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Need hint help in existing sql

Posted on 2014-03-25
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Last Modified: 2014-03-25
Hello Experts,

I have the below SQL :

EXPLAIN PLAN FOR 
SELECT  QST_RESPONSE ,
  QST_RESPONSE_ATTACHMENT ,
  QST_RESPONSE_DATE ,
  QST_ALL_AREAS ,
  QST_APPLE_DEDICATED_AREAS ,
  QST_NON_PRODUCTION_UTILITIES ,
  QST_PRODUCTION_AREAS_DEDICATED ,
  QST_COMMON_PRODUCTION_USED
FROM MS_SRA_VISIT_QUESTIONS
WHERE QUESTION_ID                          = :B2
AND REGEXP_SUBSTR(VISIT_ID ,'[^-]+' ,1 ,2) = :B1
AND QST_TYPE                              <> '1'
AND DD_CREATED_ON                          =
  (SELECT /*+ index_ss(QS MS_SRA_VISIT_QUESTIONS_PK) */ MAX(qs.DD_CREATED_ON)
  FROM MS_SRA_VISIT_QUESTIONS QS
  WHERE QS.QUESTION_ID                          = :B2
  AND REGEXP_SUBSTR(QS.VISIT_ID ,'[^-]+' ,1 ,2) = :B1
  AND qs.QST_TYPE                              <> '1'
  ) ;

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Plan hash value: 283024080
 
-----------------------------------------------------------------------------------------------------------
| Id  | Operation                     | Name                      | Rows  | Bytes | Cost (%CPU)| Time     |
-----------------------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT              |                           |     1 |  1290 |    80   (0)| 00:00:01 |
|*  1 |  TABLE ACCESS BY INDEX ROWID  | MS_SRA_VISIT_QUESTIONS    |     1 |  1290 |    40   (0)| 00:00:01 |
|*  2 |   INDEX SKIP SCAN             | MS_SRA_VISIT_QUESTIONS_PK |     1 |       |    40   (0)| 00:00:01 |
|   3 |   SORT AGGREGATE              |                           |     1 |    32 |            |          |
|*  4 |    TABLE ACCESS BY INDEX ROWID| MS_SRA_VISIT_QUESTIONS    |     1 |    32 |    40   (0)| 00:00:01 |
|*  5 |     INDEX SKIP SCAN           | MS_SRA_VISIT_QUESTIONS_PK |     1 |       |    40   (0)| 00:00:01 |
-----------------------------------------------------------------------------------------------------------
 
Outline Data
-------------
 
  /*+
      BEGIN_OUTLINE_DATA
      INDEX_SS(@"SEL$2" "QS"@"SEL$2" ("MS_SRA_VISIT_QUESTIONS"."VISIT_ID" 
              "MS_SRA_VISIT_QUESTIONS"."QUESTION_ID" "MS_SRA_VISIT_QUESTIONS"."QST_SOURCE_OBJECT_TYPE"))
      PUSH_SUBQ(@"SEL$2")
      INDEX_SS(@"SEL$1" "MS_SRA_VISIT_QUESTIONS"@"SEL$1" ("MS_SRA_VISIT_QUESTIONS"."VISIT_ID" 
              "MS_SRA_VISIT_QUESTIONS"."QUESTION_ID" "MS_SRA_VISIT_QUESTIONS"."QST_SOURCE_OBJECT_TYPE"))
      OUTLINE_LEAF(@"SEL$1")
      OUTLINE_LEAF(@"SEL$2")
      ALL_ROWS
      OPT_PARAM('optimizer_index_cost_adj' 40)
      OPT_PARAM('star_transformation_enabled' 'true')
      OPT_PARAM('_gby_hash_aggregation_enabled' 'false')
      OPT_PARAM('_optimizer_cost_based_transformation' 'off')
      OPT_PARAM('_optim_peek_user_binds' 'false')
      OPT_PARAM('_index_join_enabled' 'false')
      OPT_PARAM('query_rewrite_enabled' 'false')
      OPT_PARAM('_complex_view_merging' 'false')
      OPT_PARAM('_b_tree_bitmap_plans' 'false')
      DB_VERSION('11.2.0.3')
      OPTIMIZER_FEATURES_ENABLE('11.2.0.3')
      IGNORE_OPTIM_EMBEDDED_HINTS
      END_OUTLINE_DATA
  */
 
Predicate Information (identified by operation id):
---------------------------------------------------
 
   1 - filter("QST_TYPE"<>'1' AND "DD_CREATED_ON"= (SELECT /*+ INDEX_SS ("QS" 
              "MS_SRA_VISIT_QUESTIONS_PK") */ MAX("QS"."DD_CREATED_ON") FROM "MS_SRA_VISIT_QUESTIONS" "QS" WHERE 
              "QS"."QST_TYPE"<>'1' AND "QS"."QUESTION_ID"=TO_NUMBER(:B2) AND  REGEXP_SUBSTR 
              ("QS"."VISIT_ID",'[^-]+',1,2)=:B1))
   2 - access("QUESTION_ID"=TO_NUMBER(:B2))
       filter("QUESTION_ID"=TO_NUMBER(:B2) AND  REGEXP_SUBSTR ("VISIT_ID",'[^-]+',1,2)=:B1)
   4 - filter("QS"."QST_TYPE"<>'1')
   5 - access("QS"."QUESTION_ID"=TO_NUMBER(:B2))
       filter("QS"."QUESTION_ID"=TO_NUMBER(:B2) AND  REGEXP_SUBSTR 
              ("QS"."VISIT_ID",'[^-]+',1,2)=:B1)

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Want to change in such a way that the indexes should not be skiped and also the way IN condition are been used.
0
Comment
Question by:Swadhin Ray
3 Comments
 
LVL 34

Expert Comment

by:johnsone
ID: 39953067
The index is not being skipped.  The index is still being used.  The index being used is a composite index (it has more than one column).  The first column in the index (VISIT_ID) cannot be used because of the REGEXPR_SUBSTR call on it.  However, QUESTION_ID (the second column in the index) can be used.  Oracle is smart enough now to be able to used that index to search for QUESTION_ID.

If you want an index range scan instead of an index skip scan, then create an index on QUESTION_ID.  If you do that, I would probably add DD_CREATED_ON as a second column in that index.  You may already have that indexed, but with the hint you have, you are forcing an index to be used.

You may also consider a function based index on the REGEXP_SUBSTR.  Not sure if you would get good cardinality there or not.
0
 
LVL 73

Accepted Solution

by:
sdstuber earned 500 total points
ID: 39953230
rather than querying the table twice, have you considered using an analytic?


SELECT qst_response,
       qst_response_attachment,
       qst_response_date,
       qst_all_areas,
       qst_apple_dedicated_areas,
       qst_non_production_utilities,
       qst_production_areas_dedicated,
       qst_common_production_used
  FROM (SELECT qst_response,
               qst_response_attachment,
               qst_response_date,
               qst_all_areas,
               qst_apple_dedicated_areas,
               qst_non_production_utilities,
               qst_production_areas_dedicated,
               qst_common_production_used,
               RANK() OVER (ORDER BY dd_created_on DESC) r
          FROM ms_sra_visit_questions
         WHERE question_id = :b2
           AND REGEXP_SUBSTR(
                   visit_id,
                   '[^-]+',
                   1,
                   2
               ) = :b1
           AND qst_type <> '1')
 WHERE r = 1;


if the dd_created_on will be unique then you could use row_number() instead of rank()
0
 
LVL 16

Author Closing Comment

by:Swadhin Ray
ID: 39955098
thanks a lot
0

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