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統計信息不準導致執行計劃出錯跑不出結果，優化后只要1分鐘

來源：懂視網 責編：小采 時間：2020-11-09 15:00:58
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統計信息不準導致執行計劃出錯跑不出結果，優化后只要1分鐘

統計信息不準導致執行計劃出錯跑不出結果，優化后只要1分鐘:一天查看數據庫長會話，發現1個sql跑得很慢，1個多小時不出結果，花了點時間把它給優化了。 優化前： SELECT 20131023, A2.ORG_ID, COUNT(DISTINCT NLSSORT(CASE A2.RES_TYPE WHEN DP THEN A2.RES_CODE END, nls_sort=
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導讀統計信息不準導致執行計劃出錯跑不出結果，優化后只要1分鐘:一天查看數據庫長會話，發現1個sql跑得很慢，1個多小時不出結果，花了點時間把它給優化了。 優化前： SELECT 20131023, A2.ORG_ID, COUNT(DISTINCT NLSSORT(CASE A2.RES_TYPE WHEN DP THEN A2.RES_CODE END, nls_sort=

一天查看數據庫長會話，發現1個sql跑得很慢，1個多小時不出結果，花了點時間把它給優化了。 優化前： SELECT 20131023, A2.ORG_ID, COUNT(DISTINCT NLSSORT(CASE A2.RES_TYPE WHEN DP THEN A2.RES_CODE END, nls_sort=BINARY)), COUNT(DISTINCT NLSSORT(CASE

一天查看數據庫長會話，發現1個sql跑得很慢，1個多小時不出結果，花了點時間把它給優化了。

優化前：

SELECT 20131023,
 "A2"."ORG_ID",
 COUNT(DISTINCT NLSSORT(CASE "A2"."RES_TYPE"
 WHEN 'DP' THEN
 "A2"."RES_CODE"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE "A2"."RES_TYPE"
 WHEN 'BOX' THEN
 "A2"."RES_CODE"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE "A2"."RES_TYPE"
 WHEN 'ONU' THEN
 "A2"."RES_CODE"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE "A2"."RES_TYPE"
 WHEN 'OBD' THEN
 "A2"."RES_CODE"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE
 WHEN ("A1"."CON_TYPE" = '001' AND "A2"."RES_TYPE" = 'DP') THEN
 "A1"."RES_ID"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE
 WHEN ("A1"."CON_TYPE" = '002' AND "A2"."RES_TYPE" = 'BOX') THEN
 "A1"."RES_ID"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE
 WHEN ("A1"."CON_TYPE" = '0011' AND "A2"."RES_TYPE" = 'ONU') THEN
 "A1"."RES_ID"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE
 WHEN ("A1"."CON_TYPE" = '0022' AND "A2"."RES_TYPE" = 'OBD') THEN
 "A1"."RES_ID"
 END,
 'nls_sort=''BINARY'''))
 FROM "CRM_SZ"."AAA" "A2",
 "CRM_SZ"."BBB" "A1"
 WHERE "A1"."RES_ID"(+) = "A2"."RES_CODE"
 GROUP BY "A2"."ORG_ID"

執行計劃：
Plan hash value: 2627707252
 
---------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 1065 | 3 (34)| 00:00:01 |
| 1 | SORT GROUP BY | | 1 | 1065 | 3 (34)| 00:00:01 |
| 2 | NESTED LOOPS OUTER| | 1 | 1065 | 2 (0)| 00:00:01 |
| 3 | TABLE ACCESS FULL| AAA | 1 | 539 | 2 (0)| 00:00:01 |
|* 4 | INDEX FULL SCAN | IX_MO_CON_VALUE | 1 | 526 | 0 (0)| 00:00:01 |
---------------------------------------------------------------------------------------
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
 4 - access("A1"."RES_ID"(+)="A2"."RES_CODE")
 filter("A1"."RES_ID"(+)="A2"."RES_CODE")

cbo估算錯了，rows全是1，導致走nl
手工count了一把：
select count(*) from "CRM_SZ"."AAA" ;--1365564
select count(*) from "CRM_SZ"."BBB";--119949
走nl那豈不是sb啦。

第一次優化后：

SELECT/*+use_hash(A1,A2) swap_join_inputs(A1)*/20131023,
 "A2"."ORG_ID",
 COUNT(DISTINCT NLSSORT(CASE "A2"."RES_TYPE"
 WHEN 'DP' THEN
 "A2"."RES_CODE"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE "A2"."RES_TYPE"
 WHEN 'BOX' THEN
 "A2"."RES_CODE"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE "A2"."RES_TYPE"
 WHEN 'ONU' THEN
 "A2"."RES_CODE"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE "A2"."RES_TYPE"
 WHEN 'OBD' THEN
 "A2"."RES_CODE"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE
 WHEN ("A1"."CON_TYPE" = '001' AND "A2"."RES_TYPE" = 'DP') THEN
 "A1"."RES_ID"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE
 WHEN ("A1"."CON_TYPE" = '002' AND "A2"."RES_TYPE" = 'BOX') THEN
 "A1"."RES_ID"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE
 WHEN ("A1"."CON_TYPE" = '0011' AND "A2"."RES_TYPE" = 'ONU') THEN
 "A1"."RES_ID"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE
 WHEN ("A1"."CON_TYPE" = '0022' AND "A2"."RES_TYPE" = 'OBD') THEN
 "A1"."RES_ID"
 END,
 'nls_sort=''BINARY'''))
 FROM "CRM_SZ"."AAA" "A2",
 "CRM_SZ"."BBB" "A1"
 WHERE "A1"."RES_ID"(+) = "A2"."RES_CODE"
 GROUP BY "A2"."ORG_ID"

63 rows selected.

Elapsed: 00:00:47.64

Execution Plan
----------------------------------------------------------
Plan hash value: 3074972763

------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 1065 | 4 (50)| 00:00:01 |
| 1 | SORT GROUP BY | | 1 | 1065 | 4 (50)| 00:00:01 |
|* 2 | HASH JOIN RIGHT OUTER| | 1 | 1065 | 3 (34)| 00:00:01 |
| 3 | INDEX FULL SCAN | IX_MO_CON_VALUE | 1 | 526 | 0 (0)| 00:00:01 |
| 4 | TABLE ACCESS FULL | AAA | 1 | 539 | 2 (0)| 00:00:01 |
------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

 2 - access("A1"."RES_ID"(+)="A2"."RES_CODE")

Statistics
----------------------------------------------------------
 1065 recursive calls
 3 db block gets
 13375 consistent gets
 16369 physical reads
 0 redo size
 4862 bytes sent via SQL*Net to client
 791 bytes received via SQL*Net from client
 6 SQL*Net roundtrips to/from client
 12 sorts (memory)
 1 sorts (disk)
 63 rows processed
第二次優化后： 
SELECT/*+use_hash(A1,A2) full(A1) full(A2) parallel(A1,5) parallel(A2,5) swap_join_inputs(A1)*/20131023,
 "A2"."ORG_ID",
 COUNT(DISTINCT NLSSORT(CASE "A2"."RES_TYPE"
 WHEN 'DP' THEN
 "A2"."RES_CODE"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE "A2"."RES_TYPE"
 WHEN 'BOX' THEN
 "A2"."RES_CODE"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE "A2"."RES_TYPE"
 WHEN 'ONU' THEN
 "A2"."RES_CODE"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE "A2"."RES_TYPE"
 WHEN 'OBD' THEN
 "A2"."RES_CODE"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE
 WHEN ("A1"."CON_TYPE" = '001' AND "A2"."RES_TYPE" = 'DP') THEN
 "A1"."RES_ID"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE
 WHEN ("A1"."CON_TYPE" = '002' AND "A2"."RES_TYPE" = 'BOX') THEN
 "A1"."RES_ID"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE
 WHEN ("A1"."CON_TYPE" = '0011' AND "A2"."RES_TYPE" = 'ONU') THEN
 "A1"."RES_ID"
 END,
 'nls_sort=''BINARY''')),
 COUNT(DISTINCT NLSSORT(CASE
 WHEN ("A1"."CON_TYPE" = '0022' AND "A2"."RES_TYPE" = 'OBD') THEN
 "A1"."RES_ID"
 END,
 'nls_sort=''BINARY'''))
 FROM "CRM_SZ"."AAA" "A2",
 "CRM_SZ"."BBB" "A1"
 WHERE "A1"."RES_ID"(+) = "A2"."RES_CODE"
 GROUP BY "A2"."ORG_ID";

63 rows selected.

Elapsed: 00:00:10.21

Execution Plan
----------------------------------------------------------
Plan hash value: 4044842257

-------------------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | TQ |IN-OUT| PQ Distrib |
-------------------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 1065 | 6 (34)| 00:00:01 | | | |
| 1 | PX COORDINATOR | | | | | | | | |
| 2 | PX SEND QC (RANDOM) | :TQ10004 | 1 | 1065 | 6 (34)| 00:00:01 | Q1,04 | P->S | QC (RAND) |
| 3 | SORT GROUP BY | | 1 | 1065 | 6 (34)| 00:00:01 | Q1,04 | PCWP | |
| 4 | PX RECEIVE | | 1 | 1065 | 6 (34)| 00:00:01 | Q1,04 | PCWP | |
| 5 | PX SEND HASH | :TQ10003 | 1 | 1065 | 6 (34)| 00:00:01 | Q1,03 | P->P | HASH |
| 6 | SORT GROUP BY | | 1 | 1065 | 6 (34)| 00:00:01 | Q1,03 | PCWP | |
| 7 | PX RECEIVE | | 1 | 1065 | 6 (34)| 00:00:01 | Q1,03 | PCWP | |
| 8 | PX SEND HASH | :TQ10002 | 1 | 1065 | 6 (34)| 00:00:01 | Q1,02 | P->P | HASH |
| 9 | SORT GROUP BY | | 1 | 1065 | 6 (34)| 00:00:01 | Q1,02 | PCWP | |
|* 10 | HASH JOIN RIGHT OUTER| | 1 | 1065 | 5 (20)| 00:00:01 | Q1,02 | PCWP | |
| 11 | PX RECEIVE | | 1 | 526 | 2 (0)| 00:00:01 | Q1,02 | PCWP | |
| 12 | PX SEND HASH | :TQ10000 | 1 | 526 | 2 (0)| 00:00:01 | Q1,00 | P->P | HASH |
| 13 | PX BLOCK ITERATOR | | 1 | 526 | 2 (0)| 00:00:01 | Q1,00 | PCWC | |
| 14 | TABLE ACCESS FULL| BBB | 1 | 526 | 2 (0)| 00:00:01 | Q1,00 | PCWP | |
| 15 | PX RECEIVE | | 1 | 539 | 2 (0)| 00:00:01 | Q1,02 | PCWP | |
| 16 | PX SEND HASH | :TQ10001 | 1 | 539 | 2 (0)| 00:00:01 | Q1,01 | P->P | HASH |
| 17 | PX BLOCK ITERATOR | | 1 | 539 | 2 (0)| 00:00:01 | Q1,01 | PCWC | |
| 18 | TABLE ACCESS FULL| AAA | 1 | 539 | 2 (0)| 00:00:01 | Q1,01 | PCWP | |
-------------------------------------------------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

 10 - access("A1"."RES_ID"(+)="A2"."RES_CODE")


Statistics
----------------------------------------------------------
 585 recursive calls
 4 db block gets
 14267 consistent gets
 13126 physical reads
 808 redo size
 4888 bytes sent via SQL*Net to client
 840 bytes received via SQL*Net from client
 6 SQL*Net roundtrips to/from client
 23 sorts (memory)
 0 sorts (disk)
 63 rows processed

優化前，執行計劃走了nl，1個多小時查不出結果
第一次優化后，首次00:00:47.64可以出結果
第二次優化后，首次00:00:10.21出結果，重復執行（有緩存）的情況下3s出結果。

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統計信息不準導致執行計劃出錯跑不出結果，優化后只要1分鐘

統計信息不準導致執行計劃出錯跑不出結果，優化后只要1分鐘:一天查看數據庫長會話，發現1個sql跑得很慢，1個多小時不出結果，花了點時間把它給優化了。 優化前： SELECT 20131023, A2.ORG_ID, COUNT(DISTINCT NLSSORT(CASE A2.RES_TYPE WHEN DP THEN A2.RES_CODE END, nls_sort=
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