# DWS元数据不一致-分区索引异常
#### 问题现象
某局点查看表定义报错："The local index xxx on the partition xxx not exist."。
#### 原因分析
该问题主表索引无损坏，报错原因是由于单个分区索引记录在系统表pg_partition中与其他系统表不一致，未找到对应分区索引信息。
#### 问题复现
1. 创建分区表a_0317，含p1，p2两个分区。
   ```
   CREATE TABLE a_0317(a int) partition by range(a) (partition p1 values less than (4), partition p2 values less than (8));
   ```
   
2. 创建主表与分区索引。
   ```
   CREATE INDEX a_0317_index on a_0317(a) local (partition p1_index, partition p2_index);
   ```
   
3. 查看分区表分区索引信息如下：
   1. 查看主表索引信息。
      ```
      SELECT oid,* FROM pg_class where relname ='a_0317_index';
        oid   |   relname    | relnamespace | reltype | reloftype | relowner | relam | relfilenode | reltablespace | relpages | reltuples | relallvisible | reltoastrelid | reltoastidxid | reldeltarelid | reld
      eltaidx | relcudescrelid | relcudescidx | relhasindex | relisshared | relpersistence | relkind | relnatts | relchecks | relhasoids | relhaspkey | relhasrules | relhastriggers | relhassubclass | relcmprs
       | relhasclusterkey | relrowmovement | parttype | relfrozenxid | relacl | reloptions | relreplident | relfrozenxid64
      --------+--------------+--------------+---------+-----------+----------+-------+-------------+---------------+----------+-----------+---------------+---------------+---------------+---------------+-----
      --------+----------------+--------------+-------------+-------------+----------------+---------+----------+-----------+------------+------------+-------------+----------------+----------------+---------
      -+------------------+----------------+----------+--------------+--------+------------+--------------+----------------
       241487 | a_0317_index |         2200 |       0 |         0 |    16393 |   403 |      241487 |             0 |        0 |         0 |             0 |             0 |             0 |             0 |
            0 |              0 |            0 | f           | f           | p              | i       |        1 |         0 | f          | f          | f           | f              | f              | 0
       | f                | f              | p        | 0            |        |            | n            |              0
      (1 row)
      ```
      
   
   2. 根据主表索引信息查看分区索引信息。
      ```
      SELECT * FROM pg_partition where parentid= 241487;
       relname  | parttype | parentid | rangenum | intervalnum | partstrategy | relfilenode | reltablespace | relpages | reltuples | relallvisible | reltoastrelid | reltoastidxid | indextblid | indisusable |
      reldeltarelid | reldeltaidx | relcudescrelid | relcudescidx | relfrozenxid | intspnum | partkey | intervaltablespace | interval | boundaries | transit | reloptions | relfrozenxid64
      ----------+----------+----------+----------+-------------+--------------+-------------+---------------+----------+-----------+---------------+---------------+---------------+------------+-------------+-
      --------------+-------------+----------------+--------------+--------------+----------+---------+--------------------+----------+------------+---------+------------+----------------
       p1_index | x        |   241487 |        0 |           0 | n            |      241488 |             0 |        0 |         0 |             0 |             0 |             0 |     241485 | t           |
                  0 |           0 |              0 |            0 | 0            |          |         |                    |          |            |         |            |              0
       p2_index  | x        |   241487 |        0 |           0 | n            |      241489 |             0 |        0 |         0 |             0 |             0 |             0 |     241486 | t           |
                  0 |           0 |              0 |            0 | 0            |          |         |                    |          |            |         |            |              0
      (2 rows)
      ```
      
    
4. 连接CN开启读写事务，从pg_partition系统表删除p1分区的索引信息。
   ```
   START TRANSACTION read write;
   DELETE from pg_partition where relname = 'p1_index';
   ```
   
5. 查看表定义报错与现场报错相同，问题复现：
   ```
   \d+ a_0317
   ERROR:  The local index 700633 on the partition 700647 not exist.CONTEXT:  referenced column: pg_get_indexdef
   ```
   
 
#### 处理方法
1. 删除该表索引信息。
   ```
   DROP INDEX a_0317_index;
   ```
   
2. 对该表索引进行重建。
   ```
   CREATE INDEX a_0317_index on a_0317(a) local (partition p1_index, partition p2_index);
   ```
   
3. 查看表定义无报错。
   ```
   \d+ a_0317
                           Table "public.a_0317"
    Column |  Type   | Modifiers | Storage | Stats target | Description
   --------+---------+-----------+---------+--------------+-------------
    a      | integer |           | plain   |              |
   Indexes:
       "a_0317_index" btree (a) LOCAL(PARTITION p1_index, PARTITION p2_index)  TABLESPACE pg_default
   Range partition by(a)
   Number of partitions: 2 (View pg_partition to check each partition range.)
   Has OIDs: no
   Distribute By: HASH(a)
   Location Nodes: ALL DATANODES
   Options: orientation=row, compression=no
   ```