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96 lines
3.8 KiB
C++
96 lines
3.8 KiB
C++
#pragma once
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#include <Core/Types.h>
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#include <Core/DecimalFunctions.h>
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namespace DB
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{
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/** Tansform-type wrapper for DateTime64, simplifies DateTime64 support for given Transform.
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*
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* Depending on what overloads of Transform::execute() are available, when called with DateTime64 value,
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* invokes Transform::execute() with either:
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* * whole part of DateTime64 value, discarding fractional part (1)
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* * DateTime64 value and scale factor (2)
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* * DateTime64 broken down to components, result of execute is then re-assembled back into DateTime64 value (3)
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*
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* Suitable Transfotm-types are commonly used in Date/DateTime manipulation functions,
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* and should implement static (or const) function with following signatures:
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* 1:
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* R execute(Int64 whole_value, ... )
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* 2:
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* R execute(DateTime64 value, Int64 scale_multiplier, ... )
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* 3:
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* R execute(DecimalUtils::DecimalComponents<DateTime64> components, ... )
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*
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* Where R could be of arbitrary type, in case of (3) if R is DecimalUtils::DecimalComponents<DateTime64>, result is re-assembed back into DateTime64.
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*/
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template <typename Transform>
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class TransformDateTime64
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{
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private:
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// Detect if Transform::execute is const or static method
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// with signature defined by template args (ignoring result type).
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template<typename = void, typename... Args>
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struct TransformHasExecuteOverload : std::false_type {};
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template<typename... Args>
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struct TransformHasExecuteOverload<std::void_t<decltype(std::declval<Transform>().execute(std::declval<Args>()...))>, Args...>
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: std::true_type {};
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template<typename... Args>
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static constexpr bool TransformHasExecuteOverload_v = TransformHasExecuteOverload<void, Args...>::value;
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public:
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static constexpr auto name = Transform::name;
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// non-explicit constructor to allow creating from scale value (or with no scale at all), indispensable in some contexts.
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TransformDateTime64(UInt32 scale_ = 0)
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: scale_multiplier(DecimalUtils::scaleMultiplier<DateTime64::NativeType>(scale_))
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{}
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template <typename ... Args>
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inline auto NO_SANITIZE_UNDEFINED execute(const DateTime64 & t, Args && ... args) const
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{
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/// Type conversion from float to integer may be required.
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/// We are Ok with implementation specific result for out of range and denormals conversion.
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if constexpr (TransformHasExecuteOverload_v<DateTime64, decltype(scale_multiplier), Args...>)
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{
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return wrapped_transform.execute(t, scale_multiplier, std::forward<Args>(args)...);
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}
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else if constexpr (TransformHasExecuteOverload_v<DecimalUtils::DecimalComponents<DateTime64>, Args...>)
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{
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auto components = DecimalUtils::splitWithScaleMultiplier(t, scale_multiplier);
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const auto result = wrapped_transform.execute(components, std::forward<Args>(args)...);
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using ResultType = std::decay_t<decltype(result)>;
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if constexpr (std::is_same_v<DecimalUtils::DecimalComponents<DateTime64>, ResultType>)
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{
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return DecimalUtils::decimalFromComponentsWithMultiplier<DateTime64>(result, scale_multiplier);
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}
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else
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{
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return result;
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}
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}
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else
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{
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const auto components = DecimalUtils::splitWithScaleMultiplier(t, scale_multiplier);
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return wrapped_transform.execute(static_cast<Int64>(components.whole), std::forward<Args>(args)...);
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}
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}
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template <typename T, typename ... Args, typename = std::enable_if_t<!std::is_same_v<T, DateTime64>>>
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inline auto execute(const T & t, Args && ... args) const
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{
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return wrapped_transform.execute(t, std::forward<Args>(args)...);
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}
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private:
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DateTime64::NativeType scale_multiplier = 1;
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Transform wrapped_transform = {};
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};
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}
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