有没有办法获得Sql Server 2005+ Sequential Guid生成器的功能而不插入记录来回读或调用本机win dll调用？我看到有人用rpcrt4.dll的方式回答，但我不确定这是否可以在我的托管环境中进行生产。
编辑：使用@John Boker的回答我尝试将其转换为更多的GuidComb生成器，而不是依赖于最后生成的Guid而不是重新开始。对于种子，而不是从我使用的Guid.Empty开始
public SequentialGuid()
{
var tempGuid = Guid.NewGuid();
var bytes = tempGuid.ToByteArray();
var time = DateTime.Now;
bytes[3] = (byte) time.Year;
bytes[2] = (byte) time.Month;
bytes[1] = (byte) time.Day;
bytes[0] = (byte) time.Hour;
bytes[5] = (byte) time.Minute;
bytes[4] = (byte) time.Second;
CurrentGuid = new Guid(bytes);
}
我基于
的评论// 3 - the least significant byte in Guid ByteArray
[for SQL Server ORDER BY clause]
// 10 - the most significant byte in Guid ByteArray
[for SQL Server ORDERY BY clause]
SqlOrderMap = new[] {3, 2, 1, 0, 5, 4, 7, 6, 9, 8, 15, 14, 13, 12, 11, 10};
这看起来像我想用DateTime为guid播种的方式，还是看起来我应该反过来并从SqlOrderMap索引的末尾开始向后工作？我不太关心他们是否会在创建初始guid时进行分页，因为它只会在应用程序回收期间发生。
答案 0 :(得分：67)
您可以使用相同的Win32 API function that SQL Server uses：
UuidCreateSequential
并应用一些位移以将值设置为big-endian顺序。
因为你想在C＃中使用它：
private class NativeMethods
{
[DllImport("rpcrt4.dll", SetLastError=true)]
public static extern int UuidCreateSequential(out Guid guid);
}
public static Guid NewSequentialID()
{
//Code is released into the public domain; no attribution required
const int RPC_S_OK = 0;
Guid guid;
int result = NativeMethods.UuidCreateSequential(out guid);
if (result != RPC_S_OK)
return Guid.NewGuid();
//Endian swap the UInt32, UInt16, and UInt16 into the big-endian order (RFC specified order) that SQL Server expects
//See https://stackoverflow.com/a/47682820/12597
//Short version: UuidCreateSequential writes out three numbers in litte, rather than big, endian order
var s = guid.ToByteArray();
var t = new byte[16];
//Endian swap UInt32
t[3] = s[0];
t[2] = s[1];
t[1] = s[2];
t[0] = s[3];
//Endian swap UInt16
t[5] = s[4];
t[4] = s[5];
//Endian swap UInt16
t[7] = s[6];
t[6] = s[7];
//The rest are already in the proper order
t[8] = s[8];
t[9] = s[9];
t[10] = s[10];
t[11] = s[11];
t[12] = s[12];
t[13] = s[13];
t[14] = s[14];
t[15] = s[15];
return new Guid(t);
}
另见
Microsoft的UuidCreateSequential只是来自RFC 4122的类型1 uuid的实现。
uuid有三个重要部分：
node：（6个字节） - 计算机的MAC地址timestamp：（7个字节） - 自1582年10月15日00：00：00.00（格里高利改革为基督教历法之日）以来的100 ns间隔数clockSequenceNumber（2个字节） - 计数器，以防你生成超过100ns的guid，或者你改变你的mac地址基本算法是：
node，timestamp和clockSequenceNumber node（即MAC地址）timestamp clockSequenceNumber timestamp与保存的时间戳相同或更旧，请递增clockSequenceNumber node，timestamp和clockSequenceNumber保存回持久存储空间还有一个4位版本号和2位变种，它们也需要与数据进行AND运算：
guid = new Guid(
timestamp & 0xFFFFFFFF, //timestamp low
(timestamp >> 32) & 0xFFFF, //timestamp mid
((timestamp >> 40) & 0x0FFF), | (1 << 12) //timestamp high and version (version 1)
(clockSequenceNumber & 0x3F) | (0x80), //clock sequence number and reserved
node[0], node[1], node[2], node[3], node[4], node[5], node[6]);
注意：完全未经测试;我只是从RFC中看到它。
- 可能必须更改字节顺序（Here is byte order for sql server）
- 您可能想要创建自己的版本，例如版本6（版本1-5定义）。这样你就可以保证是普遍独特的
答案 1 :(得分：22)
这个人提出了制作顺序guid的东西，这是一个链接
http://developmenttips.blogspot.com/2008/03/generate-sequential-guids-for-sql.html
相关代码：
public class SequentialGuid {
Guid _CurrentGuid;
public Guid CurrentGuid {
get {
return _CurrentGuid;
}
}
public SequentialGuid() {
_CurrentGuid = Guid.NewGuid();
}
public SequentialGuid(Guid previousGuid) {
_CurrentGuid = previousGuid;
}
public static SequentialGuid operator++(SequentialGuid sequentialGuid) {
byte[] bytes = sequentialGuid._CurrentGuid.ToByteArray();
for (int mapIndex = 0; mapIndex < 16; mapIndex++) {
int bytesIndex = SqlOrderMap[mapIndex];
bytes[bytesIndex]++;
if (bytes[bytesIndex] != 0) {
break; // No need to increment more significant bytes
}
}
sequentialGuid._CurrentGuid = new Guid(bytes);
return sequentialGuid;
}
private static int[] _SqlOrderMap = null;
private static int[] SqlOrderMap {
get {
if (_SqlOrderMap == null) {
_SqlOrderMap = new int[16] {
3, 2, 1, 0, 5, 4, 7, 6, 9, 8, 15, 14, 13, 12, 11, 10
};
// 3 - the least significant byte in Guid ByteArray [for SQL Server ORDER BY clause]
// 10 - the most significant byte in Guid ByteArray [for SQL Server ORDERY BY clause]
}
return _SqlOrderMap;
}
}
}
答案 2 :(得分：17)
Here是NHibernate实现Guid.Comb算法的方式：
private Guid GenerateComb()
{
byte[] guidArray = Guid.NewGuid().ToByteArray();
DateTime baseDate = new DateTime(1900, 1, 1);
DateTime now = DateTime.Now;
// Get the days and milliseconds which will be used to build the byte string
TimeSpan days = new TimeSpan(now.Ticks - baseDate.Ticks);
TimeSpan msecs = now.TimeOfDay;
// Convert to a byte array
// Note that SQL Server is accurate to 1/300th of a millisecond so we divide by 3.333333
byte[] daysArray = BitConverter.GetBytes(days.Days);
byte[] msecsArray = BitConverter.GetBytes((long) (msecs.TotalMilliseconds / 3.333333));
// Reverse the bytes to match SQL Servers ordering
Array.Reverse(daysArray);
Array.Reverse(msecsArray);
// Copy the bytes into the guid
Array.Copy(daysArray, daysArray.Length - 2, guidArray, guidArray.Length - 6, 2);
Array.Copy(msecsArray, msecsArray.Length - 4, guidArray, guidArray.Length - 4, 4);
return new Guid(guidArray);
}
答案 3 :(得分：7)
可以找到经常更新（每毫秒至少3次）的顺序guid here。它是使用常规C＃代码创建的（没有本机代码调用）。
答案 4 :(得分：4)
与其他建议比较可能很有趣：
EntityFramework Core还实现了sequentialGuidValueGenerator。 它们为每个值生成randoms guids，并且仅根据时间戳和线程安全增量更改最重要的字节，以便在SQL Server中进行排序。
这会导致值非常不同，但时间戳可排序。
答案 5 :(得分：3)
我的解决方案（在VB中但很容易转换）。它将最重要的（对于SQL Server排序）GUID的前8个字节更改为DateTime.UtcNow.Ticks，并且还有额外的代码来帮助解决多次获取相同的Ticks的问题，如果您比系统更快地调用新的GUID时钟更新。
Private ReadOnly _toSeqGuidLock As New Object()
''' <summary>
''' Replaces the most significant eight bytes of the GUID (according to SQL Server ordering) with the current UTC-timestamp.
''' </summary>
''' <remarks>Thread-Safe</remarks>
<System.Runtime.CompilerServices.Extension()> _
Public Function ToSeqGuid(ByVal guid As Guid) As Guid
Static lastTicks As Int64 = -1
Dim ticks = DateTime.UtcNow.Ticks
SyncLock _toSeqGuidLock
If ticks <= lastTicks Then
ticks = lastTicks + 1
End If
lastTicks = ticks
End SyncLock
Dim ticksBytes = BitConverter.GetBytes(ticks)
Array.Reverse(ticksBytes)
Dim guidBytes = guid.ToByteArray()
Array.Copy(ticksBytes, 0, guidBytes, 10, 6)
Array.Copy(ticksBytes, 6, guidBytes, 8, 2)
Return New Guid(guidBytes)
End Function
答案 6 :(得分：3)
C＃版本
public static Guid ToSeqGuid()
{
Int64 lastTicks = -1;
long ticks = System.DateTime.UtcNow.Ticks;
if (ticks <= lastTicks)
{
ticks = lastTicks + 1;
}
lastTicks = ticks;
byte[] ticksBytes = BitConverter.GetBytes(ticks);
Array.Reverse(ticksBytes);
Guid myGuid = new Guid();
byte[] guidBytes = myGuid.ToByteArray();
Array.Copy(ticksBytes, 0, guidBytes, 10, 6);
Array.Copy(ticksBytes, 6, guidBytes, 8, 2);
Guid newGuid = new Guid(guidBytes);
string filepath = @"C:\temp\TheNewGuids.txt";
using (StreamWriter writer = new StreamWriter(filepath, true))
{
writer.WriteLine("GUID Created = " + newGuid.ToString());
}
return newGuid;
}
}
}
答案 7 :(得分：3)
我刚刚tf.constant()取了the NHibernate based answer并将其作为扩展函数：
using System;
namespace Atlas.Core.Kernel.Extensions
{
public static class Guids
{
public static Guid Comb(this Guid source)
{
byte[] guidArray = source.ToByteArray();
DateTime baseDate = new DateTime(1900, 1, 1);
DateTime now = DateTime.Now;
// Get the days and milliseconds which will be used to build the byte string
TimeSpan days = new TimeSpan(now.Ticks - baseDate.Ticks);
TimeSpan msecs = now.TimeOfDay;
// Convert to a byte array
// Note that SQL Server is accurate to 1/300th of a millisecond so we divide by 3.333333
byte[] daysArray = BitConverter.GetBytes(days.Days);
byte[] msecsArray = BitConverter.GetBytes((long)(msecs.TotalMilliseconds / 3.333333));
// Reverse the bytes to match SQL Servers ordering
Array.Reverse(daysArray);
Array.Reverse(msecsArray);
// Copy the bytes into the guid
Array.Copy(daysArray, daysArray.Length - 2, guidArray, guidArray.Length - 6, 2);
Array.Copy(msecsArray, msecsArray.Length - 4, guidArray, guidArray.Length - 4, 4);
return new Guid(guidArray);
}
}
}
答案 8 :(得分：2)
据我所知，NHibernate有一个名为GuidCombGenerator的特殊生成器。你可以看一下。
答案 9 :(得分：2)
不是特别guid，但我现在通常使用Snowflake风格的顺序id生成器。 guid具有相同的优点，同时具有比顺序guid更好的聚簇索引兼容性。
答案 10 :(得分：2)
我刚看到这个问题......我碰巧是一个用于生成COMB风格GUID的小型开源.NET库的作者。
该库支持原始方法（与SQL Server＆＃39; s datetime类型兼容）和使用Unix时间戳的方法，后者具有更高的时间精度。它还包括一个适用于PostgrSQL的变体：