From 126799d807d5b1454d0c2d72f5fb92f79fabc67f Mon Sep 17 00:00:00 2001
From: Shay Rojansky <roji@roji.org>
Date: Sat, 15 Feb 2025 00:20:32 +0200
Subject: [PATCH] Generate UUIDv7 values for value-generated strings

Fixes #3460
---
 .../Internal/NpgsqlValueGeneratorSelector.cs  | 15 ++++++++-----
 .../NpgsqlSequentialStringValueGenerator.cs   | 22 +++++++++++++++++++
 .../NpgsqlValueGeneratorSelectorTest.cs       |  4 ++--
 3 files changed, 34 insertions(+), 7 deletions(-)
 create mode 100644 src/EFCore.PG/ValueGeneration/NpgsqlSequentialStringValueGenerator.cs

diff --git a/src/EFCore.PG/ValueGeneration/Internal/NpgsqlValueGeneratorSelector.cs b/src/EFCore.PG/ValueGeneration/Internal/NpgsqlValueGeneratorSelector.cs
index a9274f617..808532b42 100644
--- a/src/EFCore.PG/ValueGeneration/Internal/NpgsqlValueGeneratorSelector.cs
+++ b/src/EFCore.PG/ValueGeneration/Internal/NpgsqlValueGeneratorSelector.cs
@@ -101,9 +101,14 @@ public override bool TrySelect(IProperty property, ITypeBase typeBase, out Value
     ///     doing so can result in application failures when updating to a new Entity Framework Core release.
     /// </summary>
     protected override ValueGenerator? FindForType(IProperty property, ITypeBase typeBase, Type clrType)
-        => property.ClrType.UnwrapNullableType() == typeof(Guid)
-            ? property.ValueGenerated == ValueGenerated.Never || property.GetDefaultValueSql() is not null
-                ? new TemporaryGuidValueGenerator()
-                : new NpgsqlSequentialGuidValueGenerator()
-            : base.FindForType(property, typeBase, clrType);
+        => property.ClrType.UnwrapNullableType() switch
+        {
+            var t when t == typeof(Guid) && property.ValueGenerated is not ValueGenerated.Never && property.GetDefaultValueSql() is null
+                => new NpgsqlSequentialGuidValueGenerator(),
+
+            var t when t == typeof(string) && property.ValueGenerated is not ValueGenerated.Never && property.GetDefaultValueSql() is null
+                => new NpgsqlSequentialStringValueGenerator(),
+
+            _ => base.FindForType(property, typeBase, clrType)
+        };
 }
diff --git a/src/EFCore.PG/ValueGeneration/NpgsqlSequentialStringValueGenerator.cs b/src/EFCore.PG/ValueGeneration/NpgsqlSequentialStringValueGenerator.cs
new file mode 100644
index 000000000..8c4f595dc
--- /dev/null
+++ b/src/EFCore.PG/ValueGeneration/NpgsqlSequentialStringValueGenerator.cs
@@ -0,0 +1,22 @@
+namespace Npgsql.EntityFrameworkCore.PostgreSQL.ValueGeneration;
+
+/// <summary>
+///     This API supports the Entity Framework Core infrastructure and is not intended to be used
+///     directly from your code. This API may change or be removed in future releases.
+/// </summary>
+public class NpgsqlSequentialStringValueGenerator : ValueGenerator<string>
+{
+    private readonly NpgsqlSequentialGuidValueGenerator _guidGenerator = new();
+
+    /// <summary>
+    ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
+    ///     directly from your code. This API may change or be removed in future releases.
+    /// </summary>
+    public override bool GeneratesTemporaryValues => false;
+
+    /// <summary>
+    ///     This API supports the Entity Framework Core infrastructure and is not intended to be used
+    ///     directly from your code. This API may change or be removed in future releases.
+    /// </summary>
+    public override string Next(EntityEntry entry) => _guidGenerator.Next(entry).ToString();
+}
diff --git a/test/EFCore.PG.Tests/NpgsqlValueGeneratorSelectorTest.cs b/test/EFCore.PG.Tests/NpgsqlValueGeneratorSelectorTest.cs
index 57b0d1b9a..9b6b3ae42 100644
--- a/test/EFCore.PG.Tests/NpgsqlValueGeneratorSelectorTest.cs
+++ b/test/EFCore.PG.Tests/NpgsqlValueGeneratorSelectorTest.cs
@@ -21,7 +21,7 @@ public void Returns_built_in_generators_for_types_setup_for_value_generation()
         AssertGenerator<TemporaryShortValueGenerator>("NullableShort");
         AssertGenerator<TemporaryByteValueGenerator>("NullableByte");
         AssertGenerator<TemporaryDecimalValueGenerator>("Decimal");
-        AssertGenerator<StringValueGenerator>("String");
+        AssertGenerator<NpgsqlSequentialStringValueGenerator>("String");
         AssertGenerator<NpgsqlSequentialGuidValueGenerator>("Guid");
         AssertGenerator<BinaryValueGenerator>("Binary");
     }
@@ -128,7 +128,7 @@ public void Returns_sequence_value_generators_when_configured_for_model()
         AssertGenerator<NpgsqlSequenceHiLoValueGenerator<int>>("NullableInt", setSequences: true);
         AssertGenerator<NpgsqlSequenceHiLoValueGenerator<long>>("NullableLong", setSequences: true);
         AssertGenerator<NpgsqlSequenceHiLoValueGenerator<short>>("NullableShort", setSequences: true);
-        AssertGenerator<StringValueGenerator>("String", setSequences: true);
+        AssertGenerator<NpgsqlSequentialStringValueGenerator>("String", setSequences: true);
         AssertGenerator<NpgsqlSequentialGuidValueGenerator>("Guid", setSequences: true);
         AssertGenerator<BinaryValueGenerator>("Binary", setSequences: true);
     }