From 8648ebf75c5b4ce8bd41e4e7e657c081414c0728 Mon Sep 17 00:00:00 2001
From: Vasily Nemkov <V.Nemkov@gmail.com>
Date: Sat, 12 Oct 2019 10:03:38 +0300
Subject: [PATCH] Initial implementation of DateTime64 parsing functions;

---
 dbms/src/DataTypes/DataTypeDateTime.cpp       |   7 +-
 dbms/src/DataTypes/DataTypeDateTime.h         |   2 +
 dbms/src/DataTypes/DataTypeDecimalBase.h      | 120 ------------------
 dbms/src/Formats/ProtobufReader.cpp           |   2 +-
 dbms/src/Functions/FunctionsConversion.cpp    |   6 +
 dbms/src/Functions/FunctionsConversion.h      |  90 ++++++++++---
 dbms/src/IO/ReadHelpers.h                     |  27 +++-
 dbms/src/IO/parseDateTimeBestEffort.cpp       |  30 ++++-
 dbms/src/IO/parseDateTimeBestEffort.h         |   4 +
 dbms/src/Interpreters/convertFieldToType.cpp  |   2 +-
 .../00921_datetime64_compatibility.python     |   3 -
 11 files changed, 141 insertions(+), 152 deletions(-)

diff --git a/dbms/src/DataTypes/DataTypeDateTime.cpp b/dbms/src/DataTypes/DataTypeDateTime.cpp
index be7f85c2bf5..985a044340a 100644
--- a/dbms/src/DataTypes/DataTypeDateTime.cpp
+++ b/dbms/src/DataTypes/DataTypeDateTime.cpp
@@ -35,14 +35,15 @@ static inline void readText(time_t & x, ReadBuffer & istr, const FormatSettings
     }
 }
 
-static inline void readText(DateTime64 & x, UInt32 scale, ReadBuffer & istr, const FormatSettings & settings, const DateLUTImpl & time_zone, const DateLUTImpl & /*utc_time_zone*/)
+static inline void readText(DateTime64 & x, UInt32 scale, ReadBuffer & istr, const FormatSettings & settings, const DateLUTImpl & time_zone, const DateLUTImpl & utc_time_zone)
 {
     switch (settings.date_time_input_format)
     {
         case FormatSettings::DateTimeInputFormat::Basic:
-            readDateTimeText(x, scale, istr, time_zone);
+            readDateTime64Text(x, scale, istr, time_zone);
             return;
-        default:
+        case FormatSettings::DateTimeInputFormat::BestEffort:
+            parseDateTime64BestEffort(x, scale, istr, time_zone, utc_time_zone);
             return;
     }
 }
diff --git a/dbms/src/DataTypes/DataTypeDateTime.h b/dbms/src/DataTypes/DataTypeDateTime.h
index a978bf6962d..0ec045ae1c0 100644
--- a/dbms/src/DataTypes/DataTypeDateTime.h
+++ b/dbms/src/DataTypes/DataTypeDateTime.h
@@ -108,5 +108,7 @@ public:
     bool equals(const IDataType & rhs) const override;
 };
 
+template <> inline constexpr bool IsDataTypeDecimal<DataTypeDateTime64> = true;
+
 }
 
diff --git a/dbms/src/DataTypes/DataTypeDecimalBase.h b/dbms/src/DataTypes/DataTypeDecimalBase.h
index 5d23cebc502..0b8ff37c480 100644
--- a/dbms/src/DataTypes/DataTypeDecimalBase.h
+++ b/dbms/src/DataTypes/DataTypeDecimalBase.h
@@ -171,7 +171,6 @@ protected:
 };
 
 
-// TODO (vnemkov): enable only if both tx and ty are derived from DecimalBase and are essentially same type with different type-params.
 template <typename T, typename U, template <typename> typename DecimalType>
 typename std::enable_if_t<(sizeof(T) >= sizeof(U)), DecimalType<T>>
 decimalResultType(const DecimalType<T> & tx, const DecimalType<U> & ty, bool is_multiply, bool is_divide)
@@ -209,128 +208,10 @@ const DecimalType<U> decimalResultType(const DataTypeNumber<T> &, const DecimalT
 }
 
 
-////// TODO (vnemkov): make that work for DecimalBase-derived types
-//template <typename T, template <typename> typename DecimalType>
-//inline const DecimalType<T> * checkDecimal(const IDataType & data_type)
-//{
-//    return typeid_cast<const DecimalType<T> *>(&data_type);
-//}
-
-//inline UInt32 getDecimalScale(const IDataType & data_type, UInt32 default_value = std::numeric_limits<UInt32>::max())
-//{
-//    if (auto * decimal_type = checkDecimal<Decimal32>(data_type))
-//        return decimal_type->getScale();
-//    if (auto * decimal_type = checkDecimal<Decimal64>(data_type))
-//        return decimal_type->getScale();
-//    if (auto * decimal_type = checkDecimal<Decimal128>(data_type))
-//        return decimal_type->getScale();
-//    return default_value;
-//}
-
 ///
-
 template <typename DataType> constexpr bool IsDataTypeDecimal = false;
 template <typename DataType> constexpr bool IsDataTypeDecimalOrNumber = IsDataTypeDecimal<DataType> || IsDataTypeNumber<DataType>;
 
-//template <typename FromDataType, typename ToDataType>
-//inline std::enable_if_t<IsDataTypeDecimal<FromDataType> && IsDataTypeDecimal<ToDataType>, typename ToDataType::FieldType>
-//convertDecimals(const typename FromDataType::FieldType & value, UInt32 scale_from, UInt32 scale_to)
-//{
-//    using FromFieldType = typename FromDataType::FieldType;
-//    using ToFieldType = typename ToDataType::FieldType;
-//    using MaxFieldType = std::conditional_t<(sizeof(FromFieldType) > sizeof(ToFieldType)), FromFieldType, ToFieldType>;
-//    using MaxNativeType = typename MaxFieldType::NativeType;
-
-//    MaxNativeType converted_value;
-//    if (scale_to > scale_from)
-//    {
-//        converted_value = DataTypeDecimal<MaxFieldType>::getScaleMultiplier(scale_to - scale_from);
-//        if (common::mulOverflow(static_cast<MaxNativeType>(value), converted_value, converted_value))
-//            throw Exception("Decimal convert overflow", ErrorCodes::DECIMAL_OVERFLOW);
-//    }
-//    else
-//        converted_value = value / DataTypeDecimal<MaxFieldType>::getScaleMultiplier(scale_from - scale_to);
-
-//    if constexpr (sizeof(FromFieldType) > sizeof(ToFieldType))
-//    {
-//        if (converted_value < std::numeric_limits<typename ToFieldType::NativeType>::min() ||
-//            converted_value > std::numeric_limits<typename ToFieldType::NativeType>::max())
-//            throw Exception("Decimal convert overflow", ErrorCodes::DECIMAL_OVERFLOW);
-//    }
-
-//    return converted_value;
-//}
-
-//template <typename FromDataType, typename ToDataType>
-//inline std::enable_if_t<IsDataTypeDecimal<FromDataType> && IsDataTypeNumber<ToDataType>, typename ToDataType::FieldType>
-//convertFromDecimal(const typename FromDataType::FieldType & value, UInt32 scale)
-//{
-//    using FromFieldType = typename FromDataType::FieldType;
-//    using ToFieldType = typename ToDataType::FieldType;
-
-//    if constexpr (std::is_floating_point_v<ToFieldType>)
-//        return static_cast<ToFieldType>(value) / FromDataType::getScaleMultiplier(scale);
-//    else
-//    {
-//        FromFieldType converted_value = convertDecimals<FromDataType, FromDataType>(value, scale, 0);
-
-//        if constexpr (sizeof(FromFieldType) > sizeof(ToFieldType) || !std::numeric_limits<ToFieldType>::is_signed)
-//        {
-//            if constexpr (std::numeric_limits<ToFieldType>::is_signed)
-//            {
-//                if (converted_value < std::numeric_limits<ToFieldType>::min() ||
-//                    converted_value > std::numeric_limits<ToFieldType>::max())
-//                    throw Exception("Decimal convert overflow", ErrorCodes::DECIMAL_OVERFLOW);
-//            }
-//            else
-//            {
-//                using CastIntType = std::conditional_t<std::is_same_v<ToFieldType, UInt64>, Int128, Int64>;
-
-//                if (converted_value < 0 ||
-//                    converted_value > static_cast<CastIntType>(std::numeric_limits<ToFieldType>::max()))
-//                    throw Exception("Decimal convert overflow", ErrorCodes::DECIMAL_OVERFLOW);
-//            }
-//        }
-//        return converted_value;
-//    }
-//}
-
-//template <typename FromDataType, typename ToDataType>
-//inline std::enable_if_t<IsDataTypeNumber<FromDataType> && IsDataTypeDecimal<ToDataType>, typename ToDataType::FieldType>
-//convertToDecimal(const typename FromDataType::FieldType & value, UInt32 scale)
-//{
-//    using FromFieldType = typename FromDataType::FieldType;
-//    using ToNativeType = typename ToDataType::FieldType::NativeType;
-
-//    if constexpr (std::is_floating_point_v<FromFieldType>)
-//    {
-//        if (!std::isfinite(value))
-//            throw Exception("Decimal convert overflow. Cannot convert infinity or NaN to decimal", ErrorCodes::DECIMAL_OVERFLOW);
-
-//        auto out = value * ToDataType::getScaleMultiplier(scale);
-//        if constexpr (std::is_same_v<ToNativeType, Int128>)
-//        {
-//            static constexpr __int128 min_int128 = __int128(0x8000000000000000ll) << 64;
-//            static constexpr __int128 max_int128 = (__int128(0x7fffffffffffffffll) << 64) + 0xffffffffffffffffll;
-//            if (out <= static_cast<ToNativeType>(min_int128) || out >= static_cast<ToNativeType>(max_int128))
-//                throw Exception("Decimal convert overflow. Float is out of Decimal range", ErrorCodes::DECIMAL_OVERFLOW);
-//        }
-//        else
-//        {
-//            if (out <= std::numeric_limits<ToNativeType>::min() || out >= std::numeric_limits<ToNativeType>::max())
-//                throw Exception("Decimal convert overflow. Float is out of Decimal range", ErrorCodes::DECIMAL_OVERFLOW);
-//        }
-//        return out;
-//    }
-//    else
-//    {
-//        if constexpr (std::is_same_v<FromFieldType, UInt64>)
-//            if (value > static_cast<UInt64>(std::numeric_limits<Int64>::max()))
-//                return convertDecimals<DataTypeDecimal<Decimal128>, ToDataType>(value, 0, scale);
-//        return convertDecimals<DataTypeDecimal<Decimal64>, ToDataType>(value, 0, scale);
-//    }
-//}
-
 template <template <typename> typename DecimalType>
 DataTypePtr createDecimal(UInt64 precision_value, UInt64 scale_value)
 {
@@ -352,5 +233,4 @@ extern template class DataTypeDecimalBase<Decimal64>;
 extern template class DataTypeDecimalBase<Decimal128>;
 extern template class DataTypeDecimalBase<DateTime64>;
 
-
 }
diff --git a/dbms/src/Formats/ProtobufReader.cpp b/dbms/src/Formats/ProtobufReader.cpp
index 50fe5702b4c..5f28828185b 100644
--- a/dbms/src/Formats/ProtobufReader.cpp
+++ b/dbms/src/Formats/ProtobufReader.cpp
@@ -616,7 +616,7 @@ public:
         if (!readTempString())
             return false;
         ReadBufferFromString buf(temp_string);
-        readDateTimeText(date_time, scale, buf);
+        readDateTime64Text(date_time, scale, buf);
         return true;
     }
 
diff --git a/dbms/src/Functions/FunctionsConversion.cpp b/dbms/src/Functions/FunctionsConversion.cpp
index 79bb70124a1..ae21433f183 100644
--- a/dbms/src/Functions/FunctionsConversion.cpp
+++ b/dbms/src/Functions/FunctionsConversion.cpp
@@ -46,6 +46,7 @@ void registerFunctionsConversion(FunctionFactory & factory)
 
     factory.registerFunction<FunctionToDate>();
     factory.registerFunction<FunctionToDateTime>();
+    factory.registerFunction<FunctionToDateTime64>();
     factory.registerFunction<FunctionToUUID>();
     factory.registerFunction<FunctionToString>();
     factory.registerFunction<FunctionToFixedString>();
@@ -65,6 +66,7 @@ void registerFunctionsConversion(FunctionFactory & factory)
     factory.registerFunction<FunctionToFloat64OrZero>();
     factory.registerFunction<FunctionToDateOrZero>();
     factory.registerFunction<FunctionToDateTimeOrZero>();
+    factory.registerFunction<FunctionToDateTime64OrZero>();
 
     factory.registerFunction<FunctionToDecimal32OrZero>();
     factory.registerFunction<FunctionToDecimal64OrZero>();
@@ -82,6 +84,7 @@ void registerFunctionsConversion(FunctionFactory & factory)
     factory.registerFunction<FunctionToFloat64OrNull>();
     factory.registerFunction<FunctionToDateOrNull>();
     factory.registerFunction<FunctionToDateTimeOrNull>();
+    factory.registerFunction<FunctionToDateTime64OrNull>();
 
     factory.registerFunction<FunctionToDecimal32OrNull>();
     factory.registerFunction<FunctionToDecimal64OrNull>();
@@ -90,6 +93,9 @@ void registerFunctionsConversion(FunctionFactory & factory)
     factory.registerFunction<FunctionParseDateTimeBestEffort>();
     factory.registerFunction<FunctionParseDateTimeBestEffortOrZero>();
     factory.registerFunction<FunctionParseDateTimeBestEffortOrNull>();
+    factory.registerFunction<FunctionParseDateTime64BestEffort>();
+    factory.registerFunction<FunctionParseDateTime64BestEffortOrZero>();
+    factory.registerFunction<FunctionParseDateTime64BestEffortOrNull>();
 
     factory.registerFunction<FunctionConvert<DataTypeInterval, NameToIntervalSecond, PositiveMonotonicity>>();
     factory.registerFunction<FunctionConvert<DataTypeInterval, NameToIntervalMinute, PositiveMonotonicity>>();
diff --git a/dbms/src/Functions/FunctionsConversion.h b/dbms/src/Functions/FunctionsConversion.h
index 8f82aa340c7..23f9880e83a 100644
--- a/dbms/src/Functions/FunctionsConversion.h
+++ b/dbms/src/Functions/FunctionsConversion.h
@@ -498,7 +498,7 @@ struct ConvertThroughParsing
         const DateLUTImpl * utc_time_zone [[maybe_unused]] = nullptr;
 
         /// For conversion to DateTime type, second argument with time zone could be specified.
-        if constexpr (std::is_same_v<ToDataType, DataTypeDateTime>)
+        if constexpr (std::is_same_v<ToDataType, DataTypeDateTime> || std::is_same_v<ToDataType, DataTypeDateTime64>)
         {
             local_time_zone = &extractTimeZoneFromFunctionArguments(block, arguments, 1, 0);
 
@@ -523,10 +523,17 @@ struct ConvertThroughParsing
         size_t size = input_rows_count;
         typename ColVecTo::MutablePtr col_to = nullptr;
 
-        if constexpr (IsDataTypeDecimal<ToDataType>)
+        if constexpr (IsDataTypeDecimal<ToDataType> || std::is_same_v<ToDataType, DataTypeDateTime64>)
         {
             UInt32 scale = additions;
-            ToDataType check_bounds_in_ctor(ToDataType::maxPrecision(), scale);
+            if constexpr (std::is_same_v<ToDataType, DataTypeDateTime64>)
+            {
+                ToDataType check_bounds_in_ctor(scale, local_time_zone ? local_time_zone->getTimeZone() : String{});
+            }
+            else
+            {
+                ToDataType check_bounds_in_ctor(ToDataType::maxPrecision(), scale);
+            }
             col_to = ColVecTo::create(size, scale);
         }
         else
@@ -570,13 +577,26 @@ struct ConvertThroughParsing
             {
                 if constexpr (parsing_mode == ConvertFromStringParsingMode::BestEffort)
                 {
-                    time_t res;
-                    parseDateTimeBestEffort(res, read_buffer, *local_time_zone, *utc_time_zone);
-                    vec_to[i] = res;
+                    if constexpr (std::is_same_v<ToDataType, DataTypeDateTime64>)
+                    {
+                        DateTime64 res;
+                        parseDateTime64BestEffort(res, vec_to.getScale(), read_buffer, *local_time_zone, *utc_time_zone);
+                        vec_to[i] = res;
+                    }
+                    else
+                    {
+                        time_t res;
+                        parseDateTimeBestEffort(res, read_buffer, *local_time_zone, *utc_time_zone);
+                        vec_to[i] = res;
+                    }
                 }
                 else
                 {
-                    if constexpr (IsDataTypeDecimal<ToDataType>)
+                    if constexpr (std::is_same_v<ToDataType, DataTypeDateTime64>)
+                    {
+                        readDateTimeText(vec_to[i], vec_to.getScale(), read_buffer, local_time_zone);
+                    }
+                    else if constexpr (IsDataTypeDecimal<ToDataType>)
                         ToDataType::readText(vec_to[i], read_buffer, ToDataType::maxPrecision(), vec_to.getScale());
                     else
                         parseImpl<ToDataType>(vec_to[i], read_buffer, local_time_zone);
@@ -591,13 +611,28 @@ struct ConvertThroughParsing
 
                 if constexpr (parsing_mode == ConvertFromStringParsingMode::BestEffort)
                 {
-                    time_t res;
-                    parsed = tryParseDateTimeBestEffort(res, read_buffer, *local_time_zone, *utc_time_zone);
-                    vec_to[i] = res;
+                    if constexpr (std::is_same_v<ToDataType, DataTypeDateTime64>)
+                    {
+                        DateTime64 res;
+                        parsed = tryParseDateTime64BestEffort(res, vec_to.getScale(), read_buffer, *local_time_zone, *utc_time_zone);
+                        vec_to[i] = res;
+                    }
+                    else
+                    {
+                        time_t res;
+                        parsed = tryParseDateTimeBestEffort(res, read_buffer, *local_time_zone, *utc_time_zone);
+                        vec_to[i] = res;
+                    }
                 }
                 else
                 {
-                    if constexpr (IsDataTypeDecimal<ToDataType>)
+                    if constexpr (std::is_same_v<ToDataType, DataTypeDateTime64>)
+                    {
+                        DateTime64 value;
+                        parsed = tryReadDateTime64Text(value, vec_to.getScale(), read_buffer, *local_time_zone);
+                        vec_to[i] = value;
+                    }
+                    else if constexpr (IsDataTypeDecimal<ToDataType>)
                         parsed = ToDataType::tryReadText(vec_to[i], read_buffer, ToDataType::maxPrecision(), vec_to.getScale());
                     else
                         parsed = tryParseImpl<ToDataType>(vec_to[i], read_buffer, local_time_zone);
@@ -746,6 +781,7 @@ struct ConvertImpl<DataTypeFixedString, DataTypeString, Name>
 /// Declared early because used below.
 struct NameToDate { static constexpr auto name = "toDate"; };
 struct NameToDateTime { static constexpr auto name = "toDateTime"; };
+struct NameToDateTime64 { static constexpr auto name = "toDateTime64"; };
 struct NameToString { static constexpr auto name = "toString"; };
 struct NameToDecimal32 { static constexpr auto name = "toDecimal32"; };
 struct NameToDecimal64 { static constexpr auto name = "toDecimal64"; };
@@ -936,9 +972,18 @@ private:
 
             if constexpr (IsDataTypeDecimal<RightDataType>)
             {
-                if (arguments.size() != 2)
+                if constexpr (std::is_same_v<RightDataType, DataTypeDateTime64>)
+                {
+                    // account for optional timezone argument
+                    if (arguments.size() != 2 && arguments.size() != 3)
+                        throw Exception{"Function " + getName() + " expects 2 or 3 arguments for DataTypeDateTime64.",
+                            ErrorCodes::TOO_FEW_ARGUMENTS_FOR_FUNCTION};
+                }
+                else if (arguments.size() != 2)
+                {
                     throw Exception{"Function " + getName() + " expects 2 arguments for Decimal.",
                         ErrorCodes::TOO_FEW_ARGUMENTS_FOR_FUNCTION};
+                }
 
                 const ColumnWithTypeAndName & scale_column = block.getByPosition(arguments[1]);
                 UInt32 scale = extractToDecimalScale(scale_column);
@@ -985,7 +1030,8 @@ public:
     static constexpr bool to_decimal =
         std::is_same_v<ToDataType, DataTypeDecimal<Decimal32>> ||
         std::is_same_v<ToDataType, DataTypeDecimal<Decimal64>> ||
-        std::is_same_v<ToDataType, DataTypeDecimal<Decimal128>>;
+        std::is_same_v<ToDataType, DataTypeDecimal<Decimal128>> ||
+        std::is_same_v<ToDataType, DataTypeDateTime64>;
 
     static FunctionPtr create(const Context &) { return std::make_shared<FunctionConvertFromString>(); }
 
@@ -1409,8 +1455,7 @@ using FunctionToFloat32 = FunctionConvert<DataTypeFloat32, NameToFloat32, ToNumb
 using FunctionToFloat64 = FunctionConvert<DataTypeFloat64, NameToFloat64, ToNumberMonotonicity<Float64>>;
 using FunctionToDate = FunctionConvert<DataTypeDate, NameToDate, ToNumberMonotonicity<UInt16>>;
 using FunctionToDateTime = FunctionConvert<DataTypeDateTime, NameToDateTime, ToNumberMonotonicity<UInt32>>;
-// TODO (vnemkov): enable and test toDateTime64 function
-//using FunctionToDateTime64 = FunctionConvert<DataTypeDateTime, NameToDateTime, UnknownMonotonicity>;
+using FunctionToDateTime64 = FunctionConvert<DataTypeDateTime, NameToDateTime64, UnknownMonotonicity>;
 using FunctionToUUID = FunctionConvert<DataTypeUUID, NameToUUID, ToNumberMonotonicity<UInt128>>;
 using FunctionToString = FunctionConvert<DataTypeString, NameToString, ToStringMonotonicity>;
 using FunctionToUnixTimestamp = FunctionConvert<DataTypeUInt32, NameToUnixTimestamp, ToNumberMonotonicity<UInt32>>;
@@ -1433,6 +1478,7 @@ template <> struct FunctionTo<DataTypeFloat32> { using Type = FunctionToFloat32;
 template <> struct FunctionTo<DataTypeFloat64> { using Type = FunctionToFloat64; };
 template <> struct FunctionTo<DataTypeDate> { using Type = FunctionToDate; };
 template <> struct FunctionTo<DataTypeDateTime> { using Type = FunctionToDateTime; };
+template <> struct FunctionTo<DataTypeDateTime64> { using Type = FunctionToDateTime64; };
 template <> struct FunctionTo<DataTypeUUID> { using Type = FunctionToUUID; };
 template <> struct FunctionTo<DataTypeString> { using Type = FunctionToString; };
 template <> struct FunctionTo<DataTypeFixedString> { using Type = FunctionToFixedString; };
@@ -1457,6 +1503,7 @@ struct NameToFloat32OrZero { static constexpr auto name = "toFloat32OrZero"; };
 struct NameToFloat64OrZero { static constexpr auto name = "toFloat64OrZero"; };
 struct NameToDateOrZero { static constexpr auto name = "toDateOrZero"; };
 struct NameToDateTimeOrZero { static constexpr auto name = "toDateTimeOrZero"; };
+struct NameToDateTime64OrZero { static constexpr auto name = "toDateTime64OrZero"; };
 struct NameToDecimal32OrZero { static constexpr auto name = "toDecimal32OrZero"; };
 struct NameToDecimal64OrZero { static constexpr auto name = "toDecimal64OrZero"; };
 struct NameToDecimal128OrZero { static constexpr auto name = "toDecimal128OrZero"; };
@@ -1473,6 +1520,7 @@ using FunctionToFloat32OrZero = FunctionConvertFromString<DataTypeFloat32, NameT
 using FunctionToFloat64OrZero = FunctionConvertFromString<DataTypeFloat64, NameToFloat64OrZero, ConvertFromStringExceptionMode::Zero>;
 using FunctionToDateOrZero = FunctionConvertFromString<DataTypeDate, NameToDateOrZero, ConvertFromStringExceptionMode::Zero>;
 using FunctionToDateTimeOrZero = FunctionConvertFromString<DataTypeDateTime, NameToDateTimeOrZero, ConvertFromStringExceptionMode::Zero>;
+using FunctionToDateTime64OrZero = FunctionConvertFromString<DataTypeDateTime64, NameToDateTime64OrZero, ConvertFromStringExceptionMode::Zero>;
 using FunctionToDecimal32OrZero = FunctionConvertFromString<DataTypeDecimal<Decimal32>, NameToDecimal32OrZero, ConvertFromStringExceptionMode::Zero>;
 using FunctionToDecimal64OrZero = FunctionConvertFromString<DataTypeDecimal<Decimal64>, NameToDecimal64OrZero, ConvertFromStringExceptionMode::Zero>;
 using FunctionToDecimal128OrZero = FunctionConvertFromString<DataTypeDecimal<Decimal128>, NameToDecimal128OrZero, ConvertFromStringExceptionMode::Zero>;
@@ -1489,6 +1537,7 @@ struct NameToFloat32OrNull { static constexpr auto name = "toFloat32OrNull"; };
 struct NameToFloat64OrNull { static constexpr auto name = "toFloat64OrNull"; };
 struct NameToDateOrNull { static constexpr auto name = "toDateOrNull"; };
 struct NameToDateTimeOrNull { static constexpr auto name = "toDateTimeOrNull"; };
+struct NameToDateTime64OrNull { static constexpr auto name = "toDateTime64OrNull"; };
 struct NameToDecimal32OrNull { static constexpr auto name = "toDecimal32OrNull"; };
 struct NameToDecimal64OrNull { static constexpr auto name = "toDecimal64OrNull"; };
 struct NameToDecimal128OrNull { static constexpr auto name = "toDecimal128OrNull"; };
@@ -1505,6 +1554,7 @@ using FunctionToFloat32OrNull = FunctionConvertFromString<DataTypeFloat32, NameT
 using FunctionToFloat64OrNull = FunctionConvertFromString<DataTypeFloat64, NameToFloat64OrNull, ConvertFromStringExceptionMode::Null>;
 using FunctionToDateOrNull = FunctionConvertFromString<DataTypeDate, NameToDateOrNull, ConvertFromStringExceptionMode::Null>;
 using FunctionToDateTimeOrNull = FunctionConvertFromString<DataTypeDateTime, NameToDateTimeOrNull, ConvertFromStringExceptionMode::Null>;
+using FunctionToDateTime64OrNull = FunctionConvertFromString<DataTypeDateTime64, NameToDateTime64OrNull, ConvertFromStringExceptionMode::Null>;
 using FunctionToDecimal32OrNull = FunctionConvertFromString<DataTypeDecimal<Decimal32>, NameToDecimal32OrNull, ConvertFromStringExceptionMode::Null>;
 using FunctionToDecimal64OrNull = FunctionConvertFromString<DataTypeDecimal<Decimal64>, NameToDecimal64OrNull, ConvertFromStringExceptionMode::Null>;
 using FunctionToDecimal128OrNull = FunctionConvertFromString<DataTypeDecimal<Decimal128>, NameToDecimal128OrNull, ConvertFromStringExceptionMode::Null>;
@@ -1512,6 +1562,10 @@ using FunctionToDecimal128OrNull = FunctionConvertFromString<DataTypeDecimal<Dec
 struct NameParseDateTimeBestEffort { static constexpr auto name = "parseDateTimeBestEffort"; };
 struct NameParseDateTimeBestEffortOrZero { static constexpr auto name = "parseDateTimeBestEffortOrZero"; };
 struct NameParseDateTimeBestEffortOrNull { static constexpr auto name = "parseDateTimeBestEffortOrNull"; };
+struct NameParseDateTime64BestEffort { static constexpr auto name = "parseDateTime64BestEffort"; };
+struct NameParseDateTime64BestEffortOrZero { static constexpr auto name = "parseDateTime64BestEffortOrZero"; };
+struct NameParseDateTime64BestEffortOrNull { static constexpr auto name = "parseDateTime64BestEffortOrNull"; };
+
 
 using FunctionParseDateTimeBestEffort = FunctionConvertFromString<
     DataTypeDateTime, NameParseDateTimeBestEffort, ConvertFromStringExceptionMode::Throw, ConvertFromStringParsingMode::BestEffort>;
@@ -1520,6 +1574,12 @@ using FunctionParseDateTimeBestEffortOrZero = FunctionConvertFromString<
 using FunctionParseDateTimeBestEffortOrNull = FunctionConvertFromString<
     DataTypeDateTime, NameParseDateTimeBestEffortOrNull, ConvertFromStringExceptionMode::Null, ConvertFromStringParsingMode::BestEffort>;
 
+using FunctionParseDateTime64BestEffort = FunctionConvertFromString<
+    DataTypeDateTime64, NameParseDateTime64BestEffort, ConvertFromStringExceptionMode::Throw, ConvertFromStringParsingMode::BestEffort>;
+using FunctionParseDateTime64BestEffortOrZero = FunctionConvertFromString<
+    DataTypeDateTime64, NameParseDateTime64BestEffortOrZero, ConvertFromStringExceptionMode::Zero, ConvertFromStringParsingMode::BestEffort>;
+using FunctionParseDateTime64BestEffortOrNull = FunctionConvertFromString<
+    DataTypeDateTime64, NameParseDateTime64BestEffortOrNull, ConvertFromStringExceptionMode::Null, ConvertFromStringParsingMode::BestEffort>;
 
 class PreparedFunctionCast : public PreparedFunctionImpl
 {
diff --git a/dbms/src/IO/ReadHelpers.h b/dbms/src/IO/ReadHelpers.h
index 356bcda3763..9a4cf56499c 100644
--- a/dbms/src/IO/ReadHelpers.h
+++ b/dbms/src/IO/ReadHelpers.h
@@ -630,12 +630,8 @@ inline ReturnType readDateTimeTextImpl(time_t & datetime, ReadBuffer & buf, cons
         return readDateTimeTextFallback<ReturnType>(datetime, buf, date_lut);
 }
 
-inline void readDateTimeText(time_t & datetime, ReadBuffer & buf, const DateLUTImpl & date_lut = DateLUT::instance())
-{
-    readDateTimeTextImpl<void>(datetime, buf, date_lut);
-}
-
-inline void readDateTimeText(DateTime64 & datetime64, UInt32 scale, ReadBuffer & buf, const DateLUTImpl & date_lut = DateLUT::instance())
+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);
@@ -645,7 +641,7 @@ inline void readDateTimeText(DateTime64 & datetime64, UInt32 scale, ReadBuffer &
     {
         if (separator != '.')
         {
-            throw Exception("Cannot parse DateTime64 from text.", ErrorCodes::CANNOT_PARSE_DATETIME);
+            return ReturnType(false);
         }
     }
 
@@ -655,6 +651,18 @@ inline void readDateTimeText(DateTime64 & datetime64, UInt32 scale, ReadBuffer &
 
     c.fractional *= common::exp10_i64(scale - fractional_length);
     datetime64 = decimalFromComponents<DateTime64>(c, scale);
+
+    return ReturnType(false);
+}
+
+inline void readDateTimeText(time_t & datetime, ReadBuffer & buf, const DateLUTImpl & date_lut = DateLUT::instance())
+{
+    readDateTimeTextImpl<void>(datetime, buf, date_lut);
+}
+
+inline void readDateTime64Text(DateTime64 & datetime64, UInt32 scale, ReadBuffer & buf, const DateLUTImpl & date_lut = DateLUT::instance())
+{
+    readDateTimeTextImpl<void>(datetime64, scale, buf, date_lut);
 }
 
 inline bool tryReadDateTimeText(time_t & datetime, ReadBuffer & buf, const DateLUTImpl & date_lut = DateLUT::instance())
@@ -662,6 +670,11 @@ inline bool tryReadDateTimeText(time_t & datetime, ReadBuffer & buf, const DateL
     return readDateTimeTextImpl<bool>(datetime, buf, date_lut);
 }
 
+inline bool tryReadDateTime64Text(DateTime64 & datetime64, UInt32 scale, ReadBuffer & buf, const DateLUTImpl & date_lut = DateLUT::instance())
+{
+    return readDateTimeTextImpl<bool>(datetime64, scale, buf, date_lut);
+}
+
 inline void readDateTimeText(LocalDateTime & datetime, ReadBuffer & buf)
 {
     char s[19];
diff --git a/dbms/src/IO/parseDateTimeBestEffort.cpp b/dbms/src/IO/parseDateTimeBestEffort.cpp
index 11208424c62..e2eaecfc68c 100644
--- a/dbms/src/IO/parseDateTimeBestEffort.cpp
+++ b/dbms/src/IO/parseDateTimeBestEffort.cpp
@@ -6,6 +6,7 @@
 #include <IO/WriteHelpers.h>
 #include <IO/parseDateTimeBestEffort.h>
 
+#include <limits>
 
 namespace DB
 {
@@ -66,7 +67,7 @@ inline void readDecimalNumber(T & res, const char * src)
 
 
 template <typename ReturnType>
-ReturnType parseDateTimeBestEffortImpl(time_t & res, ReadBuffer & in, const DateLUTImpl & local_time_zone, const DateLUTImpl & utc_time_zone)
+ReturnType parseDateTimeBestEffortImpl(time_t & res, ReadBuffer & in, const DateLUTImpl & local_time_zone, const DateLUTImpl & utc_time_zone, Int64 * fractional = nullptr)
 {
     auto on_error = [](const std::string & message [[maybe_unused]], int code [[maybe_unused]])
     {
@@ -360,7 +361,12 @@ ReturnType parseDateTimeBestEffortImpl(time_t & res, ReadBuffer & in, const Date
                 ++in.position();
 
                 /// Just ignore fractional part of second.
-                readDigits(digits, sizeof(digits), in);
+                num_digits = readDigits(digits, sizeof(digits), in);
+                if (fractional)
+                {
+                    using FractionalType = typename std::decay<decltype(*fractional)>::type;
+                    readDecimalNumber<std::numeric_limits<FractionalType>::digits10>(*fractional, digits);
+                }
             }
             else if (c == '+' || c == '-')
             {
@@ -535,4 +541,24 @@ bool tryParseDateTimeBestEffort(time_t & res, ReadBuffer & in, const DateLUTImpl
     return parseDateTimeBestEffortImpl<bool>(res, in, local_time_zone, utc_time_zone);
 }
 
+void parseDateTime64BestEffort(DateTime64 & res, UInt32 scale, ReadBuffer & in, const DateLUTImpl & local_time_zone, const DateLUTImpl & utc_time_zone)
+{
+    DateTime64::NativeType whole;
+    DateTime64::NativeType fractional;
+    parseDateTimeBestEffortImpl<void>(whole, in, local_time_zone, utc_time_zone, &fractional);
+
+    res = decimalFromComponents<DateTime64>(whole, fractional, scale);
+}
+
+bool tryParseDateTime64BestEffort(DateTime64 & res, UInt32 scale, ReadBuffer & in, const DateLUTImpl & local_time_zone, const DateLUTImpl & utc_time_zone)
+{
+    DateTime64::NativeType whole;
+    DateTime64::NativeType fractional;
+    const auto result = parseDateTimeBestEffortImpl<bool>(whole, in, local_time_zone, utc_time_zone, &fractional);
+
+    res = decimalFromComponents<DateTime64>(whole, fractional, scale);
+
+    return result;
+}
+
 }
diff --git a/dbms/src/IO/parseDateTimeBestEffort.h b/dbms/src/IO/parseDateTimeBestEffort.h
index dc416a750c5..54432b5db2f 100644
--- a/dbms/src/IO/parseDateTimeBestEffort.h
+++ b/dbms/src/IO/parseDateTimeBestEffort.h
@@ -1,6 +1,8 @@
 #include <stddef.h>
 #include <time.h>
 
+#include <Core/Types.h>
+
 class DateLUTImpl;
 
 namespace DB
@@ -55,5 +57,7 @@ class ReadBuffer;
 
 void parseDateTimeBestEffort(time_t & res, ReadBuffer & in, const DateLUTImpl & local_time_zone, const DateLUTImpl & utc_time_zone);
 bool tryParseDateTimeBestEffort(time_t & res, ReadBuffer & in, const DateLUTImpl & local_time_zone, const DateLUTImpl & utc_time_zone);
+void parseDateTime64BestEffort(DateTime64 & res, UInt32 scale, ReadBuffer & in, const DateLUTImpl & local_time_zone, const DateLUTImpl & utc_time_zone);
+bool tryParseDateTime64BestEffort(DateTime64 & res, UInt32 scale, ReadBuffer & in, const DateLUTImpl & local_time_zone, const DateLUTImpl & utc_time_zone);
 
 }
diff --git a/dbms/src/Interpreters/convertFieldToType.cpp b/dbms/src/Interpreters/convertFieldToType.cpp
index 52320339a8a..f05917ab09d 100644
--- a/dbms/src/Interpreters/convertFieldToType.cpp
+++ b/dbms/src/Interpreters/convertFieldToType.cpp
@@ -151,7 +151,7 @@ DateTime64::NativeType stringToDateTime64(const String & s, UInt32 scale)
     ReadBufferFromString in(s);
     DateTime64 datetime64 {0};
 
-    readDateTimeText(datetime64, scale, in);
+    readDateTime64Text(datetime64, scale, in);
     if (!in.eof())
         throw Exception("String is too long for DateTime64: " + s, ErrorCodes::TOO_LARGE_STRING_SIZE);
 
diff --git a/dbms/tests/queries/0_stateless/00921_datetime64_compatibility.python b/dbms/tests/queries/0_stateless/00921_datetime64_compatibility.python
index d227f64dd4d..dd4f08b13b3 100755
--- a/dbms/tests/queries/0_stateless/00921_datetime64_compatibility.python
+++ b/dbms/tests/queries/0_stateless/00921_datetime64_compatibility.python
@@ -30,7 +30,6 @@ toStartOfMinute({datetime})
 toStartOfFiveMinute({datetime})
 toStartOfTenMinutes({datetime})
 toStartOfFifteenMinutes({datetime})
-# Do not work with DateTime64
 toStartOfInterval({datetime}, INTERVAL 1 year)
 toStartOfInterval({datetime}, INTERVAL 1 month)
 toStartOfInterval({datetime}, INTERVAL 1 day)
@@ -52,7 +51,6 @@ timeSlot({datetime})
 toYYYYMM({datetime})
 toYYYYMMDD({datetime})
 toYYYYMMDDhhmmss({datetime})
-# --  Illegal type DateTime64 of argument of function addYears
 addYears({datetime}, 1)
 addMonths({datetime}, 1)
 addWeeks({datetime}, 1)
@@ -61,7 +59,6 @@ addHours({datetime}, 1)
 addMinutes({datetime}, 1)
 addSeconds({datetime}, 1)
 addQuarters({datetime}, 1)
-# -- Illegal type DateTime64 of argument of function subtractYears.
 subtractYears({datetime}, 1)
 subtractMonths({datetime}, 1)
 subtractWeeks({datetime}, 1)