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51 lines
1.4 KiB
C++
51 lines
1.4 KiB
C++
#pragma once
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#include <string>
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#include <Core/Types.h>
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#include <Interpreters/SettingsCommon.h>
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namespace DB
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{
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class IAST;
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class IStorage;
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class ASTSelectQuery;
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class Context;
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/** Scheme of operation:
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*
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* If "main" table in a query is distributed enough (thus, have at least two shards),
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* and there are non-GLOBAL subqueries in IN or JOIN,
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* and in that subqueries, there is a table
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* (in any nesting level in that subquery or in more deep subqueries),
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* that exist on local server and (according to information on local server) is also distributed enough
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* then, according to setting 'distributed_product_mode',
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* either
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* - throw an exception;
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* - or add GLOBAL to top subquery;
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* - or replace database and table name in subquery to remote database and table name,
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* as Distributed storage on local server knows it.
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*
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* Do not recursively preprocess subqueries, as it will be done by calling code.
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*/
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class InJoinSubqueriesPreprocessor
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{
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public:
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InJoinSubqueriesPreprocessor(const Context & context) : context(context) {}
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void process(ASTSelectQuery * query) const;
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/// These methods could be overriden for the need of the unit test.
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virtual bool hasAtLeastTwoShards(const IStorage & table) const;
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virtual std::pair<std::string, std::string> getRemoteDatabaseAndTableName(const IStorage & table) const;
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virtual ~InJoinSubqueriesPreprocessor() {}
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private:
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const Context & context;
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};
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}
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