[Oracle]一个通过添加本地分区索引提高SQL性能的案例
今天接到同事求助，说有一个select query，在Oracle上要跑一分多钟，他希望能在5s内出结果，该sql如下：
[sql]
Select /*+ parallel(src, 8) */ distinct
src.systemname as systemname
, src.databasename as databasename
, src.tablename as tablename
, src.username as username
from <strong>meta_dbql_table_usage_exp_hst</strong> src
inner <strong>join DR_QRY_LOG_EXP_HST</strong> rl on
<strong>src.acctstringdate = rl.acctstringdate
and src.queryid = rl.queryid</strong>
And Src.Systemname = Rl.Systemname
and src.acctstringdate > sysdate - 30
And Rl.Acctstringdate > Sysdate - 30
inner join <strong>meta_dr_qry_log_tgt_all_hst </strong>tgt on
upper(tgt.systemname) = upper('MOZART')
And Upper(tgt.Databasename) = Upper('GDW_TABLES')
And Upper(tgt.Tablename) = Upper('SSA_SLNG_LSTG_MTRC_SD')
<strong>AND src.acctstringdate = tgt.acctstringdate
and rl.statement_id = tgt.statement_id</strong>
and rl.systemname = tgt.systemname
And Tgt.Acctstringdate > Sysdate - 30
And Not(
Upper(Tgt.Systemname)=Upper(src.systemname)
And
Upper(Tgt.Databasename) = Upper(Src.Databasename)
And
Upper(Tgt.Tablename) = Upper(Src.Tablename)
)
And tgt.Systemname is not null
And tgt.Databasename Is Not Null
And tgt.tablename is not null
;
SQL的简单分析
总得来看，这个SQL就是三个表(meta_dbql_table_usage_exp_hst，DR_QRY_LOG_EXP_HST，meta_dr_qry_log_tgt_all_hst）的INNER JOIN，这三个表数据量都在百万级别，且都是分区表（以acctstringdate为分区键），执行计划如下：
[sql]
------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost | Pstart| Pstop |
------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 159 | 8654 | | |
| 1 | PX COORDINATOR | | | | | | |
| 2 | PX SEND QC (RANDOM) | :TQ10002 | 1 | 159 | 8654 | | |
| 3 | SORT UNIQUE | | 1 | 159 | 8654 | | |
| 4 | PX RECEIVE | | 1 | 36 | 3 | | |
| 5 | PX SEND HASH | :TQ10001 | 1 | 36 | 3 | | |
|* 6 | TABLE ACCESS BY LOCAL INDEX ROWID| DR_QRY_LOG_EXP_HST | 1 | 36 | 3 | | |
| 7 | NESTED LOOPS | | 1 | 159 | 8633 | | |
| 8 | NESTED LOOPS | | 8959 | 1076K| 4900 | | |
| 9 | BUFFER SORT | | | | | | |
| 10 | PX RECEIVE | | | | | | |
| 11 | PX SEND BROADCAST | :TQ10000 | | | | | |
| 12 | PARTITION RANGE ITERATOR | | 1 | 56 | 4746 | KEY | 14 |
|* 13 | TABLE ACCESS FULL | META_DR_QRY_LOG_TGT_ALL_HST | 1 | 56 | 4746 | KEY | 14 |
| 14 | PX BLOCK ITERATOR | | 8959 | 586K| 154 | KEY | KEY |
|* 15 | TABLE ACCESS FULL
