000000000 val:1500968886722363392
@8 Pd_checksum size:2 hex:0x4263 val:16995
@10 Pd_flags size:2 hex:0x45 val:69
@12 Pd_lower size:2 hex:0x310 val:784
@14 Pd_upper size:2 hex:0x1480 val:5248
@16 Pd_special size:2 hex:0x2000 val:8192
@18 Pd_pagesize_version size:2 hex:0x2006 val:8198
@20 Pd_prune_xid size:4 hex:0x0 val:0
=after modify==
@0 Pd_lsn size:8 hex:0x14d4834000000000 val:1500968886722363392
@8 Pd_checksum size:2 hex:0xa val:10
@10 Pd_flags size:2 hex:0x45 val:69
@12 Pd_lower size:2 hex:0x310 val:784
@14 Pd_upper size:2 hex:0x1480 val:5248
@16 Pd_special size:2 hex:0x2000 val:8192
@18 Pd_pagesize_version size:2 hex:0x2006 val:8198
@20 Pd_prune_xid size:4 hex:0x0 val:0
[omm2@og01 dump]$

gs_ctl start

2022-04-26 15:29:50.790 [unknown] [unknown] localhost 139845378766592 0[0:0#0] 0 [UNDO] LOG: [CheckPointUndoSystemMeta:353]undo metadata checkPointRedo = 350150888.
2022-04-26 15:29:50.794 [MOT] TID:30886/----- SID:-----/----- [INFO] MOT begin checkpoint capture. id: 1650958190, lsn: 350150888
2022-04-26 15:29:50.795 [MOT] TID:31029/00000 SID:00004/00000 [INFO] GC PARAMS: isGcEnabled = true, limboSizeLimit = 524288, limboSizeLimitHigh = 8388608, rcuFreeCount = 8192
2022-04-26 15:29:50.797 [MOT] TID:31030/00000 SID:00006/00000 [INFO] GC PARAMS: isGcEnabled = true, limboSizeLimit = 524288, limboSizeLimitHigh = 8388608, rcuFreeCount = 8192
2022-04-26 15:29:50.897 [MOT] TID:30886/----- SID:-----/----- [INFO] Checkpoint [1650958190] completed
2022-04-26 15:29:50.897 [unknown] [unknown] localhost 139845378766592 0[0:0#0] 0 [BACKEND] WARNING: replicationSlotMinLSN is InvalidXLogRecPtr!!!
2022-04-26 15:29:50.897 [unknown] [unknown] localhost 139845378766592 0[0:0#0] 0 [BACKEND] WARNING: replicationSlotMaxLSN is InvalidXLogRecPtr!!!
2022-04-26 15:29:50.898 [unknown] [unknown] localhost 139845378766592 0[0:0#0] 0 [BACKEND] LOG: CreateCheckPoint PrintCkpXctlControlFile: [checkPoint] oldCkpLoc:0/14D7B110, oldRedo:0/14D7B090, newCkpLoc:0/14DEE168, newRedo:0/14DEE0E8, preCkpLoc:0/14D7B110
2022-04-26 15:29:50.898 [unknown] [unknown] localhost 139845378766592 0[0:0#0] 0 [BACKEND] LOG: will update control file (create checkpoint), shutdown:0
2022-04-26 15:29:50.900 [unknown] [unknown] localhost 139845378766592 0[0:0#0] 0 [BACKEND] LOG: attempting to remove WAL segments older than log file 000000010000000000000002

omm2=# select * from t where id<10;
id | c
----+---
3 | c
4 | c
5 | c
6 | c
7 | c
8 | c
9 | c
1 | c
2 | c
(9 rows)

[omm2@og01 dump]$ ./dump -file /home/omm2/data/base/16385/73775 -bs 8192 -n 0 -decoder pg_header
{0 [] 24 map[Pd_checksum:0xc00008c2d0 Pd_flags:0xc00008c330 Pd_lower:0xc00008c390 Pd_lsn:0xc00008c240 Pd_pagesize_version:0xc00008c4b0 Pd_prune_xid:0xc00008c510 Pd_special:0xc00008c450 Pd_upper:0xc00008c3f0] [0xc00008c240 0xc00008c2d0 0xc00008c330 0xc00008c390 0xc00008c3f0 0xc00008c450 0xc00008c4b0 0xc00008c510]}
read and dump block 0=
@0 Pd_lsn size:8 hex:0x14dc3c0000000000 val:1503142346332569600
@8 Pd_checksum size:2 hex:0x2269 val:8809
@10 Pd_flags size:2 hex:0x41 val:65
@12 Pd_lower size:2 hex:0x478 val:1144
@14 Pd_upper size:2 hex:0x900 val:2304
@16 Pd_special size:2 hex:0x2000 val:8192
@18 Pd_pagesize_version size:2 hex:0x2006 val:8198
@20 Pd_prune_xid size:4 hex:0x2ad val:68

omm2=# vacuum t;
VACUUM
omm2=# checkpoint;
CHECKPOINT
omm2=#

omm2=# update t set c='d' where id<500;
UPDATE 499

[omm2@og01 dump]$ kill -9 30834

---資料塊修改成錯誤的lsn,可以啟動

./dump -file /home/omm2/data/base/16385/73775 -bs 8192 -n 0 -decoder pg_header -setname Pd_lsn -setval uint64#10

gs_ctl start

2022-04-26 15:34:02.760 omm2 postgres localhost 140324014712576 0[0:0#0] 0 [BACKEND] LOG: instrumention percentile started
2022-04-26 15:34:02.765 omm2 postgres localhost 140323895105280 0[0:0#0] 0 [BACKEND] LOG: process wlm thread starting up.
2022-04-26 15:34:02.766 omm2 postgres localhost 140323895105280 0[0:0#0] 0 [BACKEND] LOG: build user data finished
2022-04-26 15:34:02.766 omm2 postgres localhost 140323856250624 0[0:0#0] 0 [BACKEND] LOG: WLMmonitor thread is starting up.
2022-04-26 15:34:02.767 [unknown] [unknown] localhost 140323790059264 0[0:0#0] 0 [UNDO] LOG: [UndoRecycleMain:362]undo recycle started.
2022-04-26 15:34:02.770 omm2 postgres localhost 140323981149952 0[0:0#0] 0 [BACKEND] LOG: statement flush thread start
2022-04-26 15:34:02.772 omm2 postgres localhost 140323997931264 0[0:0#0] 0 [BACKEND] LOG: ASP thread start
2022-04-26 15:34:02.778 omm2 postgres localhost 140323832067840 0[0:0#0] 0 [BACKEND] LOG: WLMarbiter thread is starting up.
2022-04-26 15:34:17.694 [unknown] [unknown] localhost 140324246648576 0[0:0#0] 0 [BACKEND] LOG: database first startup and recovery finish,so do checkpointer
2022-04-26 15:34:17.694 [MOT] TID:00551/----- SID:-----/----- [INFO] Creating MOT checkpoint snapshot: id: 1650958457
2022-04-26 15:34:17.694 [MOT] TID:00551/----- SID:-----/----- [INFO] MOT snapshot ready. id: 1650958457, lsn: 0
2022-04-26 15:34:17.694 [unknown] [unknown] localhost 140324246648576 0[0:0#0] 0 [SLRU] LOG: remove old segments(<0) under pg_csnlog
2022-04-26 15:34:17.694 [unknown] [unknown] localhost 140324246648576 0[0:0#0] 0 [BACKEND] LOG: truncate CSN log oldestXact 47616, next xid 47619
2022-04-26 15:34:17.698 [unknown] [unknown] localhost 140324246648576 0[0:0#0] 0 [SLRU] LOG: remove old segments(<0) under pg_multixact/offsets
2022-04-26 15:34:17.698 [unknown] [unknown] localhost 140324246648576 0[0:0#0] 0 [SLRU] LOG: remove old segments(<0) under pg_multixact/members
2022-04-26 15:34:17.707 [unknown] [unknown] localhost 140324246648576 0[0:0#0] 0 [UNDO] LOG: [CheckPointUndoSystemMeta:353]undo metadata checkPointRedo = 350849296.
2022-04-26 15:34:17.713 [MOT] TID:00551/----- SID:-----/----- [INFO] MOT begin checkpoint capture. id: 1650958457, lsn: 350849296
2022-04-26 15:34:17.715 [MOT] TID:00700/00000 SID:00004/00000 [INFO] GC PARAMS: isGcEnabled = true, limboSizeLimit = 524288, limboSizeLimitHigh = 8388608, rcuFreeCount = 8192
2022-04-26 15:34:17.816 [MOT] TID:00551/----- SID:-----/----- [INFO] Checkpoint [1650958457] completed
2022-04-26 15:34:17.816 [unknown] [unknown] localhost 140324246648576 0[0:0#0] 0 [BACKEND] WARNING: replicationSlotMinLSN is InvalidXLogRecPtr!!!
2022-04-26 15:34:17.816 [unknown] [unknown] localhost 140324246648576 0[0:0#0] 0 [BACKEND] WARNING: replicationSlotMaxLSN is InvalidXLogRecPtr!!!
2022-04-26 15:34:17.817 [unknown] [unknown] localhost 140324246648576 0[0:0#0] 0 [BACKEND] LOG: CreateCheckPoint PrintCkpXctlControlFile: [checkPoint] oldCkpLoc:0/14E41FC8, oldRedo:0/14E41F48, newCkpLoc:0/14E98990, newRedo:0/14E98910, preCkpLoc:0/14E41FC8
2022-04-26 15:34:17.817 [unknown] [unknown] localhost 140324246648576 0[0:0#0] 0 [BACKEND] LOG: will update control file (create checkpoint), shutdown:0
2022-04-26 15:34:17.819 [unknown] [unknown] localhost 140324246648576 0[0:0#0] 0 [BACKEND] LOG: attempting to remove WAL segments older than log file 000000010000000000000002

omm2=# select * from t where id<10;
id | c
----+---
3 | d
4 | d
5 | d
6 | d
7 | d
8 | d
9 | d
1 | d
2 | d
(9 rows)

omm2=# update t set c='e' where id<500;
UPDATE 499

[omm2@og01 dump]$ kill -9 499

---dd一個資料塊為0,可以啟動

dd if=/dev/zero of=/home/omm2/data/base/16385/73775 conv=notrunc bs=8192 count=1
記錄了1+0 的讀入
記錄了1+0 的寫出
8192位元組(8.2 kB)已複製，0.00013172 秒，62.2 MB/秒

2022-04-26 15:39:24.369 [unknown] [unknown] localhost 140529590335232 0[0:0#0] 0 [SLRU] LOG: remove old segments(<0) under pg_csnlog
2022-04-26 15:39:24.369 [unknown] [unknown] localhost 140529590335232 0[0:0#0] 0 [BACKEND] LOG: truncate CSN log oldestXact 48052, next xid 48055
2022-04-26 15:39:24.373 [unknown] [unknown] localhost 140529590335232 0[0:0#0] 0 [SLRU] LOG: remove old segments(<0) under pg_multixact/offsets
2022-04-26 15:39:24.373 [unknown] [unknown] localhost 140529590335232 0[0:0#0] 0 [SLRU] LOG: remove old segments(<0) under pg_multixact/members
2022-04-26 15:39:24.379 [unknown] [unknown] localhost 140529590335232 0[0:0#0] 0 [UNDO] LOG: [CheckPointUndoSystemMeta:353]undo metadata checkPointRedo = 351319280.
2022-04-26 15:39:24.384 [MOT] TID:02911/----- SID:-----/----- [INFO] MOT begin checkpoint capture. id: 1650958764, lsn: 351319280
2022-04-26 15:39:24.386 [MOT] TID:03050/00000 SID:00004/00000 [INFO] GC PARAMS: isGcEnabled = true, limboSizeLimit = 524288, limboSizeLimitHigh = 8388608, rcuFreeCount = 8192
2022-04-26 15:39:24.387 [MOT] TID:03052/00000 SID:00006/00000 [INFO] GC PARAMS: isGcEnabled = true, limboSizeLimit = 524288, limboSizeLimitHigh = 8388608, rcuFreeCount = 8192
2022-04-26 15:39:24.488 [MOT] TID:02911/----- SID:-----/----- [INFO] Checkpoint [1650958764] completed
2022-04-26 15:39:24.487 [unknown] [unknown] localhost 140529590335232 0[0:0#0] 0 [BACKEND] WARNING: replicationSlotMinLSN is InvalidXLogRecPtr!!!
2022-04-26 15:39:24.487 [unknown] [unknown] localhost 140529590335232 0[0:0#0] 0 [BACKEND] WARNING: replicationSlotMaxLSN is InvalidXLogRecPtr!!!
2022-04-26 15:39:24.488 [unknown] [unknown] localhost 140529590335232 0[0:0#0] 0 [BACKEND] LOG: CreateCheckPoint PrintCkpXctlControlFile: [checkPoint] oldCkpLoc:0/14E98990, oldRedo:0/14E98910, newCkpLoc:0/14F0B570, newRedo:0/14F0B4F0, preCkpLoc:0/14E98990
2022-04-26 15:39:24.488 [unknown] [unknown] localhost 140529590335232 0[0:0#0] 0 [BACKEND] LOG: will update control file (create checkpoint), shutdown:0
2022-04-26 15:39:24.490 [unknown] [unknown] localhost 140529590335232 0[0:0#0] 0 [BACKEND] LOG: attempting to remove WAL segments older than log file 000000010000000000000002
[omm2@og01 pg_log]$

omm2=# select * from t where id<10;
id | c
----+---
3 | e
4 | e
5 | e
6 | e
7 | e
8 | e
9 | e
1 | e
2 | e
(9 rows)

omm2=# select (select setting from pg_settings where name='data_directory')||'/'||pg_relation_filepath('t');
?column?

/home/omm2/data/base/16385/73775

--full_page_writes 開啟時，每次checkpoint後第一次修改的塊，會在wal中記錄完整副本，recover時直接重寫資料檔案中的塊。
[omm2@og01 pg_log]$ gsql -c "show all"|grep full_page_writes
full_page_writes | on

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