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54 lines
1.3 KiB
C++
54 lines
1.3 KiB
C++
#pragma once
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#include <DataStreams/IBlockInputStream.h>
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namespace DB
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{
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class ExpressionActions;
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/** Executes a certain expression over the block.
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* The expression consists of column identifiers from the block, constants, common functions.
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* For example: hits * 2 + 3, url LIKE '%yandex%'
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* The expression processes each row independently of the others.
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*/
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class ExpressionBlockInputStream : public IBlockInputStream
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{
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public:
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using ExpressionActionsPtr = std::shared_ptr<ExpressionActions>;
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ExpressionBlockInputStream(const BlockInputStreamPtr & input, const ExpressionActionsPtr & expression_);
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String getName() const override;
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Block getTotals() override;
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Block getHeader() const override;
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protected:
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bool initialized = false;
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ExpressionActionsPtr expression;
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Block readImpl() override;
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private:
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Block cached_header;
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};
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/// ExpressionBlockInputStream that could generate many out blocks for single input block.
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class InflatingExpressionBlockInputStream : public ExpressionBlockInputStream
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{
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public:
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InflatingExpressionBlockInputStream(const BlockInputStreamPtr & input, const ExpressionActionsPtr & expression_)
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: ExpressionBlockInputStream(input, expression_)
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{}
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protected:
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Block readImpl() override;
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private:
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ExtraBlockPtr not_processed;
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size_t action_number = 0;
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};
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}
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