文件删除
rm -rf 1255 # pg_proc
select * from pg_class [order by oid]; ##不报错
select * from pg_class where oid = 1255; ## 报错
ERROR: could not open file "base/16397/1255": No such file or directory
zjh@test=# \d
ERROR: could not open file "base/16397/1255": No such file or directory
touch空文件
[zjh@hs-10-20-30-193 16397]$ ll | grep 1255
-rw------- 1 zjh zjh 24576 Aug 6 15:36 1255_fsm
-rw------- 1 zjh zjh 8192 Aug 6 15:36 1255_vm
[zjh@hs-10-20-30-193 16397]$ touch 1255
[zjh@hs-10-20-30-193 16397]$ ll | grep 1255
-rw-rw-r-- 1 zjh zjh 0 Sep 13 11:43 1255
-rw------- 1 zjh zjh 24576 Aug 6 15:36 1255_fsm
-rw------- 1 zjh zjh 8192 Aug 6 15:36 1255_vm
zjh@test=# select * from pg_class where oid=1255; ERROR: could not read block 3 in file "base/16397/1255": read only 0 of 8192 bytes zjh@test=# \d ERROR: could not read block 3 in file "base/16397/1255": read only 0 of 8192 bytes zjh@test=# select * from pg_proc; -- 因为系统表通过BKI初始化，所以定义存在 oid | proname | pronamespace | proowner | prolang | procost | prorows | provariadic | prosupport | prokind | prosecdef | proleakproof | proisstrict | proretset | provolatile | proparallel | pronargs | pronargdefa ults | prorettype | proaccess | proargtypes | proallargtypes | proargmodes | proargnames | proargdefaults | protrftypes | prosrc | probin | proconfig | proacl -----+---------+--------------+----------+---------+---------+---------+-------------+------------+---------+-----------+--------------+-------------+-----------+-------------+-------------+----------+------------ -----+------------+-----------+-------------+----------------+-------------+-------------+----------------+-------------+--------+--------+-----------+-------- (0 rows)
文件内容损坏（模拟裂页 partial-write）
zjh@test=# select * from pg_proc limit 247; ERROR: cache lookup failed for type 0 zjh@test=# select * from pg_proc limit 246; oid | proname | pronamespace | proowner | prolang | procost | prorows | provariadic | prosupport | prokind | prosecdef | proleakproof | proisstrict | proretset | provolatile | proparallel | pronargs | pronargdefaults | prorettype | proaccess | proargtypes | proallargtypes | proargmodes | proargnames | proargdefaults | protrftypes | prosrc | probin | proconfig | proacl ------+---------------------+--------------+----------+---------+---------+---------+-------------+---------------------+---------+-----------+--------------+-------------+-----------+-------------+-------------+- ---------+-----------------+------------+-----------+----------------------+----------------+-------------+-------------+----------------+-------------+---------------------+--------+-----------+-------- 1242 | boolin | 11 | 10 | 12 | 1 | 0 | 0 | - | f | f | f | t | f | i | s | 1 | 0 | 16 | n | 2275 | | | | | | boolin | | | 1243 | boolout | 11 | 10 | 12 | 1 | 0 | 0 | - | f | f | f | t | f | i | s | 1 | 0 | 2275 | n | 16 | | | | | | boolout | | |
(5,40) | 293 | float8eq | 11 | 10 | 12 | 1 | 0 | 0 | - | f | f | t | t | f | i | s | 2 | 0 | 16 | n | 701 701 | | | | | | float8eq | | | (5,41) | 294 | float8ne | 11 | 10 | 12 | 1 | 0 | 0 | - | f | f | t | t | f | i | s | 2 | 0 | 16 | n | 701 701 | | | | | | float8ne | | | (6,3) | 297 | float8gt | 11 | 10 | 12 | 1 | 0 | 0 | - | f | f | t | t | f | i | s | 2 | 0 | 16 | n | 701 701 | | | | | | float8gt | | | (6,4) | 298 | float8ge | 11 | 10 | 12 | 1 | 0 | 0 | - | f | f | t | t | f | i | s | 2 | 0 | 16 | n | 701 701 | | | | | | float8ge | | | (248 rows) zjh@test=# select ctid,a.* from pg_proc a where ctid='(6,2)' limit 248; ERROR: cache lookup failed for type 0
然后根据ctid过滤掉损坏的记录，然后lt_dump/lt_restore重建库即可。
zjh@test=# select ctid,a.* from pg_proc a where ctid!='(6,2)';
对于系统表，一般都是通过DDL导入的，所以可以考虑开启log_statement = 'ddl'记录所有执行过的DDL。这样可以尽量减少DDL丢失。当然，如果对库的依赖较少，可以从别的库把数据拷贝回来。如下：
[zjh@hs-10-20-30-193 16397]$ ll | grep 1255 -rw-rw-r-- 1 zjh zjh 679936 Sep 13 11:58 1255 -rw------- 1 zjh zjh 24576 Aug 6 15:36 1255_fsm -rw------- 1 zjh zjh 8192 Aug 6 15:36 1255_vm [zjh@hs-10-20-30-193 16397]$ cd ../ 1/ 13591/ 13592/ 16397/ ltsql_tmp/ [zjh@hs-10-20-30-193 16397]$ cd ../13592/ [zjh@hs-10-20-30-193 13592]$ ll | grep 1255 -rw------- 1 zjh zjh 704512 Sep 11 00:13 1255 -rw------- 1 zjh zjh 24576 Sep 10 22:43 1255_fsm -rw------- 1 zjh zjh 8192 Sep 10 17:46 1255_vm [zjh@hs-10-20-30-193 13592]$ cd ../13591/ [zjh@hs-10-20-30-193 13591]$ ll | grep 1255 -rw------- 1 zjh zjh 679936 Aug 6 15:36 1255 -rw------- 1 zjh zjh 24576 Aug 6 15:36 1255_fsm -rw------- 1 zjh zjh 8192 Aug 6 15:36 1255_vm