uuid

1、异常概述及其分析过程 在大数据同步过程中，为了数据分析同步并按天更新到关系型数据中（以MYSQL为例）且保证数据的唯一性，采用UUID所谓的永远不会重复的字符串作为数据表的ID。 但在实际操作由于数据处理基数超大（数亿的数据量），加上UUID版本选择不恰当。致使UUID出现小概率事件重复，最终导致数据同步发生异常。异常如下 图一 图2 2、解决方案 有图一所示job_1499327741859_15469作业出现异常，根据Job的ID在大数据平台（CDH的YARN中）中查Job的日志如图二所示， '28f449d76520496bba9e2e3f375b08a6' for key 'PRIMARY 的KEY存在重复。问题就来了，问什么ID重复，是什么原因导致UUID的重复，接下来 要从查找数据处理具体代码，如下图三中红框中可知java.util.UUID,random 它是产生UUID核心代码。接下来对UUID进全方位的了解，如链接 http://blog.csdn.net/qq592304796/article/details/52497940 可知上述所使用UUID为版本4，由于其产生的UUID为存在伪随机数，也就是说其有产生重复UUID的可能。 图三 3、问题结论 至此UUID重复异常原因被彻底剖析出来。所以强烈建议不要使用UUID版本4，以避免此后出现类似的异常 来源：

步骤一： 查看电脑上所有硬盘分区的卷标及uuid， sudo blkid /dev/sda1: LABEL="win7" UUID="40305E93305E9030" TYPE="ntfs" /dev/sda5: LABEL="software" UUID="823E2D6213AF89BD" TYPE="ntfs" /dev/sdb1: LABEL="learning" UUID="CCBC9A082598C349" TYPE="ntfs" /dev/sdb2: LABEL="datadisk" UUID="40e93235-b5d1-48c4-936c-212029bda05a" TYPE="ext4" /dev/sdc1: UUID="7350922f-c69c-4f33-84e0-befd8b42d2f6" TYPE="swap" /dev/sdd1: UUID="3002feb1-dceb-441d-bfd2-31243e336d39" TYPE="ext4"、 #为了更好的区分硬盘分区，修改卷标（类似于windows的C、D、E、F盘） sudo e2label /dev/sdb2 datadist 步骤二： 先卸载要修改名称的分区， sudo umount /dev/sdb2 步骤三： 挂载硬盘， # mount /dev/sdb2 /media/datadisk

iOS Simulator stores apps in ~/Library/Application Support/iPhone Simulator/4.2/Applications/APP_UUID/ But how do I find the APP_UUID for a specific Project/Target? Go to ~/Library/Developer/CoreSimulator/Devices/ and type find . -iname "*.app" in a shell. ** Updated for Xcode 8 ** The easiest way I've found is to run the app in the simulator and NSLog the result of a standard path-locating function, like this one: - (NSString *)applicationDocumentsDirectory { NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *basePath = ([paths count] >

在平时开发时，如果没有定义数据库自动生成ID的机制，可以使用java自带的uuid生成随机唯一主键，在插入数据库时，可以直接给ID主键赋值；这个uuid方法，在java自带的utils包里，就可以直接调用： 示例： public static String getUUID(){ UUID uuid=UUID.randomUUID(); String uuidStr=uuid.toString(); return uuidStr; } =======注意======= UUID随机主键的长度为36位，在数据库表设计时，注意为UUID存储列，分配足够的长度 参考地址 https://blog.csdn.net/weixin_42350212/article/details/80588471 来源： https://blog.csdn.net/weixin_44018338/article/details/100042270

I am looking for a way to get hibernate to use oracle's SYS_GUID() function when inserting new rows. Currently my DB tables have SYS_GUID() as the default so if hibernate simply generated SQL that omited the value it should work. I have everything working, but it is currently generating the UUID/GUID in code using the system-uuid generator: @Id @GeneratedValue(generator = "system-uuid") @GenericGenerator(name = "system-uuid", strategy = "uuid") @Column(name = "PRODUCT_ID", unique = true, nullable = false) public String getId() { return this.productId; } This is fine, but I would prefer that

I want generate unique ID just like auto increment in java . So previously i used current nano seconds but i end up with clash since two data comes with in same nano seconds .. Does UUID solves the above problem ? Note :: In my project i can even get 10000 rows of records for each and every minute and I will dump those records along with UIDS in to table .And there may be a situation where i would stop my product and restart it after some time ....So during that situation how could UUID class clarifies the previously generated Uids(which i stored in DB) with the new one going to created(Yet to

The uuid4() function of Python's module uuid generates a random UUID, and seems to generate a different one every time: In [1]: import uuid In [2]: uuid.uuid4() Out[2]: UUID('f6c9ad6c-eea0-4049-a7c5-56253bc3e9c0') In [3]: uuid.uuid4() Out[3]: UUID('2fc1b6f9-9052-4564-9be0-777e790af58f') I would like to be able to generate the same random UUID every time I run a script - that is, I'd like to seed the random generator in uuid4() . Is there a way to do this? (Or achieve this by some other means)? What I've tried so far I've to generate a UUID using the uuid.UUID() method with a random 128-bit

Note: This is a question-with-answer in order to document a technique that others might find useful, and in order to perhaps become aware of others’ even better solutions. Do feel free to add critique or questions as comments. Also do feel free to add additional answers. :) Visual C++ has always had a language extension __uuidof( classname ) that can retrieve an UUID , a 128 bit Universally Unique Identifier , provided that the UUID’s been associated with the class via __declspec , which also is a Visual C++ language extension: #include <guiddef.h> // GUID, another name for UUID class _