フィルタリングを実行し、ROWID で結合するこの非常に単純なクエリがあります。
SELECT *
FROM BOOKING.BOOKING_GRID BG,
BOOKING.BOOKING_STATES BS
WHERE BG.hotel=128
AND BS.ROWID =BG.BOOKINGSTATE;
計画を説明すると、次のようになります。
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 1597031677
--------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes |TempSpc| Cost (%CPU)| Time |
--------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 6137K| 1041M| | 1763K (1)| 05:48:27 |
|* 1 | HASH JOIN | | 6137K| 1041M| 538M| 1763K (1)| 05:48:27 |
|* 2 | INDEX UNIQUE SCAN| BOOKING_GRIDPK | 6137K| 468M| | 547K (1)| 01:48:05 |
|* 3 | INDEX RANGE SCAN| BOOKING_GRID_INDEX5 | 6137K| | | 90388 (1)| 00:17:52 |
| 4 | TABLE ACCESS FULL| BOOKING_STATES | 158M| 14G| | 365K (2)| 01:12:14 |
--------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
1 - access("BS".ROWID="BG"."BOOKINGSTATE")
2 - access("BG"."HOTEL"=128)
3 - access("BG"."HOTEL"=128)
BOOKING_GRID のインデックスは次のとおりです。
BOOKING BOOKING_GRIDPK UNIQUE VALID IOT - TOP N NO NO HOTEL, DAY, BOOKINGSTATE
BOOKING BOOKING_GRID_UNIQ UNIQUE VALID NORMAL N NO NO HOTEL, DAY, BOOKING, VALIDITYSTART
BOOKING BOOKING_GRID_INDEX5 NONUNIQUE VALID NORMAL N NO NO HOTEL, BOOKINGSTATUS, ISDAYUSE, DAY
BOOKING BOOKING_GRID_INDEX7 NONUNIQUE VALID NORMAL N NO NO HOTEL, BOOKING, VALIDITYSTART
BOOKING BOOKING_GRID_INDEX10 NONUNIQUE VALID NORMAL N NO NO HOTEL, ISDAYUSE, BOOKINGSTATUS, DAY
BOOKING_STATES のインデックスは次のとおりです。
BOOKING BOOKING_STATES_PK UNIQUE VALID NORMAL N NO NO HOTEL, BOOKING, VALIDITYSTART
BOOKING BOOKING_STATES_INDEX2 NONUNIQUE VALID NORMAL N NO NO HOTEL, YIELDROOMTYPE, BOOKEDROOMTYPE, ROOMTYPE
BOOKING BOOKING_STATES_BOOKING NONUNIQUE VALID NORMAL N NO NO HOTEL, BOOKING, BOOKINGSTATUS
BOOKING BOOKING_NOSEGMENT_INDEX NONUNIQUE VALID FUNCTION-BASED NORMAL N NO ENABLED NO SYS_NC00034$ TO_NUMBER(DECODE(TO_CHAR("MARKETSEGMENT"),NULL,DECODE("BOOK",0,NULL,TO_CHAR(DECODE("ISDAYUSE",'N',DECODE("ISSHARED",'N',DECODE("BOOKINGSTATUS",'B',"HOTEL"*10000+LEAST("DEPARTURE","VALIDITYEND"),'I',"HOTEL"*10000+LEAST("DEPARTURE","VALIDITYEND"),'W',"HOTEL"*10000+LEAST("DEPARTURE","VALIDITYEND"))))))))
BOOKING BOOKING_NORATE_CODE_INDEX NONUNIQUE VALID FUNCTION-BASED NORMAL N NO ENABLED NO SYS_NC00033$ TO_NUMBER(DECODE(TO_CHAR("RATECODE"),NULL,DECODE("BOOK",0,NULL,TO_CHAR(DECODE("ISDAYUSE",'N',DECODE("ISSHARED",'N',DECODE("BOOKINGSTATUS",'B',"HOTEL"*10000+LEAST("DEPARTURE","VALIDITYEND"),'I',"HOTEL"*10000+LEAST("DEPARTURE","VALIDITYEND"),'W',"HOTEL"*10000+LEAST("DEPARTURE","VALIDITYEND"))))))))
BOOKING BOOKING_NOBOOKINGTYPE_INDEX NONUNIQUE VALID FUNCTION-BASED NORMAL N NO ENABLED NO SYS_NC00032$ TO_NUMBER(DECODE(TO_CHAR("BOOKINGTYPE"),NULL,DECODE("BOOK",0,NULL,TO_CHAR(DECODE("ISDAYUSE",'N',DECODE("ISSHARED",'N',DECODE("BOOKINGSTATUS",'B',"HOTEL"*10000+LEAST("DEPARTURE","VALIDITYEND"))))))))
BOOKING BOOKING_STATES_BOOKING_TYPE NONUNIQUE VALID NORMAL N NO NO HOTEL, BOOKINGTYPE, ISDAYUSE, BOOKINGSTATUS
BOOKING BOOKING_STATES_CANCEL_INDEX NONUNIQUE VALID FUNCTION-BASED NORMAL N NO ENABLED NO SYS_NC00035$, SYS_NC00036$ DECODE("BOOKINGSTATUS",'c',"HOTEL",'C',"HOTEL")
BOOKING BOOKING_STATES_CANCEL_INDEX NONUNIQUE VALID FUNCTION-BASED NORMAL N NO ENABLED NO SYS_NC00035$, SYS_NC00036$ DECODE("BOOKINGSTATUS",'c',"CANCELREASON",'C',"CANCELREASON")
私は2つのことを理解していません:
- hotel=128でフィルタリングする前に、オラクルが参加する方が速いと判断するのはなぜですか?
- 「TABLE ACCESS BY USER ROWID」を使用できる場合にハッシュ結合を使用する理由
奇妙なことに、hotel=201 でまったく同じリクエストを実行すると、まったく問題ありません。
PLAN_TABLE_OUTPUT
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 4251203092
---------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
---------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 591K| 100M| 643K (1)| 02:07:12 |
| 1 | NESTED LOOPS | | 591K| 100M| 643K (1)| 02:07:12 |
|* 2 | INDEX UNIQUE SCAN | BOOKING_GRIDPK | 591K| 45M| 52686 (1)| 00:10:25 |
|* 3 | INDEX RANGE SCAN | BOOKING_GRID_INDEX5 | 591K| | 8707 (1)| 00:01:44 |
| 4 | TABLE ACCESS BY USER ROWID| BOOKING_STATES | 1 | 98 | 1 (0)| 00:00:01 |
---------------------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("BG"."HOTEL"=201)
3 - access("BG"."HOTEL"=201)
そこで何が起こっているかについて何か考えはありますか?
ありがとうございました、
ルノー