From 8b37c3f19ef3e0fb0155fa43cda2a01d7a5e4e80 Mon Sep 17 00:00:00 2001
From: Sergei Pavlov <spavlov@servicetitan.com>
Date: Thu, 26 Jun 2025 13:01:32 -0700
Subject: [PATCH] Optimize `TruncateToNetDecimal()`: use `Span`

---
 .../Sql.Drivers.SqlServer/InternalHelpers.cs  |  8 ++++--
 .../Sql.Drivers.SqlServer/v09/TypeMapper.cs   | 28 +------------------
 2 files changed, 6 insertions(+), 30 deletions(-)

diff --git a/Orm/Xtensive.Orm.SqlServer/Sql.Drivers.SqlServer/InternalHelpers.cs b/Orm/Xtensive.Orm.SqlServer/Sql.Drivers.SqlServer/InternalHelpers.cs
index 6e2e5770e..57d8c718c 100644
--- a/Orm/Xtensive.Orm.SqlServer/Sql.Drivers.SqlServer/InternalHelpers.cs
+++ b/Orm/Xtensive.Orm.SqlServer/Sql.Drivers.SqlServer/InternalHelpers.cs
@@ -131,17 +131,19 @@ public static bool ShouldRetryOn(Exception ex)
     return ex is TimeoutException;
   }
 
-  private static UInt128 FromSqlDecimalData(int[] a) =>
-    new((uint) a[2] | ((ulong) (uint) a[3] << 32), (uint) a[0] | ((ulong) (uint) a[1] << 32));
+  private static UInt128 FromSqlDecimalData(ReadOnlySpan<uint> a) =>
+    new(((ulong) a[3] << 32) | a[2], ((ulong) a[1] << 32) | a[0]);
 
   internal static decimal TruncateToNetDecimal(SqlDecimal sqlDecimal)
   {
+    Span<uint> data = stackalloc uint[4];
     try {
       return sqlDecimal.Value; // throws an OverflowException if the value is out of the decimal range.
     }
     catch (OverflowException) {
       var scale = sqlDecimal.Scale;
-      var u128 = FromSqlDecimalData(sqlDecimal.Data);   // sqlDecimal.Data allocates a new array
+      sqlDecimal.WriteTdsValue(data);
+      var u128 = FromSqlDecimalData(data);
 
       for (; scale > 0 && u128 > Max96bitValue; --scale) {
         u128 /= Ten;
diff --git a/Orm/Xtensive.Orm.SqlServer/Sql.Drivers.SqlServer/v09/TypeMapper.cs b/Orm/Xtensive.Orm.SqlServer/Sql.Drivers.SqlServer/v09/TypeMapper.cs
index 8530d9aaa..df0a0edd8 100644
--- a/Orm/Xtensive.Orm.SqlServer/Sql.Drivers.SqlServer/v09/TypeMapper.cs
+++ b/Orm/Xtensive.Orm.SqlServer/Sql.Drivers.SqlServer/v09/TypeMapper.cs
@@ -4,7 +4,6 @@
 // Created by: Denis Krjuchkov
 // Created:    2009.07.02
 
-using System;
 using System.Data;
 using System.Data.Common;
 using Microsoft.Data.SqlClient;
@@ -13,7 +12,7 @@
 
 namespace Xtensive.Sql.Drivers.SqlServer.v09
 {
-  internal class TypeMapper : Sql.TypeMapper
+  internal class TypeMapper(SqlDriver driver) : Sql.TypeMapper(driver)
   {
     private static readonly SqlValueType
       Decimal20Type = new(SqlType.Decimal, 20, 0);
@@ -128,24 +127,6 @@ public override void Initialize()
       dateTimeRange = (ValueRange<DateTime>) Driver.ServerInfo.DataTypes.DateTime.ValueRange;
     }
 
-    private bool TryConvert(SqlDecimal sqlDecimal, out decimal result)
-    {
-      var data = sqlDecimal.Data;
-      if (data[3]==0 && sqlDecimal.Scale <= 28) {
-        result = new decimal(data[0], data[1], data[2], !sqlDecimal.IsPositive, sqlDecimal.Scale);
-        return true;
-      }
-      result = decimal.Zero;
-      return false;
-    }
-
-    private SqlDecimal ReducePrecision(SqlDecimal d, int newPrecision)
-    {
-      var newScale = newPrecision - d.Precision + d.Scale;
-      var truncated = SqlDecimal.Truncate(d, newScale);
-      return SqlDecimal.ConvertToPrecScale(truncated, newPrecision, newScale);
-    }
-
     private bool ShouldCompareValues(SqlDecimal valueFromDatabase)
     {
       var floorDigitCount = valueFromDatabase.Precision - valueFromDatabase.Scale;
@@ -153,12 +134,5 @@ private bool ShouldCompareValues(SqlDecimal valueFromDatabase)
         return true;
       return false;
     }
-
-    // Constructors
-
-    public TypeMapper(SqlDriver driver)
-      : base(driver)
-    {
-    }
   }
 }