Add Count() method with iterator-based scan for entry count

src/RocksDb.Extensions/IRocksDbAccessor.cs

@@ -21,6 +21,7 @@ public interface IRocksDbAccessor<TKey, TValue>
     IEnumerable<TValue> GetAll();
     bool HasKey(TKey key);
     void Clear();
+    int Count();
 }
 
 #pragma warning restore CS1591

src/RocksDb.Extensions/IRocksDbStore.cs

@@ -81,4 +81,17 @@ public abstract class RocksDbStore<TKey, TValue>
     /// can impact performance during execution. Use with caution in high-frequency workflows.
     /// </summary>
     public void Clear() => _rocksDbAccessor.Clear();
+
+    /// <summary>
+    /// Gets the number of key-value pairs currently stored.
+    /// </summary>
+    /// <remarks>
+    /// This method is <b>not</b> a constant-time operation. Internally, it iterates over all entries in the store
+    /// to compute the count. While the keys and values are not deserialized during iteration, this process may still
+    /// be expensive for large datasets.
+    ///
+    /// Use this method with caution in performance-critical paths, especially if the store contains a high number of entries.
+    /// </remarks>
+    /// <returns>The total count of items in the store.</returns>
+    public int Count() => _rocksDbAccessor.Count();
 }

src/RocksDb.Extensions/RocksDbAccessor.cs

@@ -309,6 +309,20 @@ public IEnumerable<TValue> GetAll()
             _ = iterator.Next();
         }
     }
+
+    public int Count()
+    {
+        using var iterator = _rocksDbContext.Db.NewIterator(_columnFamily.Handle);
+        _ = iterator.SeekToFirst();
+        var count = 0;
+        while (iterator.Valid())
+        {
+            count++;
+            _ = iterator.Next();
+        }
+
+        return count;
+    }
 
     public bool HasKey(TKey key)
     {

test/RocksDb.Extensions.Tests/ClearStoreTests.cs

@@ -7,7 +7,7 @@ namespace RocksDb.Extensions.Tests;
 public class ClearStoreTests
 {
     [Test]
-    public void should_reset_store_range_data_to_store()
+    public void should_clear_and_repopulate_store_data()
     {
         // Setup RocksDbStore
         using var testFixture = CreateTestFixture<int, string>();
@@ -27,6 +27,7 @@ public void should_reset_store_range_data_to_store()
             store.TryGet(key, out var value).ShouldBeTrue();
             value.ShouldBe(expectedValue);
         }
+        Assert.That(store.Count(), Is.EqualTo(100));
 
         // Clear the store
         store.Clear();
@@ -37,6 +38,7 @@ public void should_reset_store_range_data_to_store()
             store.HasKey(key).ShouldBeFalse();
             store.TryGet(key, out _).ShouldBeFalse();
         }
+        Assert.That(store.Count(), Is.EqualTo(0));
 
         // Try to put the data again
         store.PutRange(cacheKeys);
@@ -48,6 +50,7 @@ public void should_reset_store_range_data_to_store()
             store.TryGet(key, out var value).ShouldBeTrue();
             value.ShouldBe(expectedValue);
         }
+        Assert.That(store.Count(), Is.EqualTo(100));
     }
 
     private static TestFixture CreateTestFixture<TKey, TValue>()