thevar1able/ClickHouse
1
0
Fork 0
mirror of https://github.com/ClickHouse/ClickHouse.git synced 2024-09-20 16:50:48 +00:00
Code Issues Packages Projects Releases Wiki Activity

Moved code; added comment #3926

Browse Source
This commit is contained in:
Alexey Milovidov 2018-12-27 03:34:49 +03:00
parent 3c84e47419
commit c20f05875a
5 changed files with 43 additions and 20 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
dbms/src/Columns/ColumnDecimal.h
View File

@ -3,6 +3,7 @@
#include <cmath>
#include <Columns/IColumn.h>
#include <Columns/ColumnVectorHelper.h>
namespace DB

3
dbms/src/Columns/ColumnFixedString.h
View File

@ -1,9 +1,10 @@
#pragma once
#include <string.h> // memcpy
#include <string.h> // memcmp
#include <Common/PODArray.h>
#include <Columns/IColumn.h>
#include <Columns/ColumnVectorHelper.h>
namespace DB

1
dbms/src/Columns/ColumnVector.h
View File

@ -2,6 +2,7 @@
#include <cmath>
#include <Columns/IColumn.h>
#include <Columns/ColumnVectorHelper.h>
#include <common/unaligned.h>

39
dbms/src/Columns/ColumnVectorHelper.h Normal file
View File

@ -0,0 +1,39 @@
#pragma once
#include <Columns/IColumn.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:
const char * getRawDataBegin() const
{
return *reinterpret_cast<const char * const *>(reinterpret_cast<const char *>(this) + sizeof(*this));
}
template <size_t ELEMENT_SIZE>
void insertRawData(const char * ptr)
{
return reinterpret_cast<PODArrayBase<ELEMENT_SIZE, 4096, Allocator<false>, 15, 16> *>(reinterpret_cast<char *>(this) + sizeof(*this))->push_back_raw(ptr);
}
};
}

19
dbms/src/Columns/IColumn.h
View File

@ -389,23 +389,4 @@ struct IsMutableColumns<Arg, Args ...>
template <>
struct IsMutableColumns<> { static const bool value = true; };
/// Allows to access internal array of ColumnVector or ColumnFixedString without cast to concrete type.
/// Inherit ColumnVector and ColumnFixedString from this class instead of IColumn.
/// Assumes data layout of ColumnVector, ColumnFixedString and PODArray.
class ColumnVectorHelper : public IColumn
{
public:
const char * getRawDataBegin() const
{
return *reinterpret_cast<const char * const *>(reinterpret_cast<const char *>(this) + sizeof(*this));
}
template <size_t ELEMENT_SIZE>
void insertRawData(const char * ptr)
{
return reinterpret_cast<PODArrayBase<ELEMENT_SIZE, 4096, Allocator<false>, 15, 16> *>(reinterpret_cast<char *>(this) + sizeof(*this))->push_back_raw(ptr);
}
};
}