在某些情况下,由于PostgreSQL表文件损坏导致无法正常访问,可以通过pdu把好的block中的数据恢复出来
准备一张测试表,里面有97条记录

his5_dms=# \d hiscrm.t_sys_oper_log;
                                            Table "hiscrm.t_sys_oper_log"
       Column       |          Type          | Collation | Nullable |Default                     
--------------------+------------------------+-----------+----------+------------
 id                 | bigint                 |           | not null | 
 module             | character varying(50)  |           |          | 
 title              | character varying(50)  |           |          | 
 alias              | character varying(50)  |           |          | 
 business_type      | integer                |           |          | 0
 method             | character varying(200) |           |          | 
 request_method     | character varying(10)  |           |          | 
 operator_type      | integer                |           |          | 0
 oper_name          | character varying(50)  |           |          | 
 dept_name          | character varying(50)  |           |          | 
 oper_url           | character varying(255) |           |          | 
 oper_ip            | character varying(50)  |           |          | 
 oper_location      | character varying(255) |           |          | 
 oper_param         | text                   |           |          | 
 json_result        | text                   |           |          | 
 status             | integer                |           |          | 0
 error_msg          | text                   |           |          | 
 oper_time          | date                   |           |          | 
 create_id          | bigint                 |           |          | 
 create_time        | bigint                 |           |          | 
 clinic_id          | bigint                 |           |          | 
 group_id           | bigint                 |           |          | 
 patient_id         | bigint                 |           |          | 
 is_patient_related | integer                |           |          | 
 business_content   | json                   |           |          | 

his5_dms=# select count(1) from hiscrm.t_sys_oper_log;
 count 
-------
    97
(1 row)

查询表对应的具体文件

his5_dms=# SELECT oid,relfilenode FROM pg_class WHERE relname='t_sys_oper_log';
  oid  | relfilenode 
-------+-------------
 16850 |       16850
(1 row)

his5_dms=# SELECT pg_relation_filepath('hiscrm.t_sys_oper_log');
 pg_relation_filepath 
----------------------
 base/16386/16850
(1 row)

his5_dms=# SHOW data_directory;
     data_directory     
------------------------
 /var/lib/pgsql/12/data
(1 row)

使用dd对文件进行破坏

[postgres@xifenfeidg ~]$ ls -l  /var/lib/pgsql/12/data/base/16386/16850
-rw-------. 1 postgres postgres 90112 Sep  5 20:26 /var/lib/pgsql/12/data/base/16386/16850
[postgres@xifenfeidg ~]$ dd if=/dev/zero of=/var/lib/pgsql/12/data/base/16386/16850 bs=512 count=1 conv=notrunc
1+0 records in
1+0 records out
512 bytes copied, 0.000158756 s, 3.2 MB/s

重启pg库

[postgres@xifenfeidg bin]$ ./pg_ctl -m fast -D /var/lib/pgsql/12/data/ stop
waiting for server to shut down.... done
server stopped
[postgres@xifenfeidg bin]$ ./pg_ctl -D /var/lib/pgsql/12/data/ start
waiting for server to start....2025-03-02 19:02:11.395 HKT [64515] LOG:  
  starting PostgreSQL 12.20 on x86_64-pc-linux-gnu, 
  compiled by gcc (GCC) 8.5.0 20210514 (Red Hat 8.5.0-22), 64-bit
2025-03-02 19:02:11.396 HKT [64515] LOG:  listening on IPv6 address "::1", port 5432
2025-03-02 19:02:11.396 HKT [64515] LOG:  listening on IPv4 address "127.0.0.1", port 5432
2025-03-02 19:02:11.396 HKT [64515] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
2025-03-02 19:02:11.397 HKT [64515] LOG:  listening on Unix socket "/tmp/.s.PGSQL.5432"
2025-03-02 19:02:11.403 HKT [64515] LOG:  redirecting log output to logging collector process
2025-03-02 19:02:11.403 HKT [64515] HINT:  Future log output will appear in directory "log".
 done
server started

查询数据报错

[postgres@xifenfeidg bin]$ psql
psql (16.8, server 12.20)
Type "help" for help.

postgres=# \c his5_dms;
psql (16.8, server 12.20)
You are now connected to database "his5_dms" as user "postgres".
his5_dms=#  select count(1) from hiscrm.t_sys_oper_log;
ERROR:  invalid page in block 0 of relation base/16386/16850

通过pdu进行恢复
跳过了坏块,把好的block中数据均恢复出来

his5_dms.hiscrm=# unload tab t_sys_oper_log;
正在解析表 <t_sys_oper_log>. 已解析数据页: 0, 已解析数据: 0 条
        |-块号0 空页面或页面已损坏，已跳过
正在解析表 <t_sys_oper_log>. 已解析数据页: 11, 已解析数据: 86 条
表名<t_sys_oper_log>-</var/lib/pgsql/12/data/base/16386/16850> 
    解析完成, 11 个数据页 ,共计 86 条数据. 成功 86 条; 失败【0】条 
COPY文件路径为:<his5_dms/hiscrm/t_sys_oper_log.csv>

导入pg库中

his5_dms=# truncate table hiscrm.t_sys_oper_log;
TRUNCATE TABLE
his5_dms=# \i his5_dms/COPY/hiscrm_copy.sql
SET
COPY 86
his5_dms=#