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50 lines
1.3 KiB
C++
50 lines
1.3 KiB
C++
#pragma once
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#include <DB/Storages/IStorage.h>
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#include <DB/DataStreams/IProfilingBlockInputStream.h>
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namespace DB
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{
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class OneValueBlockInputStream : public IProfilingBlockInputStream
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{
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public:
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OneValueBlockInputStream();
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Block readImpl();
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String getName() const { return "OneValueBlockInputStream"; }
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BlockInputStreamPtr clone() { return new OneValueBlockInputStream(); }
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private:
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bool has_been_read;
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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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StorageSystemOne(const std::string & name_);
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std::string getName() const { return "SystemOne"; }
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std::string getTableName() const { return "One"; }
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const NamesAndTypesList & getColumnsList() const { 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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size_t max_block_size = DEFAULT_BLOCK_SIZE,
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unsigned max_threads = 1);
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private:
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const std::string name;
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NamesAndTypesList columns;
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};
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}
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