2019-10-07 18:56:03 +00:00
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/**
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* This file implements template methods of IColumn that depend on other types
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* we don't want to include.
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* Currently, this is only the scatterImpl method that depends on PODArray
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* implementation.
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*/
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#pragma once
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#include <Columns/IColumn.h>
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#include <Common/PODArray.h>
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namespace DB
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{
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2020-02-25 18:10:48 +00:00
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namespace ErrorCodes
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{
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extern const int SIZES_OF_COLUMNS_DOESNT_MATCH;
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}
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2019-10-07 18:56:03 +00:00
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template <typename Derived>
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std::vector<IColumn::MutablePtr> IColumn::scatterImpl(ColumnIndex num_columns,
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const Selector & selector) const
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{
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size_t num_rows = size();
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if (num_rows != selector.size())
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throw Exception(
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"Size of selector: " + std::to_string(selector.size()) + " doesn't match size of column: " + std::to_string(num_rows),
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ErrorCodes::SIZES_OF_COLUMNS_DOESNT_MATCH);
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std::vector<MutablePtr> columns(num_columns);
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for (auto & column : columns)
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column = cloneEmpty();
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{
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size_t reserve_size = num_rows * 1.1 / num_columns; /// 1.1 is just a guess. Better to use n-sigma rule.
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if (reserve_size > 1)
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for (auto & column : columns)
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column->reserve(reserve_size);
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}
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for (size_t i = 0; i < num_rows; ++i)
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static_cast<Derived &>(*columns[selector[i]]).insertFrom(*this, i);
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return columns;
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}
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}
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