[20190423]那个更快的疑问3.txt

--//前一阵子,做了11g在单表单条记录唯一索引扫描的测试,摘要如下:
--//参考链接:
http://blog.itpub.net/267265/viewspace-2636321/
http://blog.itpub.net/267265/viewspace-2636342/

--//在链接中我解析唯一索引查询的情况，为什么10g快于11g，链接：http://blog.itpub.net/267265/viewspace-2639920/
--//差异在于10g很少做times的系统调用上.10g下仅仅116次.而11g高达200179.(getrusage与times调用次数比大约是7:2)
--//我当时的感觉10g漏写times系统函数调用，导致这样的情况，11g把它补上了。
--//实际上有网友提出疑问.我的测试下的结论有问题.当时测试的情况如下:
--//11g的测试:
$ strace -f -c sqlplus -s -l scott/book @m1.txt 1e5 id=1_unique_index 0 >/dev/null
...
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 72.78    0.043919           0    700708           getrusage
 19.80    0.011947           0    200179           times
  6.67    0.004024         671         6         3 wait4
  0.24    0.000147          29         5           clone
  0.18    0.000106           0       375         2 read
  0.16    0.000096           0       264       106 open
...
------ ----------- ----------- --------- --------- ----------------
100.00    0.060341                902967       206 total

--//1e5次执行times调用消耗0.011947秒,放大10倍(我每个session执行次数是1e6)也就是0.119470秒,什么可能产生这么大的差异.
--//仔细查看,我觉得strace跟踪记录的syscallsyscall.linux标准C函数.看不出oracle内部函数调用次数.
--//我当时的解析是这增加的times调用一定是11g版本唯一索引扫描中增加几个oracle内部函数调用,导致11g的唯一索引
--//扫描更慢,如何验证我当时确实不知道? 最近shared latch测试,建立一些gdb脚本,有了这些脚本可以latch获得释放的情况.

1.环境:
SCOTT@book> @ ver1
PORT_STRING                    VERSION        BANNER
------------------------------ -------------- --------------------------------------------------------------------------------
x86_64/Linux 2.4.xx            11.2.0.4.0     Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

2.建立测试脚本:

create table t as select rownum id from dual ;
create unique index pk_t on t(id);
alter table t modify id  not null ;
create table job_times (sid number, time_ela number,method varchar2(20));
--//分析表略.

$ cat z1.txt
set verify off
host sleep $(echo &&3/50 | bc -l )
variable vmethod varchar2(20);
exec :vmethod := '&&2';
insert into job_times values ( sys_context ('userenv', 'sid') ,dbms_utility.get_time ,:vmethod) ;
commit ;
declare
v_id number;
v_d date;
begin
    for i in 1 .. &&1 loop
        select /*+  &&3 */ count (*) into v_id from t where id=1 ;
    end loop;
end ;
/
update job_times set time_ela = dbms_utility.get_time - time_ela where sid=sys_context ('userenv', 'sid') and method=:vmethod;
commit;
quit

3.分别测试:
$ sqlplus -s -l scott/book @z1.txt 1e6 id=unindex 0 >/dev/null

SCOTT@book> Select method,count(*),round(avg(TIME_ELA),0),sum(TIME_ELA) from job_times group by method order by 3 ;
METHOD                 COUNT(*) ROUND(AVG(TIME_ELA),0) SUM(TIME_ELA)
-------------------- ---------- ---------------------- -------------
id=unindex                    1                   2723          2723

--//在10g下重复测试:
SCOTT@test> @ &r/ver1
PORT_STRING                    VERSION        BANNER
------------------------------ -------------- ----------------------------------------------------------------
x86_64/Linux 2.4.xx            10.2.0.4.0     Oracle Database 10g Enterprise Edition Release 10.2.0.4.0 - 64bi

SCOTT@test> select method,count(*),round(avg(TIME_ELA),0),sum(TIME_ELA) from job_times group by method order by 3 ;
METHOD                 COUNT(*) ROUND(AVG(TIME_ELA),0) SUM(TIME_ELA)
-------------------- ---------- ---------------------- -------------
id=unindex                    1                   1591          1591
--//即使单用户执行10g下比11g快许多.

3.通过gdb脚本分析:
--//11g:
SCOTT@book> @ spid
       SID    SERIAL# PROCESS                  SERVER    SPID       PID  P_SERIAL# C50
---------- ---------- ------------------------ --------- ------ ------- ---------- --------------------------------------------------
        88         89 65066                    DEDICATED 65067       30         65 alter system kill session '88,89' immediate;

--//执行多次3次以上避免递归.
select count(*) from t where id=1;
--//打开window 2:
$ gdb -p 65067 -x latch11g.gdb
(gdb) c
Continuing.
ksl_get_shared_latch laddr:85f7fe28, willing:1, where:-2050764096, why:95, mode:8
ksl_get_shared_latch laddr:85f7fe28, willing:1, where:-2050764096, why:96, mode:16
ksl_get_shared_latch laddr:85f7fe28, willing:1, where:-2050764096, why:95, mode:8
kslgetl 844ed538, 0, 49, 2062
kslgetl 8353a258, 1, 16777771, 2053
ksl_get_shared_latch laddr:85f7fe28, willing:1, where:-2050764096, why:96, mode:16
ksl_get_shared_latch laddr:85f7fe28, willing:1, where:-2050764096, why:95, mode:8
ksl_get_shared_latch laddr:85f7fe28, willing:1, where:-2050764096, why:96, mode:16

--//看到ksl_get_shared_latch 6次,kslgetl 2次,看看是什么latch.
> select addr,name,level#,latch#,gets,misses,sleeps,immediate_gets,immediate_misses,waiters_woken,waits_holding_latch,spin_gets,wait_time from v$latch_children where addr=lpad(upper('85f7fe28'),'16','0')
ADDR             NAME             LEVEL#     LATCH#       GETS     MISSES     SLEEPS IMMEDIATE_GETS IMMEDIATE_MISSES WAITERS_WOKEN WAITS_HOLDING_LATCH  SPIN_GETS  WAIT_TIME
---------------- ---------------- ------ ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------
0000000085F7FE28 session idle bit      1         14       1095          0          0              0                0             0                   0          0          0

--//session idle bit 第一次看见,我看了我的测试机器,一共24次children latch.估计跟CPU数量有关.我在另外的会话重复测试
--//ksl_get_shared_latch的地址不一样,而kslgetl 也是2次都是一样.

> select addr,name,level#,latch#,gets,misses,sleeps,immediate_gets,immediate_misses,waiters_woken,waits_holding_latch,spin_gets,wait_time from v$latch_children where addr=lpad(upper('844ed538'),'16','0')
ADDR             NAME                LEVEL#     LATCH#       GETS     MISSES     SLEEPS IMMEDIATE_GETS IMMEDIATE_MISSES WAITERS_WOKEN WAITS_HOLDING_LATCH  SPIN_GETS  WAIT_TIME
---------------- ------------------- ------ ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------
00000000844ED538 simulator lru latch      6        185        560          1          0       72795239          3207148             0                   0          1          0

> select addr,name,level#,latch#,gets,misses,sleeps,immediate_gets,immediate_misses,waiters_woken,waits_holding_latch,spin_gets,wait_time from v$latch_children where addr=lpad(upper('8353a258'),'16','0')
ADDR             NAME                 LEVEL#     LATCH#       GETS     MISSES     SLEEPS IMMEDIATE_GETS IMMEDIATE_MISSES WAITERS_WOKEN WAITS_HOLDING_LATCH  SPIN_GETS  WAIT_TIME
---------------- -------------------- ------ ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------
000000008353A258 simulator hash latch      7        186   72792634          0          0              0                0             0                   0          0          0

--//奇怪这两个latch我从来没有过,而且奇怪的是根本看不到cbc latch.
--//在10g下重复测试看看(注10g shared latch 的函数是kslgetsl )

Breakpoint 1 at 0x7a0644
Breakpoint 2 at 0x7a0a44
Breakpoint 3 at 0x3bccd52
Breakpoint 4 at 0x3be9a04
Breakpoint 5 at 0x3181cd6400
Breakpoint 6 at 0x78ef44
Function "ksl_get_shared_latch" not defined.
Make breakpoint pending on future shared library load? (y or [n]) [answered N; input not from terminal]
Breakpoint 7 at 0x78f4bc
Breakpoint 8 at 0x79054c
--//奇怪10g没有ksl_get_shared_latchoracle内部函数.注解这部分内容.

(gdb) c
Continuing.
kslgetsl laddr:7cfb24f8, willing:1, where:2096584384, why:80, mode:8
kslgetsl laddr:7cfb24f8, willing:1, where:2096584384, why:81, mode:16
kslgetsl laddr:7cfb24f8, willing:1, where:2096584384, why:80, mode:8
kslgetl 7a10aaa0, 1, 0, 2741
kslgetsl laddr:7cfb24f8, willing:1, where:2096584384, why:81, mode:16
kslgetsl laddr:7cfb24f8, willing:1, where:2096584384, why:80, mode:8
kslgetsl laddr:7cfb24f8, willing:1, where:2096584384, why:81, mode:16
--//看到kslgetsl 6次,kslgetl 1次,看看是什么latch.
SYS@test> select addr,name,level#,latch#,gets,misses,sleeps,immediate_gets,immediate_misses,waiters_woken,waits_holding_latch,spin_gets,wait_time from v$latch_children where addr=lpad(upper('7cfb24f8'),'16','0');
ADDR             NAME                 LEVEL#     LATCH#       GETS     MISSES     SLEEPS IMMEDIATE_GETS IMMEDIATE_MISSES WAITERS_WOKEN WAITS_HOLDING_LATCH  SPIN_GETS  WAIT_TIME
---------------- -------------------- ------ ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------
000000007CFB24F8 session idle bit          1          7       7112          0          0              0                0             0                   0          0          0

SYS@test> select addr,name,level#,latch#,gets,misses,sleeps,immediate_gets,immediate_misses,waiters_woken,waits_holding_latch,spin_gets,wait_time from v$latch_children where addr=lpad(upper('7a10aaa0'),'16','0');
ADDR             NAME                   LEVEL#     LATCH#       GETS     MISSES     SLEEPS IMMEDIATE_GETS IMMEDIATE_MISSES WAITERS_WOKEN WAITS_HOLDING_LATCH  SPIN_GETS  WAIT_TIME
---------------- ---------------------- ------ ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------
000000007A10AAA0 shared pool simulator       8        241     146325          1          0              0                0             0                   0          1          0

--//你可以再次执行sql语句看看gets的变化:
SYS@test> select addr,name,level#,latch#,gets,misses,sleeps,immediate_gets,immediate_misses,waiters_woken,waits_holding_latch,spin_gets,wait_time from v$latch_children where addr=lpad(upper('7cfb24f8'),'16','0');
ADDR             NAME             LEVEL#     LATCH#       GETS     MISSES     SLEEPS IMMEDIATE_GETS IMMEDIATE_MISSES WAITERS_WOKEN WAITS_HOLDING_LATCH  SPIN_GETS  WAIT_TIME
---------------- ---------------- ------ ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------
000000007CFB24F8 session idle bit      1          7       7118          0          0              0                0             0                   0          0          0

SYS@test> select addr,name,level#,latch#,gets,misses,sleeps,immediate_gets,immediate_misses,waiters_woken,waits_holding_latch,spin_gets,wait_time from v$latch_children where addr=lpad(upper('7a10aaa0'),'16','0');
ADDR             NAME                  LEVEL#     LATCH#       GETS     MISSES     SLEEPS IMMEDIATE_GETS IMMEDIATE_MISSES WAITERS_WOKEN WAITS_HOLDING_LATCH  SPIN_GETS  WAIT_TIME
---------------- --------------------- ------ ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------
000000007A10AAA0 shared pool simulator      8        241     146326          1          0              0                0             0                   0          1          0

--//说明跟踪到的get变化没有问题.我在11g看了latch的变化,只不过simulator lru latch 变成了IMMEDIATE_GETS数量增加:
> select addr,name,level#,latch#,gets,misses,sleeps,immediate_gets,immediate_misses,waiters_woken,waits_holding_latch,spin_gets,wait_time from v$latch_children where addr=lpad(upper('8353a258'),'16','0')
ADDR             NAME                                         LEVEL#     LATCH#       GETS     MISSES     SLEEPS IMMEDIATE_GETS IMMEDIATE_MISSES WAITERS_WOKEN WAITS_HOLDING_LATCH  SPIN_GETS  WAIT_TIME
---------------- ---------------------------------------- ---------- ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------
000000008353A258 simulator hash latch                              7        186   72792639          0          0              0                0             0                   0          0          0

> select addr,name,level#,latch#,gets,misses,sleeps,immediate_gets,immediate_misses,waiters_woken,waits_holding_latch,spin_gets,wait_time from v$latch_children where addr=lpad(upper('844ed538'),'16','0')
ADDR             NAME                                         LEVEL#     LATCH#       GETS     MISSES     SLEEPS IMMEDIATE_GETS IMMEDIATE_MISSES WAITERS_WOKEN WAITS_HOLDING_LATCH  SPIN_GETS  WAIT_TIME
---------------- ---------------------------------------- ---------- ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------
00000000844ED538 simulator lru latch                               6        185        563          1          0       72795248          3207148             0                   0          1          0

--//执行sql语句再查看.
> select addr,name,level#,latch#,gets,misses,sleeps,immediate_gets,immediate_misses,waiters_woken,waits_holding_latch,spin_gets,wait_time from v$latch_children where addr=lpad(upper('8353a258'),'16','0')
ADDR             NAME                                         LEVEL#     LATCH#       GETS     MISSES     SLEEPS IMMEDIATE_GETS IMMEDIATE_MISSES WAITERS_WOKEN WAITS_HOLDING_LATCH  SPIN_GETS  WAIT_TIME
---------------- ---------------------------------------- ---------- ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------
000000008353A258 simulator hash latch                              7        186   72792640          0          0              0                0             0                   0          0          0

> select addr,name,level#,latch#,gets,misses,sleeps,immediate_gets,immediate_misses,waiters_woken,waits_holding_latch,spin_gets,wait_time from v$latch_children where addr=lpad(upper('844ed538'),'16','0')
ADDR             NAME                                         LEVEL#     LATCH#       GETS     MISSES     SLEEPS IMMEDIATE_GETS IMMEDIATE_MISSES WAITERS_WOKEN WAITS_HOLDING_LATCH  SPIN_GETS  WAIT_TIME
---------------- ---------------------------------------- ---------- ---------- ---------- ---------- ---------- -------------- ---------------- ------------- ------------------- ---------- ----------
00000000844ED538 simulator lru latch                               6        185        563          1          0       72795249          3207148             0                   0          1          0

--//我估计跟一些参数有关:
kslgetl 844ed538, 0, 49, 2062
kslgetl 8353a258, 1, 16777771, 2053
--//我猜测0表示no willing等待. 1表示willing等待.
--//我最后猜测也许正是11g下代码改动使用ksl_get_shared_latch,多了1次kslgetl调用,使用导致11g下每次执行多了2次times syscall,
--//可以讲11g下唯一索引扫描是一个退步.
--//至于为什么没有阻塞看不到cbc latch获取和释放,我给再探究看看...

4.我加入1个字段看看:
drop table t purge ;
create table t as select rownum id,'test' name  from dual ;
create unique index pk_t on t(id);
alter table t modify id  not null ;

$ cat z1.txt
set verify off
host sleep $(echo &&3/50 | bc -l )
variable vmethod varchar2(20);
exec :vmethod := '&&2';
insert into job_times values ( sys_context ('userenv', 'sid') ,dbms_utility.get_time ,:vmethod) ;
commit ;
declare
v_id number;
v_d date;
v_name varchar2(4) ;
begin
    for i in 1 .. &&1 loop
        select /*+  &&3 */ name  into v_name from t where id=1 ;
    end loop;
end ;
/
update job_times set time_ela = dbms_utility.get_time - time_ela where sid=sys_context ('userenv', 'sid') and method=:vmethod;
commit;
quit

--//重复测试:
--//11g:
SCOTT@book> Select method,count(*),round(avg(TIME_ELA),0),sum(TIME_ELA) from job_times group by method order by 3 ;
METHOD                 COUNT(*) ROUND(AVG(TIME_ELA),0) SUM(TIME_ELA)
-------------------- ---------- ---------------------- -------------
id=unindex_name               1                   2135          2135
id=unindex                    1                   2723          2723

--//10g:
SCOTT@test> select method,count(*),round(avg(TIME_ELA),0),sum(TIME_ELA) from job_times group by method order by 3 ;
METHOD                 COUNT(*) ROUND(AVG(TIME_ELA),0) SUM(TIME_ELA)
-------------------- ---------- ---------------------- -------------
id=unindex_name               1                   1359          1359
id=unindex                    1                   1591          1591

--//真心搞不懂,回表反而更快一些.oracle许多东西真心搞不懂....
--//感觉如果访问数据块缓存数据块,没有阻塞无需要获取cbc latch吗?

5.附上gdb脚本:
--//11g版本:
$ cat latch11g.gdb
break kslgetl
  commands
    silent
    printf "kslgetl %x, %d, %d, %d\n", $rdi, $rsi, $rdx, $rcx
    c
  end

break kslges
  commands
    silent
    printf "kslges %x, %d, %d, %d\n", $rdi, $rsi, $rdx, $rcx
    c
  end

break skgpwwait
  commands
    silent
    printf "skgpwwait %d, %d, %d, %d\n", $rdi, $rsi, $rdx, $rcx
    c
  end

break sskgpwwait
  commands
    silent
    printf "sskgpwwait %d, %d, %d, %d\n", $rdi, $rsi, $rdx, $rcx
    c
  end

break semop
  commands
    silent
    printf "semop %d, %d, %d, %d\n", $rdi, $rsi, $rdx, $rcx
    c
  end

#break *0x93f9ddc
#  commands
#    silent
#    printf " spin count loop: %d %d %x\n", $rax,$rcx,$rip
#    c
#  end

##
break kslgetsl_w
  commands
    silent
    printf "kslgetsl_w laddr:%x, willing:%d, where:%d, why:%d, mode:%d\n", $rdi, $rsi, $rdx, $rcx, $r8
    c
  end

break ksl_get_shared_latch
  commands
    silent
    printf "ksl_get_shared_latch laddr:%x, willing:%d, where:%d, why:%d, mode:%d\n", $rdi, $rsi, $rdx, $rcx, $r8
    c
  end

break kslgess
  commands
    silent
    printf "kslgess %x, %d, %d, %d\n", $rdi, $rsi, $rdx, $rcx
    c
  end

break kslskgs
  commands
    silent
    printf "kslskgs %x, %d, %d, %d\n", $rdi, $rsi, $rdx, $rcx
    c
  end

break kslfre
  commands
    silent
    printf "kslfre %x, %d, %d, %d\n", $rdi, $rsi, $rdx, $rcx
    c
  end

#break *0xa875be
#  commands
#    silent
#    printf " spin count loop: %d %x\n", $r13,$rip
#    c
#  end

--//10g版本:
$ cat latch10g.gdb
break kslgetl
  commands
    silent
    printf "kslgetl %x, %d, %d, %d\n", $rdi, $rsi, $rdx, $rcx
    c
  end

break kslges
  commands
    silent
    printf "kslges %x, %d, %d, %d\n", $rdi, $rsi, $rdx, $rcx
    c
  end

break skgpwwait
  commands
    silent
    printf "skgpwwait %d, %d, %d, %d\n", $rdi, $rsi, $rdx, $rcx
    c
  end

break sskgpwwait
  commands
    silent
    printf "sskgpwwait %d, %d, %d, %d\n", $rdi, $rsi, $rdx, $rcx
    c
  end

break semop
  commands
    silent
    printf "semop %d, %d, %d, %d\n", $rdi, $rsi, $rdx, $rcx
    c
  end

#break *0x93f9ddc
#  commands
#    silent
#    printf " spin count loop: %d %d %x\n", $rax,$rcx,$rip
#    c
#  end

##
break kslgetsl
  commands
    silent
    printf "kslgetsl laddr:%x, willing:%d, where:%d, why:%d, mode:%d\n", $rdi, $rsi, $rdx, $rcx, $r8
    c
  end

#break ksl_get_shared_latch
#  commands
#    silent
#    printf "ksl_get_shared_latch laddr:%x, willing:%d, where:%d, why:%d, mode:%d\n", $rdi, $rsi, $rdx, $rcx, $r8
#    c
#  end

break kslgess
  commands
    silent
    printf "kslgess %x, %d, %d, %d\n", $rdi, $rsi, $rdx, $rcx
    c
  end

break kslskgs
  commands
    silent
    printf "kslskgs %x, %d, %d, %d\n", $rdi, $rsi, $rdx, $rcx
    c
  end

#break *0xa875be
#  commands
#    silent
#    printf " spin count loop: %d %x\n", $r13,$rip
#    c
#  end

[20190423]那个更快的疑问3.txt的更多相关文章

  1. [20190401]那个更快的疑问.txt

    [20190401]那个更快的疑问.txt --//前一阵子,做了11g于10g下,单表单条记录唯一索引扫描的测试,摘要如下:--//参考链接:http://blog.itpub.net/267265 ...

  2. [20190219]那个更快(11g).txt

    [20190219]那个更快(11g).txt --//前几天测试11g Query Result Cache RC Latches时,链接http://blog.itpub.net/267265/v ...

  3. 让你的 Node.js 应用跑得更快的 10 个技巧(转)

    Node.js 受益于它的事件驱动和异步的特征,已经很快了.但是,在现代网络中只是快是不行的.如果你打算用 Node.js 开发你的下一个Web 应用的话,那么你就应该无所不用其极,让你的应用更快,异 ...

  4. 让你的 Node.js 应用跑得更快的 10 个技巧

    Node.js 受益于它的事件驱动和异步的特征,已经很快了.但是,在现代网络中只是快是不行的.如果你打算用 Node.js 开发你的下一个Web 应用的话,那么你就应该无所不用其极,让你的应用更快,异 ...

  5. [20190312]关于增量检查点的疑问(补充).txt

    [20190312]关于增量检查点的疑问(补充).txt --//有人问我以前写一个帖子的问题,关于增量检查点的问题,链接如下:http://blog.itpub.net/267265/viewspa ...

  6. Gradle更小、更快构建APP的奇淫技巧

    本文已获得原作者授权同意,翻译以及转载原文链接:Build your Android app Faster and Smaller than ever作者:Jirawatee译文链接:Gradle更小 ...

  7. linux 下程序员专用搜索源码用来替代grep的软件ack(后来发现一个更快的: ag)， 且有vim插件的

    发现一个比ack更快更好用的:  https://github.com/ggreer/the_silver_searcher   , 使用时命令为ag,它是基于ack的代码二次开发的,所有使用方法基本 ...

  8. freopen stdout 真的更快？

    freopen stdout 真的更快? 在一次数独作业中,我发现大部分同学提交的代码中都使用 freopen 来将 stdout 重新指向目标文件进行文件输出操作.我感到十分好奇,关于 freope ...

  9. 正则表达式匹配可以更快更简单 (but is slow in Java, Perl, PHP, Python, Ruby, ...)

    source: https://swtch.com/~rsc/regexp/regexp1.html translated by trav, travmymail@gmail.com 引言 下图是两种 ...

随机推荐

  1. Unity 捏脸整理及基于骨骼的捏脸功能实现

    目前实现捏脸功能的方式主要有两种.一个是Blendshape(融合变形),一个是基于骨骼驱动的方式,通过修改骨骼矩阵(bindpose)来影响SkinMesh.这两种方式的最终原理都是在shader ...

  2. 【4】Asp.Net Core2.2中间件多扩展对应应用

    [前言] 上一篇完成了Asp.Net Core 2.2全新的管道处理模型解析,“俄罗斯套娃”式的委托嵌套和传递,组建了扩展性无与伦比的管道模型!与此同时,委托嵌套过于复杂,使用起来并不友好,然后多种扩 ...

  3. IDEA编写css样式报错

    粗心大意!浪费了30分钟时间,必须记录一下! 报错图片 琢磨了半天,没想出是哪里错了,很无奈!!!!!!!!! 度娘:ctrl+shift+alt+H,设置成NONE就可以了 试了一下,果然好使,不再 ...

  4. Angular（03）-- lint风格规范和WebStorm小技巧

    在开始讲 Angular 各个核心知识点之前,想先来讲讲开发工具 WebStorm 的一些配置以及相应配置文件如 tslint.json 的配置. 因为我个人比较注重代码规范.代码风格,而对于这些规范 ...

  5. 安卓开发笔记（十二）：SQLite数据库储存（上）

    SQLite数据库存储(上) 创建数据库 Android专门提供了一个 SQLiteOpenHelper帮助类对数据库进行创建和升级 SQLiteOpenHelper需要创建一个自己的帮助类去继承它并 ...

  6. July 05th. 2018, Week 27th. Thursday

    Pleasure in the job puts perfection in the work. 乐于工作才能有完美表现. From Aristole. Do you want promotion? ...

  7. 关于bootstrap报错

    在使用bootstrap报错.报错的位置如下 if("undefined"==typeof jQuery)throw new Error("Bootstrap's Jav ...

  8. 实现iframe高度自适应

    iframe高度自适应使用场景是类似于微博,新闻等点击加载更多这种功能实现,要求iframe的高度能够跟随内容的变化而变化. 父html文件,也就是引用ifram的文件 src="blog/ ...

  9. IIS系统短文件名漏洞猜解过程

    今天看教程的时候,老师关于后台管理说到了短文件名漏洞,我就随便找了个网站猜解,可能是运气太好了,有了这次实践的过程,因为这个漏洞是13年的时候比较火,现在差不多都修复了,抓到一条漏网之鱼, 短文件名漏 ...

  10. 部署tomcat环境

    1.安装java jdk Java环境变量配置 2.下载64位tomcat https://tomcat.apache.org/download-70.cgi 3.配置service 打开cmd,执行 ...