測試JAVA生成短8位UUID，是否重復問題，100萬數據耗時26秒，越往后性能成指數增加

在網上有一種短8位UUID生成的方法，代碼來源：

JAVA生成短8位UUID

public static String[] chars = new String[] { "a", "b", "c", "d", "e", "f",
            "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s",
            "t", "u", "v", "w", "x", "y", "z", "0", "1", "2", "3", "4", "5",
            "6", "7", "8", "9", "A", "B", "C", "D", "E", "F", "G", "H", "I",
            "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V",
            "W", "X", "Y", "Z" };
 
 
public static String generateShortUuid() {
    StringBuffer shortBuffer = new StringBuffer();
    String uuid = UUID.randomUUID().toString().replace("-", "");
    for (int i = 0; i < 8; i++) {
        String str = uuid.substring(i * 4, i * 4 + 4);
        int x = Integer.parseInt(str, 16);
        shortBuffer.append(chars[x % 0x3E]);
    }
    return shortBuffer.toString();
 
}

我們進行測試看到底多少會出現重復，寫了一個比較簡單的方法：

設置了線程池，數據庫連接池，每一個線程進行處理一百萬條數據，每次攜帶7萬條數據進行數據庫的插入。我們將ID設置為數據庫的主鍵，如果出現錯誤，則表示數據庫ID出現重復現象。

如果需要一次性插入更多的數據，或者在插入的時候報下面的錯誤：

Packet for query is too large (4,800,048 > 4,194,304)

修改 my.ini 加上 max_allowed_packet =67108864
67108864=64M
默認大小4194304  也就是4M
修改完成之后要重啟mysql服務，如果通過命令行修改就不用重啟mysql服務。
命令修改：
設置為500M
mysql> set global max_allowed_packet = 500*1024*1024; 
 
查看mysql的max_allowed_packet大小,運行
show VARIABLES like '%max_allowed_packet%';

下面是插入數據代碼，進行測試：

 private static ThreadPoolExecutor threadPoolExecutor=new ThreadPoolExecutor(50, 100,
            0L, TimeUnit.MILLISECONDS,
            new LinkedBlockingQueue<Runnable>(1024),new DefaultManagedAwareThreadFactory(), new ThreadPoolExecutor.AbortPolicy());
 
 
 
 @Override
    public void saveTest() {
        threadPoolExecutor.execute(new saveUUID());
    }
    /**
     * 設置保存信息的線程
     */
    class saveUUID implements Runnable{
        public saveUUID(){
        }
        @Override
        public void run() {
            System.out.println("===================>>>>>" +  Thread.currentThread().getName());
            List<Map<String,Object>> userList = new ArrayList<>();
            int index=0;
            for(int i = 0; i< 1000000;i++){
                long  startTime = System.currentTimeMillis();
                Map<String,Object> map = new HashMap<>();
                map.put("id",getUUID8());
                userList.add(map);
                index++;
                if (index==70000) {
                    int count = testMapper.saveTest(userList);
                    if (count > 0) {
                        userList.clear();
                        index=0;
                        long time =System.currentTimeMillis()-startTime;
                        System.out.println( Thread.currentThread().getName() + "======>>>>"  +time );
                    }
                }
            }
            if(!userList.isEmpty()){
                testMapper.saveTest(userList);
            }
 
        }
    }

XML文件：

  <insert id="saveTest" parameterType="java.util.List">
        insert into tb_user(id,user_name)
        values
        <foreach item="item" index="index" collection="list" separator=",">
            (#{item.id},#{item.id})
        </foreach>
    </insert>

進行測試當數據達到：2129580，也就是兩百萬的時候出現第一次重復，進行數據庫數據查詢，發現重復原因是因為MySQL不區分大小寫。

關於MySQL主鍵不區分大小寫，或則其他查詢不區分大小寫 Duplicate entry 'AOVbrXXF' for key 'PRIMARY'
將MySQL進行大小寫區分。再進行測試。

數據達到400萬條無重復，系統插入緩慢。

在基礎數據為0的情況下，插入數據100萬。系統花費時間為：

 

 

 

 

26.318秒

 

在基礎數據為0的情況下，插入數據200萬。系統花費的時間為：

 

 

 

 

64.097秒

 

在基礎數據為0的情況下，插入數據，系統花費時間：

DefaultManagedAwareThreadFactory-1======>>>>3209
DefaultManagedAwareThreadFactory-1======>>>>1033
DefaultManagedAwareThreadFactory-1======>>>>1089
DefaultManagedAwareThreadFactory-1======>>>>952
DefaultManagedAwareThreadFactory-1======>>>>921
DefaultManagedAwareThreadFactory-1======>>>>1119
DefaultManagedAwareThreadFactory-1======>>>>825
DefaultManagedAwareThreadFactory-1======>>>>911
DefaultManagedAwareThreadFactory-1======>>>>919
DefaultManagedAwareThreadFactory-1======>>>>850
DefaultManagedAwareThreadFactory-1======>>>>949
DefaultManagedAwareThreadFactory-1======>>>>983
DefaultManagedAwareThreadFactory-1======>>>>720
DefaultManagedAwareThreadFactory-1======>>>>1097
DefaultManagedAwareThreadFactory-1======>>>>862
DefaultManagedAwareThreadFactory-1======>>>>1173
DefaultManagedAwareThreadFactory-1======>>>>942
DefaultManagedAwareThreadFactory-1======>>>>808
DefaultManagedAwareThreadFactory-1======>>>>1159
DefaultManagedAwareThreadFactory-1======>>>>845
DefaultManagedAwareThreadFactory-1======>>>>998
DefaultManagedAwareThreadFactory-1======>>>>1478
DefaultManagedAwareThreadFactory-1======>>>>1420
DefaultManagedAwareThreadFactory-1======>>>>974
DefaultManagedAwareThreadFactory-1======>>>>1398
DefaultManagedAwareThreadFactory-1======>>>>4005
DefaultManagedAwareThreadFactory-1======>>>>2922
DefaultManagedAwareThreadFactory-1======>>>>2126
DefaultManagedAwareThreadFactory-1======>>>>1198
DefaultManagedAwareThreadFactory-1======>>>>931
DefaultManagedAwareThreadFactory-1======>>>>2197
DefaultManagedAwareThreadFactory-1======>>>>1014
DefaultManagedAwareThreadFactory-1======>>>>1231
DefaultManagedAwareThreadFactory-1======>>>>3416
DefaultManagedAwareThreadFactory-1======>>>>4471
DefaultManagedAwareThreadFactory-1======>>>>960
DefaultManagedAwareThreadFactory-1======>>>>1199
DefaultManagedAwareThreadFactory-1======>>>>1142
DefaultManagedAwareThreadFactory-1======>>>>940
DefaultManagedAwareThreadFactory-1======>>>>2211
DefaultManagedAwareThreadFactory-1======>>>>23994
DefaultManagedAwareThreadFactory-1======>>>>37751
DefaultManagedAwareThreadFactory-1======>>>>51163
DefaultManagedAwareThreadFactory-1======>>>>66993
DefaultManagedAwareThreadFactory-1======>>>>79591
DefaultManagedAwareThreadFactory-1======>>>>91846

由上可見當數據量達到一定量的時候，時間成指數上升。

 

 

 

 

如何能突破這個時間節點，估計還需要進一步優化。

生產UUID滿足千萬條數據

目前1147萬條數據，沒有出現重復，滿足原作者說的千萬條數據不重復