ClickHouse/src/Functions/FunctionDateOrDateTimeToSomething.h

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#pragma once
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#include <Functions/IFunctionDateOrDateTime.h>
namespace DB
{
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namespace ErrorCodes
{
extern const int ILLEGAL_TYPE_OF_ARGUMENT;
extern const int NOT_IMPLEMENTED;
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}
/// See DateTimeTransforms.h
template <typename ToDataType, typename Transform>
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class FunctionDateOrDateTimeToSomething : public IFunctionDateOrDateTime<Transform>
{
public:
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static FunctionPtr create(ContextPtr) { return std::make_shared<FunctionDateOrDateTimeToSomething>(); }
DataTypePtr getReturnTypeImpl(const ColumnsWithTypeAndName & arguments) const override
{
this->checkArguments(arguments, (std::is_same_v<ToDataType, DataTypeDate> || std::is_same_v<ToDataType, DataTypeDate32>));
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/// For DateTime, if time zone is specified, attach it to type.
/// If the time zone is specified but empty, throw an exception.
if constexpr (std::is_same_v<ToDataType, DataTypeDateTime>)
{
std::string time_zone = extractTimeZoneNameFromFunctionArguments(arguments, 1, 0, false);
/// only validate the time_zone part if the number of arguments is 2. This is mainly
/// to accommodate functions like toStartOfDay(today()), toStartOfDay(yesterday()) etc.
if (arguments.size() == 2 && time_zone.empty())
throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
"Function {} supports a 2nd argument (optional) that must be a valid time zone",
this->getName());
return std::make_shared<ToDataType>(time_zone);
}
if constexpr (std::is_same_v<ToDataType, DataTypeDateTime64>)
{
Int64 scale = DataTypeDateTime64::default_scale;
if (const auto * dt64 = checkAndGetDataType<DataTypeDateTime64>(arguments[0].type.get()))
scale = dt64->getScale();
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auto source_scale = scale;
if constexpr (std::is_same_v<ToStartOfMillisecondImpl, Transform>)
{
scale = std::max(source_scale, static_cast<Int64>(3));
}
else if constexpr (std::is_same_v<ToStartOfMicrosecondImpl, Transform>)
{
scale = std::max(source_scale, static_cast<Int64>(6));
}
else if constexpr (std::is_same_v<ToStartOfNanosecondImpl, Transform>)
{
scale = std::max(source_scale, static_cast<Int64>(9));
}
return std::make_shared<ToDataType>(scale, extractTimeZoneNameFromFunctionArguments(arguments, 1, 0, false));
}
else
return std::make_shared<ToDataType>();
}
ColumnPtr executeImpl(const ColumnsWithTypeAndName & arguments, const DataTypePtr & result_type, size_t input_rows_count) const override
{
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const IDataType * from_type = arguments[0].type.get();
WhichDataType which(from_type);
if (which.isDate())
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return DateTimeTransformImpl<DataTypeDate, ToDataType, Transform>::execute(arguments, result_type, input_rows_count);
else if (which.isDate32())
return DateTimeTransformImpl<DataTypeDate32, ToDataType, Transform>::execute(arguments, result_type, input_rows_count);
else if (which.isDateTime())
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return DateTimeTransformImpl<DataTypeDateTime, ToDataType, Transform>::execute(arguments, result_type, input_rows_count);
else if (which.isDateTime64())
{
const auto scale = static_cast<const DataTypeDateTime64 *>(from_type)->getScale();
Extended range of DateTime64 to years 1925 - 2238 The Year 1925 is a starting point because most of the timezones switched to saner (mostly 15-minutes based) offsets somewhere during 1924 or before. And that significantly simplifies implementation. 2238 is to simplify arithmetics for sanitizing LUT index access; there are less than 0x1ffff days from 1925. * Extended DateLUTImpl internal LUT to 0x1ffff items, some of which represent negative (pre-1970) time values. As a collateral benefit, Date now correctly supports dates up to 2149 (instead of 2106). * Added a new strong typedef ExtendedDayNum, which represents dates pre-1970 and post 2149. * Functions that used to return DayNum now return ExtendedDayNum. * Refactored DateLUTImpl to untie DayNum from the dual role of being a value and an index (due to negative time). Index is now a different type LUTIndex with explicit conversion functions from DatNum, time_t, and ExtendedDayNum. * Updated DateLUTImpl to properly support values close to epoch start (1970-01-01 00:00), including negative ones. * Reduced resolution of DateLUTImpl::Values::time_at_offset_change to multiple of 15-minutes to allow storing 64-bits of time_t in DateLUTImpl::Value while keeping same size. * Minor performance updates to DateLUTImpl when building month LUT by skipping non-start-of-month days. * Fixed extractTimeZoneFromFunctionArguments to work correctly with DateTime64. * New unit-tests and stateless integration tests for both DateTime and DateTime64.
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const TransformDateTime64<Transform> transformer(scale);
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return DateTimeTransformImpl<DataTypeDateTime64, ToDataType, decltype(transformer)>::execute(arguments, result_type, input_rows_count, transformer);
}
else
throw Exception(ErrorCodes::ILLEGAL_TYPE_OF_ARGUMENT,
"Illegal type {} of argument of function {}",
arguments[0].type->getName(), this->getName());
}
bool hasInformationAboutPreimage() const override { return Transform::hasPreimage(); }
RangeOrNull getPreimage(const IDataType & type, const Field & point) const override
{
if constexpr (Transform::hasPreimage())
return Transform::getPreimage(type, point);
else
throw Exception(ErrorCodes::NOT_IMPLEMENTED,
"Function {} has no information about its preimage",
Transform::name);
}
};
}