uuid | 易学教程

Generating a UUID in Postgres for Insert statement?

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问题 My question is rather simple. I\'m aware of the concept of a UUID and I want to generate one to refer to each \'item\' from a \'store\' in my DB with. Seems reasonable right? The problem is the following line returns an error: honeydb=# insert into items values( uuid_generate_v4(), 54.321, 31, \'desc 1\', 31.94); ERROR: function uuid_generate_v4() does not exist LINE 2: uuid_generate_v4(), 54.321, 31, \'desc 1\', 31.94); ^ HINT: No function matches the given name and argument types. You might

How to test valid UUID/GUID?

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问题 How to check if variable contains valid UUID/GUID identifier ? I\'m currently interested only in validating types 1 and 4, but it\'s not limit for your answer. 回答1: Currently, UUID's are as specified in RFC4122. An often neglected edge case is the NIL UUID, noted here. The following regex takes this into account and will return a match for a NIL UUID. See below for a UUID which only accepts non-NIL UUIDs. Both of these solutions are for versions 1 to 5 (see the first character of the third

Likelihood of collision using most significant bits of a UUID in Java

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问题 If I\'m using Long uuid = UUID.randomUUID().getMostSignificantBits() how likely is it to get a collision. It cuts off the least significant bits, so there is a possibility that you run into a collision, right? 回答1: According to the documentation, the static method UUID.randomUUID() generates a type 4 UUID. This means that six bits are used for some type information and the remaining 122 bits are assigned randomly. The six non-random bits are distributed with four in the most significant half

How good is Java's UUID.randomUUID?

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问题 I know that randomized UUIDs have a very, very, very low probability for collision in theory, but I am wondering, in practice, how good Java\'s randomUUID() is in terms of not having collision? Does anybody have any experience to share? 回答1: UUID uses java.security.SecureRandom, which is supposed to be "cryptographically strong". While the actual implementation is not specified and can vary between JVMs (meaning that any concrete statements made are valid only for one specific JVM), it does

How to get a unique computer identifier in Java (like disk ID or motherboard ID)?

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问题 I\'d like to get an id unique to a computer with Java, on Windows, MacOS and, if possible, Linux. It could be a disk UUID, motherboard S/N... Runtime.getRuntime().exec can be used (it is not an applet). Ideas? 回答1: It is common to use the MAC address is associated with the network card. The address is available in Java 6 through through the following API: Java 6 Docs for Hardware Address I haven't used it in Java, but for other network identification applications it has been helpful. 回答2: The

Is there any difference between a GUID and a UUID?

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问题 I see these 2 acronyms thrown around, and I was wondering if there are any differences between a GUID and a UUID? 回答1: The simple answer is: no difference , they are the same thing. Treat them as a 16 byte (128 bits) value that is used as a unique value. In Microsoft-speak they are called GUIDs, but call them UUIDs when not using Microsoft-speak. Even the authors of the UUID specification and Microsoft claim they are synonyms: From the introduction to IETF RFC 4122 " A Universally Unique

iOS开发，Bluetooth你应该了解一些！

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API结构导图 CoreBluetooth中，需要用到的类和协议( 完整导图 )：基础知识蓝牙分类中心端和外设端( 完整导图 )。中心端（接收端） 1 .创建中心端控制器（CBCentralManager) 2 .扫描设备（Discover） 3 .连接（Connect） 4 .获取Service和Characteristic 扫描Service （一个service中包含一个或多个Characteristic）获取Service中Characteristic 获取Characteristic的值 5 . 数据交互（explore and interact) 订阅Characteristic的通知 6 . 断开链接外设端（发送端）创建Peripheral管理对象创建Service和Characteristic树发送广告处理读写请求和订阅蓝牙状态 typedef NS_ENUM(NSInteger, CBManagerState) { CBManagerStateUnknown = 0, CBManagerStateResetting, CBManagerStateUnsupported, //不支持 CBManagerStateUnauthorized, //未授权 CBManagerStatePoweredOff, //关闭

Advantages and disadvantages of GUID / UUID database keys

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问题 I\'ve worked on a number of database systems in the past where moving entries between databases would have been made a lot easier if all the database keys had been GUID / UUID values. I\'ve considered going down this path a few times, but there\'s always a bit of uncertainty, especially around performance and un-read-out-over-the-phone-able URLs. Has anyone worked extensively with GUIDs in a database? What advantages would I get by going that way, and what are the likely pitfalls? 回答1:

How to preserve identifierForVendor in ios after uninstalling ios app on device?

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问题 I am developing an iOS app which calls web-service for login and at that time i send login credentials to web server along with vendor identifier (identifierForVendor),to identify device uniquely for those credentials.So user can have only one device and one credential. I got identifierForVendor with NSString *uuid = [[UIDevice currentDevice] identifierForVendor].UUIDString This identifier will then store in database of web server and also in device database.Next time when user opens

PHP function to generate v4 UUID

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问题 So I\'ve been doing some digging around and I\'ve been trying to piece together a function that generates a valid v4 UUID in PHP. This is the closest I\'ve been able to come. My knowledge in hex, decimal, binary, PHP\'s bitwise operators and the like is nearly non existant. This function generates a valid v4 UUID up until one area. A v4 UUID should be in the form of: xxxxxxxx-xxxx- 4 xxx- y xxx-xxxxxxxxxxxx where y is 8, 9, A, or B. This is where the functions fails as it doesn\'t adhere to