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  • ... i just avoid GUID

    - by Tomaz.tsql
    Our partner was explaining to me that they are using GUID as primary key on all the tables. My immediate reaction was - why? and couple of basic doubts were: - since I can read uniqueidentifier, it does not tell me absolutely anything - if I will use my relational table, i sure will use other columns to get the information out - SQL is terrible when setting up clustered index on GUID columns (and hence performance problems) - why not use INT? it will save you space on disk, optimizer will be able...(read more)

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  • MS SQL Database with clustered GUID PKs - switch clustered index or switch to sequential (comb) GUID

    - by Eyvind
    We have a database in which all the PKs are GUIDs, and most of the PKs are also the clustered index for the table. We know that this is bad (due to the random nature of GUIDs). So, it seems there are basically two options here (short of throwing out GUIDs as PKs altogether, which we cannot do (at least not at this time)). We could change the GUID generation algorithm to e.g. the one that NHibernate uses, as detailed in this post, or we could, for the tables that are under the heaviest use, change to a different clustered index, e.g. an IDENTITY column, and keep the "random" GUIDs as PKs. Is it possible to give any general recommendations in such a scenario? The application in question has 500+ tables, the largest one presently at about 1,5 million rows, a few tables around 500 000 rows, and the rest significantly lower (most of them well below 10K). Furthermore, the application is installed at several customer sites already, so we have to take any possible negative effects for existing customer into consideration. Thanks!

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  • Compact representation of GUID/UUID?

    - by chakrit
    I need to generate a GUID and save it via a string representation. The string representation should be as short as possible as it will be used as part of an already-long URL string. Right now, instead of using the normal abcd-efgh-... representation, I use the raw bytes generated and base64-encode them instead, which results in a somewhat shorter string. But is it possible to make it even shorter? I'm OK with losing some degree of uniqueness and keeping a counter, but scanning all existing keys is not an option. Suggestions?

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  • Nhibernate Guid with PK MySQL

    - by Andrew Kalashnikov
    Hello colleagues. I've got a question. I use NHibernate with MySql. At my entities I use Id(PK) for my business-logic usage and Guid(for replication). So my BaseDomain: public class BaseDomain { public virtual int Id { get; set; } public virtual Guid Guid { get; set; } public class Properties { public const string Id = "Id"; public const string Guid = "Guid"; } public BaseDomain() { } } My usage domain: public class ActivityCategory : BaseDomain { public ActivityCategory() { } public virtual string Name { get; set; } public new class Properties { public const string Id = "Id"; public const string Guid = "Guid"; public const string Name = "Name"; private Properties() { } } } Mapping: <class name="ActivityCategory, Clients.Core" table='Activity_category'> <id name="Id" unsaved-value="0" type="int"> <column name="Id" not-null="true"/> <generator class="native"/> </id> <property name="Guid"/> <property name="Name"/> </class> But when I insert my entity: [Test] public void Test() { ActivityCategory ac = new ActivityCategory(); ac.Name = "Test"; using (var repo = new Repository<ActivityCategory>()) repo.Save(ac); } I always get '00000000-0000-0000-0000-000000000000' at my Guid field. What should I do for generate right Guid. May be mapping? Thanks a lot!

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  • opening a GUID usb stick in windows 7

    - by altomic
    so I have a mac which I have files on. I put in a GUID formatted usb stick and dropped some files on to it. took the stick and plugged in to my netbook with win7. In Devices & Printers it shows up. It also appears in "safely remove hardware". no actual letter or device when i search for it in other ways. Question - how do I access the files of my GUID usb stick on my windows 7 netbook? thanks

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  • Database Design Question: GUID + Natural Numbers

    - by Alan
    For a database I'm building, I've decided to use natural numbers as the primary key. I'm aware of the advantages that GUID's allow, but looking at the data, the bulk of row's data were GUID keys. I want to generate XML records from the database data, and one problem with natural numbers is that I don't want to expose my database key's to the outside world, and allow users to guess "keys." I believe GUID's solve this problem. So, I think the solution is to generate a sparse, unique iD derived from the natural ID (hopefully it would be 2-way), or just add an extra column in the database and store a guid (or some other multibyte id) The derived value is nicer because there is no storage penalty, but it would be easier to reverse and guess compared to a GUID. I'm (buy) curious as to what others on SO have done, and what insights they have.

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  • c# Create a unique name with a GUID

    - by Dave Rook
    I am creating a back up solution. I doubt there is anything new in what I'm trying to achieve. Before copying the file I want to take a backup of the destination file in case anything becomes corrupt. This means renaming the file. I have to be careful when renaming in case the file already exists and adding a 01 to the end is not safe. My question is, based upon not finding the answer else where, would adding a GUID to the file name work. So, if my file was called file01.txt, renaming the file to file01.txtGUID (where GUID is the generated GUID), I could then perform my back up of that file (at this instance having 2 back ups) and then, after ensuring the file has copied (by comparing length of file to the source), delete the file with the GUID in the name. I know the GUID is not 100% guaranteed to be unique but would this suffice?

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  • Last GUID used up - new ScottGuID unique ID to replace it

    - by Eilon
    You might have heard in recent news that the last ever GUID was used up. The GUID {FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF} was just consumed by a soon to be released project at Microsoft. Immediately after the GUID's creation the word spread around the Microsoft campuses around the globe. Microsoft's approximately 100,000 worldwide employees then started blogging, tweeting, and facebooking about the dubious "achievement." The following screenshot shows GUIDGEN (the Windows tool for creating GUIDs) with the last ever GUID. All GUIDs created by projects at Microsoft must be registered in a central repository for record keeping. This allows quick-fix engineers, security engineers, anti-malware developers, and testers to do a quick look up of an unknown GUID and find out if it belongs to Microsoft. The following screenshot shows the Microsoft GUID Tracker internal application and the last few GUIDs being used up by various Microsoft projects. What is perhaps more interesting than the news about the GUID is the project that used that last GUID. The recent announcements regarding the development experience for the Windows Phone 7 Series (WP7S) all involve free editions of Visual Studio 2010. One of the lesser known developer tools is based on a resurrected project that many of you are probably familiar with, but have never used. The tool is in fact Microsoft Bob 7 Series (MB7S). MB7S is an agent-based approach for mobile phone app development. The UI incorporates both natural language interfaces and motion gesture behaviors, similar to the Windows Phone 7 Series “Metro” interface. If it works, it will help to expand the breadth of mobile app developers. After the GUID: The ScottGuID It came as no big surprise that eventually the last GUID would be used up. Knowing this, a group of engineers at Microsoft has designed, implemented, and tested a replacement to the GUID: The ScottGuID. There are several core principles of the ScottGuID: 1. The concepts used in ScottGuIDs must be easily understood by a developer who is already familiar with GUIDs 2. There must exist a compatibility layer between ScottGuIDs and GUIDs 3. A ScottGuID must be usable in a practical manner in non-computing environments 4. There must exist ScottGuID APIs for all common platforms: Win32/Win64/WinCE, .NET (incl. Silverlight), Linux, FreeBSD, MacOS (incl. iPhone OS), Symbian, RIM BlackBerry, Google Android, etc. 5. ScottGuIDs must never run out ScottGuID use cases One of the more subtle principles of the ScottGuID is principle #3. While technically a GUID could be used in any environment, it was not practical to do so in terms of data entry and error detection. In order to have the ScottGuID be a true universal ID it must be usable in non-computing environments. Prior to the announcement of the ScottGuID there have been a number of until-now confidential projects. One of the tools that will soon become public is ScottGuIDGen, which is in essence an updated version of GUIDGEN that can create ScottGuIDs. The following screenshot shows a sample ScottGuID. To demonstrate the various applications of the ScottGuID there were test deployments around the globe. The following examples are a small showcase of the applications that have already been prototyped. Log in to Hotmail: Pay for gas: Sign in to Twitter: Dispense cat food: Conclusion I hope that this brief introduction to the ScottGuID shows how technology can continue to move forward, even when it appears there is a point that cannot be passed. With a small number of principles, a team of smart engineers, and a passion for "getting it right" the ScottGuID should last well past our lifetimes. In the coming months expect further announcements regarding additional developer tools, samples, whitepapers, podcasts, and videos. Please leave a comment on this post if you have any questions about the ScottGuID or what you would like to see us do with it. With ScottGuID, the possibilities are nearly endless and we want to stretch their reach as far as possible.

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  • Convert string to GUID with sscanf

    - by Andy Li
    I'm trying to convert a string to GUID with sscanf: GUID guid; sscanf( "11111111-2222-3333-4455-667788995511", "%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x", &guid.Data1, &guid.Data2, &guid.Data3, &guid.Data4[0], &guid.Data4[1], &guid.Data4[2], &guid.Data4[3], &guid.Data4[4], &guid.Data4[5], &guid.Data4[6], &guid.Data4[7]); However, in runtime, it fails and exits with "Error: Command failed". Why? How to fix it? I do not want to compile with /clr so cannot use System.

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  • Mercurial Hg Clone fails on C# project with GUID

    - by AnneTheAgile
    UPDATE: In trying to replicate this problem one more time to answer your questions I could not! I can only conclude that my initial setup of Mercurial was problematic and/or possibly I was trying to checkin a build that failed compilation before the checkin. Sigh! Thank you so very much for your help. I gave credit for the help on how to do a script. I need to try that for general purposes. hi all, I hope you can help me :). I am trying to see if Mercurial would be a good DCVS for my project at work, and I'm surely a newbie to many things. We have a fairly large codebase in C# (Dotnet3.0 not 3.5 , WindowsXP) and it utilizes the GUID feature. I confess to know little about how or why we use the GUID, but I do know that I cannot touch it. So, when I try hg clone, it fails unless I change the GUID in the cloned directory (ie create new GUID in Visual Studio and then paste that new GUID to replace the old one). To me, this completely defeats the purpose and utility of quick easy clones. It also makes difficult all the many workflows that require multiple clones. Is there a workaround, or is there something I'm doing wrong? How can I simplify and/or remove this problem? Would Bazaar make this easier? Thank you!

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  • Sequential GUID in Linq-to-Sql?

    - by JacobE
    I just read a blog post about NHibernate's ability to create a GUID from the system time (Guid.Comb), thus avoiding a good amount of database fragmentation. You could call it the client-side equivalent to the SQL Server Sequential ID. Is there a way I could use a similar strategy in my Linq-to-Sql project (by generating the Guid in code)?

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  • GUID.TryParse() ?

    - by Jack Marchetti
    Obviously there is no public GUID.TryParse() in .NET CLR 2.0. So, I was looking into regular expressions [aka googling around to find one] and each time I found one there was a heated argument in the comments section about RegEx A doesn't work, use RegEx B. Then someone would write Regex C yadda yadda So anyway, What I decided to do was this, but I feel bad about it. public static bool IsGuid (string possibleGuid) { try { Guid gid = new Guid(possibleGuid); return true; } catch (Exception ex) { return false; } } Obviously I don't really like this since it's been drilled into me since day one to avoid throwing exceptions if you can defensibly code around it. Does anyonek now why there is no public Guid.TryParse() in the .NET Framework? Does anyone have a real Regular Expression that will work for all GUIDs?

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  • SQL Server 2008 GUID column is all 0's

    - by Andy Evans
    I'm hoping this is a simple goof I did on my end ... I have a table in my database set up like so: column name: widget_guid data type: uniqueidentifier allow nulls: false default value: newid() identity: false row guid: true When records are created (via LINQ to SQL) that the values in this field are formatted as a GUID but contain all 0's My assumption was that when a new record was created, that a guid would be autogenerated for that column, much like an auto-incrementing row id. Is this not true? Any help would be greatly appreciated. Thanks.

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  • Approach for altering Primary Key from GUID to BigInt in SQL Server related tables

    - by Tom
    I have two tables with 10-20 million rows that have GUID primary keys and at leat 12 tables related via foreign key. The base tables have 10-20 indexes each. We are moving from GUID to BigInt primary keys. I'm wondering if anyone has any suggestions on an approach. Right now this is the approach I'm pondering: Drop all indexes and fkeys on all the tables involved. Add 'NewPrimaryKey' column to each table Make the key identity on the two base tables Script the data change "update table x, set NewPrimaryKey = y where OldPrimaryKey = z Rename the original primarykey to 'oldprimarykey' Rename the 'NewPrimaryKey' column 'PrimaryKey' Script back all the indexes and fkeys Does this seem like a good approach? Does anyone know of a tool or script that would help with this? TD: Edited per additional information. See this blog post that addresses an approach when the GUID is the Primary: http://www.sqlmag.com/blogs/sql-server-questions-answered/sql-server-questions-answered/tabid/1977/entryid/12749/Default.aspx

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  • SQL 2008 GUID column is all 0's

    - by Andy Evans
    I'm hoping this is a simple goof I did on my end ... I have a table in my database set up like so: column name: widget_guid data type: uniqueidentifier allow nulls: false default value: newid() identity: false row guid: true When records are created (via LINQ to SQL) that the values in this field are formatted as a GUID but contain all 0's My assumption was that when a new record was created, that a guid would be autogenerated for that column, much like an auto-incrementing row id. Is this not true? Any help would be greatly appreciated. Thanks.

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  • simple proof that GUID is not unique

    - by Kai
    I'd like to prove that a GUID is not unique in a simple test program. I expected this to run for hours but it's not working. How can I make it work? BigInteger begin = new BigInteger((long)0); BigInteger end = new BigInteger("340282366920938463463374607431768211456",10); //2^128 for(begin; begin<end; begin++) Console.WriteLine(System.Guid.NewGuid().ToString()); I'm using C#

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  • Why GUID is returned as empty?

    - by jess
    Hi, After loading an entity from the database using LINQ-to_SQL,I pass the entity.ID to a method having argument of type GUID.When I access this parameter in the method,I get an empty value,and not the GUID.Why is it so?

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  • SQL GUID Vs Integer

    - by Dal
    Hi I have recently started a new job and noticed that all the SQL tables use the GUID data type for the primary key. In my previous job we used integers (Auto-Increment) for the primary key and it was a lot more easier to work with in my opinion. For example, say you had two related tables; Product and ProductType - I could easily cross check the 'ProductTypeID' column of both tables for a particular row to quickly map the data in my head because its easy to store the number (2,4,45 etc) as opposed to (E75B92A3-3299-4407-A913-C5CA196B3CAB). The extra frustration comes from me wanting to understand how the tables are related, sadly there is no Database diagram :( A lot of people say that GUID's are better because you can define the unique identifer in your C# code for example using NewID() without requiring SQL SERVER to do it - this also allows you to know provisionally what the ID will be.... but I've seen that it is possible to still retrieve the 'next auto-incremented integer' too. A DBA contractor reported that our queries could be up to 30% faster if we used the Integer type instead of GUIDS... Why does the GUID data type exist, what advantages does it really provide?... Even if its a choice by some professional there must be some good reasons as to why its implemented?

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  • Guid Primary /Foreign Key dilemma SQL Server

    - by Xience
    Hi guys, I am faced with the dilemma of changing my primary keys from int identities to Guid. I'll put my problem straight up. It's a typical Retail management app, with POS and back office functionality. Has about 100 tables. The database synchronizes with other databases and receives/ sends new data. Most tables don't have frequent inserts, updates or select statements executing on them. However, some do have frequent inserts and selects on them, eg. products and orders tables. Some tables have upto 4 foreign keys in them. If i changed my primary keys from 'int' to 'Guid', would there be a performance issue when inserting or querying data from tables that have many foreign keys. I know people have said that indexes will be fragmented and 16 bytes is an issue. Space wouldn't be an issue in my case and apparently index fragmentation can also be taken care of using 'NEWSEQUENTIALID()' function. Can someone tell me, from there experience, if Guid will be problematic in tables with many foreign keys. I'll be much appreciative of your thoughts on it...

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  • Guid Generation

    - by StuartBrierley
    If you need to create a guid you can obviously make use of the Microsoft GuidGen tool, but what if this tool is not available on the system you are using? I recently came across the online guid gen tool which may be able to come to your rescue:   To get a new guid pres the "Create New Guid" button and away you go!

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  • Generate GUID from any string using C#

    - by Haitham Khedre
    Some times you need to generate GUID from a string which is not valid for GUID constructor . so what we will do is to get a valid input from string that the GUID constructor will accept it. It is recommended to be sure that the string that you will generate a GUID from it some how unique. The Idea is simple is to convert the string to 16 byte Array which the GUID constructor will accept it. The code will talk : using System; using System.Text; namespace StringToGUID { class Program { static void Main(string[] args) { int tokenLength = 32; int guidByteSize = 16; string token = "BSNAItOawkSl07t77RKnMjYwYyG4bCt0g8DVDBv5m0"; byte[] b = new UTF8Encoding().GetBytes(token.Substring(token.Length - tokenLength, tokenLength).ToCharArray(), 0, guidByteSize); Guid g = new Guid(b); Console.WriteLine(g.ToString()); token = "BSNePf57YwhzeE9QfOyepPfIPao4UD5UohG_fI-#eda7d"; b = new UTF8Encoding().GetBytes(token.Substring(token.Length - tokenLength, tokenLength).ToCharArray(), 0, guidByteSize); g = new Guid(b); Console.WriteLine(g.ToString()); Console.Read(); } } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; }   And The output: 37306c53-3774-5237-4b6e-4d6a59775979 66513945-794f-7065-5066-4950616f3455

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  • Entity Framework - SaveChanges with GUID as EntityKey

    - by MissingLinq
    I have a SQL Server 2008 database table that uses uniqueidentifier as a primary key. On inserts, the key is generated on the database side using the newid() function. This works fine with ADO.NET. But when I set up this table as an entity in an Entity Framework 4 model, there's a problem. I am able to query the entity just fine, but when creating a new entity and invoking SaveChanges() on the context, the generated uniqueidentifier on the database is all zeros. I understand there was an issue with EF v1 where this scenario did not work, requiring creating the GUID on the client prior to calling SaveChanges. However, I had read in many places that they were planning to fix this in EF 4. My question -- is this scenario (DB-side generation of uniqueidentifier) still not supported in EF4? Are we still stuck with generating the GUID on the client?

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  • Failed to convert parameter value from a Guid to a String

    - by user320460
    Hello, I am at the end of my knowledge and googled for the answer too but no luck :/ Week ago everything worked well. I did a revert on the repository, recreated the tableadapter etc... nothing helped. When I try to save in my application I get an SystemInvalidCastException at this point: PersonListDataSet.cs: partial class P_GroupTableAdapter { public int Update(PersonListDataSet.P_GroupDataTable dataTable, string userId) { this.Adapter.InsertCommand.Parameters["@userId"].Value = userId; this.Adapter.DeleteCommand.Parameters["@userId"].Value = userId; this.Adapter.UpdateCommand.Parameters["@userId"].Value = userId; return this.Update(dataTable); **<-- Exception occurs here** } } Everything is stuck here because a Guid - and I checked the datatable preview with the magnifier tool its really a true Guid in the column of the datatable - can not be converted to a string ??? How can that happen?

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