Caching improvements

Author: surgicalcoder

LiteDBX.Tests/Internals/CacheTrim_Tests.cs

@@ -0,0 +1,112 @@
+using System;
+using FluentAssertions;
+using LiteDbX.Engine;
+using Xunit;
+
+namespace LiteDbX.Internals;
+
+public class CacheTrim_Tests
+{
+    [Fact]
+    public void Discarded_Page_Tracks_TimestampFree_And_Clears_It_On_Reuse()
+    {
+        var cache = CreateTrimEnabledCache();
+        var page = cache.NewPage();
+
+        page.TimestampFree.Should().BeNull();
+
+        cache.DiscardPage(page);
+
+        page.TimestampFree.Should().NotBeNull();
+
+        var reused = cache.NewPage();
+
+        reused.TimestampFree.Should().BeNull();
+
+        cache.DiscardPage(reused);
+    }
+
+    [Fact]
+    public void Cache_Trim_Retires_A_Fully_Free_Idle_Segment()
+    {
+        var cache = CreateTrimEnabledCache();
+        var first = cache.NewPage();
+        var second = cache.NewPage();
+
+        cache.DiscardPage(first);
+        cache.DiscardPage(second);
+
+        cache.ActiveSegments.Should().Be(1);
+        cache.RetiredSegments.Should().Be(0);
+        cache.FreePages.Should().Be(2);
+
+        var reused = cache.NewPage();
+
+        cache.RetiredSegments.Should().Be(1);
+        cache.ActiveSegments.Should().Be(1);
+        cache.FreePages.Should().Be(1);
+        reused.SegmentId.Should().NotBe(0);
+
+        cache.DiscardPage(reused);
+    }
+
+    [Fact]
+    public void Cache_Trim_Does_Not_Retire_Segment_When_A_Writable_Sibling_Is_Still_In_Use()
+    {
+        var cache = CreateTrimEnabledCache();
+        var first = cache.NewPage();
+        var second = cache.NewPage();
+
+        cache.DiscardPage(first);
+
+        var reused = cache.NewPage();
+
+        cache.RetiredSegments.Should().Be(0);
+        cache.ActiveSegments.Should().Be(1);
+        reused.UniqueID.Should().Be(first.UniqueID);
+
+        cache.DiscardPage(reused);
+        cache.DiscardPage(second);
+    }
+
+    [Fact]
+    public void Cache_Trim_Does_Not_Retire_Segment_When_A_Readable_Sibling_Is_Still_Cached()
+    {
+        var cache = CreateTrimEnabledCache();
+        var readableSource = cache.NewPage();
+        var writableSibling = cache.NewPage();
+
+        readableSource.Origin = FileOrigin.Log;
+        readableSource.Position = 0;
+        cache.TryMoveToReadable(readableSource).Should().BeTrue();
+
+        cache.DiscardPage(writableSibling);
+
+        var reused = cache.NewPage();
+
+        cache.RetiredSegments.Should().Be(0);
+        cache.ActiveSegments.Should().Be(1);
+        reused.UniqueID.Should().Be(writableSibling.UniqueID);
+
+        var readable = cache.GetReadablePage(0, FileOrigin.Log, (_, _) => { });
+        readable.UniqueID.Should().Be(readableSource.UniqueID);
+        readable.Release();
+
+        cache.DiscardPage(reused);
+    }
+
+    private static MemoryCache CreateTrimEnabledCache(int segmentSize = 2)
+    {
+        return new MemoryCache(
+            new[] { segmentSize },
+            new MemoryCacheConfig
+            {
+                Enabled = true,
+                MaxFreePages = 0,
+                MaxIdleTime = TimeSpan.Zero,
+                CleanupInterval = TimeSpan.Zero,
+                BatchSize = 10
+            });
+    }
+}
+

LiteDBX/Engine/Disk/DiskService.cs

@@ -50,7 +50,7 @@ public DiskService(
         EngineState state,
         int[] memorySegmentSizes)
     {
-        Cache = new MemoryCache(memorySegmentSizes);
+        Cache = new MemoryCache(memorySegmentSizes, settings.MemoryCacheConfig);
         _state = state;
 
         _dataFactory = settings.CreateDataFactory();