KingbaseES V8R6数据库运维案例之---索引坏块故障处理

案例说明：
在执行表数据查询时，出现下图所示错误，索引故障导致表无法访问，后重建索引问题解决。本案例复现了此类故障解决过程。

适用版本：
KingbaseES V8R3/R6

一、创建测试环境

# 表结构信息
prod=# \d+ test1
                                   Table "public.test1"
 Column |  Type   | Collation | Nullable | Default | Storage  | Stats target | Description
--------+---------+-----------+----------+---------+----------+--------------+-------------
 id     | integer |           | not null |         | plain    |              |
 v_name | varchar |           |          |         | extended |              |
Indexes:
    "test1_pkey" PRIMARY KEY, btree (id)
    "test1_name_ind" btree (v_name)
Access method: heap

# 插入测试数据
prod=# insert into test1 values (generate_series(1,10000),'usr'||generate_series(1,10000));
INSERT 0 10000
prod=# select count(*) from test1;
 count
-------
 10000
(1 row)

# 查看索引应用
prod=# explain analyze select * from  test1 where v_name='usr2';
                                                      QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------
 Index Scan using test1_name_ind on test1  (cost=0.29..8.30 rows=1 width=11) (actual time=0.023..0.024 rows=1 loops=1)
   Index Cond: ((v_name)::text = 'usr2'::text)
 Planning Time: 0.055 ms
 Execution Time: 0.038 ms
(4 rows)

二、模拟数据文件故障

1、查看索引文件存储路径

prod=# select pg_relation_filepath('test1_name_ind');
 pg_relation_filepath
----------------------
 base/16385/26800
(1 row)

2、模拟数据文件被破坏

[kingbase@node102 data]$ ls -lh  base/16385/26800
-rw------- 1 kingbase kingbase 240K Nov 17 15:01 base/16385/26800

[kingbase@node102 data]$ dd if=/dev/zero of=/data/kingbase/v8r6_c6/data/base/16385/26800 bs=8k count=2
2+0 records in
2+0 records out
16384 bytes (16 kB) copied, 0.000147959 s, 111 MB/s

[kingbase@node102 data]$ ls -lh  base/16385/26800
-rw------- 1 kingbase kingbase 16K Nov 17 15:04 base/16385/26800

# 如下所示索引故障导致表访问错误
prod=# select * from  test1;
ERROR:  index "test1_name_ind" contains unexpected zero page at block 0
HINT:  Please REINDEX it.

三、重建索引解决故障

1、查看表索引信息

prod=# \d+ test1;
                                   Table "public.test1"
 Column |  Type   | Collation | Nullable | Default | Storage  | Stats target | Description
--------+---------+-----------+----------+---------+----------+--------------+-------------
 id     | integer |           | not null |         | plain    |              |
 v_name | varchar |           |          |         | extended |              |
Indexes:
    "test1_pkey" PRIMARY KEY, btree (id)
    "test1_name_ind" btree (v_name)
Access method: heap

2、重建索引

# 索引重建
prod=# reindex index test1_name_ind;
REINDEX

#如下所示，重建索引后表数据访问正常
prod=# select * from  test1 limit 3;
 id | v_name
----+--------
  1 | usr1
  2 | usr2
  3 | usr3
(3 rows)

prod=# select * from  test1 where v_name='usr2';
 id | v_name
----+--------
  2 | usr2
(1 row)

prod=# explain analyze select * from  test1 where v_name='usr2';
                                                      QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------
 Index Scan using test1_name_ind on test1  (cost=0.29..8.30 rows=1 width=11) (actual time=0.023..0.024 rows=1 loops=1)
   Index Cond: ((v_name)::text = 'usr2'::text)
 Planning Time: 0.055 ms
 Execution Time: 0.038 ms
(4 rows)

四、总结
对于KingbaseES数据库，索引块的损坏会影响到表数据的正常访问，对于索引块故障处理比较简单，直接重建索引一般都可以解决此类问题。