Reduce Logical IO [db block gets/consistent gets]

Question

Hi,
Still I'm unsure about the Logical IO (db block gets + consistent gets).
I want to reduce 'consistent gets' for this query
SQL> set autotrace traceonly
SQL> select * from cm_per_phone_vw;
905 rows selected.
Execution Plan
Plan hash value: 524433310
| Id  | Operation                    | Name         | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT             |              |   868 | 38192 |     8   (0)| 00:00:01 |
|   1 |  SORT GROUP BY NOSORT        |              |   868 | 38192 |     8   (0)| 00:00:01 |
|   2 |   TABLE ACCESS BY INDEX ROWID| CI_PER_PHONE |  1238 | 54472 |     8   (0)| 00:00:01 |
|   3 |    INDEX FULL SCAN           | CM172C0      |  1238 |       |     1   (0)| 00:00:01 |
Statistics
          8  recursive calls
          0  db block gets
        922  consistent gets
          4  physical reads
          0  redo size
      39151  bytes sent via SQL*Net to client
       1045  bytes received via SQL*Net from client
         62  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
        905  rows processedFollowing is the view it's accessing
CREATE OR REPLACE VIEW CM_PER_PHONE_VW
AS
SELECT
  per_id
  , MAX(DECODE(TRIM(phone_type_cd), 'MOB', phone)) AS MOB
  , MAX(DECODE(TRIM(phone_type_cd), 'HOME', phone)) AS HOME
  , MAX(DECODE(TRIM(phone_type_cd), 'BUSN', TRIM(phone) || ' ' || TRIM(extension))) AS BUSN
  , MAX(DECODE(TRIM(phone_type_cd), 'FAX', phone)) AS FAX
  , MAX(DECODE(TRIM(phone_type_cd), 'INT', phone)) AS INT
FROM
  ci_per_phone
GROUP BY
  per_idI have following indexes on table ci_per_phone
INDEX_NAME                     COLUMN_NAME                    COLUMN_POSITION
XM172P0                        PER_ID                                       1
XM172P0                        SEQ_NUM                                      2
XM172S1                        PHONE                                        1
CM172C0                        PER_ID                                       1I tried creating indexes on PER_ID and PHONE_TYPE_CD but the consistent gets reduces to 920 instead of 922.
Just for curiosity, how can I reduce this?
secondly, is there any explanation on 'OPERATION' break of the plan, e.g. TABLE ACCESS BY INDEX ROWID ?
Please advice.
Luckys.

Answer 1

Further I'm having problem with another query which is a view
CREATE OR REPLACE VIEW CM_PER_CHAR_VW
AS
SELECT
/*+ full (a) */
  a.acct_id
  , MAX(DECODE(a.char_type_cd, 'ACCTYPE', a.char_val)) acct_type
  , MAX(DECODE(a.char_type_cd, 'PRVBLCYC', a.adhoc_char_val)) prev_bill_cyc
FROM
  ci_acct_char a
WHERE
  a.effdt =
    (SELECT
      MAX(a1.effdt)
    FROM
      ci_acct_char a1
    WHERE a1.acct_id = a.acct_id
    AND a1.char_type_cd = a.char_type_cd)
GROUP BY
  a.acct_idI'm not able to reduce the consistent gets and even the filter appears.
I've analyzed the table as well as the index on the table.
cisadm@CCBDEV> select * from cm_acct_char_vw;
2649 rows selected.
Execution Plan
Plan hash value: 132362271
| Id  | Operation              | Name         | Rows  | Bytes | Cost (%CPU)| Time     |
|   0 | SELECT STATEMENT       |              |    27 |  4536 |    14   (8)| 00:00:01 |
|   1 |  HASH GROUP BY         |              |    27 |  4536 |    14   (8)| 00:00:01 |
|   2 |   VIEW                 |              |    27 |  4536 |    14   (8)| 00:00:01 |
|*  3 |    FILTER              |              |       |       |            |          |
|   4 |     HASH GROUP BY      |              |    27 |  2916 |    14   (8)| 00:00:01 |
|   5 |      NESTED LOOPS      |              |  2686 |   283K|    13   (0)| 00:00:01 |
|   6 |       TABLE ACCESS FULL| CI_ACCT_CHAR |  2686 |   157K|    12   (0)| 00:00:01 |
|*  7 |       INDEX RANGE SCAN | XM064P0      |     1 |    48 |     1   (0)| 00:00:01 |
Predicate Information (identified by operation id):
   3 - filter("A"."EFFDT"=MAX("A1"."EFFDT"))
   7 - access("A1"."ACCT_ID"="A"."ACCT_ID" AND
              "A1"."CHAR_TYPE_CD"="A"."CHAR_TYPE_CD")
Statistics
          0  recursive calls
          0  db block gets
       2754  consistent gets
          0  physical reads
          0  redo size
      76517  bytes sent via SQL*Net to client
       2321  bytes received via SQL*Net from client
        178  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
       2649  rows processedhere's the tkprof
select *
from
cm_acct_char_vw
call     count       cpu    elapsed       disk      query    current        rows
Parse        2      0.00       0.00          0          0          0           0
Execute      1      0.00       0.00          0          0          0           0
Fetch      178      0.07       0.05          0       2754          0        2649
total      181      0.07       0.05          0       2754          0        2649
Misses in library cache during parse: 1
Optimizer mode: CHOOSE
Parsing user id: 63  (CISADM)
Rows     Execution Plan
      0  SELECT STATEMENT   MODE: CHOOSE
      0   HASH (GROUP BY)
      0    VIEW
      0     FILTER
      0      HASH (GROUP BY)
      0       NESTED LOOPS
      0        TABLE ACCESS   MODE: ANALYZED (FULL) OF 'CI_ACCT_CHAR'
                   (TABLE)
      0        INDEX   MODE: ANALYZED (RANGE SCAN) OF 'XM064P0'
                   (INDEX (UNIQUE))
Elapsed times include waiting on following events:
  Event waited on                             Times   Max. Wait  Total Waited
  ----------------------------------------   Waited  ----------  ------------
  SQL*Net message to client                     179        0.00          0.00
  SQL*Net message from client                   179        0.00          0.08
********************************************************************************I've an similar query for another table, where there are 1110 rows, but in the explain, no filter appears in the predicate
Predicate Information (identified by operation id):
   2 - access("P"."EFFDT"="VW_COL_1" AND "PER_ID"="P"."PER_ID" AND
              "CHAR_TYPE_CD"="P"."CHAR_TYPE_CD")Both the queries have somewhat similar views.
I've got 2 questions,
Is there a way I can reduce the consistent gets( I've tried with/without HINTS),
secondly whats the predicate access shows as 'VW_COL_1'
please advice.