Add a bunch of fixes around empty transactions (that broke the UI). N…

…ow we no longer advance the TxId if no datoms were inserted as part of the tx.

Also includes some read benchmarks I was working on

benchmarks/NexusMods.MnemonicDB.Benchmarks/Benchmarks/ColdStartBenchmarks.cs

@@ -0,0 +1,98 @@
+using System.Linq;
+using System.Threading.Tasks;
+using BenchmarkDotNet.Attributes;
+using NexusMods.MnemonicDB.Abstractions;
+using NexusMods.MnemonicDB.Abstractions.ElementComparers;
+using NexusMods.MnemonicDB.Abstractions.IndexSegments;
+using NexusMods.MnemonicDB.TestModel;
+using NexusMods.Paths;
+
+namespace NexusMods.MnemonicDB.Benchmarks.Benchmarks;
+
+[MemoryDiagnoser]
+public class ColdStartBenchmarks : ABenchmark
+{
+    [GlobalSetup]
+    public async ValueTask GlobalSetup()
+    {
+        await InitializeAsync();
+        await InsertData();
+    }
+
+    private async Task InsertData()
+    {
+        foreach (var loadout in Enumerable.Range(0, 10))
+        {
+            using var tx = Connection.BeginTransaction();
+            var loadoutEntity = new Loadout.New(tx)
+            {
+                Name = $"Loadout {loadout}"
+            };
+            foreach (var mod in Enumerable.Range(0, 1000))
+            {
+                var modEntity = new Mod.New(tx)
+                {
+                    Name = $"Mod {mod}",
+                    Source = new System.Uri($"http://mod{mod}.com"),
+                    LoadoutId = loadoutEntity,
+                    OptionalHash = Hashing.xxHash3.Hash.FromLong(0)
+                };
+                foreach (var file in Enumerable.Range(0, 100))
+                {
+                    _ = new File.New(tx)
+                    {
+                        Path = $"File {file}",
+                        ModId = modEntity,
+                        Size = Size.FromLong(file),
+                        Hash = Hashing.xxHash3.Hash.FromLong(file)
+                    };
+                }
+            }
+            await tx.Commit();
+        }
+    }
+
+    [IterationSetup]
+    public void IterationSetup()
+    {
+        Connection.Db.ClearIndexCache();
+    }
+
+    [Benchmark]
+    public Size TotalSizeEAVT()
+    {
+        var loadout = Loadout.FindByName(Connection.Db, "Loadout 5").First();
+        var totalSize = Size.FromLong(0);
+
+        foreach (var mod in loadout.Mods)
+        {
+            foreach (var file in mod.Files)
+            {
+                totalSize += file.Size;
+            }
+        }
+
+        return totalSize;
+    }
+
+
+    [Benchmark]
+    public Size TotalSizeAEVT()
+    {
+        var loadoutId = Connection.Db.Datoms(Loadout.Name, "Loadout 5").First();
+        var modIds = Connection.Db.Datoms(Mod.LoadoutId, loadoutId.E).Select(e => e.E).ToHashSet();
+        var fileIds = Connection.Db.Datoms(File.ModId).ToLookup(d => ValueTag.Reference.Read<EntityId>(d.ValueSpan), d => d.E);
+        var fileSizes = Connection.Db.Datoms(File.Size)
+            .ToDictionary(d => d.E, d => Size.From(ValueTag.UInt64.Read<ulong>(d.ValueSpan)));
+
+        var totalSize = Size.FromLong(0);
+        foreach (var modId in modIds)
+        {
+            foreach (var fileId in fileIds[modId])
+            {
+                totalSize += fileSizes[fileId];
+            }
+        }
+        return totalSize;
+    }
+}

benchmarks/NexusMods.MnemonicDB.Benchmarks/Program.cs

@@ -29,7 +29,7 @@
 
 #else
 
-BenchmarkRunner.Run<ReadThenWriteBenchmarks>(config: DefaultConfig.Instance.WithOption(ConfigOptions.DisableOptimizationsValidator, true));
+BenchmarkRunner.Run<ColdStartBenchmarks>();
 #endif
 
 

src/NexusMods.MnemonicDB.Abstractions/IDb.cs

@@ -85,4 +85,9 @@ public interface IDb : IEquatable<IDb>
     /// </summary>
     TReturn AnalyzerData<TAnalyzer, TReturn>() 
         where TAnalyzer : IAnalyzer<TReturn>;
+
+    /// <summary>
+    /// Clears the internal cache of the database.
+    /// </summary>
+    void ClearIndexCache();
 }

src/NexusMods.MnemonicDB/Caching/IndexSegmentCache.cs

@@ -283,5 +283,12 @@ private void UpdateEntry(CacheKey key, IndexSegment segment)
                 return;
         }
     }
-
+
+    /// <summary>
+    /// Clears the cache.
+    /// </summary>
+    public void Clear()
+    {
+        _root = new CacheRoot(ImmutableDictionary<CacheKey, CacheValue>.Empty);
+    }
 }

src/NexusMods.MnemonicDB/Db.cs

@@ -114,6 +114,11 @@ TReturn IDb.AnalyzerData<TAnalyzer, TReturn>()
         throw new KeyNotFoundException($"Analyzer {typeof(TAnalyzer).Name} not found");
     }
 
+    public void ClearIndexCache()
+    {
+        _cache.Clear();
+    }
+
     public IndexSegment Datoms<TValue>(IWritableAttribute<TValue> attribute, TValue value)
     {
         return Datoms(SliceDescriptor.Create(attribute, value, AttributeCache));

src/NexusMods.MnemonicDB/Storage/DatomStore.cs

@@ -103,7 +103,8 @@ public DatomStore(
 
         Backend.Init(settings.Path);
 
-        if (bootstrap) Bootstrap();
+        if (bootstrap) 
+            Bootstrap();
     }
 
     /// <inheritdoc />
@@ -308,7 +309,7 @@ private StoreResult Log(IInternalTxFunctionImpl pendingTransaction)
 
         return new StoreResult
         {
-            AssignedTxId = _thisTx,
+            AssignedTxId = _asOfTx,
             Remaps = _remaps.ToFrozenDictionary(),
             Snapshot = CurrentSnapshot
         };

tests/NexusMods.MnemonicDB.Tests/ComplexModelTests.cs

@@ -173,7 +173,15 @@ public async Task CanRestartStorage(int modCount, int filesPerMod, int extraFile
         await extraTx.Commit();
 
         Logger.LogInformation("Restarting storage");
+        Connection.Db.RecentlyAdded.Should().NotBeEmpty("the last transaction added data");
+
+        var lastTxId = Connection.TxId;
         await RestartDatomStore();
+
+        Connection.TxId.Should().Be(lastTxId, "the transaction id should be the same after a restart");
+        Connection.Db.BasisTxId.Should().Be(lastTxId, "the basis transaction id should be the same after a restart");
+
+        Connection.Db.RecentlyAdded.Should().NotBeEmpty("the restarted database should populate the recently added");
         Logger.LogInformation("Storage restarted");