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42 lines
1.1 KiB
C++
42 lines
1.1 KiB
C++
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#pragma once
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#include <DB/Storages/IStorage.h>
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namespace DB
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{
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/** Реализует хранилище для системной таблицы One.
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* Таблица содержит единственный столбец dummy UInt8 и единственную строку со значением 0.
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* Используется, если в запросе не указана таблица.
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* Аналог таблицы DUAL в Oracle и MySQL.
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*/
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class StorageSystemOne : public IStorage
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{
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public:
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static StoragePtr create(const std::string & name_);
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std::string getName() const override { return "SystemOne"; }
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std::string getTableName() const override { return name; }
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const NamesAndTypesList & getColumnsListImpl() const override { return columns; }
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BlockInputStreams read(
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const Names & column_names,
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ASTPtr query,
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const Context & context,
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const Settings & settings,
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QueryProcessingStage::Enum & processed_stage,
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size_t max_block_size = DEFAULT_BLOCK_SIZE,
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unsigned threads = 1) override;
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private:
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const std::string name;
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NamesAndTypesList columns;
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StorageSystemOne(const std::string & name_);
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};
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}
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