SORT (UNIQUE STOPKEY)/ SORT GROUP BY STOPKEY

最新推荐文章于 2022-11-21 14:45:44 发布
转载 最新推荐文章于 2022-11-21 14:45:44 发布 · 197 阅读 · 0

本文通过具体实例详细解析了SQL执行计划，包括不同操作符的作用、过滤条件的应用以及统计信息的解读，有助于理解数据库如何高效执行查询。
Description

Removes duplicates from sorted list of rows. Number of rows returned is restricted using the ROWNUM pseudo-column

SQL>   CREATE TABLE t1 (c1 NUMBER);

Table created.

SQL> set autot traceonly
SQL>  SELECT * FROM
  2      (
  3        SELECT DISTINCT c1 FROM t1
  4      )
  5      WHERE ROWNUM < 10;

no rows selected


Execution Plan
----------------------------------------------------------
Plan hash value: 2221909342

--------------------------------------------------------------------------------
| Id  | Operation               | Name | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------
|   0 | SELECT STATEMENT        |      |     1 |    13 |     3  (34)| 00:00:01 |
|*  1 |  COUNT STOPKEY          |      |       |       |            |          |
|   2 |   VIEW                  |      |     1 |    13 |     3  (34)| 00:00:01 |
|*  3 |    SORT GROUP BY STOPKEY|      |     1 |    13 |     3  (34)| 00:00:01 |
|   4 |     TABLE ACCESS FULL   | T1   |     1 |    13 |     2   (0)| 00:00:01 |
--------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter(ROWNUM<10)
   3 - filter(ROWNUM<10)

Note
-----
   - dynamic sampling used for this statement


Statistics
----------------------------------------------------------
          0  recursive calls
          0  db block gets
          3  consistent gets
          0  physical reads
          0  redo size
        319  bytes sent via SQL*Net to client
        481  bytes received via SQL*Net from client
          1  SQL*Net roundtrips to/from client
          1  sorts (memory)
          0  sorts (disk)
          0  rows processed

SQL>  ALTER SESSION SET "_gby_hash_aggregation_enabled" = FALSE;

Session altered.

SQL>  SELECT * FROM
  2      (
  3        SELECT DISTINCT c1 FROM t1
  4      )
  5      WHERE ROWNUM < 10;

no rows selected


Execution Plan
----------------------------------------------------------
Plan hash value: 3413338077

------------------------------------------------------------------------------
| Id  | Operation             | Name | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------
|   0 | SELECT STATEMENT      |      |     1 |    13 |     3  (34)| 00:00:01 |
|*  1 |  COUNT STOPKEY        |      |       |       |            |          |
|   2 |   VIEW                |      |     1 |    13 |     3  (34)| 00:00:01 |
|*  3 |    SORT UNIQUE STOPKEY|      |     1 |    13 |     3  (34)| 00:00:01 |
|   4 |     TABLE ACCESS FULL | T1   |     1 |    13 |     2   (0)| 00:00:01 |
------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter(ROWNUM<10)
   3 - filter(ROWNUM<10)

Note
-----
   - dynamic sampling used for this statement


Statistics
----------------------------------------------------------
          1  recursive calls
          0  db block gets
          5  consistent gets
          0  physical reads
          0  redo size
        319  bytes sent via SQL*Net to client
        481  bytes received via SQL*Net from client
          1  SQL*Net roundtrips to/from client
          1  sorts (memory)
          0  sorts (disk)
          0  rows processed

SQL> ALTER SESSION SET "_gby_hash_aggregation_enabled" = true;

Session altered.

SQL>  SELECT * FROM
  2      (
  3        SELECT DISTINCT c1 FROM t1
  4      )
  5      WHERE ROWNUM < 10;

no rows selected


Execution Plan
----------------------------------------------------------
Plan hash value: 2221909342

--------------------------------------------------------------------------------
| Id  | Operation               | Name | Rows  | Bytes | Cost (%CPU)| Time     |
--------------------------------------------------------------------------------
|   0 | SELECT STATEMENT        |      |     1 |    13 |     3  (34)| 00:00:01 |
|*  1 |  COUNT STOPKEY          |      |       |       |            |          |
|   2 |   VIEW                  |      |     1 |    13 |     3  (34)| 00:00:01 |
|*  3 |    SORT GROUP BY STOPKEY|      |     1 |    13 |     3  (34)| 00:00:01 |
|   4 |     TABLE ACCESS FULL   | T1   |     1 |    13 |     2   (0)| 00:00:01 |
--------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter(ROWNUM<10)
   3 - filter(ROWNUM<10)

Note
-----
   - dynamic sampling used for this statement


Statistics
----------------------------------------------------------
          0  recursive calls
          0  db block gets
          3  consistent gets
          0  physical reads
          0  redo size
        319  bytes sent via SQL*Net to client
        481  bytes received via SQL*Net from client
          1  SQL*Net roundtrips to/from client
          1  sorts (memory)
          0  sorts (disk)
          0  rows processed

 

 

SQL> create table test_stopkey as

SQL> select * from dba_objects;

54828 rows selected.


Execution Plan
----------------------------------------------------------
Plan hash value: 2960989055

----------------------------------------------------------------------------------------------
| Id  | Operation                      | Name        | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT               |             | 52295 |  9039K|   160   (5)| 00:00:02 |
|   1 |  VIEW                          | DBA_OBJECTS | 52295 |  9039K|   160   (5)| 00:00:02 |
|   2 |   UNION-ALL                    |             |       |       |            |          |
|*  3 |    FILTER                      |             |       |       |            |          |
|*  4 |     HASH JOIN                  |             | 55438 |  5089K|   157   (6)| 00:00:02 |
|   5 |      TABLE ACCESS FULL         | USER$       |    66 |   990 |     3   (0)| 00:00:01 |
|*  6 |      TABLE ACCESS FULL         | OBJ$        | 55438 |  4276K|   152   (4)| 00:00:02 |
|*  7 |     TABLE ACCESS BY INDEX ROWID| IND$        |     1 |     8 |     1   (0)| 00:00:01 |
|*  8 |      INDEX UNIQUE SCAN         | I_IND1      |     1 |       |     1   (0)| 00:00:01 |
|   9 |    NESTED LOOPS                |             |     2 |    76 |     3   (0)| 00:00:01 |
|  10 |     TABLE ACCESS FULL          | LINK$       |     2 |    46 |     2   (0)| 00:00:01 |
|  11 |     TABLE ACCESS CLUSTER       | USER$       |     1 |    15 |     1   (0)| 00:00:01 |
|* 12 |      INDEX UNIQUE SCAN         | I_USER#     |     1 |       |     1   (0)| 00:00:01 |
----------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   3 - filter("O"."TYPE#"<>1 AND "O"."TYPE#"<>10 OR "O"."TYPE#"=1 AND  (SELECT 1 FROM
              "SYS"."IND$" "I" WHERE "I"."OBJ#"=:B1 AND ("I"."TYPE#"=1 OR "I"."TYPE#"=2 OR
              "I"."TYPE#"=3 OR "I"."TYPE#"=4 OR "I"."TYPE#"=6 OR "I"."TYPE#"=7 OR "I"."TYPE#"=9))=1)
   4 - access("O"."OWNER#"="U"."USER#")
   6 - filter("O"."NAME"<>'_NEXT_OBJECT' AND "O"."NAME"<>'_default_auditing_options_'
              AND "O"."LINKNAME" IS NULL AND BITAND("O"."FLAGS",128)=0)
   7 - filter("I"."TYPE#"=1 OR "I"."TYPE#"=2 OR "I"."TYPE#"=3 OR "I"."TYPE#"=4 OR
              "I"."TYPE#"=6 OR "I"."TYPE#"=7 OR "I"."TYPE#"=9)
   8 - access("I"."OBJ#"=:B1)
  12 - access("L"."OWNER#"="U"."USER#")


Statistics
----------------------------------------------------------
          8  recursive calls
          0  db block gets
      10516  consistent gets
          0  physical reads
          0  redo size
    2777255  bytes sent via SQL*Net to client
      40697  bytes received via SQL*Net from client
       3657  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
      54828  rows processed

SQL> create table test_stopkey as select * from dba_objects;

Table created.

SQL> insert into test_stopkey select * from dba_objects;

commit

54829 rows created.


Execution Plan
----------------------------------------------------------
Plan hash value: 2960989055

----------------------------------------------------------------------------------------------
| Id  | Operation                      | Name        | Rows  | Bytes | Cost (%CPU)| Time     |
----------------------------------------------------------------------------------------------
|   0 | INSERT STATEMENT               |             | 52295 |  9039K|   160   (5)| 00:00:02 |
|   1 |  VIEW                          | DBA_OBJECTS | 52295 |  9039K|   160   (5)| 00:00:02 |
|   2 |   UNION-ALL                    |             |       |       |            |          |
|*  3 |    FILTER                      |             |       |       |            |          |
|*  4 |     HASH JOIN                  |             | 55438 |  5089K|   157   (6)| 00:00:02 |
|   5 |      TABLE ACCESS FULL         | USER$       |    66 |   990 |     3   (0)| 00:00:01 |
|*  6 |      TABLE ACCESS FULL         | OBJ$        | 55438 |  4276K|   152   (4)| 00:00:02 |
|*  7 |     TABLE ACCESS BY INDEX ROWID| IND$        |     1 |     8 |     1   (0)| 00:00:01 |
|*  8 |      INDEX UNIQUE SCAN         | I_IND1      |     1 |       |     1   (0)| 00:00:01 |
|   9 |    NESTED LOOPS                |             |     2 |    76 |     3   (0)| 00:00:01 |
|  10 |     TABLE ACCESS FULL          | LINK$       |     2 |    46 |     2   (0)| 00:00:01 |
|  11 |     TABLE ACCESS CLUSTER       | USER$       |     1 |    15 |     1   (0)| 00:00:01 |
|* 12 |      INDEX UNIQUE SCAN         | I_USER#     |     1 |       |     1   (0)| 00:00:01 |
----------------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   3 - filter("O"."TYPE#"<>1 AND "O"."TYPE#"<>10 OR "O"."TYPE#"=1 AND  (SELECT 1 FROM
              "SYS"."IND$" "I" WHERE "I"."OBJ#"=:B1 AND ("I"."TYPE#"=1 OR "I"."TYPE#"=2 OR
              "I"."TYPE#"=3 OR "I"."TYPE#"=4 OR "I"."TYPE#"=6 OR "I"."TYPE#"=7 OR "I"."TYPE#"=9))=1)
   4 - access("O"."OWNER#"="U"."USER#")
   6 - filter("O"."NAME"<>'_NEXT_OBJECT' AND "O"."NAME"<>'_default_auditing_options_'
              AND "O"."LINKNAME" IS NULL AND BITAND("O"."FLAGS",128)=0)
   7 - filter("I"."TYPE#"=1 OR "I"."TYPE#"=2 OR "I"."TYPE#"=3 OR "I"."TYPE#"=4 OR
              "I"."TYPE#"=6 OR "I"."TYPE#"=7 OR "I"."TYPE#"=9)
   8 - access("I"."OBJ#"=:B1)
  12 - access("L"."OWNER#"="U"."USER#")


Statistics
----------------------------------------------------------
        681  recursive calls
       4308  db block gets
       8215  consistent gets
          0  physical reads
    6205852  redo size
        828  bytes sent via SQL*Net to client
        743  bytes received via SQL*Net from client
          3  SQL*Net roundtrips to/from client
          1  sorts (memory)
          0  sorts (disk)
      54829  rows processed

SQL> SQL>   2 
SQL>
SQL>
SQL> select count(*) from test_stopkey;


Execution Plan
----------------------------------------------------------
Plan hash value: 184875565

---------------------------------------------------------------------------
| Id  | Operation          | Name         | Rows  | Cost (%CPU)| Time     |
---------------------------------------------------------------------------
|   0 | SELECT STATEMENT   |              |     1 |   337   (1)| 00:00:05 |
|   1 |  SORT AGGREGATE    |              |     1 |            |          |
|   2 |   TABLE ACCESS FULL| TEST_STOPKEY |   108K|   337   (1)| 00:00:05 |
---------------------------------------------------------------------------

Note
-----
   - dynamic sampling used for this statement


Statistics
----------------------------------------------------------
         28  recursive calls
          0  db block gets
       1592  consistent gets
        759  physical reads
          0  redo size
        517  bytes sent via SQL*Net to client
        492  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          1  rows processed

SQL> select * from (select rownum rn,t.* from test_stopkey t) where rn > 1000 and rn <= 2000;

1000 rows selected.


Execution Plan
----------------------------------------------------------
Plan hash value: 594950436

------------------------------------------------------------------------------------
| Id  | Operation           | Name         | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT    |              |   108K|    19M|   340   (2)| 00:00:05 |
|*  1 |  VIEW               |              |   108K|    19M|   340   (2)| 00:00:05 |
|   2 |   COUNT             |              |       |       |            |          |
|   3 |    TABLE ACCESS FULL| TEST_STOPKEY |   108K|    18M|   340   (2)| 00:00:05 |
------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter("RN"<=2000 AND "RN">1000)

Note
-----
   - dynamic sampling used for this statement


Statistics
----------------------------------------------------------
          8  recursive calls
          0  db block gets
       1725  consistent gets
          0  physical reads
          0  redo size
      57379  bytes sent via SQL*Net to client
       1218  bytes received via SQL*Net from client
         68  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
       1000  rows processed

SQL> select * from
  2  (select rownum rn,t.* from test_stopkey t
  3  where rownum <= 2000)
  4  where rn > 1000;

1000 rows selected.


Execution Plan
----------------------------------------------------------
Plan hash value: 3382644055

------------------------------------------------------------------------------------
| Id  | Operation           | Name         | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT    |              |  2000 |   371K|    11  (28)| 00:00:01 |
|*  1 |  VIEW               |              |  2000 |   371K|    11  (28)| 00:00:01 |
|*  2 |   COUNT STOPKEY     |              |       |       |            |          |
|   3 |    TABLE ACCESS FULL| TEST_STOPKEY |   108K|    18M|    11  (28)| 00:00:01 |
------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter("RN">1000)
   2 - filter(ROWNUM<=2000)

Note
-----
   - dynamic sampling used for this statement


Statistics
----------------------------------------------------------
          7  recursive calls
          0  db block gets
        231  consistent gets
          0  physical reads
          0  redo size
      57379  bytes sent via SQL*Net to client
       1218  bytes received via SQL*Net from client
         68  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
       1000  rows processed

SQL> select * from test_stopkey t where rownum < 5;


Execution Plan
----------------------------------------------------------
Plan hash value: 4076471010

-----------------------------------------------------------------------------------
| Id  | Operation          | Name         | Rows  | Bytes | Cost (%CPU)| Time     |
-----------------------------------------------------------------------------------
|   0 | SELECT STATEMENT   |              |     4 |   708 |     5  (60)| 00:00:01 |
|*  1 |  COUNT STOPKEY     |              |       |       |            |          |
|   2 |   TABLE ACCESS FULL| TEST_STOPKEY |   108K|    18M|     5  (60)| 00:00:01 |
-----------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter(ROWNUM<5)

Note
-----
   - dynamic sampling used for this statement


Statistics
----------------------------------------------------------
          7  recursive calls
          0  db block gets
        141  consistent gets
          0  physical reads
          0  redo size
       1578  bytes sent via SQL*Net to client
        492  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          4  rows processed

SQL> select * from
  2  (select rownum rn,t.* from test_stopkey t
  3  where rownum <= 150000)
  4  where rn > 149000;

no rows selected


Execution Plan
----------------------------------------------------------
Plan hash value: 3382644055

------------------------------------------------------------------------------------
| Id  | Operation           | Name         | Rows  | Bytes | Cost (%CPU)| Time     |
------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT    |              |   108K|    19M|   340   (2)| 00:00:05 |
|*  1 |  VIEW               |              |   108K|    19M|   340   (2)| 00:00:05 |
|*  2 |   COUNT STOPKEY     |              |       |       |            |          |
|   3 |    TABLE ACCESS FULL| TEST_STOPKEY |   108K|    18M|   340   (2)| 00:00:05 |
------------------------------------------------------------------------------------

Predicate Information (identified by operation id):
---------------------------------------------------

   1 - filter("RN">149000)
   2 - filter(ROWNUM<=150000)

Note
-----
   - dynamic sampling used for this statement


Statistics
----------------------------------------------------------
          7  recursive calls
          0  db block gets
       1658  consistent gets
          0  physical reads
          0  redo size
       1199  bytes sent via SQL*Net to client
        481  bytes received via SQL*Net from client
          1  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          0  rows processed

 

----end----

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转载于:http://blog.itpub.net/13750068/viewspace-734522/

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