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#pragma once
#include <Columns/IColumn.h>
#include <Common/PODArray.h>
namespace DB
{
/** Allows to access internal array of ColumnVector or ColumnFixedString without cast to concrete type.
* We will inherit ColumnVector and ColumnFixedString from this class instead of IColumn.
* Assumes data layout of ColumnVector, ColumnFixedString and PODArray.
*
* Why it is needed?
*
* There are some algorithms that specialize on the size of data type but doesn't care about concrete type.
* The same specialization may work for UInt64, Int64, Float64, FixedString(8), if it only does byte moving and hashing.
* To avoid code bloat and compile time increase, we can use single template instantiation for these cases
* and just static_cast pointer to some single column type (e. g. ColumnUInt64) assuming that all types have identical memory layout.
*
* But this static_cast (downcast to unrelated type) is illegal according to the C++ standard and UBSan warns about it.
* To allow functional tests to work under UBSan we have to separate some base class that will present the memory layout in explicit way,
* and we will do static_cast to this class.
*/
class ColumnVectorHelper : public IColumn
{
public:
template <size_t ELEMENT_SIZE>
const char * getRawDataBegin() const
{
return reinterpret_cast<const PODArrayBase<ELEMENT_SIZE, 4096, Allocator<false>, PADDING_FOR_SIMD - 1, PADDING_FOR_SIMD> *>(
reinterpret_cast<const char *>(this) + sizeof(*this))
->raw_data();
}
template <size_t ELEMENT_SIZE>
void insertRawData(const char * ptr)
{
return reinterpret_cast<PODArrayBase<ELEMENT_SIZE, 4096, Allocator<false>, PADDING_FOR_SIMD - 1, PADDING_FOR_SIMD> *>(
reinterpret_cast<char *>(this) + sizeof(*this))
->push_back_raw(ptr);
}
};
}
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