From cb0b74af863cd35e69bcdcf0ac2aaea0ec430452 Mon Sep 17 00:00:00 2001
From: Alexey Milovidov <milovidov@yandex-team.ru>
Date: Tue, 14 Jul 2020 11:56:01 +0300
Subject: [PATCH] Fix AggregateFunctionAvg serialization backwards
 compatibility

---
 src/AggregateFunctions/AggregateFunctionAvg.h | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/AggregateFunctions/AggregateFunctionAvg.h b/src/AggregateFunctions/AggregateFunctionAvg.h
index 95b4836c336..73b250547ea 100644
--- a/src/AggregateFunctions/AggregateFunctionAvg.h
+++ b/src/AggregateFunctions/AggregateFunctionAvg.h
@@ -20,6 +20,7 @@ template <typename T, typename Denominator>
 struct AggregateFunctionAvgData
 {
     using NumeratorType = T;
+    using DenominatorType = Denominator;
 
     T numerator = 0;
     Denominator denominator = 0;
@@ -73,13 +74,21 @@ public:
     void serialize(ConstAggregateDataPtr place, WriteBuffer & buf) const override
     {
         writeBinary(this->data(place).numerator, buf);
-        writeBinary(this->data(place).denominator, buf);
+
+        if constexpr (std::is_integral_v<typename Data::DenominatorType>)
+            writeVarUInt(this->data(place).denominator, buf);
+        else /// Floating point denominator type can be used
+            writeBinary(this->data(place).denominator, buf);
     }
 
     void deserialize(AggregateDataPtr place, ReadBuffer & buf, Arena *) const override
     {
         readBinary(this->data(place).numerator, buf);
-        readBinary(this->data(place).denominator, buf);
+
+        if constexpr (std::is_integral_v<typename Data::DenominatorType>)
+            readVarUInt(this->data(place).denominator, buf);
+        else /// Floating point denominator type can be used
+            readBinary(this->data(place).denominator, buf);
     }
 
     void insertResultInto(AggregateDataPtr place, IColumn & to, Arena *) const override