ClickHouse/src/Common/SharedBlockRowRef.h

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#pragma once
#include <algorithm>
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#include <Core/Block.h>
#include <Columns/IColumn.h>
#include <boost/smart_ptr/intrusive_ptr.hpp>
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namespace DB
{
/// Allows you refer to the row in the block and hold the block ownership,
/// and thus avoid creating a temporary row object.
/// Do not use std::shared_ptr, since there is no need for a place for `weak_count` and `deleter`;
/// does not use Poco::SharedPtr, since you need to allocate a block and `refcount` in one piece;
/// does not use Poco::AutoPtr, since it does not have a `move` constructor and there are extra checks for nullptr;
/// The reference counter is not atomic, since it is used from one thread.
namespace detail
{
struct SharedBlock : Block
{
int refcount = 0;
ColumnRawPtrs all_columns;
ColumnRawPtrs sort_columns;
SharedBlock(Block && block) : Block(std::move(block)) {}
};
}
inline void intrusive_ptr_add_ref(detail::SharedBlock * ptr)
{
++ptr->refcount;
}
inline void intrusive_ptr_release(detail::SharedBlock * ptr)
{
if (0 == --ptr->refcount)
delete ptr;
}
using SharedBlockPtr = boost::intrusive_ptr<detail::SharedBlock>;
struct SharedBlockRowRef
{
ColumnRawPtrs * columns = nullptr;
size_t row_num;
SharedBlockPtr shared_block;
void swap(SharedBlockRowRef & other)
{
std::swap(columns, other.columns);
std::swap(row_num, other.row_num);
std::swap(shared_block, other.shared_block);
}
/// The number and types of columns must match.
bool operator==(const SharedBlockRowRef & other) const
{
size_t size = columns->size();
for (size_t i = 0; i < size; ++i)
if (0 != (*columns)[i]->compareAt(row_num, other.row_num, *(*other.columns)[i], 1))
return false;
return true;
}
bool operator!=(const SharedBlockRowRef & other) const
{
return !(*this == other);
}
void reset()
{
SharedBlockRowRef empty;
swap(empty);
}
bool empty() const { return columns == nullptr; }
size_t size() const { return empty() ? 0 : columns->size(); }
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void set(SharedBlockPtr & shared_block_, ColumnRawPtrs * columns_, size_t row_num_)
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{
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shared_block = shared_block_;
columns = columns_;
row_num = row_num_;
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}
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};
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}