void loadMetadata(Context & context)
{
String path = context.getPath() + "metadata";
/** There may exist 'force_restore_data' file, that means,
* skip safety threshold on difference of data parts while initializing tables.
* This file is deleted after successful loading of tables.
* (flag is "one-shot")
*/
Poco::File force_restore_data_flag_file(context.getFlagsPath() + "force_restore_data");
bool has_force_restore_data_flag = force_restore_data_flag_file.exists();
/// For parallel tables loading.
ThreadPool thread_pool(SettingMaxThreads().getAutoValue());
/// Loop over databases.
Poco::DirectoryIterator dir_end;
for (Poco::DirectoryIterator it(path); it != dir_end; ++it)
{
if (!it->isDirectory())
continue;
/// For '.svn', '.gitignore' directory and similar.
if (it.name().at(0) == '.')
continue;
String database = unescapeForFileName(it.name());
/// There may exist .sql file with database creation statement.
/// Or, if it is absent, then database with default engine is created.
String database_attach_query;
String database_metadata_file = it->path() + ".sql";
if (Poco::File(database_metadata_file).exists())
{
ReadBufferFromFile in(database_metadata_file, 1024);
readStringUntilEOF(database_attach_query, in);
}
else
database_attach_query = "ATTACH DATABASE " + backQuoteIfNeed(database);
executeCreateQuery(database_attach_query, context, database, it->path(), thread_pool, has_force_restore_data_flag);
}
thread_pool.wait();
if (has_force_restore_data_flag)
force_restore_data_flag_file.remove();
}
void loadMetadata(Context & context)
{
String path = context.getPath() + "metadata";
/// Используется для параллельной загрузки таблиц.
ThreadPool thread_pool(SettingMaxThreads().getAutoValue());
/// Цикл по базам данных
Poco::DirectoryIterator dir_end;
for (Poco::DirectoryIterator it(path); it != dir_end; ++it)
{
if (!it->isDirectory())
continue;
/// Для директории .svn
if (it.name().at(0) == '.')
continue;
String database = unescapeForFileName(it.name());
/// Для базы данных может быть расположен .sql файл, где описан запрос на её создание.
/// А если такого файла нет, то создаётся база данных с движком по-умолчанию.
String database_attach_query;
String database_metadata_file = it->path() + ".sql";
if (Poco::File(database_metadata_file).exists())
{
ReadBufferFromFile in(database_metadata_file, 1024);
readStringUntilEOF(database_attach_query, in);
}
else
database_attach_query = "ATTACH DATABASE " + backQuoteIfNeed(database);
executeCreateQuery(database_attach_query, context, database, it->path(), thread_pool);
}
thread_pool.wait();
}
