本篇文章给大家谈谈(SqlServer)不公开存储过程sp_Msforeachtable与sp_Msforeachdb详解，同时本文还将给你拓展c#–如何使用foreach或foreach迭代IEnu

本篇文章给大家谈谈(SqlServer)不公开存储过程sp_Msforeachtable与sp_Msforeachdb详解，同时本文还将给你拓展c# – 如何使用for each或foreach迭代IEnumerable集合？、C＃在foreach中重用变量是否有原因？ - Is there a reason for C#''s reuse of the variable in a foreach?、foreach Transform 同时chils.setParent引起的bug、Increase memory usage for InnoDB MySQL database to improve p_MySQL等相关知识，希望对各位有所帮助，不要忘了收藏本站喔。

• (SqlServer)不公开存储过程sp_Msforeachtable与sp_Msforeachdb详解
• c# – 如何使用for each或foreach迭代IEnumerable集合？
• C＃在foreach中重用变量是否有原因？ - Is there a reason for C#''s reuse of the variable in a foreach?
• foreach Transform 同时chils.setParent引起的bug
• Increase memory usage for InnoDB MySQL database to improve p_MySQL

(SqlServer)不公开存储过程sp_Msforeachtable与sp_Msforeachdb详解

又如：

我想更新Table1/Table2/Table3中NOTE列为NULL的值

c# – 如何使用for each或foreach迭代IEnumerable集合？

IEnumerable<Customer> items = new Customer[] 
{ 
     new Customer { Name = "test1",Id = 111},new Customer { Name = "test2",Id = 222} 
};

public async void Set(IEnumerable collection)
{
   RedisDictionary<object,IEnumerable <T>> dictionary = new RedisDictionary>(Settings,typeof(T).Name);
// Add collection to dictionary;
   for (int i = 0; i < collection.Count(); i++)
   { 
     await dictionary.Set(new[] { new keyvaluePair<object,IEnumerable <T>  ( i,collection) });
   }
}

var dictionary = items.Zip(Enumerable.Range(1,int.MaxValue - 1),(o,i) => new { Index = i,Customer = (object)o });

C＃在foreach中重用变量是否有原因？ - Is there a reason for C#''s reuse of the variable in a foreach?

问题：

When using lambda expressions or anonymous methods in C#, we have to be wary of the access to modified closure pitfall. 在C＃中使用lambda表达式或匿名方法时，我们必须警惕对修改后的闭包陷阱的访问 。 For example: 例如：

foreach (var s in strings)
{
   query = query.Where(i => i.Prop == s); // access to modified closure
   ...
}

Due to the modified closure, the above code will cause all of the Where clauses on the query to be based on the final value of s . 由于修改了闭包，上面的代码将使查询上的所有Where子句都基于s的最终值。

As explained here , this happens because the s variable declared in foreach loop above is translated like this in the compiler: 正如解释在这里 ，这是因为在s中声明的变量foreach上面的循环被翻译这样的编译：

string s;
while (enumerator.MoveNext())
{
   s = enumerator.Current;
   ...
}

instead of like this: 而不是像这样：

while (enumerator.MoveNext())
{
   string s;
   s = enumerator.Current;
   ...
}

As pointed out here , there are no performance advantages to declaring a variable outside the loop, and under normal circumstances the only reason I can think of for doing this is if you plan to use the variable outside the scope of the loop: 如此处所指出的， 在循环外声明变量没有任何性能优势，在正常情况下，我可以想到的唯一原因是如果您打算在循环范围外使用变量：

string s;
while (enumerator.MoveNext())
{
   s = enumerator.Current;
   ...
}
var finalString = s;

However variables defined in a foreach loop cannot be used outside the loop: 但是，在foreach循环中定义的变量不能在循环外使用：

foreach(string s in strings)
{
}
var finalString = s; // won''t work: you''re outside the scope.

So the compiler declares the variable in a way that makes it highly prone to an error that is often difficult to find and debug, while producing no perceivable benefits. 因此，编译器以某种方式声明该变量，使其极易出现通常难以查找和调试的错误，同时不会产生明显的收益。

Is there something you can do with foreach loops this way that you couldn''t if they were compiled with an inner-scoped variable, or is this just an arbitrary choice that was made before anonymous methods and lambda expressions were available or common, and which hasn''t been revised since then? 是否可以使用foreach循环以这种方式进行处理，如果它们是使用内部作用域变量编译的，则无法做到，还是只是在匿名方法和lambda表达式可用或通用之前做出的任意选择，以及从那以后没有修改过？

解决方案：

foreach Transform 同时chils.setParent引起的bug

Transform继承自IEnumerable，可以对它进行迭代。但当你在迭代的同时，又对child进行setParent操作时，会出现意想不到的结果。

下面是我使用foreach和getchild得到的bug，及解决办法。

使用foreach

当在使用foreach获取所有的child，并且同时修改child的parent为其它，会出现只能修改部分，但不会报错。

foreach (var tran in rideEffect.InstanceAsset.transform)
{
    var child = tran as Transform;
    if (child == null)
    {
        continue;
    }
    KTool.SetChild(child,boneTrans.transform);
}

使用GetChild

使用getchild获取每一个child，同时设置child的parent为其它时，会报：Transform child out of bounds

解决办法

添加一个扩展方法获取所有的childs，存起来。

或者也可以不写扩展方法，直接使用List<Transform>存child。

调用方法，这样就可以修改完全部的child

Increase memory usage for InnoDB MySQL database to improve p_MySQL

if your mysql database tables still run on the myisam engine (formerly the default), you may want to consider switching to the innodb engine instead, for better reliability and scalability. to update a table from myisam to innodb you can run this sql:

ALTER TABLE table_name ENGINE = InnoDB;

Once you’ve switched all your tables to InnoDB, you can adjust some memory usage settings.

Update MySQL memory usage settings for InnoDB

Firstly, check the current settings for innerdb_buffer_pool_size . You can view these settings by running the following SQL (you can run this in phpMyAdmin):

SHOW VARIABLES;

Look for innerdb_buffer_pool_size . You’ll see it’s been assigned a particular number of bytes. This allocated cache stores table and index data, and keeps queries and query results in memory for faster lookup. So the more memory you can afford to dedicate to it the better – MySQL recommends to use 80% of the available memory. You can read about it here .

I had 2GB of server memory to play with, so I chose a moderate 1GB to allocate to the innerdb_buffer_pool_size . To add this setting, we’ll create and load our own custom MySQL cnf file, which will house some extra settings.

On Linux Ubuntu , add a new cnf file here:

sudo nano /etc/mysql/conf.d/innodb.cnf

The file name must end in .cnf , but call it whatever you like, so long as it’s not clashing with another file name.

Inside of this file, we add our new memory allocation:

[mysqld]innodb_buffer_pool_size = 1024Mkey_buffer_size = 8M

I’ve also added a new key_buffer_size value of 8MB. If you’ve deprecated your use of the MyISAM engine, it’s recommended to reduce this memory allocation. Previously I had 16M for key_buffer_size , so I decided to half it.

Finish off by restarting MySQL so that the changes can be applied:

sudo service mysql restart

If you check the MySQL variables once more:

SHOW VARIABLES;

You’ll hopefully now have some new and importantly increased memory values for innodb_buffer_pool_size and key_buffer_size

You’ve successfully optimised your MySQL database a bit more!

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