表上索引过多，引发db file sequential read 等待事件

问题描述：用户BM0658告诉我说下面这个delete语句运行很长一段时间(4个多小时还在跑)

delete from ADWGU.SHPMT_CURR_FCT_NEW where LOAD_REGN_ABBR_NAME in ('NALA','APAC');

于是查询 会话

SQL> select sid,username,osuser,sql_id,sql_child_number from v$session where username='BM0658' and osuser='luobi';



SID USERNAME OSUSER SQL_ID SQL_CHILD_NUMBER

---------- ------------------------------ ------------------------------ ------------- ----------------

4530 BM0658 luobi

4735 BM0658 luobi g69rr33fyxgfw 0

4803 BM0658 luobi 6p7qw296ajga7 0



SQL> select * from table(dbms_xplan.display_cursor('g69rr33fyxgfw',0));



PLAN_TABLE_OUTPUT

--------------------------------------------------------------------------------

SQL_ID g69rr33fyxgfw, child number 0

-------------------------------------

delete from ADWGU.SHPMT_CURR_FCT_NEW where LOAD_REGN_ABBR_NAME in ('NALA','APAC'

Plan hash value: 2407586203

--------------------------------------------------------------------------------

| Id | Operation | Name | Rows | Bytes | Cost (%CP

--------------------------------------------------------------------------------

| 0 | DELETE STATEMENT | | | | 52353 (10

| 1 | DELETE | SHPMT_CURR_FCT_NEW | | |

| 2 | PARTITION RANGE ALL | | 62M| 3353M| 52353 (1

| 3 | PARTITION LIST INLIST| | 62M| 3353M| 52353 (1

| 4 | TABLE ACCESS FULL | SHPMT_CURR_FCT_NEW | 62M| 3353M| 52353 (1

--------------------------------------------------------------------------------



16 rows selected

从执行计划中可以看出这个表是分区表，delete操作对表做了全表扫描，于是查看当前等待事件，连续查看多次

从当前等待事件中，我看到db file sequential read居多(怀疑delete时候没有禁止索引)，另外还出现了一个latch竞争。全表扫描竟然会引起

db file sequential read 等待事件，有点反常，猜测索引过多



SQL> select event,p1,p2,p3 from v$session where sid=4735;



EVENT P1 P2 P3

---------------------------------------------------------------- ---------- ---------- ----------

db file sequential read 249 190176 1

SQL> select event,p1,p2,p3 from v$session where sid=4735;



EVENT P1 P2 P3

---------------------------------------------------------------- ---------- ---------- ----------

latch: cache buffers lru chain 1.38350580 117 0

SQL> select event,p1,p2,p3 from v$session where sid=4735;



EVENT P1 P2 P3

---------------------------------------------------------------- ---------- ---------- ----------

db file sequential read 39 178963 1

SQL> select event,p1,p2,p3 from v$session where sid=4735;



EVENT P1 P2 P3

---------------------------------------------------------------- ---------- ---------- ----------

db file sequential read 39 179011 1

SQL> select event,p1,p2,p3 from v$session where sid=4735;



EVENT P1 P2 P3

---------------------------------------------------------------- ---------- ---------- ----------

db file sequential read 85 186128 1

SQL> select event,p1,p2,p3 from v$session where sid=4735;



EVENT P1 P2 P3

---------------------------------------------------------------- ---------- ---------- ----------

db file sequential read 467 1603930 1

SQL> select event,p1,p2,p3 from v$session where sid=4735;



EVENT P1 P2 P3

---------------------------------------------------------------- ---------- ---------- ----------

db file sequential read 23 1503552 1

SQL> select event,p1,p2,p3 from v$session where sid=4735;



EVENT P1 P2 P3

---------------------------------------------------------------- ---------- ---------- ----------

db file sequential read 251 2283082 1



2270000



首先看ADWGU.SHPMT_CURR_FCT_NEW是什么类型

SQL> select owner,object_name,object_type from dba_objects where owner='ADWGU' and object_name='SHPMT_CURR_FCT_NEW';



OWNER OBJECT_NAME OBJECT_TYPE

------------------------------ -------------------------------------------------------------------------------- -------------------

ADWGU SHPMT_CURR_FCT_NEW SYNONYM

查出它是同义词，现在查看它是哪个表的同义词

SQL> select owner,synonym_name,table_owner,table_name from dba_synonyms where synonym_name='SHPMT_CURR_FCT_NEW' and owner='ADWGU';



OWNER SYNONYM_NAME TABLE_OWNER TABLE_NAME

------------------------------ ------------------------------ ------------------------------ ------------------------------

ADWGU SHPMT_CURR_FCT_NEW ADWU SHPMT_CURR_FCT_NEW

这里可以看到它是ADWU.SHPMT_CURR_FCT_NEW的同义词

查询表上的索引

SQL> select index_owner,index_name,table_owner,column_name,column_position from dba_ind_columns where table_name='SHPMT_CURR_FCT_NEW' and table_owner='ADWU';



INDEX_OWNE INDEX_NAME TABLE_OWNER COLUMN_NAME COLUMN_POSITION

---------- ------------------------------ ------------------------------ ------------------------------ ---------------

ADWU SHPMT_CURR_FCT_NEW_BX20 ADWU PROD_CSU_TYPE_CODE 1

ADWU SHPMT_CURR_FCT_NEW_BX10 ADWU SHPMT_FINAL_CLASS_IND_SKID 1

ADWU SHPMT_CURR_FCT_NEW_BX1 ADWU DAY_SKID 1

ADWU SHPMT_CURR_FCT_NEW_NX8 ADWU SHPMT_FACT_SKID 1

ADWU SHPMT_CURR_FCT_NEW_BX14 ADWU PROFT_CTR_SKID 1

ADWU SHPMT_CURR_FCT_NEW_BX5 ADWU GEO_SKID 1

ADWU SHPMT_CURR_FCT_NEW_BX2 ADWU CUST_SHIPT_SKID 1

ADWU SHPMT_CURR_FCT_NEW_BX11 ADWU PROD_SOLD_SKID 1

ADWU SHPMT_CURR_FCT_NEW_BX4 ADWU TRADE_CHANL_SKID 1

ADWU SHPMT_CURR_FCT_NEW_BX15 ADWU CRNCY_SKID 1

ADWU SHPMT_CURR_FCT_NEW_BX21 ADWU DAY_SKID 2

ADWU SHPMT_CURR_FCT_NEW_BX21 ADWU LOAD_REGN_ABBR_NAME 1



12 rows selected



查询表上面的索引类型

SQL>cselect owner,index_name,index_type,status from dba_indexes where table_owner='ADWU' and table_name='SHPMT_CURR_FCT_NEW';



OWNER INDEX_NAME INDEX_TYPE STATUS

------------------------------ ------------------------------ --------------------------- --------

ADWU SHPMT_CURR_FCT_NEW_BX20 BITMAP N/A

ADWU SHPMT_CURR_FCT_NEW_BX10 BITMAP N/A

ADWU SHPMT_CURR_FCT_NEW_BX1 BITMAP N/A

ADWU SHPMT_CURR_FCT_NEW_NX8 NORMAL N/A

ADWU SHPMT_CURR_FCT_NEW_BX14 BITMAP N/A

ADWU SHPMT_CURR_FCT_NEW_BX5 BITMAP N/A

ADWU SHPMT_CURR_FCT_NEW_BX2 BITMAP N/A

ADWU SHPMT_CURR_FCT_NEW_BX11 BITMAP N/A

ADWU SHPMT_CURR_FCT_NEW_BX4 BITMAP N/A

ADWU SHPMT_CURR_FCT_NEW_BX15 BITMAP N/A

ADWU SHPMT_CURR_FCT_NEW_BX21 BITMAP N/A



11 rows selected



N/A表示 这个索引是分区表上的索引



解决方案：先kill session，然后 disable 所有索引

alter index ADWU.SHPMT_CURR_FCT_NEW_BX20 unusable;

alter index ADWU.SHPMT_CURR_FCT_NEW_BX20 unusable;

alter index ADWU.SHPMT_CURR_FCT_NEW_BX20 unusable;

alter index ADWU.SHPMT_CURR_FCT_NEW_BX20 unusable;

alter index ADWU.SHPMT_CURR_FCT_NEW_BX20 unusable;

alter index ADWU.SHPMT_CURR_FCT_NEW_BX20 unusable;

alter index ADWU.SHPMT_CURR_FCT_NEW_BX20 unusable;

alter index ADWU.SHPMT_CURR_FCT_NEW_BX20 unusable;

alter index ADWU.SHPMT_CURR_FCT_NEW_BX20 unusable;

alter index ADWU.SHPMT_CURR_FCT_NEW_BX21 unusable;

alter index ADWU.SHPMT_CURR_FCT_NEW_BX20 unusable;



重新运行SQL语句



最后rebuild index parallel 8 nologging

注意，本案例发生在数据仓库，非OLTP环境