From f1b8d1d9d722d09a279b36f2b91b7887c025e7e2 Mon Sep 17 00:00:00 2001
From: Alexey Milovidov <milovidov@clickhouse.com>
Date: Tue, 7 Feb 2023 00:27:12 +0100
Subject: [PATCH] Improve performance of Decimal conversion when scale does not
 change

---
 src/DataTypes/DataTypesDecimal.h | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/DataTypes/DataTypesDecimal.h b/src/DataTypes/DataTypesDecimal.h
index 88b3a33a5b8..7a49238b5be 100644
--- a/src/DataTypes/DataTypesDecimal.h
+++ b/src/DataTypes/DataTypesDecimal.h
@@ -100,7 +100,7 @@ inline UInt32 getDecimalScale(const DataTypeDecimal<T> & data_type)
 
 template <typename FromDataType, typename ToDataType, typename ReturnType = void>
 requires (IsDataTypeDecimal<FromDataType> && IsDataTypeDecimal<ToDataType>)
-inline ReturnType convertDecimalsImpl(const typename FromDataType::FieldType & value, UInt32 scale_from, UInt32 scale_to, typename ToDataType::FieldType& result)
+inline ReturnType convertDecimalsImpl(const typename FromDataType::FieldType & value, UInt32 scale_from, UInt32 scale_to, typename ToDataType::FieldType & result)
 {
     using FromFieldType = typename FromDataType::FieldType;
     using ToFieldType = typename ToDataType::FieldType;
@@ -121,8 +121,14 @@ inline ReturnType convertDecimalsImpl(const typename FromDataType::FieldType & v
                 return ReturnType(false);
         }
     }
+    else if (scale_to == scale_from)
+    {
+        converted_value = value.value;
+    }
     else
+    {
         converted_value = value.value / DecimalUtils::scaleMultiplier<MaxNativeType>(scale_from - scale_to);
+    }
 
     if constexpr (sizeof(FromFieldType) > sizeof(ToFieldType))
     {
@@ -155,7 +161,7 @@ inline typename ToDataType::FieldType convertDecimals(const typename FromDataTyp
 
 template <typename FromDataType, typename ToDataType>
 requires (IsDataTypeDecimal<FromDataType> && IsDataTypeDecimal<ToDataType>)
-inline bool tryConvertDecimals(const typename FromDataType::FieldType & value, UInt32 scale_from, UInt32 scale_to, typename ToDataType::FieldType& result)
+inline bool tryConvertDecimals(const typename FromDataType::FieldType & value, UInt32 scale_from, UInt32 scale_to, typename ToDataType::FieldType & result)
 {
     return convertDecimalsImpl<FromDataType, ToDataType, bool>(value, scale_from, scale_to, result);
 }