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63 lines
1.8 KiB
C++
63 lines
1.8 KiB
C++
#pragma once
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#include <DB/Columns/ColumnConst.h>
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#include <DB/DataTypes/DataTypeNullable.h>
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#include <DB/DataTypes/DataTypesNumberFixed.h>
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#include <DB/DataStreams/IBlockOutputStream.h>
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#include <ext/range.hpp>
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namespace DB
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{
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/** Преобразует столбцы-константы в полноценные столбцы ("материализует" их).
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*/
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class MaterializingBlockOutputStream : public IBlockOutputStream
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{
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public:
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MaterializingBlockOutputStream(const BlockOutputStreamPtr & output)
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: output{output} {}
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void write(const Block & block) override
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{
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output->write(materialize(block));
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}
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void flush() override { output->flush(); }
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void writePrefix() override { output->writePrefix(); }
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void writeSuffix() override { output->writeSuffix(); }
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void setRowsBeforeLimit(size_t rows_before_limit) override { output->setRowsBeforeLimit(rows_before_limit); }
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void setTotals(const Block & totals) override { output->setTotals(materialize(totals)); }
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void setExtremes(const Block & extremes) override { output->setExtremes(materialize(extremes)); }
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String getContentType() const override { return output->getContentType(); }
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private:
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BlockOutputStreamPtr output;
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static Block materialize(const Block & original_block)
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{
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/// copy block to get rid of const
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auto block = original_block;
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for (const auto i : ext::range(0, block.columns()))
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{
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auto & src = block.getByPosition(i).column;
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ColumnPtr converted = src->convertToFullColumnIfConst();
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if (converted)
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{
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src = converted;
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auto & type = block.getByPosition(i).type;
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if (type.get()->isNull())
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{
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/// A ColumnNull that is converted to a full column has the type DataTypeUInt8.
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type = std::make_shared<DataTypeNullable>(std::make_shared<DataTypeUInt8>());
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}
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}
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}
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return block;
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}
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};
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}
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