guid | 易学教程

Best way to create unique token in Rails?

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问题 Here\'s what I\'m using. The token doesn\'t necessarily have to be heard to guess, it\'s more like a short url identifier than anything else, and I want to keep it short. I\'ve followed some examples I\'ve found online and in the event of a collision, I think the code below will recreate the token, but I\'m not real sure. I\'m curious to see better suggestions, though, as this feels a little rough around the edges. def self.create_token random_number = SecureRandom.hex(3) \"1X#{random_number}

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

Create a GUID in Java

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问题 What are some of the best ways to create a GUID in Java? 回答1: Have a look at the UUID class bundled with Java 5 and later. For example: If you want a random UUID you can use the randomUUID method. If you want a UUID initialized to a specific value you can use the UUID constructor or the fromString method. 回答2: java.util.UUID.randomUUID(); 回答3: It depends what kind of UUID you want. The standard Java UUID class generates Version 4 (random) UUIDs. ( UPDATE - Version 3 (name) UUIDs can also be

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

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 unique is the php session id

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问题 How unique is the php session id? I got the impression from various things that I\'ve read that I should not rely on two users never getting the same sessionid. Isn\'t it a GUID? 回答1: Session_id can indeed be duplicated, but the probability is very low. If you have a website with a fair traffic, it may happens once in you web site life, and will just annoy one user for one session. This is not worth to care about unless you expect to build a very high traffic website or a service for the bank

What are the performance improvement of Sequential Guid over standard Guid?

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问题 Has someone ever measured performance of Sequential Guid vs. Standard Guid when used as Primary Keys inside a database? 回答1: GUID vs.Sequential GUID A typical pattern it's to use Guid as PK for tables, but, as referred in other discussions (see Advantages and disadvantages of GUID / UUID database keys) there are some performance issues. This is a typical Guid sequence f3818d69-2552-40b7-a403-01a6db4552f7 7ce31615-fafb-42c4-b317-40d21a6a3c60 94732fc7-768e-4cf2-9107-f0953f6795a5 Problems of

How to create a GUID/UUID in Python

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问题 How do I create a GUID in Python that is platform independent? I hear there is a method using ActivePython on Windows but it\'s Windows only because it uses COM. Is there a method using plain Python? 回答1: The uuid module, in Python 2.5 and up, provides RFC compliant UUID generation. See the module docs and the RFC for details. [source] Docs: Python 2: http://docs.python.org/2/library/uuid.html Python 3: https://docs.python.org/3/library/uuid.html Example (working on 2 and 3): >>> import uuid

What are the performance improvement of Sequential Guid over standard Guid?

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Has someone ever measured performance of Sequential Guid vs. Standard Guid when used as Primary Keys inside a database? massimogentilini GUID vs.Sequential GUID A typical pattern it's to use Guid as PK for tables, but, as referred in other discussions (see Advantages and disadvantages of GUID / UUID database keys ) there are some performance issues. This is a typical Guid sequence f3818d69-2552-40b7-a403-01a6db4552f7 7ce31615-fafb-42c4-b317-40d21a6a3c60 94732fc7-768e-4cf2-9107-f0953f6795a5 Problems of this kind of data are:< - Wide distributions of values Almost randomically ones Index usage

Simple proof that GUID is not unique [closed]

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问题 As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. Closed 7 years ago . Locked . This question and its answers are locked because the question is off-topic but has historical significance. It is not