fix: improve buffer management in BufferV1 by resetting line start length

Author: RaphDal

src/net-questdb-client-tests/TcpTests.cs

@@ -560,23 +560,23 @@ public async Task CancelLine()
 
         using var sender = Sender.New($"tcp::addr={_host}:{_port};");
 
-        sender.Table("good");
-        sender.Symbol("asdf", "sdfad");
-        sender.Column("ddd", 123);
-#pragma warning disable CS0618 // Type or member is obsolete
-        await sender.AtNowAsync();
-#pragma warning restore CS0618 // Type or member is obsolete
+        await sender
+            .Table("good")
+            .Symbol("asdf", "sdfad")
+            .Column("ddd", 123)
+            .AtAsync(DateTime.UtcNow);
+
+        await sender
+            .Table("bad")
+            .Symbol("asdf", "sdfad")
+            .Column("asdf", 123)
+            .AtAsync(DateTime.UtcNow);
 
-        sender.Table("bad");
-        sender.Symbol("asdf", "sdfad");
-        sender.Column("asdf", 123);
-#pragma warning disable CS0618 // Type or member is obsolete
-        await sender.AtNowAsync();
-#pragma warning restore CS0618 // Type or member is obsolete
         sender.CancelRow();
 
-        sender.Table("good");
-        await sender.AtAsync(new DateTime(1970, 1, 2));
+        await sender
+            .Table("good")
+            .AtAsync(new DateTime(1970, 1, 2));
         await sender.SendAsync();
 
         var expected = "good,asdf=sdfad ddd=123i\n" +

src/net-questdb-client/Buffers/BufferV1.cs

@@ -40,6 +40,7 @@ public class BufferV1 : IBuffer
     private int _currentBufferIndex;
     private string _currentTableName = null!;
     private bool _hasTable;
+    private int _lineStartLength;
     private int _lineStartBufferIndex;
     private int _lineStartBufferPosition;
     private bool _noFields = true;
@@ -158,6 +159,7 @@ public void Clear()
         Length = 0;
         WithinTransaction = false;
         _currentTableName = "";
+        _lineStartLength = 0;
         _lineStartBufferIndex = 0;
         _lineStartBufferPosition = 0;
     }
@@ -182,9 +184,11 @@ public void TrimExcessBuffers()
     public void CancelRow()
     {
         _currentBufferIndex = _lineStartBufferIndex;
-        Length -= Position - _lineStartBufferPosition;
+        Chunk = _buffers[_currentBufferIndex].Buffer;
+        Length = _lineStartLength;
         Position = _lineStartBufferPosition;
         _hasTable = false;
+        
     }
 
     /// <inheritdoc />
@@ -264,6 +268,7 @@ public IBuffer Table(ReadOnlySpan<char> name)
         _quoted = false;
         _hasTable = true;
 
+        _lineStartLength = Length;
         _lineStartBufferIndex = _currentBufferIndex;
         _lineStartBufferPosition = Position;