ColumnsDb snapshot

src/Nethermind/Nethermind.Core.Test/TestMemColumnDb.cs

@@ -1,6 +1,7 @@
 // SPDX-FileCopyrightText: 2023 Demerzel Solutions Limited
 // SPDX-License-Identifier: LGPL-3.0-only
 
+using System;
 using System.Collections.Generic;
 using Nethermind.Db;
 
@@ -30,6 +31,12 @@ public IColumnsWriteBatch<TKey> StartWriteBatch()
     {
         return new InMemoryColumnWriteBatch<TKey>(this);
     }
+
+    public IColumnDbSnapshot<TKey> CreateSnapshot()
+    {
+        throw new NotSupportedException("Snapshot not implemented");
+    }
+
     public void Dispose() { }
     public void Flush(bool onlyWal = false) { }
 }

src/Nethermind/Nethermind.Db.Rocks/ColumnDb.cs

@@ -181,7 +181,7 @@ public void Compact()
     public void Clear() { throw new NotSupportedException(); }
 
     // Maybe it should be column specific metric?
-    public IDbMeta.DbMetric GatherMetric(bool includeSharedCache = false) => _mainDb.GatherMetric(includeSharedCache);
+    public IDbMeta.DbMetric GatherMetric() => _mainDb.GatherMetric();
 
     public byte[]? FirstKey
     {

src/Nethermind/Nethermind.Db.Rocks/ColumnsDb.cs

@@ -156,4 +156,37 @@ public void Merge(ReadOnlySpan<byte> key, ReadOnlySpan<byte> value, WriteFlags f
             _writeBatch._writeBatch.Merge(key, value, _column._columnFamily, flags);
         }
     }
+
+    IColumnDbSnapshot<T> IColumnsDb<T>.CreateSnapshot()
+    {
+        Snapshot snapshot = _db.CreateSnapshot();
+        return new ColumnDbSnapshot(this, snapshot);
+    }
+
+    private class ColumnDbSnapshot(
+        ColumnsDb<T> columnsDb,
+        Snapshot snapshot
+    ) : IColumnDbSnapshot<T>
+    {
+        private readonly Dictionary<T, IReadOnlyKeyValueStore> _columnDbs = columnsDb.ColumnKeys.ToDictionary(k => k, k =>
+            (IReadOnlyKeyValueStore)new RocksDbReader(
+                columnsDb,
+                () =>
+                {
+                    ReadOptions options = new ReadOptions();
+                    options.SetSnapshot(snapshot);
+                    return options;
+                },
+                columnFamily: columnsDb._columnDbs[k]._columnFamily));
+
+        public IReadOnlyKeyValueStore GetColumn(T key)
+        {
+            return _columnDbs[key];
+        }
+
+        public void Dispose()
+        {
+            snapshot.Dispose();
+        }
+    }
 }

src/Nethermind/Nethermind.Db.Rpc/RpcColumnsDb.cs

@@ -45,6 +45,12 @@ public IColumnsWriteBatch<T> StartWriteBatch()
         {
             return new InMemoryColumnWriteBatch<T>(this);
         }
+
+        public IColumnDbSnapshot<T> CreateSnapshot()
+        {
+            throw new NotSupportedException("Snapshot not implemented");
+        }
+
         public void Dispose() { }
         public void Flush(bool onlyWal = false) { }
     }

src/Nethermind/Nethermind.Db.Test/ColumnsDbTests.cs

@@ -107,4 +107,21 @@ public void TestWriteBatch_WriteToAllColumn()
         _db.GetColumnDb(ReceiptsColumns.Transactions).Get(TestItem.KeccakA).Should()
             .BeEquivalentTo(TestItem.KeccakB.BytesToArray());
     }
+
+    [Test]
+    public void SmokeTest_Snapshot()
+    {
+        IColumnsDb<ReceiptsColumns> asColumnsDb = _db;
+        IDb colA = _db.GetColumnDb(ReceiptsColumns.Blocks);
+
+        colA.Set(TestItem.KeccakA, TestItem.KeccakA.BytesToArray());
+
+        using IColumnDbSnapshot<ReceiptsColumns> snapshot = asColumnsDb.CreateSnapshot();
+
+        colA.Set(TestItem.KeccakA, TestItem.KeccakB.BytesToArray());
+        colA.Get(TestItem.KeccakA).Should().BeEquivalentTo(TestItem.KeccakB.BytesToArray());
+
+        snapshot.GetColumn(ReceiptsColumns.Blocks)
+            .Get(TestItem.KeccakA).Should().BeEquivalentTo(TestItem.KeccakA.BytesToArray());
+    }
 }

src/Nethermind/Nethermind.Db/IColumnsDb.cs

@@ -13,10 +13,17 @@ public interface IColumnsDb<TKey> : IDbMeta, IDisposable
         IEnumerable<TKey> ColumnKeys { get; }
         public IReadOnlyColumnDb<TKey> CreateReadOnly(bool createInMemWriteStore) => new ReadOnlyColumnsDb<TKey>(this, createInMemWriteStore);
         IColumnsWriteBatch<TKey> StartWriteBatch();
+        IColumnDbSnapshot<TKey> CreateSnapshot();
     }
 
     public interface IColumnsWriteBatch<in TKey> : IDisposable
     {
         IWriteBatch GetColumnBatch(TKey key);
     }
+
+
+    public interface IColumnDbSnapshot<in TKey> : IDisposable
+    {
+        IReadOnlyKeyValueStore GetColumn(TKey key);
+    }
 }

src/Nethermind/Nethermind.Db/MemColumnsDb.cs

@@ -3,6 +3,8 @@
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
+using Nethermind.Core;
 
 namespace Nethermind.Db
 {
@@ -38,6 +40,12 @@ public IColumnsWriteBatch<TKey> StartWriteBatch()
         {
             return new InMemoryColumnWriteBatch<TKey>(this);
         }
+
+        public IColumnDbSnapshot<TKey> CreateSnapshot()
+        {
+            throw new NotSupportedException("Snapshot not supported");
+        }
+
         public void Dispose() { }
         public void Flush(bool onlyWal = false) { }
     }

src/Nethermind/Nethermind.Db/ReadOnlyColumnsDb.cs

@@ -10,9 +10,11 @@ namespace Nethermind.Db
     public class ReadOnlyColumnsDb<T> : IReadOnlyColumnDb<T>, IDisposable
     {
         private readonly IDictionary<T, IReadOnlyDb> _readOnlyColumns;
+        private readonly IColumnsDb<T> _baseColumnDb;
 
         public ReadOnlyColumnsDb(IColumnsDb<T> baseColumnDb, bool createInMemWriteStore)
         {
+            _baseColumnDb = baseColumnDb;
             _readOnlyColumns = baseColumnDb.ColumnKeys
                 .Select(key => (key, db: baseColumnDb.GetColumnDb(key).CreateReadOnly(createInMemWriteStore)))
                 .ToDictionary(it => it.key, it => it.db);
@@ -29,6 +31,11 @@ public IColumnsWriteBatch<T> StartWriteBatch()
             return new InMemoryColumnWriteBatch<T>(this);
         }
 
+        public IColumnDbSnapshot<T> CreateSnapshot()
+        {
+            return _baseColumnDb.CreateSnapshot();
+        }
+
         public void ClearTempChanges()
         {
             foreach (KeyValuePair<T, IReadOnlyDb> readOnlyColumn in _readOnlyColumns)