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45 lines
1.0 KiB
C++
45 lines
1.0 KiB
C++
#pragma once
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#include <Parsers/IAST_fwd.h>
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#include <Storages/IStorage_fwd.h>
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#include <memory>
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#include <string>
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namespace DB
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{
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class Context;
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/** Interface for table functions.
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*
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* Table functions are not relevant to other functions.
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* The table function can be specified in the FROM section instead of the [db.]Table
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* The table function returns a temporary StoragePtr object that is used to execute the query.
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*
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* Example:
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* SELECT count() FROM remote('example01-01-1', merge, hits)
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* - go to `example01-01-1`, in `merge` database, `hits` table.
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*/
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class ITableFunction
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{
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public:
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/// Get the main function name.
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virtual std::string getName() const = 0;
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/// Create storage according to the query.
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StoragePtr execute(const ASTPtr & ast_function, const Context & context) const;
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virtual ~ITableFunction() {}
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private:
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virtual StoragePtr executeImpl(const ASTPtr & ast_function, const Context & context) const = 0;
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};
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using TableFunctionPtr = std::shared_ptr<ITableFunction>;
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}
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