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46 lines
1.1 KiB
C++
46 lines
1.1 KiB
C++
#pragma once
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#include <ext/shared_ptr_helper.h>
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#include <Storages/IStorage.h>
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namespace DB
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{
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class Context;
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/** Implements storage for the system table One.
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* The table contains a single column of dummy UInt8 and a single row with a value of 0.
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* Used when the table is not specified in the query.
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* Analog of the DUAL table in Oracle and MySQL.
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*/
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class StorageSystemOne : private ext::shared_ptr_helper<StorageSystemOne>, public IStorage
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{
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friend class ext::shared_ptr_helper<StorageSystemOne>;
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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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const ASTPtr & query,
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const Context & context,
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QueryProcessingStage::Enum & processed_stage,
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size_t max_block_size,
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unsigned num_streams) 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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