guid

Why are UUID's presented in the format "8-4-4-4-12" (digits)? I've had a look around for the reason but can't find the decision that calls for it. Example of UUID formatted as hex string: 58D5E212-165B-4CA0-909B-C86B9CEE0111 It's separated by time, version, clock_seq_hi, clock_seq_lo, node , as indicated in the followoing rfc. From the IETF RFC4122: 4.1.2. Layout and Byte Order To minimize confusion about bit assignments within octets, the UUID record definition is defined only in terms of fields that are integral numbers of octets. The fields are presented with the most significant one first.

I've just imported a bunch of data to a MySQL table and I have a column "GUID" that I want to basically fill down all existing rows with new and unique random GUID's. How do I do this in MySQL ? I tried UPDATE db.tablename SET columnID = UUID() where columnID is not null And just get every field the same I'm not sure if it's the easiest way, but it works. The idea is to create a trigger that does all work for you, then, to execute a query that updates your table, and finally to drop this trigger: delimiter // create trigger beforeYourTableUpdate BEFORE UPDATE on YourTable FOR EACH ROW BEGIN

I'm assigning all my MongoDB documents a GUID using uuid.uuid1(). I want a way I can derive an 11 character, unique, case-sensitive YouTube-like ID, such as 1_XmY09uRJ4 from uuid's resulting hex string which looks like ae0a0c98-f1e5-11e1-9t2b-1231381dac60 I want to be able to match the shortened ID to the hex and vice-versa, dynamically without having to store another string in the database. Does anyone have some sample code or can point me in the direction of the module or formula that can do this? Convert the underlying bytes to a base64 value, stripping the = padding and the newline. You

I have a big dictionary where the key is decimal, but the GetHashCode() of System.Decimal is disasterously bad. To prove my guess, I ran a for loop with 100.000 neigboring decimals and checked the distribution. 100.000 different decimal numbers used only 2 (two!!!) different hashcodes. Decimal is represented as 16 bytes. Just like Guid! But the GetHashCode() distribution of Guid is pretty good. How can I convert a decimal to Guid in C# as cheap as possible? Unsafe code is OK! EDIT: The test was requested, so here is the code: decimal d = 96000000000000000000m; Dictionary<int, int> hashcount =

Are the automatically generated GUIDs for C# Types consistent? For example, if I get a GUID for my interface, IFoo ( typeof(IFoo).GUID ), the first time a run the program, will I get that same GUID everytime I run the program? I have tested it locally on my machine, and it seems to always be the same, but I'm not sure if I can rely on it always being the same across machines. See: System.Type.GUID stability . It appears that the current implementation of the method relies an internal call that is implemented by the CLR itself. Unless Microsoft clarifies the contracts for the auto-generated