Fixed compilation errors on Clang-8

dbms/src/Formats/ProtobufReader.h

@@ -229,6 +229,7 @@ public:
     bool readUUID(UUID &) { return false; }
     bool readDate(DayNum &) { return false; }
     bool readDateTime(time_t &) { return false; }
+    bool readDateTime64(DateTime64 & /*tm*/, UInt32 /*scale*/) { return false; }
     bool readDecimal(Decimal32 &, UInt32, UInt32) { return false; }
     bool readDecimal(Decimal64 &, UInt32, UInt32) { return false; }
     bool readDecimal(Decimal128 &, UInt32, UInt32) { return false; }

dbms/src/Formats/ProtobufWriter.h

@@ -262,6 +262,7 @@ public:
     bool writeUUID(const UUID & /* value */) { return false; }
     bool writeDate(DayNum /* date */) { return false; }
     bool writeDateTime(time_t /* tm */) { return false; }
+    bool writeDateTime64(DateTime64 /*tm*/, UInt32 /*scale*/) { return false; }
     bool writeDecimal(Decimal32 /* decimal */, UInt32 /* scale */) { return false; }
     bool writeDecimal(Decimal64 /* decimal */, UInt32 /* scale */) { return false; }
     bool writeDecimal(const Decimal128 & /* decimal */, UInt32 /* scale */) { return false; }

dbms/src/IO/ReadHelpers.h

@@ -633,8 +633,9 @@ inline ReturnType readDateTimeTextImpl(time_t & datetime, ReadBuffer & buf, cons
 template <typename ReturnType>
 inline ReturnType readDateTimeTextImpl(DateTime64 & datetime64, UInt32 scale, ReadBuffer & buf, const DateLUTImpl & date_lut)
 {
-    DB::DecimalComponents<DateTime64::NativeType> c;
-    readDateTimeTextImpl<void>(c.whole, buf, date_lut);
+    time_t whole;
+    readDateTimeTextImpl<void>(whole, buf, date_lut);
+    DB::DecimalComponents<DateTime64::NativeType> c{static_cast<DateTime64::NativeType>(whole), 0};
 
     char separator;
     if (buf.read(separator))