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浅谈APM在电子交易系统中的应用 - 更多技术 - 清泛网 - 专注C/C++及内核技术
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慢的原因是因为执行了两条 Database dt_manager_log-select 语句。还有更详细的的，看看是怎么调用的
清晰的看到具体的语句，是怎么调用， 很明显这就是一个查询语句而查询的速度这么慢肯定是不正常的
接...
Design Patterns: Factory vs Factory method vs Abstract Factory
...vide hotels or / and provide tourist attraction packages. Now, when a user selects next, the website needs to decide what objects it needs to create. Should it only create the travel or hotel object too.
Now, if you envision adding another website to your portfolio, and you believe that the same co...
How To Create Table with Identity Column
...ues ('NULL','address2')
insert into teppp ( addresss) values ('address3')
select * from teppp
null string , address1
NULL,address2
NULL,address3
If you try inserting same values as below:
insert into teppp ( name,addresss) values ('','address4')
insert into teppp ( name,addresss) values ('NULL',...
How many bytes does one Unicode character take?
...fer UTF-16 over UTF-8, for instance. Developers of different software may select different encodings based upon which Unicode characters are more likely to be used. In China/Japan for instance, UTF-16 (2-bytes) makes more sense than UTF-8 for them, because the same characters often would need twice...
Performance differences between debug and release builds
...al in the x86 jitter because it has few registers to work with. Having it select the right ones is critical to perf.
These are very important optimizations that can make a great deal of difference when, for example, you profile the Debug build of your app and compare it to the Release build. Tha...
How does the Brainfuck Hello World actually work?
...e same way.
For the space and capital letters, different array cells are selected
and incremented or decremented as needed.
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Create Django model or update if exists
...large collection it won't scale well. update_or_create always first runs a SELECT and thereafter an UPDATE.
for the_bar in bars:
updated_rows = SomeModel.objects.filter(bar=the_bar).update(foo=100)
if not updated_rows:
# if not exists, create new
SomeModel.object...
iOS Tests/Specs TDD/BDD and Integration & Acceptance Testing
...discount code; it may differ if the specified item can't be shipped by the selected shipping method; etc. As these possible conditions intersect with one another you end up with a geometrically increasing number of possible contexts; in xUnit-style testing this often leads to a lot of methods with ...
Bootstrap full-width text-input within inline-form
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The bootstrap docs says about this:
Requires custom widths Inputs, selects, and textareas are 100% wide by
default in Bootstrap. To use the inline form, you'll have to set a
width on the form controls used within.
The default width of 100% as all form elements gets when they got the cl...
What is scope/named_scope in rails?
...Zombie.rotting.fresh.recent.limit(3)
It translates to the below in SQL,
select "zombies.*" from "zombies" where "zombies"."rotting" = 't' and (age<20) order by create_at desc limit 3
Example above is based on rails 4 syntax
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