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    2010年2月3日

    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(dòng)態(tài)語言的能力
    6. 偏好無狀態(tài)的 函數(shù)
    posted @ 2010-02-03 11:43 西津渡 閱讀(263) | 評(píng)論 (0)編輯 收藏

    2010年1月15日

        只有注冊(cè)用戶登錄后才能閱讀該文。閱讀全文
    posted @ 2010-01-15 12:22 西津渡 閱讀(102) | 評(píng)論 (0)編輯 收藏

    2010年1月5日

    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/

    posted @ 2010-01-05 13:38 西津渡 閱讀(391) | 評(píng)論 (0)編輯 收藏

    2010年1月4日

        只有注冊(cè)用戶登錄后才能閱讀該文。閱讀全文
    posted @ 2010-01-04 15:11 西津渡 閱讀(78) | 評(píng)論 (0)編輯 收藏

    2009年12月30日


    從時(shí)序圖中可以看到,createNewIO()就是新建了一個(gè)com.mysql.jdbc.MysqlIO,利用 com.mysql.jdbc.StandardSocketFactory來創(chuàng)建一個(gè)socket。然后就由這個(gè)mySqlIO來與MySql服務(wù)器進(jìn)行握手(doHandshake()),這個(gè)doHandshake主要用來初始化與Mysql server的連接,負(fù)責(zé)登陸服務(wù)器和處理連接錯(cuò)誤。在其中會(huì)分析所連接的mysql server的版本,根據(jù)不同的版本以及是否使用SSL加密數(shù)據(jù)都有不同的處理方式,并把要傳輸給數(shù)據(jù)庫server的數(shù)據(jù)都放在一個(gè)叫做packet的 buffer中,調(diào)用send()方法往outputStream中寫入要發(fā)送的數(shù)據(jù)。


    useServerPreparedStmts置為true的話,mysql驅(qū)動(dòng)可以通過PreparedStatement的子類ServerPreparedStatement來實(shí)現(xiàn)真正的PreparedStatement的功能




    第一位表示數(shù)據(jù)包的開始位置,就是數(shù)據(jù)存放的起始位置,一般都設(shè)置為0,就是從第一個(gè)位置開始。第二和第三個(gè)字節(jié)標(biāo)識(shí)了這個(gè)數(shù)據(jù)包的大小,注意的是,這個(gè)大小是出去標(biāo)識(shí)的4個(gè)字節(jié)的大小,對(duì)于非最后一個(gè)數(shù)據(jù)包來說,這個(gè)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(gè)字節(jié)中存放的就是數(shù)據(jù)包的編號(hào)了,從0開始遞增。
    在標(biāo)識(shí)位設(shè)置完畢之后,就可以把255 * 255 * 255大小的數(shù)據(jù)從我們準(zhǔn)備好的待發(fā)送數(shù)據(jù)包中copy出來了,注意,前4位已經(jīng)是標(biāo)識(shí)位了,所以應(yīng)該從第五個(gè)位置開始copy數(shù)據(jù)

     # 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(hù)性
    2.最重要的一點(diǎn)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(wǎng)上其他人的經(jīng)驗(yàn),基本和我的判斷一致,有兩點(diǎn)要特別提請(qǐng)大家注意:

    1.并不是說PreparedStatement在所有的DB上都不會(huì)提高效率,PreparedStatement需要服務(wù)器端的支持,比如在 Oracle上就會(huì)有顯著效果。上面說的測(cè)試都是在MySQL上測(cè)試的,我找到了一個(gè)MySQL架構(gòu)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(shù)使用時(shí)甚至?xí)档托剩匀粦?yīng)該使用PreparedStatement!因?yàn)槠渌? 處實(shí)在是太大了!當(dāng)然,當(dāng)SQL查詢比較復(fù)雜時(shí),可能PreparedStatement好處會(huì)更大,只是我沒有測(cè)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(shí)在很大,因此Connection Pool絕對(duì)必要。



    posted @ 2009-12-30 12:41 西津渡 閱讀(385) | 評(píng)論 (0)編輯 收藏

    2009年12月14日

    download ,annatation and tools 兩個(gè)項(xiàng)目。
    添加相關(guān)的 jar.

    <taskdef name="hibernatetool" classname="org.hibernate.tool.ant.HibernateToolTask" classpathref="master.classpath" />

    <target name="create_table">

    <hibernatetool destdir="${script.dir}">
        <annotationconfiguration configurationfile="src/hibernate.cfg.xml" />
        <hbm2ddl export="false" create="true" delimiter=";" format="true" outputfilename="create-tables.sql" />
    </hibernatetool>

    </target>

    <!DOCTYPE hibernate-configuration PUBLIC
        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

    <hibernate-configuration>
        <session-factory name="logi">
            <property name="show_sql">true</property>
            <mapping class="com.tt.logi.target.Target"/>
       
        </session-factory>
    </hibernate-configuration>

    import java.io.Serializable;

    import javax.persistence.Basic;
    import javax.persistence.Entity;
    import javax.persistence.Id;

    @Entity
    public class Target implements Serializable{
       
        private Long id;
        private String name;
        @Id
        public Long getId() {
            return id;
        }
        public void setId(Long id) {
            this.id = id;
        }
        @Basic
        public String getName() {
            return name;
        }
        public void setName(String name) {
            this.name = name;
        }
       
       
       

    posted @ 2009-12-14 19:04 西津渡 閱讀(100) | 評(píng)論 (0)編輯 收藏
     
    wget ftp://ftp.jaist.ac.jp/pub/mysql/Downloads/MySQL-5.1/mysql-5.1.41.tar.gz
    tar -xzf



    ./configure --prefix=/usr/local/mysql51m --without-debug  --enable-local-infile --enable-assembler --enable-thread-safe-client --with-plugins=all

    make
    su -
    make install


    groupadd mysql
    useradd -g mysql mysql


    bin/mysql_install_db --user=mysql  --datadir=/var/lib/mysql51m/data

    chown -R mysql /var/lib/mysql51m/
    chgrp -R mysql /var/lib/mysql51m/


    cp share/mysql/my-innodb-heavy-4G.cnf my.cnf
    vi my.cnf

    datadir = /var/lib/mysql51m/data

    .bin/mysqld_safe --defaults-file=/usr/local/mysql51m/my.cnf &

    bin/mysql  --defaults-file=my.cnf -uroot

    ./mysqladmin -u root password ‘humber’
    grant all on *.* to root@% identified by 'humber'

    default-character-set=utf8
    init_connect='SET NAMES utf8'
    default-storage-engine = INNODB

    posted @ 2009-12-14 14:44 西津渡 閱讀(118) | 評(píng)論 (0)編輯 收藏

    2009年12月7日

    jmap -heap 16761
    jstat -gcutil 16761
    jmap -finalizerinfo 16761
    jmap -histo 16761
    jstack -l 16761
    jinfo 16761

    Examine the fatal error log file. Default file name is hs_err_pidpid.log in the working-directory.

    -XX:+HeapDumpOnOutOfMemoryError
    java -agentlib:hprof=heap=dump,format=b application
    $ jmap -dump:format=b,file=snapshot.jmap process-pid

    1、在jvm啟動(dòng)時(shí)加上:-agentlib:hprof=heap=sites,file=heap.txt  ,然后執(zhí)行一段時(shí)間后執(zhí)行 kill -3 <pid>,就可以獲取jvm的內(nèi)存鏡像。類似的通過-agentlib:hprof=cpu=samples,file=cpu.txt查 看cpu的狀況。

    http://java.sun.com/javase/6/webnotes/trouble/other/matrix6-Unix.html


    Quick Troubleshooting Tips on Solaris OS and Linux for Java SE 6

    This "Quick Start Guide" gives you some quick tips for troubleshooting. The subsections list some typical functions that can help you in troubleshooting, including one or more ways to get the information or perform the action.

    These tips are organized as follows:

    Hung, Deadlocked, or Looping Process
    Post-mortem Diagnostics, Memory Leaks
    Monitoring
    Actions on a Remote Debug Server
    Other Functions

    Hung, Deadlocked, or Looping Process

    • Print thread stack for all Java threads:
      • Control-"
      • kill -QUIT pid
      • jstack pid (or jstack -F pid if jstack pid does not respond)
    • Detect deadlocks:
      • Request deadlock detection: JConsole tool, Threads tab
      • Print information on deadlocked threads: Control-"
      • Print list of concurrent locks owned by each thread: -XX:+PrintConcurrentLocks set, then Control-"
      • Print lock information for a process: jstack -l pid
    • Get a heap histogram for a process:
      • Start Java process with -XX:+PrintClassHistogram, then Control-"
      • jmap -histo pid (with -F option if pid does not respond)
    • Dump Java heap for a process in binary format to file:
      • jmap -dump:format=b,file=filename pid (with -F option if pid does not respond)
    • Print shared object mappings for a process:
      • jmap pid
    • Print heap summary for a process:
      • Control-"
      • jmap -heap pid
    • Print finalization information for a process:
      • jmap -finalizerinfo pid
    • Attach the command-line debugger to a process:
      • jdb -connect sun.jvm.hotspot.jdi.SAPIDAttachingConnector:pid=pid

    Post-mortem Diagnostics, Memory Leaks

    • Examine the fatal error log file. Default file name is hs_err_pidpid.log in the working-directory.
    • Create a heap dump:
      • Start the application with HPROF enabled: java -agentlib:hprof=file=file,format=b application; then Control-"
      • Start the application with HPROF enabled: java -agentlib:hprof=heap=dump application
      • JConsole tool, MBeans tab
      • Start VM with -XX:+HeapDumpOnOutOfMemoryError; if OutOfMemoryError is thrown, VM generates a heap dump.
    • Browse Java heap dump:
      • jhat heap-dump-file
    • Dump Java heap from core file in binary format to a file:
      • jmap -dump:format=b,file=filename corefile
    • Get a heap histogram for a process:
      • Start Java process with -XX:+PrintClassHistogram, then Control-"
      • jmap -histo pid (with -F option if pid does not respond)
    • Get a heap histogram from a core file:
      • jmap -histo corefile
    • Print shared object mappings from a core file:
      • jmap corefile
    • Print heap summary from a core file:
      • jmap -heap corefile
    • Print finalization information from a core file:
      • jmap -finalizerinfo corefile
    • Print Java configuration information from a core file:
      • jinfo corefile
    • Print thread trace from a core file:
      • jstack corefile
    • Print lock information from a core file:
      • jstack -l corefile
    • Attach the command-line debugger to a core file on the same machine:
      • jdb -connect sun.jvm.hotspot.jdi.SACoreAttachingConnector:javaExecutable=path,core=corefile
    • Attach the command-line debugger to a core file on a different machine:
      • On the machine with the core file: jsadebugd path corefile
        and on the machine with the debugger: jdb -connect sun.jvm.hotspot.jdi.SADebugServerAttachingConnector:debugServerName=machine
    • libumem can be used to debug memory leaks.

    Monitoring

    Note: The vmID argument for the jstat command is the virtual machine identifier. See the jstat man page for a detailed explanation.

    • Print statistics on the class loader:
      • jstat -class vmID
    • Print statistics on the compiler:
      • Compiler behavior: jstat -compiler vmID
      • Compilation method statistics: jstat -printcompilation vmID
    • Print statistics on garbage collection:
      • Summary of statistics: jstat -gcutil vmID
      • Summary of statistics, with causes: jstat -gccause vmID
      • Behavior of the gc heap: jstat -gc vmID
      • Capacities of all the generations: jstat -gccapacity vmID
      • Behavior of the new generation: jstat -gcnew vmID
      • Capacity of the new generation: jstat -gcnewcapacity vmID
      • Behavior of the old and permanent generations: jstat -gcold vmID
      • Capacity of the old generation: jstat -gcoldcapacity vmID
      • Capacity of the permanent generation: jstat -gcpermcapacity vmID
    • Monitor objects awaiting finalization:
      • JConsole tool, VM Summary tab
      • jmap -finalizerinfo pid
      • getObjectPendingFinalizationCount method in java.lang.management.MemoryMXBean class
    • Monitor memory:
      • Heap allocation profiles via HPROF: java -agentlib:hprof=heap=sites
      • JConsole tool, Memory tab
      • Control-" prints generation information.
    • Monitor CPU usage:
      • By thread stack: java -agentlib:hprof=cpu=samples application
      • By method: java -agentlib:hprof=cpu=times application
      • JConsole tool, Overview and VM Summary tabs
    • Monitor thread activity:
      • JConsole tool, Threads tab
    • Monitor class activity:
      • JConsole tool, Classes tab

    Actions on a Remote Debug Server

    First, attach the debug daemon jsadebugd, then execute the command:

    • Dump Java heap in binary format to a file: jmap -dump:format=b,file=filename hostID
    • Print shared object mappings: jmap hostID
    • Print heap summary : jmap -heap hostID
    • Print finalization information : jmap -finalizerinfo hostID
    • Print lock information : jstack -l hostID
    • Print thread trace : jstack hostID
    • Print Java configuration information: jinfo hostID

    Other Functions

    • Interface with the instrumented Java virtual machines:
      • Monitor for the creation and termination of instrumented VMs: jstatd daemon
      • List the instrumented VMs: jps
      • Provide interface between remote monitoring tools and local VMs: jstatd daemon
      • Request garbage collection: JConsole tool, Memory tab
    • Print Java configuration information from a running process:
      • jinfo pid
    • Dynamically set, unset, or change the value of certain Java VM flags for a process:
      • jinfo -flag flag
    • Print command-line flags passed to the VM:
      • jinfo -flags
    • Print Java system properties:
      • jinfo -sysprops
    • Pass a Java VM flag to the virtual machine:
      • jconsole -Jflag ...
      • jhat -Jflag ...
      • jmap -Jflag ...
    • Print statistics of permanent generation of Java heap, by class loader:
      • jmap -permstat
    • Report on monitor contention.
      • java -agentlib:hprof=monitor=y application
    • Evaluate or execute a script in interactive or batch mode:
      • jrunscript
    • Interface dynamically with an MBean, via JConsole tool, MBean tab:
      • Show tree structure.
      • Set an attribute value.
      • Invoke an operation.
      • Subscribe to notification.
    • Run interactive command-line debugger:
      • Launch a new VM for the class: jdb class
      • Attach debugger to a running VM: jdb -attach address
      http://m.tkk7.com/justinchen/archive/2009/01/08/248738.html
    posted @ 2009-12-07 14:16 西津渡 閱讀(431) | 評(píng)論 (0)編輯 收藏
     
    netstat -n | awk '/^tcp/ {++state[$NF]} END {for(key in state) print key,""t",state[key]}'

    posted @ 2009-12-07 13:42 西津渡| 編輯 收藏

    2009年10月29日

    set nocompatible
    set autoindent
    set smartindent
    set ignorecase
    syntax enable
    set wrap
    set showmatch
    set foldmarker={{{,}}}
    set tabstop=4
    set shiftwidth=4
    set ruler
    set expandtab
    set backspace=eol,start,indent
    set whichwrap+=<,>,h,l
    set nobackup
    setlocal noswapfile
    set bufhidden=hide
    syntax on
    set tags=./tags,~/apsara/tags
    set path+=/usr/include/c++/**,~/apsara/include/**
    filetype plugin on
    filetype indent on
    autocmd filetype java,c,cpp setlocal textwidth=100
    set pastetoggle=<F7>

    nmap <F2>  :set nonumber!<CR>
    nmap <F8>  :TlistToggle<CR>
    imap <F11> <C-x><C-p>
    map <F12>  :!ctags -R --c++-kinds=+p --fields=+iaS --exclude=build --extra=+q .<CR>
    map <F6> :w<CR>
    imap <F6> <ESC>:w<CR>a
    map <F3> /<C-R><C-W><CR>

    有 c support 支持,很棒。

    posted @ 2009-10-29 11:42 西津渡 閱讀(243) | 評(píng)論 (0)編輯 收藏
    僅列出標(biāo)題  下一頁
     
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