c++ difference from java
1. take charge of object management , negotiate ownershiop ,use scoped_ptr,
   not to transfer other's ownership
2. use c++ template to express seperation corncern ,such as (static)polymorphy and policy
3. disable copy constructor and assign operator by yourself
4. polymorphy by pointer
5. 使用 template ,macro 取得類似動態語言的能力
6. 偏好無狀態的 函數

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Myisam is preferred without transaction and little update(delete)

Big than 4G datafile can user Myisam merge table.

InnoDB with auto_increment primary key is preferred.

Few storage process

Guess: 20m records max per table , 500G data max per tablespace , 256 tables per database (may problem)

Use prepared statement and  batch

Optimize Your Queries For the Query Cache

// query cache does NOT work

$r = mysql_query("SELECT username FROM user WHERE signup_date >= CURDATE()");

// query cache works!

$today = date("Y-m-d");

$r = mysql_query("SELECT username FROM user WHERE signup_date >= '$today'");

EXPLAIN Your SELECT Queries

LIMIT 1 When Getting a Unique Row

Index and Use Same Column Types for Joins

Do Not ORDER BY RAND()

Avoid SELECT *

t is a good habit to always specify which columns you need when you are doing your SELECT’s.

Use ENUM over VARCHAR

Use NOT NULL If You Can

Store IP Addresses as UNSIGNED INT (?)

Fixed-length (Static) Tables are Faster

Vertical Partitioning

Vertical Partitioning is the act of splitting your table structure in a vertical manner for optimization reasons.

Example 1: You might have a users table that contains home addresses, that do not get read often. You can choose to split your table and store the address info on a separate table. This way your main users table will shrink in size. As you know, smaller tables perform faster.

Example 2: You have a “last_login” field in your table. It updates every time a user logs in to the website. But every update on a table causes the query cache for that table to be flushed. You can put that field into another table to keep updates to your users table to a minimum.

But you also need to make sure you don’t constantly need to join these 2 tables after the partitioning or you might actually suffer performance decline.

Split the Big DELETE or INSERT Queries

If you have some kind of maintenance script that needs to delete large numbers of rows, just use the LIMIT clause to do it in smaller batches to avoid this congestion.

Smaller Columns Are Faster

Use an Object Relational Mapper

f you do not need the time component, use DATE instead of DATETIME.

Consider horizontally spitting many-columned tables if they contain a lot of NULLs or rarely used columns.

Be an SQL programmer who thinks in sets, not procedural programming paradigms

InnoDB can’t optimize SELECT COUNT(*) queries. Use counter tables! That’s how to scale InnoDB.

Prefer MM with hive

refer :

http://blog.tuvinh.com/top-20-mysql-best-practices/

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從時序圖中可以看到，createNewIO()就是新建了一個com.mysql.jdbc.MysqlIO，利用 com.mysql.jdbc.StandardSocketFactory來創建一個socket。然后就由這個mySqlIO來與MySql服務器進行握手(doHandshake())，這個doHandshake主要用來初始化與Mysql server的連接，負責登陸服務器和處理連接錯誤。在其中會分析所連接的mysql server的版本，根據不同的版本以及是否使用SSL加密數據都有不同的處理方式，并把要傳輸給數據庫server的數據都放在一個叫做packet的 buffer中，調用send()方法往outputStream中寫入要發送的數據。


useServerPreparedStmts置為true的話，mysql驅動可以通過PreparedStatement的子類ServerPreparedStatement來實現真正的PreparedStatement的功能




第一位表示數據包的開始位置，就是數據存放的起始位置，一般都設置為0，就是從第一個位置開始。第二和第三個字節標識了這個數據包的大小，注意的是，這個大小是出去標識的4個字節的大小，對于非最后一個數據包來說，這個大小都是一樣的，就是splitSize，也就是maxThreeBytes，它的值是 255 * 255 * 255。
最后一個字節中存放的就是數據包的編號了，從0開始遞增。
在標識位設置完畢之后，就可以把255 * 255 * 255大小的數據從我們準備好的待發送數據包中copy出來了，注意，前4位已經是標識位了，所以應該從第五個位置開始copy數據

 # packetToSend = compressPacket(headerPacket, HEADER_LENGTH,    
#                 splitSize, HEADER_LENGTH); 

LoadBalancingConnectionProxy
package java.lang.reflect 。 proxy .


http://developer.51cto.com/art/200907/137823.htm

http://dev.mysql.com/doc/refman/5.1/en/connector-j-reference-implementation-notes.html

PreparedStatements are implemented by the driver, as MySQL does not have a prepared statement feature. Because of this, the driver does not implement getParameterMetaData() or getMetaData() as it would require the driver to have a complete SQL parser in the client.

Starting with version 3.1.0 MySQL Connector/J, server-side prepared statements and binary-encoded result sets are used when the server supports them.

但這是不是說PreparedStatement沒用呢？不是的，PreparedStatement有其他的好處：
1.代碼的可讀性和可維護性
2.最重要的一點是極大地提高了安全性，可以防止SQL注入

然后我又看了一些網上其他人的經驗，基本和我的判斷一致，有兩點要特別提請大家注意：

1.并不是說PreparedStatement在所有的DB上都不會提高效率，PreparedStatement需要服務器端的支持，比如在 Oracle上就會有顯著效果。上面說的測試都是在MySQL上測試的，我找到了一個MySQL架構師的帖子，比較明確地說明了MySQL不支持 PreparedStatement。

2.即便PreparedStatement不能提高性能，在少數使用時甚至會降低效率，但仍然應該使用PreparedStatement！因為其他好 處實在是太大了！當然，當SQL查詢比較復雜時，可能PreparedStatement好處會更大，只是我沒有測試，不敢肯定。

3.既然PreparedStatement不能提高效率，那PreparedStatement Pool也就沒有必要了。但可以看到每次新建Connection的開銷實在很大，因此Connection Pool絕對必要。