Method updateMetadataFile

src/Interpreters/DatabaseCatalog.cpp:777–812

}

void DatabaseCatalog::updateMetadataFile(const String & database_name, const ASTPtr & create_query)
{
    std::lock_guard lock{databases_mutex};
    if (!create_query)
        throw Exception(ErrorCodes::THERE_IS_NO_QUERY, "Unable to show the create query of database {}", backQuoteIfNeed(database_name));

    auto * ast_create_query = create_query->as<ASTCreateQuery>();
    ast_create_query->attach = true;

    WriteBufferFromOwnString statement_buf;
    IAST::FormatSettings format_settings(/*one_line=*/false);
    ast_create_query->format(statement_buf, format_settings);
    writeChar('\n', statement_buf);
    String statement = statement_buf.str();

    auto metadata_file_path = getMetadataFilePath(database_name);
    auto metadata_tmp_file_path = getMetadataTmpFilePath(database_name);
    auto default_db_disk = getContext()->getDatabaseDisk();

    writeMetadataFile(
        default_db_disk,
        /*file_path=*/metadata_tmp_file_path,
        /*content=*/statement,
        getContext()->getSettingsRef()[Setting::fsync_metadata]);

    try
    {
        /// rename atomically replaces the old file with the new one.
        default_db_disk->replaceFile(metadata_tmp_file_path, metadata_file_path);
    }
    catch (...)
    {
        default_db_disk->removeFileIfExists(metadata_tmp_file_path);
        throw;
    }
}

DatabasePtr DatabaseCatalog::getDatabase(std::string_view database_name) const
{