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116 lines
2.8 KiB
C++
116 lines
2.8 KiB
C++
#pragma once
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#include <Poco/SharedPtr.h>
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#include <DB/Core/Field.h>
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#include <DB/Core/Exception.h>
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#include <DB/Core/ErrorCodes.h>
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#include <DB/Columns/ColumnVector.h>
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#include <DB/Columns/IColumn.h>
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namespace DB
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{
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using Poco::SharedPtr;
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class IColumnConst : public IColumn
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{
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public:
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bool isConst() const { return true; }
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virtual ColumnPtr convertToFullColumn() const = 0;
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};
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/** шаблон для столбцов-констант (столбцов одинаковых значений).
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*/
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template <typename T>
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class ColumnConst : public IColumnConst
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{
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public:
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typedef T Type;
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ColumnConst(size_t s_, const T & data_) : s(s_), data(data_) {}
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std::string getName() const { return "ColumnConst<" + TypeName<T>::get() + ">"; }
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bool isNumeric() const { return IsNumber<T>::value; }
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size_t sizeOfField() const { return sizeof(T); }
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ColumnPtr cloneEmpty() const { return new ColumnConst(0, data); }
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size_t size() const { return s; }
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Field operator[](size_t n) const { return typename NearestFieldType<T>::Type(data); }
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void cut(size_t start, size_t length) { s = length; }
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void clear() { s = 0; }
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void insert(const Field & x)
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{
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throw Exception("Cannot insert element into constant column " + getName(), ErrorCodes::CANNOT_INSERT_ELEMENT_INTO_CONSTANT_COLUMN);
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}
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void insertDefault() { ++s; }
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void filter(const Filter & filt)
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{
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size_t new_size = 0;
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for (Filter::const_iterator it = filt.begin(); it != filt.end(); ++it)
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if (*it)
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++new_size;
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s = new_size;
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}
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size_t byteSize() const { return sizeof(data) + sizeof(s); }
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void permute(const Permutation & perm)
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{
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if (s != perm.size())
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throw Exception("Size of permutation doesn't match size of column.", ErrorCodes::SIZES_OF_COLUMNS_DOESNT_MATCH);
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}
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int compareAt(size_t n, size_t m, const IColumn & rhs_) const
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{
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const ColumnConst<T> & rhs = static_cast<const ColumnConst<T> &>(rhs_);
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return data < rhs.data
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? -1
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: (data == rhs.data
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? 0
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: 1);
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}
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Permutation getPermutation() const
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{
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Permutation res(s);
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for (size_t i = 0; i < s; ++i)
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res[i] = i;
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return res;
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}
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/** Более эффективные методы манипуляции */
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T & getData() { return data; }
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const T & getData() const { return data; }
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/** Преобразование из константы в полноценный столбец */
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ColumnPtr convertToFullColumn() const;
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private:
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size_t s;
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T data;
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};
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typedef ColumnConst<String> ColumnConstString;
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template <typename T> ColumnPtr ColumnConst<T>::convertToFullColumn() const
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{
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ColumnVector<T> * res = new ColumnVector<T>;
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res->getData().assign(s, data);
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return res;
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}
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template <> ColumnPtr ColumnConst<String>::convertToFullColumn() const;
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// TODO: convertToFullColumn для остальных типов столбцов.
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}
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