[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))))

[20190524]使用use_concat or_expand提示优化.txt的更多相关文章

  1. [20181220]使用提示OR_EXPAND优化.txt

    [20181220]使用提示OR_EXPAND优化.txt --//链接http://www.itpub.net/thread-2107240-2-1.html,http://www.itpub.ne ...

  2. [20191213]toad 12下BIND_AWARE提示无效.txt

    [20191213]toad 12下BIND_AWARE提示无效.txt --//链接http://blog.itpub.net/267265/viewspace-2130781/的测试,发现当时测试 ...

  3. [20181116]18c DML 日志优化.txt

    [20181116]18c DML 日志优化.txt 1.环境:xxxxxxxx> select banner_full from v$version;BANNER_FULL---------- ...

  4. [20200223]关于latch and mutext的优化.txt

    [20200223]关于latch and mutext的优化.txt --//前一段时间一直在测试使用DBMS_SHARED_POOL.MARKHOT标识热对象以及sql语句的优化.--//有别人问 ...

  5. SQL Server 利用锁提示优化Row_number()-程序员需知

    网站中一些老页面仍采用Row_number类似的开窗函数进行分页处理,此时如果遭遇挖坟帖的情形可能就需要漫长的等待且消耗巨大.这里给大家介绍根据Row_number()特性采用特定锁Hint提升查询速 ...

  6. 利用查询提示优化SQL

    数据库环境:SQL SERVER 2005 我们来看一下SQL语句及对应的数据量 SELECT COUNT(*) FROM cinvout_02 a WHERE ( a.dept_id IN ( SE ...

  7. eclipse代码提示优化

    用Eclipse编写Android程序的代码提示功能主要是在java和xml文件中,有时候会失效,默认的提示功能有限. 1)java文件自动提示      Window->Preferences ...

  8. cognos report利用文本框提示优化日期维度

    为了尽量减少手工对日期维度的维护,在日期维度表中年份已经到了2099年,把年份作为下拉框或者月份作为下拉框的时候,选择起来颇为麻烦(当然也可以在此基础之上设置默认为当前月) 如图:提示页面以及html ...

  9. eclipse智能提示优化

    1.Windows→Preferences→Java→Editor→Content Assist 其中的AutoActivation Delay默认值为200(单位是毫秒)也就是说在打“.”之后停留2 ...

随机推荐

  1. .Net Core权限认证基于Cookie的认证&授权.Scheme、Policy扩展

    在身份认证中,如果某个Action需要权限才能访问,最开始的想法就是,哪个Action需要权限才能访问,我们写个特性标注到上面即可,[TypeFilter(typeof(CustomAuthorize ...

  2. Spring Boot + Redis实战-利用自定义注解+分布式锁实现接口幂等性

    场景 不管是传统行业还是互联网行业,我们都需要保证大部分操作是幂等性的,简单点说,就是无论用户点击多少次,操作多少遍,产生的结果都是一样的,是唯一的.而今次公司的项目里,又被我遇到了这么一个幂等性的问 ...

  3. iOS----------iPhone导出手机所有短信

    第一步:手机连接到itunes  选择本电脑备份   备份的时候不要加密  然后立即备份 第二步:前往文件夹,找到itunes的备份路径~/Library/Application Support/Mo ...

  4. HTML5应用 转 Android、Windows Phone 应用

    一.HTML5 转 Android 目标SDK:API 20 1.新建一个 Blank Activity 的应用 2.在 AndroidManifest.xml 文件中添加联网权限 <uses- ...

  5. Django celery 使用

    0.安装包 cachetools 3.1.1 celery 3.1.26.post2 celery-with-redis 3.0 certifi 2019.9.11 Django 2.2.6 djan ...

  6. 《专访 RocketMQ 联合创始人:项目思路、技术细节和未来规划》

    专访 RocketMQ 联合创始人:项目思路.技术细节和未来规划   木环 阅读数:138092017 年 2 月 20 日 18:00   编者按 这些年开源氛围越来越好,各大 IT 公司都纷纷将一 ...

  7. vue-cil3 运行报错 --- warnings potentially fixable with the `--fix` option

    warnings potentially fixable with the `--fix` option. 将一下部分:"lint": "vue-cli-service ...

  8. Win32 程序开发:窗口类结构体 WNDCLASS 和 WNDCLASSEX

    一.窗口类结构体简介 窗口类结构体包含了窗口的各种参数信息.比如:窗口的图标.菜单栏.背景颜色.窗口的消息处理等等. 窗口类结构体有两个:WNDCLASS(早期版本) 和 WNDCLASSEX(新版本 ...

  9. python 各层级目录下的import方法

    ---恢复内容开始--- 以前经常使用python2.现在很多东西都切换到了python3,发现很多东西还是存在一些差异化的.跨目录import是常用的一种方法,并且有不同的表现形式,新手很容易搞混. ...

  10. SQLServer某个库log日志过大,无法收缩日志文件 ,因为该文件结尾的逻辑日志文件正在使用

    问题描述: 今天看到user库日志备份方面很久,然后查看到user库这个log日志很大 图片是我已经解决了,然后现在可以收缩的大小 解决方法: 1.先备份user库日志,因为很大,所以要等很久,这个只 ...