oracle 收集直方图不走索引

1    Plan hash value: 1138811981
2     
3    ----------------------------------------------------------------------------------------------
4    | Id  | Operation          | Name            | Rows  | Bytes |TempSpc| Cost (%CPU)| Time     |
5    ----------------------------------------------------------------------------------------------
6    |   0 | SELECT STATEMENT   |                 |  1132K|   725M|       |   185K  (1)| 00:37:10 |
7    |   1 |  SORT ORDER BY     |                 |  1132K|   725M|  1608M|   185K  (1)| 00:37:10 |
8    |*  2 |   TABLE ACCESS FULL| MMS_SWFINFO0001 |  1132K|   725M|       | 24884   (1)| 00:04:59 |
9    ----------------------------------------------------------------------------------------------
10     
11    Predicate Information (identified by operation id):
12    ---------------------------------------------------
13     
14       2 - filter("TXTID"='TRAN,MMS_SWFINFO0001,MMS_SWFINFO,B4,SWFO201808090002')


       PLAN_TABLE_OUTPUT
1    Plan hash value: 1138811981
2     
3    ----------------------------------------------------------------------------------------------
4    | Id  | Operation          | Name            | Rows  | Bytes |TempSpc| Cost (%CPU)| Time     |
5    ----------------------------------------------------------------------------------------------
6    |   0 | SELECT STATEMENT   |                 |  1128K|   724M|       |   185K  (1)| 00:37:06 |
7    |   1 |  SORT ORDER BY     |                 |  1128K|   724M|  1602M|   185K  (1)| 00:37:06 |
8    |*  2 |   TABLE ACCESS FULL| MMS_SWFINFO0001 |  1128K|   724M|       | 24884   (1)| 00:04:59 |
9    ----------------------------------------------------------------------------------------------
10     
11    Predicate Information (identified by operation id):
12    ---------------------------------------------------
13     
14       2 - filter("TXTID"='TRAN,MMS_SWFINFO0001,MMS_SWFINFO,B4,SWFO201808090002')


select count(distinct(TXTID)) from MMS_SWFINFO0001

       COUNT(DISTINCT(TXTID))
1    1096192


select  count(*),count(distinct(TXTID)) ,count(*) /count(distinct(TXTID))  from MMS_SWFINFO0001

       COUNT(*)    COUNT(DISTINCT(TXTID))    COUNT(*)/COUNT(DISTINCT(TXTID)
1    1128455    1096192    1.02943188784447


       PLAN_TABLE_OUTPUT
1    Plan hash value: 22513045
2     
3    -------------------------------------------------------------------------------------------------
4    | Id  | Operation                   | Name              | Rows  | Bytes | Cost (%CPU)| Time     |
5    -------------------------------------------------------------------------------------------------
6    |   0 | SELECT STATEMENT            |                   |     1 |   673 |     5   (0)| 00:00:01 |
7    |   1 |  TABLE ACCESS BY INDEX ROWID| MMS_SWFINFO0001   |     1 |   673 |     5   (0)| 00:00:01 |
8    |*  2 |   INDEX RANGE SCAN          | P_SWFINFO0001_KEY |     1 |       |     4   (0)| 00:00:01 |
9    -------------------------------------------------------------------------------------------------
10     
11    Predicate Information (identified by operation id):
12    ---------------------------------------------------
13     
14       2 - access("TXTID"='aa')
15           filter("TXTID"='aa')


       PLAN_TABLE_OUTPUT
1    Plan hash value: 22513045
2     
3    -------------------------------------------------------------------------------------------------
4    | Id  | Operation                   | Name              | Rows  | Bytes | Cost (%CPU)| Time     |
5    -------------------------------------------------------------------------------------------------
6    |   0 | SELECT STATEMENT            |                   |  1128K|   724M|   493K  (1)| 01:38:44 |
7    |   1 |  TABLE ACCESS BY INDEX ROWID| MMS_SWFINFO0001   |  1128K|   724M|   493K  (1)| 01:38:44 |
8    |*  2 |   INDEX RANGE SCAN          | P_SWFINFO0001_KEY |  1128K|       | 26319   (1)| 00:05:16 |
9    -------------------------------------------------------------------------------------------------
10     
11    Predicate Information (identified by operation id):
12    ---------------------------------------------------
13     
14       2 - access("TXTID"='TRAN,MMS_SWFINFO0001,MMS_SWFINFO,B4,SWFO201808090002')
15           filter("TXTID"='TRAN,MMS_SWFINFO0001,MMS_SWFINFO,B4,SWFO201808090002')



 COLUMN_NAME    NUM_ROWS    CARDINALITY    SELECTIVITY    HISTOGRAM    NUM_BUCKETS
1    TXTID           1128461    4                   0          FREQUENCY    4
2    TXTNO    1128461    8    0    NONE    1
3    TABNAME    1128461    1    0    NONE    1
4    FLDNAME    1128461    2    0    NONE    1
5    KEYVALUE    1128461    608224    53.9    NONE    1
6    TXTDATA    1128461    634070    56.19    NONE    1
7    TRXKEY    1128461    608224    53.9    NONE    1
8    TRXREF    1128461    608224    53.9    NONE    1

BEGIN
  DBMS_STATS.GATHER_TABLE_STATS(ownname          => 'UTAN',
                                tabname          => 'MMS_SWFINFO0001',
                                estimate_percent => 100,
                                method_opt       => 'for columns TXTID size 1',
                                no_invalidate    => FALSE,
                                degree           => 8,
                                cascade          => TRUE);
END;


干掉直方图:
method_opt       => 'for columns TXTID size 1',
 

 COLUMN_NAME    NUM_ROWS    CARDINALITY    SELECTIVITY    HISTOGRAM    NUM_BUCKETS
1    TXTID            1128461      1096198           97.14    NONE          1
2    TXTNO    1128461    8    0    FREQUENCY    8
3    TABNAME    1128461    1    0    FREQUENCY    1
4    FLDNAME    1128461    2    0    FREQUENCY    2
5    KEYVALUE    1128461    608224    53.9    HEIGHT BALANCED    254
6    TXTDATA    1128461    576701    51.11    HEIGHT BALANCED    254
7    TRXKEY    1128461    608224    53.9    HEIGHT BALANCED    254
8    TRXREF    1128461    608224    53.9    HEIGHT BALANCED    254


explain plan for select  * from MMS_SWFINFO0001 a where TXTID  = 'TRAN,MMS' order by TXTNO ;

SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY());

1    Plan hash value: 22513045
2     
3    -------------------------------------------------------------------------------------------------
4    | Id  | Operation                   | Name              | Rows  | Bytes | Cost (%CPU)| Time     |
5    -------------------------------------------------------------------------------------------------
6    |   0 | SELECT STATEMENT            |                   |     1 |   673 |     5   (0)| 00:00:01 |
7    |   1 |  TABLE ACCESS BY INDEX ROWID| MMS_SWFINFO0001   |     1 |   673 |     5   (0)| 00:00:01 |
8    |*  2 |   INDEX RANGE SCAN          | P_SWFINFO0001_KEY |     1 |       |     4   (0)| 00:00:01 |
9    -------------------------------------------------------------------------------------------------
10     
11    Predicate Information (identified by operation id):
12    ---------------------------------------------------
13     
14       2 - access("TXTID"='TRAN,MMS')
15           filter("TXTID"='TRAN,MMS')

干掉直方图后走索引