[20220414]Function based indexes and cursor sharing2.txt
[20220414]Function based indexes and cursor sharing2.txt
--//以前的測試：http://blog.itpub.net/267265/viewspace-2737440/ =>[20202117]Function based indexes and cursor sharing.txt
--//也就是從19c開始如果你設定cursor_sharing=force; 一些函式里面帶有引數的依舊可以使用索引。但是最近我最佳化遇到的問題，不
--//知道為什麼不能使用索引。
1.環境：
> @ pr
==============================
PORT_STRING : x86_64/Linux 2.4.xx
VERSION : 19.0.0.0.0
BANNER : Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
BANNER_FULL : Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
Version 19.9.0.0.0
BANNER_LEGACY : Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production
CON_ID : 0
PL/SQL procedure successfully completed.
2.分析：
> @ash/ash_index_helper % XXXXXX_YYY.TEMP_HSDJ &day 1 1
-- Santa's Little (Index) Helper BETA v0.5 - by Tanel Poder ( )
SECONDS AAS CPU WAIT Accessed_Table Plan_Operation PLAN_CARD TABLE_ROWS FILTER_PCT SQL_EXECS ELA_SEC/EXEC PREDICATES SQL_ID MODULE1
---------- ------- ----- ----- -------------------- ---------------------------------------- --------- ---------- ---------- ---------- ------------ ------------------------------------------------------------ ------------- --------
50 .0 100% 0% TEMP_HSDJ TABLE ACCESS FULL [XXXXXX_YYY.TEMP_HSDJ] 1552 156391 .992384472 1040 0.059 [F:] (TO_CHAR(INTERNAL_FUNCTION("T"."DJDATE"),:SYS_B_38)=:S 8y1j8tf28h2w8 w3wp.exe
YS_B_39 AND "T"."DJSTATUS" IS NULL)
> @ sql_id 8y1j8tf28h2w8
--SQL_ID = 8y1j8tf28h2w8
select * from (select ...
from temp_hsdj t
where t.djstatus is null and to_char(t.djdate,:"SYS_B_38") = :"SYS_B_39" order by djdate desc ) where :"SYS_B_40"=:"SYS_B_41" and rownum < = :"SYS_B_42" ;
> @ bind_cap 8y1j8tf28h2w8 :sys_B_3
SQL_ID CHILD_NUMBER WAS NAME POSITION MAX_LENGTH LAST_CAPTURED DATATYPE_STRING VALUE_STRING
------------- ------------ --- ---------------------------------------- ---------- ---------- ------------------- --------------- ------------
8y1j8tf28h2w8 1 YES :SYS_B_38 39 32 2022-04-13 17:34:04 VARCHAR2(32) yyyy-mm-dd
YES :SYS_B_39 40 32 2022-04-13 17:34:04 VARCHAR2(32) 2022-04-13
--//注太長我僅僅列出where部分。
--//我已經建立了函式索引。
CREATE INDEX XXXXXX_YYY.IF_TEMP_HSDJ_DJDATE ON XXXXXX_YYY.TEMP_HSDJ (TO_CHAR("DJDATE",'yyyy-mm-dd'))
LOGGING
TABLESPACE XXXXXX_YYY
PCTFREE 10
INITRANS 2
MAXTRANS 255
STORAGE (
INITIAL 64K
NEXT 1M
MAXSIZE UNLIMITED
MINEXTENTS 1
MAXEXTENTS UNLIMITED
PCTINCREASE 0
FREELISTS 1
FREELIST GROUPS 1
BUFFER_POOL DEFAULT
FLASH_CACHE DEFAULT
CELL_FLASH_CACHE DEFAULT
)
NOPARALLEL
COMPRESS 1;
--//為了測試需要，我簡單改寫指令碼如下，便於重複測試：
$ cat 8y1j8tf28h2w8.sql9_x
set termout off
alter session set current_schema=XXXXXX_YYY;
alter session set statistics_level=all;
alter session set cursor_sharing = force;
select t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' ;
set termout on
@dpc '' outline ''
rollback;
alter session set current_schema=SYS ;
PLAN_TABLE_OUTPUT
-------------------------------------
SQL_ID fatkcpsnxa2g8, child number 0
-------------------------------------
select t.section ,t.brxm from temp_hsdj t where t.djstatus is null and
to_char(t.djdate,:"SYS_B_0") = :"SYS_B_1"
Plan hash value: 1883277554
-----------------------------------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time | A-Rows | A-Time | Buffers |
-----------------------------------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | | 30 (100)| | 1219 |00:00:00.01 | 60 |
|* 1 | TABLE ACCESS BY INDEX ROWID BATCHED| TEMP_HSDJ | 1 | 1084 | 32520 | 30 (0)| 00:00:01 | 1219 |00:00:00.01 | 60 |
|* 2 | INDEX RANGE SCAN | IF_TEMP_HSDJ_DJDATE | 1 | 1086 | | 2 (0)| 00:00:01 | 1221 |00:00:00.01 | 16 |
-----------------------------------------------------------------------------------------------------------------------------------------------------
--//你可以發現確實可以使用我建立的函式索引，注意看sql語句輸出部分，說明cursor_sharing = force是起作用的。
--//按照生產系統的執行條件修改如下：
$ cat 8y1j8tf28h2w8.sql9_x
$ cat 8y1j8tf28h2w8.sql9_x
set termout off
alter session set current_schema=XXXXXX_YYY;
alter session set statistics_level=all;
alter session set cursor_sharing = force;
--select t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' ;
select * from (select t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' order by djdate desc ) where 1=1 and rownum < = 30 ;
set termout on
@dpc '' outline ''
rollback;
alter session set current_schema=SYS ;
--//執行計劃如下：
Plan hash value: 1191506493
----------------------------------------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time | A-Rows | A-Time | Buffers | OMem | 1Mem | Used-Mem |
----------------------------------------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | | 1079 (100)| | 30 |00:00:00.06 | 3967 | | | |
|* 1 | COUNT STOPKEY | | 1 | | | | | 30 |00:00:00.06 | 3967 | | | |
| 2 | VIEW | | 1 | 1562 | 128K| 1079 (1)| 00:00:01 | 30 |00:00:00.06 | 3967 | | | |
|* 3 | SORT ORDER BY STOPKEY| | 1 | 1562 | 42174 | 1079 (1)| 00:00:01 | 30 |00:00:00.06 | 3967 | 20480 | 20480 |18432 (0)|
|* 4 | FILTER | | 1 | | | | | 1219 |00:00:00.06 | 3967 | | | |
|* 5 | TABLE ACCESS FULL | TEMP_HSDJ | 1 | 1562 | 42174 | 1078 (1)| 00:00:01 | 1219 |00:00:00.06 | 3967 | | | |
----------------------------------------------------------------------------------------------------------------------------------------------------------
Query Block Name / Object Alias (identified by operation id):
-------------------------------------------------------------
1 - SEL$1
2 - SEL$2 / from$_subquery$_001@SEL$1
3 - SEL$2
5 - SEL$2 / T@SEL$2
Outline Data
-------------
/*+
BEGIN_OUTLINE_DATA
IGNORE_OPTIM_EMBEDDED_HINTS
OPTIMIZER_FEATURES_ENABLE('19.1.0')
DB_VERSION('19.1.0')
ALL_ROWS
OUTLINE_LEAF(@"SEL$2")
OUTLINE_LEAF(@"SEL$1")
NO_ACCESS(@"SEL$1" "from$_subquery$_001"@"SEL$1")
FULL(@"SEL$2" "T"@"SEL$2")
END_OUTLINE_DATA
*/
Peeked Binds (identified by position):
--------------------------------------
5 - (NUMBER): 30
Predicate Information (identified by operation id):
---------------------------------------------------
1 - filter(ROWNUM<=:SYS_B_4)
3 - filter(ROWNUM<=:SYS_B_4)
4 - filter(:SYS_B_2=:SYS_B_3)
5 - filter((TO_CHAR(INTERNAL_FUNCTION("T"."DJDATE"),:SYS_B_0)=:SYS_B_1 AND "T"."DJSTATUS" IS NULL))
--//我僅僅加了order by以及取前面幾行的語句，導致無法使用函式索引，到底是那裡導致該問題。
$ cat 8y1j8tf28h2w8.sql9_x
set termout off
alter session set current_schema=XXXXXX_YYY;
alter session set statistics_level=all;
alter session set cursor_sharing = force;
--select t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' ;
--select * from (select t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' order by djdate desc ) where 1=1 and rownum < = 30 ;
select t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' order by djdate desc ;
set termout on
@dpc '' outline ''
rollback;
alter session set current_schema=SYS ;
Plan hash value: 3530033302
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time | A-Rows | A-Time | Buffers | OMem | 1Mem | Used-Mem |
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | | 31 (100)| | 1219 |00:00:00.01 | 35 | | | |
| 1 | SORT ORDER BY | | 1 | 1084 | 41192 | 31 (4)| 00:00:01 | 1219 |00:00:00.01 | 35 | 106K| 106K|96256 (0)|
|* 2 | TABLE ACCESS BY INDEX ROWID BATCHED| TEMP_HSDJ | 1 | 1084 | 41192 | 30 (0)| 00:00:01 | 1219 |00:00:00.01 | 35 | | | |
|* 3 | INDEX RANGE SCAN | IF_TEMP_HSDJ_DJDATE | 1 | 1086 | | 2 (0)| 00:00:01 | 1221 |00:00:00.01 | 3 | | | |
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
--//排除了order by djdate desc 可能性。
$ cat 8y1j8tf28h2w8.sql9_x
set termout off
alter session set current_schema=XXXXXX_YYY;
alter session set statistics_level=all;
alter session set cursor_sharing = force;
--select t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' ;
--select * from (select t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' order by djdate desc ) where 1=1 and rownum < = 30 ;
--select t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' order by djdate desc ;
select * from (select t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' order by djdate ) where rownum < = 30 ;
set termout on
@dpc '' outline ''
rollback;
alter session set current_schema=SYS ;
Plan hash value: 4209826087
----------------------------------------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time | A-Rows | A-Time | Buffers | OMem | 1Mem | Used-Mem |
----------------------------------------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | | 1079 (100)| | 30 |00:00:00.06 | 3967 | | | |
|* 1 | COUNT STOPKEY | | 1 | | | | | 30 |00:00:00.06 | 3967 | | | |
| 2 | VIEW | | 1 | 1562 | 128K| 1079 (1)| 00:00:01 | 30 |00:00:00.06 | 3967 | | | |
|* 3 | SORT ORDER BY STOPKEY| | 1 | 1562 | 42174 | 1079 (1)| 00:00:01 | 30 |00:00:00.06 | 3967 | 4096 | 4096 | 4096 (0)|
|* 4 | TABLE ACCESS FULL | TEMP_HSDJ | 1 | 1562 | 42174 | 1078 (1)| 00:00:01 | 1219 |00:00:00.06 | 3967 | | | |
----------------------------------------------------------------------------------------------------------------------------------------------------------
--//可以發現只要在外面加入rownum < = 30 限制條件，oracle就不再使用函式索引。
$ cat 8y1j8tf28h2w8.sql9_x
set termout off
alter session set current_schema=XXXXXX_YYY;
alter session set statistics_level=all;
alter session set cursor_sharing = force;
--select t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' ;
--select * from (select t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' order by djdate desc ) where 1=1 and rownum < = 30 ;
--select t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' order by djdate desc ;
--select * from (select t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' order by djdate ) where rownum < = 30 ;
select * from (select /*+ MATERIALIZE index(t if_temp_hsdj_djdate) */ t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' order by djdate ) where rownum < = 30 ;
set termout on
@dpc '' outline ''
rollback;
alter session set current_schema=SYS ;
--//依舊不使用我建立的索引。修改約束限制DJDATE not null呢？
Plan hash value: 3895191266
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time | A-Rows | A-Time | Buffers | OMem | 1Mem | Used-Mem |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | | 4235 (100)| | 30 |00:00:00.10 | 4239 | | | |
|* 1 | COUNT STOPKEY | | 1 | | | | | 30 |00:00:00.10 | 4239 | | | |
| 2 | VIEW | | 1 | 1562 | 128K| 4235 (1)| 00:00:01 | 30 |00:00:00.10 | 4239 | | | |
|* 3 | SORT ORDER BY STOPKEY | | 1 | 1562 | 42174 | 4235 (1)| 00:00:01 | 30 |00:00:00.10 | 4239 | 4096 | 4096 | 4096 (0)|
|* 4 | TABLE ACCESS BY INDEX ROWID BATCHED| TEMP_HSDJ | 1 | 1562 | 42174 | 4234 (1)| 00:00:01 | 1219 |00:00:00.10 | 4239 | | | |
| 5 | INDEX FULL SCAN | IF_TEMP_HSDJ_DJDATE | 1 | 156K| | 243 (1)| 00:00:01 | 156K|00:00:00.02 | 243 | | | |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
--//可以使用，但是操作=INDEX FULL SCAN,執行效率低下。
--//如果我使用with改寫:
$ cat 8y1j8tf28h2w8.sql9_x
set termout off
alter session set current_schema=XXXXXX_YYY;
alter session set statistics_level=all;
alter session set cursor_sharing = force;
--select t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' ;
--select * from (select t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' order by djdate desc ) where 1=1 and rownum < = 30 ;
--select t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' order by djdate desc ;
--select * from (select t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' order by djdate ) where rownum < = 30 ;
--select * from (select /*+ MATERIALIZE INDEX_ASC(t if_temp_hsdj_djdate) */ t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' order by to_char(t.djdate,'yyyy-mm-dd') desc) where rownum < = 30 ;
with a as (select /*+ MATERIALIZE INDEX_ASC(t if_temp_hsdj_djdate) */ t.section ,t.brxm from temp_hsdj t where t.djstatus is null and to_char(t.djdate,'yyyy-mm-dd') = '2022-04-13' order by t.djdate desc)
select * from a where rownum < = 30 ;
set termout on
@dpc '' outline ''
rollback;
alter session set current_schema=SYS ;
Plan hash value: 138295244
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time | A-Rows | A-Time | Buffers | OMem | 1Mem | Used-Mem |
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | | 34 (100)| | 30 |00:00:00.01 | 37 | | | |
| 1 | TEMP TABLE TRANSFORMATION | | 1 | | | | | 30 |00:00:00.01 | 37 | | | |
| 2 | LOAD AS SELECT (CURSOR DURATION MEMORY)| SYS_TEMP_0FD9D8104_1930D14 | 1 | | | | | 0 |00:00:00.01 | 36 | 1024 | 1024 | |
| 3 | SORT ORDER BY | | 1 | 1084 | 41192 | 31 (4)| 00:00:01 | 1219 |00:00:00.01 | 35 | 106K| 106K|96256 (0)|
|* 4 | TABLE ACCESS BY INDEX ROWID BATCHED | TEMP_HSDJ | 1 | 1084 | 41192 | 30 (0)| 00:00:01 | 1219 |00:00:00.01 | 35 | | | |
|* 5 | INDEX RANGE SCAN | IF_TEMP_HSDJ_DJDATE | 1 | 1086 | | 2 (0)| 00:00:01 | 1221 |00:00:00.01 | 3 | | | |
|* 6 | COUNT STOPKEY | | 1 | | | | | 30 |00:00:00.01 | 0 | | | |
| 7 | VIEW | | 1 | 1084 | 91056 | 3 (0)| 00:00:01 | 30 |00:00:00.01 | 0 | | | |
| 8 | TABLE ACCESS FULL | SYS_TEMP_0FD9D8104_1930D14 | 1 | 1084 | 18428 | 3 (0)| 00:00:01 | 30 |00:00:00.01 | 0 | | | |
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
--//取消MATERIALIZE ，INDEX_ASC(t if_temp_hsdj_djdate)提示看到如下：
Plan hash value: 2137499364
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time | A-Rows | A-Time | Buffers | OMem | 1Mem | Used-Mem |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | | 31 (100)| | 30 |00:00:00.01 | 35 | | | |
|* 1 | COUNT STOPKEY | | 1 | | | | | 30 |00:00:00.01 | 35 | | | |
| 2 | VIEW | | 1 | 1084 | 91056 | 31 (4)| 00:00:01 | 30 |00:00:00.01 | 35 | | | |
|* 3 | SORT ORDER BY STOPKEY | | 1 | 1084 | 41192 | 31 (4)| 00:00:01 | 30 |00:00:00.01 | 35 | 20480 | 20480 |18432 (0)|
|* 4 | TABLE ACCESS BY INDEX ROWID BATCHED| TEMP_HSDJ | 1 | 1084 | 41192 | 30 (0)| 00:00:01 | 1219 |00:00:00.01 | 35 | | | |
|* 5 | INDEX RANGE SCAN | IF_TEMP_HSDJ_DJDATE | 1 | 1086 | | 2 (0)| 00:00:01 | 1221 |00:00:00.01 | 3 | | | |
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
--//最終我也不知道問題在那裡。實際上最佳的方式提示開發在where條件裡面使用to_char,trunc之類的函式儘可能避免，可以開發一直
--//沒長大，不斷反反覆覆範這類錯誤。
SELECT /*+ gather_plan_statistics */ *
FROM ( SELECT t.section, t.brxm
FROM temp_hsdj t
WHERE t.djstatus IS NULL
AND t.djdate BETWEEN TO_DATE ('2022-04-13', 'yyyy-mm-dd')
AND TO_DATE ('2022-04-13', 'yyyy-mm-dd')
+ 86359 / 86400
ORDER BY djdate DESC)
WHERE 1 = 1 AND ROWNUM <= 30;
-----------------------------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time | A-Rows | A-Time | Buffers |
-----------------------------------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | | | 3 (100)| | 30 |00:00:00.01 | 4 |
|* 1 | COUNT STOPKEY | | 1 | | | | | 30 |00:00:00.01 | 4 |
| 2 | VIEW | | 1 | 30 | 2520 | 3 (0)| 00:00:01 | 30 |00:00:00.01 | 4 |
|* 3 | TABLE ACCESS BY INDEX ROWID | TEMP_HSDJ | 1 | 1023 | 27621 | 3 (0)| 00:00:01 | 30 |00:00:00.01 | 4 |
|* 4 | INDEX RANGE SCAN DESCENDING| I_TEMP_HSDJ_DJDATE | 1 | 30 | | 2 (0)| 00:00:01 | 31 |00:00:00.01 | 2 |
-----------------------------------------------------------------------------------------------------------------------------------------------
--//你可以發現操作id=4 充分利用了 INDEX RANGE SCAN DESCENDING ,降序讀取的方式。前面的讀取IF_TEMP_HSDJ_DJDATE是3(注意我還建立的索引是壓縮的)
--//而前面I_TEMP_HSDJ_DJDATE的邏輯讀是2。最終的邏輯讀更小。
3.總結：
--//再次提醒開發在謂詞條件裡面在使用to_char,trunc,lower,upper之類的函式要小心，不要反反覆覆的範低階錯誤，看上去一輩子也長不大。
--//至少對於自己所從事的職業附上一點點責任，看上去更加專業一點。
來自 “ ITPUB部落格 ” ，連結：http://blog.itpub.net/267265/viewspace-2887038/，如需轉載，請註明出處，否則將追究法律責任。
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