Need help th tuning query or re write the query--

Question

Hi,
Need help to tune the below query or rewrite th query for reducing the execution time Please find the query and explain plan.
QUERY
explain plan FOR SELECT consumer_key,product_key,days_in_product,20100201 period_key FROM
(SELECT consumer_key,
  product_key,
  days_in_product,
  row_number() over ( Partition BY consumer_key order by Days_in_product DESC) row_num
FROM
  (SELECT consumer_key,
    product_key,
    SUM(no_ofdays) days_in_product
  FROM
    (SELECT pcv.consumer_key,
      pcv.product_key,
      pcv.product_consumer_valid_from,
      pcv.product_consumer_valid_to,
      DECODE (SIGN(20100201000000-product_consumer_valid_from),1,20100201000000,product_consumer_valid_from) period_start,
      DECODE (SIGN(20100228235959-product_consumer_valid_to),1,product_consumer_valid_to,20100228235959) period_end,
      CASE
        WHEN to_number(TO_CHAR(cd.activation_date,'YYYYMMDDHH24MISS')) BETWEEN 20100201000000 AND 20100228235959
        AND activation_date > to_Date(product_consumer_valid_to,'YYYYMMDDHH24MISS')
        THEN 0
        WHEN to_number(TO_CHAR(cd.activation_date,'YYYYMMDDHH24MISS')) BETWEEN 20100201000000 AND 20100228235959
        AND activation_date BETWEEN to_Date(product_consumer_valid_from,'YYYYMMDDHH24MISS') AND to_Date(product_consumer_valid_to,'YYYYMMDDHH24MISS')
        THEN
          --to_char(activation_date,'MON-YYYY')='PERIOD_ACTIVE'  and activation_date >= to_Date(product_consumer_valid_from,'YYYYMMDDHH24MISS') then
          (to_date(DECODE (SIGN(20100228235959-product_consumer_valid_to),1,product_consumer_valid_to,20100228235959),'YYYYMMDDHH24MISS') - to_date(TO_CHAR(activation_date,'YYYYMMDDHH24MISS'),'YYYYMMDDHH24MISS') )
        WHEN to_number(TO_CHAR(cd.activation_date,'YYYYMMDDHH24MISS')) < 20100201000000
        THEN (to_date(DECODE (SIGN(20100228235959-product_consumer_valid_to),1,product_consumer_valid_to,20100228235959),'YYYYMMDDHH24MISS') - to_Date(DECODE (SIGN(20100201000000-product_consumer_valid_from),1,20100201000000,product_consumer_valid_from),'YYYYMMDDHH24MISS') )
        WHEN to_number(TO_CHAR(cd.activation_date,'YYYYMMDDHH24MISS')) > 20100228235959
        THEN 0
        ELSE
          --unusual situation
          (to_date(DECODE (SIGN(20100228235959-product_consumer_valid_to),1,product_consumer_valid_to,20100228235959),'YYYYMMDDHH24MISS') - to_Date(DECODE (SIGN(20100201000000-product_consumer_valid_from),1,20100201000000,product_consumer_valid_from),'YYYYMMDDHH24MISS') )
      END No_ofDays
    FROM cimtran.product_consumer_validity pcv,
      consumer_dimension cd
    WHERE pcv.consumer_key           =cd.consumer_key
    AND product_consumer_valid_to   >= 20100201000000
    AND product_consumer_valid_from <= 20100228235959
      --and product_consumer_valid_from > '20090801000000'
    ORDER BY consumer_key,
      product_key,
      product_consumer_valid_from
    ) a
  GROUP BY consumer_key,
    product_key
  ORDER BY consumer_key,
    product_key
) WHERE row_num=1 ;EXPLAIN PLAN
"PLAN_TABLE_OUTPUT"
"Plan hash value: 3823907703"
"| Id  | Operation                | Name                      | Rows  | Bytes |TempSpc| Cost (%CPU)| Time     |"
"|   0 | SELECT STATEMENT         |                           |  4665K|   231M|       |   133K  (1)| 00:31:08 |"
"|*  1 |  VIEW                    |                           |  4665K|   231M|       |   133K  (1)| 00:31:08 |"
"|*  2 |   WINDOW SORT PUSHED RANK|                           |  4665K|   173M|   232M|   133K  (1)| 00:31:08 |"
"|   3 |    VIEW                  |                           |  4665K|   173M|       |   104K  (1)| 00:24:18 |"
"|   4 |     SORT GROUP BY        |                           |  4665K|   182M|   729M|   104K  (1)| 00:24:18 |"
"|*  5 |      HASH JOIN           |                           |    13M|   533M|    65M| 44241   (1)| 00:10:20 |"
"|   6 |       TABLE ACCESS FULL  | CONSUMER_DIMENSION        |  2657K|    35M|       |  4337   (1)| 00:01:01 |"
"|*  7 |       TABLE ACCESS FULL  | PRODUCT_CONSUMER_VALIDITY |    13M|   351M|       | 15340   (2)| 00:03:35 |"
"Predicate Information (identified by operation id):"
"   1 - filter(""ROW_NUM""=1)"
"   2 - filter(ROW_NUMBER() OVER ( PARTITION BY ""CONSUMER_KEY"" ORDER BY "
"              INTERNAL_FUNCTION(""DAYS_IN_PRODUCT"") DESC )<=1)"
"   5 - access(""PCV"".""CONSUMER_KEY""=""CD"".""CONSUMER_KEY"")"
"   7 - filter(""PRODUCT_CONSUMER_VALID_FROM""<=20100228235959 AND "
"              ""PRODUCT_CONSUMER_VALID_TO"">=20100201000000)"

Answer 1

I doubt that this query can be tuned without using indexes. There is a lot of unnecessary work specified in your query, like unnecessary intermediate sorting and selecting unused columns. The cost based optimizer recognized it and skips some of that unnecessary work, it seems. For clarity's sake, I would rewrite your query like below. Note that the query is untested:
select consumer_key
     , max(product_key) keep (dense_rank last order by days_in_product) product_key
     , max(days_in_product) days_in_product
     , 20100201 period_key
  from ( select pcv.consumer_key
              , pcv.product_key
              , sum
                ( case
                  when to_number(to_char(cd.activation_date,'yyyymmddhh24miss')) between 20100201000000 and 20100228235959
                  then
                    case
                    when cd.activation_date > to_date(pcv.product_consumer_valid_to,'yyyymmddhh24miss')
                    then
                      0
                    when cd.activation_date between to_date(pcv.product_consumer_valid_from,'yyyymmddhh24miss') and to_date(product_consumer_valid_to,'yyyymmddhh24miss')
                    then
                      to_date(to_char(pcv.product_consumer_valid_to),'yyyymmddhh24miss'))
                      - to_date(to_char(activation_date,'yyyymmddhh24miss'),'yyyymmddhh24miss')
                    end
                  when to_number(to_char(cd.activation_date,'yyyymmddhh24miss')) < 20100201000000
                  then
                    to_date(to_char(pcv.product_consumer_valid_to),'yyyymmddhh24miss'))
                    - to_date(to_char(pcv.product_consumer_valid_from),'yyyymmddhh24miss'))
                  when to_number(to_char(cd.activation_date,'yyyymmddhh24miss')) > 20100228235959
                  then
                    0
                  end
                ) days_in_product
           from cimtran.product_consumer_validity pcv
              , consumer_dimension cd
          where pcv.consumer_key             = cd.consumer_key
            and product_consumer_valid_to   >= 20100201000000
            and product_consumer_valid_from <= 20100228235959
          group by consumer_key
              , product_key
group by consumer_keyRegards,
Rob.