ClickHouse/src/Storages/StorageNull.cpp

#include <Storages/StorageNull.h>
#include <Storages/StorageFactory.h>
#include <Storages/AlterCommands.h>

#include <Interpreters/InterpreterAlterQuery.h>
#include <Interpreters/Context.h>
#include <Databases/IDatabase.h>

#include <IO/WriteHelpers.h>


namespace DB
{

namespace ErrorCodes
{
    extern const int NOT_IMPLEMENTED;
    extern const int NUMBER_OF_ARGUMENTS_DOESNT_MATCH;
    extern const int ALTER_OF_COLUMN_IS_FORBIDDEN;
}


void registerStorageNull(StorageFactory & factory)
{
    factory.registerStorage("Null", [](const StorageFactory::Arguments & args)
    {
        if (!args.engine_args.empty())
            throw Exception(
                "Engine " + args.engine_name + " doesn't support any arguments (" + toString(args.engine_args.size()) + " given)",
                ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH);

        return StorageNull::create(args.table_id, args.columns, args.constraints, args.comment);
    },
    {
        .supports_parallel_insert = true,
    });
}

void StorageNull::checkAlterIsPossible(const AlterCommands & commands, ContextPtr context) const
{
    auto name_deps = getDependentViewsByColumn(context);
    for (const auto & command : commands)
    {
        if (command.type != AlterCommand::Type::ADD_COLUMN && command.type != AlterCommand::Type::MODIFY_COLUMN
            && command.type != AlterCommand::Type::DROP_COLUMN && command.type != AlterCommand::Type::COMMENT_COLUMN)
            throw Exception(
                "Alter of type '" + alterTypeToString(command.type) + "' is not supported by storage " + getName(),
                ErrorCodes::NOT_IMPLEMENTED);
        if (command.type == AlterCommand::DROP_COLUMN && !command.clear)
        {
            const auto & deps_mv = name_deps[command.column_name];
            if (!deps_mv.empty())
            {
                throw Exception(
                    "Trying to ALTER DROP column " + backQuoteIfNeed(command.column_name) + " which is referenced by materialized view "
                        + toString(deps_mv),
                    ErrorCodes::ALTER_OF_COLUMN_IS_FORBIDDEN);
            }
        }
    }
}


void StorageNull::alter(const AlterCommands & params, ContextPtr context, TableLockHolder &)
{
    auto table_id = getStorageID();

    StorageInMemoryMetadata new_metadata = getInMemoryMetadata();
    params.apply(new_metadata, context);
    DatabaseCatalog::instance().getDatabase(table_id.database_name)->alterTable(context, table_id, new_metadata);
    setInMemoryMetadata(new_metadata);
}

}