PostgreSQL 索引坏块处理

今天应用反应有张表查询报错，报错信息如下

back=# select max(create_time) from public.tbl_index_table where create_time>='2010-10-08';
ERROR:  could not read block 41381 of relation 16779/24769/24938: read only 0 of 8192 bytes

看到这个错误信息，首先想到的是表 tbl_index_table 上有坏块，估计需要表重建下。
   
--查看执行计划
back=# \d tbl_index_table;
                 Table "public.tbl_index_table"
     Column     |            Type             |       Modifiers       
----------------+-----------------------------+------------------------
 total          | integer                     |
 logined        | integer                     |
 logining       | integer                     |
 http           | integer                     |
 rawtcp         | integer                     |
 create_time    | timestamp without time zone | not null default now()
 logincountdesc | character varying           |
 logincountaddr | character varying           | not null
Indexes:
    "tbl_index_table_pkey" PRIMARY KEY, btree (create_time, logincountaddr)
    "index_tbl_index_table_create_time" btree (create_time)

back=#  select max(create_time) from public.tbl_index_table where create_time>='2010-10-08';
ERROR:  could not read block 41381 of relation 16779/24769/24938: read only 0 of 8192 bytes

back=# explain  select max(create_time) from public.tbl_index_table where create_time>='2010-10-08';
                                                                   QUERY PLAN                                                                  
------------------------------------------------------------------------------------------------------------------------------------------------
 Result  (cost=0.04..0.05 rows=1 width=0)
   InitPlan
     ->  Limit  (cost=0.00..0.04 rows=1 width=8)
           ->  Index Scan Backward using index_tbl_index_table_create_time on tbl_index_table  (cost=0.00..66.28 rows=1507 width=8)
                 Index Cond: (create_time >= '2010-10-08 00:00:00'::timestamp without time zone)
                 Filter: (create_time IS NOT NULL)
(6 rows)

发现上面的查询走的索引 index_tbl_index_table_create_time,猜测索引可能有问题。
   
--根据报错信息,从relation后面的数字分析
back=# select oid,relname from pg_class where oid=24938;
  oid  |                 relname                
-------+-----------------------------------------
 24938 | index_tbl_index_table_create_time
(1 row)

Time: 0.596 ms
back=# select oid,relname from pg_class where oid=24769;
 oid | relname
-----+---------
(0 rows)

Time: 0.369 ms
back=# select oid,relname from pg_class where oid=16779;
 oid | relname
-----+---------
(0 rows)

发现 24938正好是表上的索引 index_tbl_index_table_create_time。

--查看索引状态
back=# select * from pg_index where indexrelid=24938;
 indexrelid | indrelid | indnatts | indisunique | indisprimary | indisclustered | indisvalid | indcheckxmin | indisready | indkey | indclass | indoption | indexprs | indpred
------------+----------+----------+-------------+--------------+----------------+------------+--------------+------------+--------+----------+-----------+----------+---------
      24938 |    24823 |        1 | f           | f            | f              | t          | f            | t          | 6      | 10053    | 0         |          |
(1 row)

indisvalid=t 表示索引处于可用状态。

--尝试下重建索引

back=# select current_query from pg_stat_activity;
                current_query               
---------------------------------------------
 <IDLE>
 <IDLE>
 <IDLE>
 <IDLE>
 <IDLE>
 select current_query from pg_stat_activity;
 <IDLE>
 <IDLE>
 <IDLE>
 <IDLE>
 <IDLE>
 <IDLE>
 <IDLE>
 <IDLE>
 <IDLE>
 <IDLE>
 <IDLE>
 <IDLE>
 <IDLE>
 <IDLE>
 <IDLE>
 <IDLE>
(22 rows)

back=# \timing
Timing is on.

back=# reindex index index_tbl_index_table_create_time;
REINDEX
Time: 107796.232 ms

--索引重建后，查询恢复正常
back=# select max(create_time) from public.tbl_index_table where create_time>='2010-10-08';
 max
-----
 
(1 row)

Time: 73.600 ms

back=# select pg_size_pretty(pg_relation_size('index_tbl_index_table_create_time'));
 pg_size_pretty
----------------
 327 MB
(1 row)

总结： 1 网上查了下，说是 Postgresql 的bug 2197, 但从上面的处理过程来看，应该是索引上有坏块，
               索引重建后，查询恢复正常。

转载自：http://francs3.blog.163.com/blog/static/40576727201099257873/