Sequential GUIDs

src/Pomelo.EntityFrameworkCore.MySql/ValueGeneration/Internal/MySqlSequentialGuidValueGenerator.cs

@@ -0,0 +1,68 @@
+using System;
+using System.Security.Cryptography;
+using Microsoft.EntityFrameworkCore.ChangeTracking;
+using Microsoft.EntityFrameworkCore.Storage.Internal;
+
+// ReSharper disable once CheckNamespace
+namespace Microsoft.EntityFrameworkCore.ValueGeneration.Internal
+{
+ public class MySqlSequentialGuidValueGenerator : ValueGenerator<Guid>
+ {
+
+ private readonly MySqlScopedTypeMapper _mySqlTypeMapper;
+
+ public MySqlSequentialGuidValueGenerator(MySqlScopedTypeMapper mySqlTypeMapper)
+ {
+ _mySqlTypeMapper = mySqlTypeMapper;
+ }
+
+ private static readonly RandomNumberGenerator Rng = RandomNumberGenerator.Create();
+
+ /// <summary>
+ /// Gets a value to be assigned to a property.
+ /// Creates a GUID where the first 8 bytes are the current UTC date/time (in ticks)
+ /// and the last 8 bytes are cryptographically random. This allows for better performance
+ /// in clustered index scenarios.
+ /// </summary>
+ /// <para>The change tracking entry of the entity for which the value is being generated.</para>
+ /// <returns> The value to be assigned to a property. </returns>
+ public override Guid Next(EntityEntry entry)
+ {
+ var randomBytes = new byte[8];
+ Rng.GetBytes(randomBytes);
+ var ticks = (ulong) DateTime.UtcNow.Ticks;
+
+ if (_mySqlTypeMapper.ConnectionSettings.OldGuids)
+ {
+ var guidBytes = new byte[16];
+ var tickBytes = BitConverter.GetBytes(ticks);
+ if (BitConverter.IsLittleEndian)
+ Array.Reverse(tickBytes);
+
+ Buffer.BlockCopy(tickBytes, 0, guidBytes, 0, 8);
+ Buffer.BlockCopy(randomBytes, 0, guidBytes, 8, 8);
+
+ return new Guid(guidBytes);
+ }
+
+ var guid = new Guid((uint) (ticks >> 32), (ushort) (ticks << 32 >> 48), (ushort) (ticks << 48 >> 48),
+ randomBytes[0],
+ randomBytes[1],
+ randomBytes[2],
+ randomBytes[3],
+ randomBytes[4],
+ randomBytes[5],
+ randomBytes[6],
+ randomBytes[7]);
+
+ return guid;
+ }
+
+ /// <summary>
+ /// Gets a value indicating whether the values generated are temporary or permanent. This implementation
+ /// always returns false, meaning the generated values will be saved to the database.
+ /// </summary>
+ public override bool GeneratesTemporaryValues => false;
+
+ }
+}

src/Pomelo.EntityFrameworkCore.MySql/ValueGeneration/Internal/MySqlValueGeneratorSelector.cs

@@ -1,18 +1,24 @@
 using System;
 using JetBrains.Annotations;
 using Microsoft.EntityFrameworkCore.Metadata;
+using Microsoft.EntityFrameworkCore.Storage;
+using Microsoft.EntityFrameworkCore.Storage.Internal;
 using Microsoft.EntityFrameworkCore.Utilities;
 
 // ReSharper disable once CheckNamespace
 namespace Microsoft.EntityFrameworkCore.ValueGeneration.Internal
 {
  public class MySqlValueGeneratorSelector : RelationalValueGeneratorSelector
  {
+ private readonly MySqlScopedTypeMapper _mySqlTypeMapper;
+
  public MySqlValueGeneratorSelector(
  [NotNull] IValueGeneratorCache cache,
- [NotNull] IRelationalAnnotationProvider relationalExtensions)
+ [NotNull] IRelationalAnnotationProvider relationalExtensions,
+ [NotNull] IRelationalTypeMapper typeMapper)
  : base(cache, relationalExtensions)
  {
+ _mySqlTypeMapper = typeMapper as MySqlScopedTypeMapper;
  }
 
  public override ValueGenerator Create(IProperty property, IEntityType entityType)
@@ -24,9 +30,9 @@ public override ValueGenerator Create(IProperty property, IEntityType entityType
  ? property.ValueGenerated == ValueGenerated.Never
  || property.MySql().DefaultValueSql != null
  ? (ValueGenerator)new TemporaryGuidValueGenerator()
- : new SequentialGuidValueGenerator()
+ : new MySqlSequentialGuidValueGenerator(_mySqlTypeMapper)
  : base.Create(property, entityType);
  return ret;
  }
  }
-}
+}

test/Pomelo.EntityFrameworkCore.MySql.PerfTests/Models/GeneratedTypes.cs

@@ -45,7 +45,7 @@ public static void OnModelCreating(ModelBuilder modelBuilder)
 
  public class GeneratedContact
  {
-  public int Id { get; set; }
+  public Guid Id { get; set; }
 
  public string Name { get; set; }
 

test/Pomelo.EntityFrameworkCore.MySql.PerfTests/Tests/Models/GeneratedTypesTest.cs

@@ -1,7 +1,9 @@
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Threading.Tasks;
 using Microsoft.EntityFrameworkCore;
+using MySql.Data.MySqlClient;
 using Pomelo.EntityFrameworkCore.MySql.PerfTests.Models;
 using Xunit;
 
@@ -19,14 +21,22 @@ public async Task TestGeneratedContact()
  const string zip = "99999";
  var addressFormatted = string.Join(", ", address, city, state, zip);
 
-  Action<GeneratedContact> testContact = contact =>
+  using (var db = new AppDb())
  {
- Assert.Equal(email, contact.Email);
- Assert.Equal(addressFormatted, contact.Address);
- };
+ void TestContact(GeneratedContact contact)
+ {
+ var csb = new MySqlConnectionStringBuilder(db.Database.GetDbConnection().ConnectionString);
+ var guidHexStr = csb.OldGuids
+ ? BitConverter.ToString(contact.Id.ToByteArray().Take(8).ToArray()).Replace("-", "")
+ : contact.Id.ToString().Replace("-", "").Substring(0, 16);
+ var guidTicks = Convert.ToInt64("0x" + guidHexStr, 16);
+ var guidDateTime = new DateTime(guidTicks);
+
+ Assert.InRange(guidDateTime - DateTime.UtcNow, TimeSpan.FromSeconds(-5), TimeSpan.FromSeconds(5));
+ Assert.Equal(email, contact.Email);
+ Assert.Equal(addressFormatted, contact.Address);
+ }
 
- using (var db = new AppDb())
- {
  var gen = new GeneratedContact
  {
  Names = new JsonObject<List<string>>(new List<string> {"Bob", "Bobby"}),
@@ -43,11 +53,11 @@ public async Task TestGeneratedContact()
  // test the entity after saving to the db
  db.GeneratedContacts.Add(gen);
  await db.SaveChangesAsync();
- testContact(gen);
+ TestContact(gen);
 
  // test the entity after fresh retreival from the database
  var genDb = await db.GeneratedContacts.FirstOrDefaultAsync(m => m.Id == gen.Id);
- testContact(genDb);
+ TestContact(genDb);
  }
  }