Non-transactional upsert method cannot return upsert status.

src/ZoneTree/Core/ZoneTree.cs

@@ -182,7 +182,8 @@ public sealed class ZoneTree<TKey, TValue> : IZoneTree<TKey, TValue>, IZoneTreeM
         {
             if (ContainsKey(key))
                 return false;
-            return Upsert(key, value);
+            Upsert(key, value);
+            return true;
         }
     }
 
@@ -194,7 +195,8 @@ public sealed class ZoneTree<TKey, TValue> : IZoneTree<TKey, TValue>, IZoneTreeM
         {
             if (!ContainsKey(key))
                 return false;
-            return Upsert(key, value);
+            Upsert(key, value);
+            return true;
         }
     }
 
@@ -241,15 +243,15 @@ public sealed class ZoneTree<TKey, TValue> : IZoneTree<TKey, TValue>, IZoneTreeM
         }
     }
 
-    public bool AtomicUpsert(in TKey key, in TValue value)
+    public void AtomicUpsert(in TKey key, in TValue value)
     {
         lock (AtomicUpdateLock)
         {
-            return Upsert(in key, in value);
+            Upsert(in key, in value);
         }
     }
 
-    public bool Upsert(in TKey key, in TValue value)
+    public void Upsert(in TKey key, in TValue value)
     {
         if (key == null)
             throw new ArgumentNullException(nameof(key));
@@ -265,7 +267,7 @@ public sealed class ZoneTree<TKey, TValue> : IZoneTree<TKey, TValue>, IZoneTreeM
                     MoveSegmentZeroForward(segmentZero);
                     continue;
                 default:
-                    return status == AddOrUpdateResult.ADDED;
+                    return;
             }
         }
     }
@@ -351,7 +353,6 @@ public sealed class ZoneTree<TKey, TValue> : IZoneTree<TKey, TValue>, IZoneTreeM
                 DiskSegment.SegmentId,
                 ReadOnlySegmentQueue.Select(x => x.SegmentId).Reverse().ToArray());
         }
-
     }
 
     public async ValueTask<MergeResult> StartMergeOperation()

src/ZoneTree/ITransactionalZoneTree.cs

@@ -29,7 +29,8 @@ public interface ITransactionalZoneTree<TKey, TValue> : IDisposable
     /// <param name="transactionId">Transaction Id</param>
     /// <param name="key">Key</param>
     /// <param name="value">Value</param>
-    /// <returns></returns>
+    /// /// <returns>true if the key/value pair was inserted;
+    /// false if the key/value pair was updated.</returns>
     /// <exception cref="TransactionAbortedException"></exception>
     bool Upsert(long transactionId, in TKey key, in TValue value);
 
@@ -112,8 +113,7 @@ public interface ITransactionalZoneTree<TKey, TValue> : IDisposable
     /// </summary>
     /// <param name="key">Key</param>
     /// <param name="value">Value</param>
-    /// <returns></returns>
-    bool UpsertAutoCommit(in TKey key, in TValue value);
+    void UpsertAutoCommit(in TKey key, in TValue value);
 
     /// <summary>
     /// Starts a transaction,

src/ZoneTree/IZoneTree.cs

@@ -55,10 +55,8 @@ public interface IZoneTree<TKey, TValue> : IDisposable
     /// </summary>
     /// <param name="key">The key of the element to upsert.</param>
     /// <param name="value">The value of the element to upsert. It can be null.</param>
-    /// <returns>true if the key/value pair was inserted;
-    /// false if the key/value pair was updated.</returns>
     /// <exception cref="ArgumentNullException">key is null.</exception>
-    bool AtomicUpsert(in TKey key, in TValue value);
+    void AtomicUpsert(in TKey key, in TValue value);
 
     /// <summary>
     /// Adds or updates the specified key/value pair.
@@ -89,10 +87,8 @@ public interface IZoneTree<TKey, TValue> : IDisposable
     /// </remarks>    
     /// <param name="key">The key of the element to upsert.</param>
     /// <param name="value">The value of the element to upsert. It can be null.</param>
-    /// <returns>true if the key/value pair was inserted;
-    /// false if the key/value pair was updated.</returns>
     /// <exception cref="ArgumentNullException">key is null.</exception>
-    bool Upsert(in TKey key, in TValue value);
+    void Upsert(in TKey key, in TValue value);
 
     /// <summary>
     /// Attempts to delete the specified key.

src/ZoneTree/Transactional/OptimisticZoneTree.cs

@@ -366,21 +366,18 @@ public sealed class OptimisticZoneTree<TKey, TValue> :
         }
     }
 
-    public bool UpsertAutoCommit(in TKey key, in TValue value)
+    public void UpsertAutoCommit(in TKey key, in TValue value)
     {
         lock (this)
         {
             var transactionId = BeginTransaction();
             var transaction = GetOrCreateTransaction(transactionId);
-            var readWriteStamp = new ReadWriteStamp
-            {
-                WriteStamp = transactionId
-            };
+            TransactionLog.TryGetReadWriteStamp(key, out var readWriteStamp);
+            readWriteStamp.WriteStamp = transactionId;
             TransactionLog.AddOrUpdateReadWriteStamp(key, in readWriteStamp);
-            var result = ZoneTree.Upsert(in key, in value);
+            ZoneTree.Upsert(in key, in value);
             transaction.IsReadyToCommit = true;
             DoCommit(transaction);
-            return result;
         }
     }
 
@@ -390,10 +387,8 @@ public sealed class OptimisticZoneTree<TKey, TValue> :
         {
             var transactionId = BeginTransaction();
             var transaction = GetOrCreateTransaction(transactionId);
-            var readWriteStamp = new ReadWriteStamp
-            {
-                WriteStamp = transactionId
-            };
+            TransactionLog.TryGetReadWriteStamp(key, out var readWriteStamp);
+            readWriteStamp.WriteStamp = transactionId;
             TransactionLog.AddOrUpdateReadWriteStamp(key, in readWriteStamp);
             ZoneTree.ForceDelete(in key);
             transaction.IsReadyToCommit = true;