ClickHouse/dbms/src/Interpreters/InterpreterRenameQuery.cpp

#include <Parsers/ASTRenameQuery.h>
#include <Databases/IDatabase.h>
#include <Interpreters/Context.h>
#include <Interpreters/InterpreterRenameQuery.h>
#include <Storages/IStorage.h>
#include <Interpreters/DDLWorker.h>
#include <Access/AccessRightsElement.h>
#include <Common/typeid_cast.h>


namespace DB
{


InterpreterRenameQuery::InterpreterRenameQuery(const ASTPtr & query_ptr_, Context & context_)
    : query_ptr(query_ptr_), context(context_)
{
}


struct RenameDescription
{
    RenameDescription(const ASTRenameQuery::Element & elem, const String & current_database) :
        from_database_name(elem.from.database.empty() ? current_database : elem.from.database),
        from_table_name(elem.from.table),
        to_database_name(elem.to.database.empty() ? current_database : elem.to.database),
        to_table_name(elem.to.table)
    {}

    String from_database_name;
    String from_table_name;

    String to_database_name;
    String to_table_name;
};


BlockIO InterpreterRenameQuery::execute()
{
    const auto & rename = query_ptr->as<const ASTRenameQuery &>();

    if (!rename.cluster.empty())
        return executeDDLQueryOnCluster(query_ptr, context, getRequiredAccess());

    context.checkAccess(getRequiredAccess());

    String path = context.getPath();
    String current_database = context.getCurrentDatabase();

    /** In case of error while renaming, it is possible that only part of tables was renamed
      *  or we will be in inconsistent state. (It is worth to be fixed.)
      */

    std::vector<RenameDescription> descriptions;
    descriptions.reserve(rename.elements.size());

    /// To avoid deadlocks, we must acquire locks for tables in same order in any different RENAMES.
    struct UniqueTableName
    {
        String database_name;
        String table_name;

        UniqueTableName(const String & database_name_, const String & table_name_)
            : database_name(database_name_), table_name(table_name_) {}

        bool operator< (const UniqueTableName & rhs) const
        {
            return std::tie(database_name, table_name) < std::tie(rhs.database_name, rhs.table_name);
        }
    };

    /// Don't allow to drop tables (that we are renaming); don't allow to create tables in places where tables will be renamed.
    std::map<UniqueTableName, std::unique_ptr<DDLGuard>> table_guards;

    for (const auto & elem : rename.elements)
    {
        descriptions.emplace_back(elem, current_database);
        const auto & description = descriptions.back();

        UniqueTableName from(description.from_database_name, description.from_table_name);
        UniqueTableName to(description.to_database_name, description.to_table_name);

        table_guards[from];
        table_guards[to];
    }

    auto & database_catalog = DatabaseCatalog::instance();

    /// Must do it in consistent order.
    for (auto & table_guard : table_guards)
        table_guard.second = database_catalog.getDDLGuard(table_guard.first.database_name, table_guard.first.table_name);

    for (auto & elem : descriptions)
    {
        database_catalog.assertTableDoesntExist(StorageID(elem.to_database_name, elem.to_table_name));

        database_catalog.getDatabase(elem.from_database_name)->renameTable(
            context,
            elem.from_table_name,
            *database_catalog.getDatabase(elem.to_database_name),
            elem.to_table_name);
    }

    return {};
}

AccessRightsElements InterpreterRenameQuery::getRequiredAccess() const
{
    AccessRightsElements required_access;
    const auto & rename = query_ptr->as<const ASTRenameQuery &>();
    for (const auto & elem : rename.elements)
    {
        required_access.emplace_back(AccessType::SELECT | AccessType::DROP_TABLE, elem.from.database, elem.from.table);
        required_access.emplace_back(AccessType::CREATE_TABLE | AccessType::INSERT, elem.to.database, elem.to.table);
    }
    return required_access;
}

}