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  • [20190524]使用use_concat or_expand提示优化.txt

    [20190524]使用use_concat or_expand提示优化.txt

    --//上午看了链接https://connor-mcdonald.com/2019/05/22/being-generous-to-the-optimizer,突然想起我们生产系统类似语句。
    --//现在想想觉得开发的想象力太丰富,写这些语句是否考虑长期运行导致的结果。对方例子相对简单,我优化的例子简直就是变态。
    --//链接:[20150814]使用use_concat提示.txt => http://blog.itpub.net/267265/viewspace-1771727/
    --//实际上看了马上想到使用use_concat or_expand提示优化sql语句.同时看了链接
    --//https://jonathanlewis.wordpress.com/2019/05/22/danger-hints/,一起测试看看。

    1.环境:
    SCOTT@test01p> @ ver1
    PORT_STRING                    VERSION        BANNER                                                                               CON_ID
    ------------------------------ -------------- -------------------------------------------------------------------------------- ----------
    IBMPC/WIN_NT64-9.1.0           12.2.0.1.0     Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production              0

    create table address ( street int, suburb int, post_code int,  data char(100));
    insert into address select mod(rownum,1e4), mod(rownum,10), mod(rownum,1e2), rownum from dual connect by level  <= 1e5;
    commit;
     
    exec dbms_stats.gather_table_stats('','ADDRESS')

    create index i_address_stress on address ( street );
    create index i_address_suburb on address ( suburb );
    create index i_address_post_code on address ( post_code );

    2.测试:

    variable val number = 6
    variable choice number = 1
    alter session set statistics_level = all;

    SCOTT@test01p> select data from   address where ( :choice = 1 and street = :val ) or ( :choice = 2 and suburb = :val );
    DATA
    -----
    6
    10006
    20006
    30006
    40006
    50006
    60006
    70006
    80006
    90006
    10 rows selected.


    Plan hash value: 3645838471
    -----------------------------------------------------------------------------------------------------------------------
    | Id  | Operation         | Name    | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers |
    -----------------------------------------------------------------------------------------------------------------------
    |   0 | SELECT STATEMENT  |         |      1 |        |       |   445 (100)|          |     10 |00:00:00.02 |    1636 |
    |*  1 |  TABLE ACCESS FULL| ADDRESS |      1 |    100 | 10800 |   445   (1)| 00:00:01 |     10 |00:00:00.02 |    1636 |
    -----------------------------------------------------------------------------------------------------------------------
    Query Block Name / Object Alias (identified by operation id):
    -------------------------------------------------------------
       1 - SEL$1 / ADDRESS@SEL$1
    Peeked Binds (identified by position):
    --------------------------------------
       2 - :2 (NUMBER): 6
       4 - :2 (NUMBER, Primary=2)
    Predicate Information (identified by operation id):
    ---------------------------------------------------
       1 - filter(((:CHOICE=2 AND "SUBURB"=:VAL) OR ("STREET"=:VAL AND :CHOICE=1)))

    --//选择全表扫描.加入提示:/*+ or_expand(@sel$1) */

    select /*+ or_expand(@sel$1) */ data from   address where ( :choice = 1 and street = :val ) or ( :choice = 2 and suburb = :val );

    SCOTT@test01p> @ dpc '' outline
    Plan hash value: 1427591975
    --------------------------------------------------------------------------------------------------------------------------------------------------------------
    | Id  | Operation                              | Name             | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers | Reads  |
    --------------------------------------------------------------------------------------------------------------------------------------------------------------
    |   0 | SELECT STATEMENT                       |                  |      1 |        |       |   456 (100)|          |     10 |00:00:00.06 |      13 |      4 |
    |   1 |  VIEW                                  | VW_ORE_B7380F92  |      1 |  10010 |   997K|   456   (1)| 00:00:01 |     10 |00:00:00.06 |      13 |      4 |
    |   2 |   UNION-ALL                            |                  |      1 |        |       |            |          |     10 |00:00:00.06 |      13 |      4 |
    |*  3 |    FILTER                              |                  |      1 |        |       |            |          |     10 |00:00:00.06 |      13 |      4 |
    |   4 |     TABLE ACCESS BY INDEX ROWID BATCHED| ADDRESS          |      1 |     10 |  1050 |    11   (0)| 00:00:01 |     10 |00:00:00.06 |      13 |      4 |
    |*  5 |      INDEX RANGE SCAN                  | I_ADDRESS_STRESS |      1 |     10 |       |     1   (0)| 00:00:01 |     10 |00:00:00.06 |       3 |      4 |
    |*  6 |    FILTER                              |                  |      1 |        |       |            |          |      0 |00:00:00.01 |       0 |      0 |
    |*  7 |     TABLE ACCESS FULL                  | ADDRESS          |      0 |  10000 |  1054K|   445   (1)| 00:00:01 |      0 |00:00:00.01 |       0 |      0 |
    --------------------------------------------------------------------------------------------------------------------------------------------------------------
    Query Block Name / Object Alias (identified by operation id):
    -------------------------------------------------------------
       1 - SET$9162BF3C   / VW_ORE_B7380F92@SEL$B7380F92
       2 - SET$9162BF3C
       3 - SET$9162BF3C_1
       4 - SET$9162BF3C_1 / ADDRESS@SEL$1
       5 - SET$9162BF3C_1 / ADDRESS@SEL$1
       6 - SET$9162BF3C_2
       7 - SET$9162BF3C_2 / ADDRESS@SEL$1
    Outline Data
    -------------
      /*+
          BEGIN_OUTLINE_DATA
          IGNORE_OPTIM_EMBEDDED_HINTS
          OPTIMIZER_FEATURES_ENABLE('12.2.0.1')
          DB_VERSION('12.2.0.1')
          ALL_ROWS
          OUTLINE_LEAF(@"SET$9162BF3C_2")
          OUTLINE_LEAF(@"SET$9162BF3C_1")
          OUTLINE_LEAF(@"SET$9162BF3C")
          OR_EXPAND(@"SEL$1" (1) (2))
          OUTLINE_LEAF(@"SEL$B7380F92")
          OUTLINE(@"SET$9162BF3C")
          OR_EXPAND(@"SEL$1" (1) (2))
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~      
          OUTLINE(@"SEL$1")
          NO_ACCESS(@"SEL$B7380F92" "VW_ORE_B7380F92"@"SEL$B7380F92")
          INDEX_RS_ASC(@"SET$9162BF3C_1" "ADDRESS"@"SEL$1" ("ADDRESS"."STREET"))
          BATCH_TABLE_ACCESS_BY_ROWID(@"SET$9162BF3C_1" "ADDRESS"@"SEL$1")
          FULL(@"SET$9162BF3C_2" "ADDRESS"@"SEL$1")
          END_OUTLINE_DATA
      */
    Peeked Binds (identified by position):
    --------------------------------------
       2 - :2 (NUMBER): 6
       4 - :2 (NUMBER, Primary=2)
    Predicate Information (identified by operation id):
    ---------------------------------------------------
       3 - filter(:CHOICE=1)
       5 - access("STREET"=:VAL)
       6 - filter(:CHOICE=2)
       7 - filter(("SUBURB"=:VAL AND (LNNVL(:CHOICE=1) OR LNNVL("STREET"=:VAL))))
    --//注意看下划线.
    --//但是使用下划线提示,改动代码的情况下如何呢?

    SELECT /*+ or_expand(@sel$1 (1) (2) ) */ data
      FROM address
     WHERE ( :choice = 1 AND street = :val )
        OR ( :choice = 2 AND suburb = :val )
        OR ( :choice = 3 AND post_code = :val);

    SCOTT@test01p> @ dpc '' outline
    ...
    Plan hash value: 1427591975
    -----------------------------------------------------------------------------------------------------------------------------------------------------
    | Id  | Operation                              | Name             | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers |
    -----------------------------------------------------------------------------------------------------------------------------------------------------
    |   0 | SELECT STATEMENT                       |                  |      1 |        |       |   456 (100)|          |     10 |00:00:00.01 |      13 |
    |   1 |  VIEW                                  | VW_ORE_B7380F92  |      1 |  10010 |   997K|   456   (1)| 00:00:01 |     10 |00:00:00.01 |      13 |
    |   2 |   UNION-ALL                            |                  |      1 |        |       |            |          |     10 |00:00:00.01 |      13 |
    |*  3 |    FILTER                              |                  |      1 |        |       |            |          |     10 |00:00:00.01 |      13 |
    |   4 |     TABLE ACCESS BY INDEX ROWID BATCHED| ADDRESS          |      1 |     10 |  1050 |    11   (0)| 00:00:01 |     10 |00:00:00.01 |      13 |
    |*  5 |      INDEX RANGE SCAN                  | I_ADDRESS_STRESS |      1 |     10 |       |     1   (0)| 00:00:01 |     10 |00:00:00.01 |       3 |
    |*  6 |    FILTER                              |                  |      1 |        |       |            |          |      0 |00:00:00.01 |       0 |
    |*  7 |     TABLE ACCESS FULL                  | ADDRESS          |      0 |  10000 |  1054K|   445   (1)| 00:00:01 |      0 |00:00:00.01 |       0 |
    -----------------------------------------------------------------------------------------------------------------------------------------------------
    Query Block Name / Object Alias (identified by operation id):
    -------------------------------------------------------------

       1 - SET$9162BF3C   / VW_ORE_B7380F92@SEL$B7380F92
       2 - SET$9162BF3C
       3 - SET$9162BF3C_1
       4 - SET$9162BF3C_1 / ADDRESS@SEL$1
       5 - SET$9162BF3C_1 / ADDRESS@SEL$1
       6 - SET$9162BF3C_2
       7 - SET$9162BF3C_2 / ADDRESS@SEL$1

    Outline Data
    -------------

      /*+
          BEGIN_OUTLINE_DATA
          IGNORE_OPTIM_EMBEDDED_HINTS
          OPTIMIZER_FEATURES_ENABLE('12.2.0.1')
          DB_VERSION('12.2.0.1')
          ALL_ROWS
          OUTLINE_LEAF(@"SET$9162BF3C_2")
          OUTLINE_LEAF(@"SET$9162BF3C_1")
          OUTLINE_LEAF(@"SET$9162BF3C")
          OR_EXPAND(@"SEL$1" (1) (2))
          OUTLINE_LEAF(@"SEL$B7380F92")
          OUTLINE(@"SET$9162BF3C")
          OR_EXPAND(@"SEL$1" (1) (2))
          OUTLINE(@"SEL$1")
          NO_ACCESS(@"SEL$B7380F92" "VW_ORE_B7380F92"@"SEL$B7380F92")
          INDEX_RS_ASC(@"SET$9162BF3C_1" "ADDRESS"@"SEL$1" ("ADDRESS"."STREET"))
          BATCH_TABLE_ACCESS_BY_ROWID(@"SET$9162BF3C_1" "ADDRESS"@"SEL$1")
          FULL(@"SET$9162BF3C_2" "ADDRESS"@"SEL$1")
          END_OUTLINE_DATA
      */

    Peeked Binds (identified by position):
    --------------------------------------

       2 - :2 (NUMBER): 6
       4 - :2 (NUMBER, Primary=2)

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

       3 - filter(:CHOICE=1)
       5 - access("STREET"=:VAL)
       6 - filter(:CHOICE=2)
       7 - filter(("SUBURB"=:VAL AND (LNNVL(:CHOICE=1) OR LNNVL("STREET"=:VAL))))

    --//正像链接讲的那样如果增加1个或条件,导致执行计划变得不合理.实际上跟严重的是查询发生了错误.
    --//如果仔细看Predicate Information 就很容易发现没有:CHOICE=1的filter.如果查询:

    SCOTT@test01p> variable choice number = 3
    SELECT /*+ or_expand(@sel$1 (1) (2) ) */ data
      FROM address
     WHERE ( :choice = 1 AND street = :val )
        OR ( :choice = 2 AND suburb = :val )
        OR ( :choice = 3 AND post_code = :val);

    no rows selected.

    --//取消提示:
    SELECT data  FROM address WHERE ( :choice = 1 AND street = :val ) OR ( :choice = 2 AND suburb = :val ) OR ( :choice = 3 AND post_code = :val);
    ...
    1000 rows selected.

    --//两者的结果集不一样.明显这个是一个bug.

    修改如下:

    SELECT /*+ or_expand(@sel$1 (1) (2) (3) ) */ data
      FROM address
     WHERE ( :choice = 1 AND street = :val )
        OR ( :choice = 2 AND suburb = :val )
        OR ( :choice = 3 AND post_code = :val);
    ...

    --//注使用提示/*+ or_expand(@sel$1 ) */结果是正确的.

    SCOTT@test01p> @ dpc '' outline    
    Plan hash value: 3525475520
    -----------------------------------------------------------------------------------------------------------------------------------------------------
    | Id  | Operation                              | Name             | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers |
    -----------------------------------------------------------------------------------------------------------------------------------------------------
    |   0 | SELECT STATEMENT                       |                  |      1 |        |       |   900 (100)|          |   1000 |00:00:00.02 |    1640 |
    |   1 |  VIEW                                  | VW_ORE_B7380F92  |      1 |  11009 |  1096K|   900   (1)| 00:00:01 |   1000 |00:00:00.02 |    1640 |
    |   2 |   UNION-ALL                            |                  |      1 |        |       |            |          |   1000 |00:00:00.02 |    1640 |
    |*  3 |    FILTER                              |                  |      1 |        |       |            |          |      0 |00:00:00.01 |       0 |
    |   4 |     TABLE ACCESS BY INDEX ROWID BATCHED| ADDRESS          |      0 |     10 |  1050 |    11   (0)| 00:00:01 |      0 |00:00:00.01 |       0 |
    |*  5 |      INDEX RANGE SCAN                  | I_ADDRESS_STRESS |      0 |     10 |       |     1   (0)| 00:00:01 |      0 |00:00:00.01 |       0 |
    |*  6 |    FILTER                              |                  |      1 |        |       |            |          |      0 |00:00:00.01 |       0 |
    |*  7 |     TABLE ACCESS FULL                  | ADDRESS          |      0 |  10000 |  1054K|   445   (1)| 00:00:01 |      0 |00:00:00.01 |       0 |
    |*  8 |    FILTER                              |                  |      1 |        |       |            |          |   1000 |00:00:00.02 |    1640 |
    |*  9 |     TABLE ACCESS FULL                  | ADDRESS          |      1 |    999 |   108K|   445   (1)| 00:00:01 |   1000 |00:00:00.02 |    1640 |
    -----------------------------------------------------------------------------------------------------------------------------------------------------
    Query Block Name / Object Alias (identified by operation id):
    -------------------------------------------------------------
       1 - SET$49E1C21B   / VW_ORE_B7380F92@SEL$B7380F92
       2 - SET$49E1C21B
       3 - SET$49E1C21B_1
       4 - SET$49E1C21B_1 / ADDRESS@SEL$1
       5 - SET$49E1C21B_1 / ADDRESS@SEL$1
       6 - SET$49E1C21B_2
       7 - SET$49E1C21B_2 / ADDRESS@SEL$1
       8 - SET$49E1C21B_3
       9 - SET$49E1C21B_3 / ADDRESS@SEL$1
    Outline Data
    -------------
      /*+
          BEGIN_OUTLINE_DATA
          IGNORE_OPTIM_EMBEDDED_HINTS
          OPTIMIZER_FEATURES_ENABLE('12.2.0.1')
          DB_VERSION('12.2.0.1')
          ALL_ROWS
          OUTLINE_LEAF(@"SET$49E1C21B_3")
          OUTLINE_LEAF(@"SET$49E1C21B_2")
          OUTLINE_LEAF(@"SET$49E1C21B_1")
          OUTLINE_LEAF(@"SET$49E1C21B")
          OR_EXPAND(@"SEL$1" (1) (2) (3))
          OUTLINE_LEAF(@"SEL$B7380F92")
          OUTLINE(@"SET$49E1C21B")
          OR_EXPAND(@"SEL$1" (1) (2) (3))
          OUTLINE(@"SEL$1")
          NO_ACCESS(@"SEL$B7380F92" "VW_ORE_B7380F92"@"SEL$B7380F92")
          INDEX_RS_ASC(@"SET$49E1C21B_1" "ADDRESS"@"SEL$1" ("ADDRESS"."STREET"))
          BATCH_TABLE_ACCESS_BY_ROWID(@"SET$49E1C21B_1" "ADDRESS"@"SEL$1")
          FULL(@"SET$49E1C21B_2" "ADDRESS"@"SEL$1")
          FULL(@"SET$49E1C21B_3" "ADDRESS"@"SEL$1")
          END_OUTLINE_DATA
      */
    Peeked Binds (identified by position):
    --------------------------------------
       2 - :2 (NUMBER): 6
       4 - :2 (NUMBER, Primary=2)
       6 - :2 (NUMBER, Primary=2)
    Predicate Information (identified by operation id):
    ---------------------------------------------------
       3 - filter(:CHOICE=1)
       5 - access("STREET"=:VAL)
       6 - filter(:CHOICE=2)
       7 - filter(("SUBURB"=:VAL AND (LNNVL(:CHOICE=1) OR LNNVL("STREET"=:VAL))))
       8 - filter(:CHOICE=3)
       9 - filter(("POST_CODE"=:VAL AND (LNNVL(:CHOICE=1) OR LNNVL("STREET"=:VAL)) AND (LNNVL(:CHOICE=2) OR LNNVL("SUBURB"=:VAL))))

    3.测试使用use_concate看看:
    set linesize 100
    SELECT /*+ use_concat */ data
      FROM address
     WHERE ( :choice = 1 AND street = :val )
        OR ( :choice = 2 AND suburb = :val )
        OR ( :choice = 3 AND post_code = :val);

    SCOTT@test01p> @ dpc '' outline
    ...
    Plan hash value: 2048882018
    ----------------------------------------------------------------------------------------------------------------------------------------------------
    | Id  | Operation                             | Name             | Starts | E-Rows |E-Bytes| Cost (%CPU)| E-Time   | A-Rows |   A-Time   | Buffers |
    ----------------------------------------------------------------------------------------------------------------------------------------------------
    |   0 | SELECT STATEMENT                      |                  |      1 |        |       |   900 (100)|          |   1000 |00:00:00.01 |    1640 |
    |   1 |  CONCATENATION                        |                  |      1 |        |       |            |          |   1000 |00:00:00.01 |    1640 |
    |*  2 |   FILTER                              |                  |      1 |        |       |            |          |      0 |00:00:00.01 |       0 |
    |   3 |    TABLE ACCESS BY INDEX ROWID BATCHED| ADDRESS          |      0 |     10 |  1110 |    11   (0)| 00:00:01 |      0 |00:00:00.01 |       0 |
    |*  4 |     INDEX RANGE SCAN                  | I_ADDRESS_STRESS |      0 |     10 |       |     1   (0)| 00:00:01 |      0 |00:00:00.01 |       0 |
    |*  5 |   FILTER                              |                  |      1 |        |       |            |          |   1000 |00:00:00.01 |    1640 |
    |*  6 |    TABLE ACCESS FULL                  | ADDRESS          |      1 |   1000 |   108K|   445   (1)| 00:00:01 |   1000 |00:00:00.01 |    1640 |
    |*  7 |   FILTER                              |                  |      1 |        |       |            |          |      0 |00:00:00.01 |       0 |
    |*  8 |    TABLE ACCESS FULL                  | ADDRESS          |      0 |   9999 |  1083K|   445   (1)| 00:00:01 |      0 |00:00:00.01 |       0 |
    ----------------------------------------------------------------------------------------------------------------------------------------------------

    Query Block Name / Object Alias (identified by operation id):
    -------------------------------------------------------------

       1 - SEL$1
       3 - SEL$1_1 / ADDRESS@SEL$1
       4 - SEL$1_1 / ADDRESS@SEL$1
       6 - SEL$1_2 / ADDRESS@SEL$1_2
       8 - SEL$1_3 / ADDRESS@SEL$1_3

    Outline Data
    -------------

      /*+
          BEGIN_OUTLINE_DATA
          IGNORE_OPTIM_EMBEDDED_HINTS
          OPTIMIZER_FEATURES_ENABLE('12.2.0.1')
          DB_VERSION('12.2.0.1')
          ALL_ROWS
          OUTLINE_LEAF(@"SEL$1")
          OUTLINE_LEAF(@"SEL$1_1")
          USE_CONCAT(@"SEL$1" 8 OR_PREDICATES(1) PREDICATE_REORDERS((5 2) (6 3) (7 4) (8 5) (9 6) (10 7) (2 8) (4 9) (3 10)))
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~      
    --//始终不明白里面那一串表示什么?

          OUTLINE_LEAF(@"SEL$1_2")
          OUTLINE_LEAF(@"SEL$1_3")
          OUTLINE(@"SEL$1")
          INDEX_RS_ASC(@"SEL$1_1" "ADDRESS"@"SEL$1" ("ADDRESS"."STREET"))
          BATCH_TABLE_ACCESS_BY_ROWID(@"SEL$1_1" "ADDRESS"@"SEL$1")
          FULL(@"SEL$1_2" "ADDRESS"@"SEL$1_2")
          FULL(@"SEL$1_3" "ADDRESS"@"SEL$1_3")
          END_OUTLINE_DATA
      */

    Peeked Binds (identified by position):
    --------------------------------------

       2 - :2 (NUMBER): 6
       4 - :2 (NUMBER, Primary=2)
       6 - :2 (NUMBER, Primary=2)

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

       2 - filter(:CHOICE=1)
       4 - access("STREET"=:VAL)
       5 - filter(:CHOICE=3)
       6 - filter(("POST_CODE"=:VAL AND (LNNVL("STREET"=:VAL) OR LNNVL(:CHOICE=1))))
       7 - filter(:CHOICE=2)
       8 - filter(("SUBURB"=:VAL AND (LNNVL(:CHOICE=3) OR LNNVL("POST_CODE"=:VAL)) AND (LNNVL("STREET"=:VAL) OR LNNVL(:CHOICE=1))))

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  • 原文地址:https://www.cnblogs.com/lfree/p/10920426.html
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