From 879273894422d240b0753e1c4f7c06a4cc976d2c Mon Sep 17 00:00:00 2001
From: Vasily Nemkov <V.Nemkov@gmail.com>
Date: Tue, 8 Oct 2019 10:01:17 +0300
Subject: [PATCH] Prohibit implicit conversion of UInt64-Field to DateTime64

---
 dbms/src/Interpreters/convertFieldToType.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/dbms/src/Interpreters/convertFieldToType.cpp b/dbms/src/Interpreters/convertFieldToType.cpp
index 1fed7bb712f..52320339a8a 100644
--- a/dbms/src/Interpreters/convertFieldToType.cpp
+++ b/dbms/src/Interpreters/convertFieldToType.cpp
@@ -208,11 +208,12 @@ Field convertFieldToTypeImpl(const Field & src, const IDataType & type, const ID
             return dynamic_cast<const IDataTypeEnum &>(type).castToValue(src);
         }
 
-        if (which_type.isDateOrDateTime() && src.getType() == Field::Types::UInt64)
+        if (which_type.isDateOrDateTime() && !which_type.isDateTime64() && src.getType() == Field::Types::UInt64)
         {
             /// We don't need any conversion UInt64 is under type of Date and DateTime
             return src;
         }
+        // TODO (vnemkov): extra cases for DateTime64: converting from integer, converting from Decimal
 
         if (src.getType() == Field::Types::String)
         {