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#pragma once
#include <Interpreters/Context_fwd.h>
#include <Parsers/IAST_fwd.h>
#include <Storages/IStorage_fwd.h>
#include <base/types.h>
#include <memory>
#include <string>
namespace DB
{
class ASTSelectQuery;
/** Scheme of operation:
*
* If "main" table in a query is distributed enough (thus, have at least two shards),
* and there are non-GLOBAL subqueries in IN or JOIN,
* and in that subqueries, there is a table
* (in any nesting level in that subquery or in more deep subqueries),
* that exist on local server and (according to information on local server) is also distributed enough
* then, according to setting 'distributed_product_mode',
* either
* - throw an exception;
* - or add GLOBAL to top subquery;
* - or replace database and table name in subquery to remote database and table name,
* as Distributed storage on local server knows it.
*
* Do not recursively preprocess subqueries, as it will be done by calling code.
*/
class InJoinSubqueriesPreprocessor : WithContext
{
public:
using SubqueryTables = std::vector<std::pair<ASTPtr, std::vector<ASTPtr>>>; /// {subquery, renamed_tables}
struct CheckShardsAndTables
{
using Ptr = std::unique_ptr<CheckShardsAndTables>;
/// These methods could be overridden for the need of the unit test.
virtual bool hasAtLeastTwoShards(const IStorage & table) const;
virtual std::pair<std::string, std::string> getRemoteDatabaseAndTableName(const IStorage & table) const;
virtual ~CheckShardsAndTables() = default;
};
InJoinSubqueriesPreprocessor(
ContextPtr context_,
SubqueryTables & renamed_tables_,
CheckShardsAndTables::Ptr _checker = std::make_unique<CheckShardsAndTables>())
: WithContext(context_), renamed_tables(renamed_tables_), checker(std::move(_checker))
{
}
void visit(ASTPtr & ast) const;
private:
SubqueryTables & renamed_tables;
CheckShardsAndTables::Ptr checker;
};
}
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