ClickHouse/dbms/src/Databases/DatabaseOrdinary.cpp

#include <Poco/DirectoryIterator.h>
#include <common/logger_useful.h>

#include <DB/Databases/DatabaseOrdinary.h>
#include <DB/Databases/DatabaseMemory.h>
#include <DB/Databases/DatabasesCommon.h>
#include <DB/Common/escapeForFileName.h>
#include <DB/Common/StringUtils.h>
#include <DB/Common/Stopwatch.h>
#include <DB/Parsers/ASTCreateQuery.h>
#include <DB/Parsers/parseQuery.h>
#include <DB/Parsers/ParserCreateQuery.h>
#include <DB/Interpreters/Context.h>
#include <DB/Interpreters/Settings.h>
#include <DB/Interpreters/InterpreterCreateQuery.h>
#include <DB/IO/WriteBufferFromFile.h>
#include <DB/IO/ReadBufferFromFile.h>


namespace DB
{

namespace ErrorCodes
{
	extern const int TABLE_ALREADY_EXISTS;
	extern const int UNKNOWN_TABLE;
	extern const int TABLE_METADATA_DOESNT_EXIST;
	extern const int CANNOT_CREATE_TABLE_FROM_METADATA;
	extern const int INCORRECT_FILE_NAME;
	extern const int LOGICAL_ERROR;
}


static constexpr size_t PRINT_MESSAGE_EACH_N_TABLES = 256;
static constexpr size_t PRINT_MESSAGE_EACH_N_SECONDS = 5;
static constexpr size_t METADATA_FILE_BUFFER_SIZE = 32768;
static constexpr size_t TABLES_PARALLEL_LOAD_BUNCH_SIZE = 100;


static String getTableMetadataPath(const String & base_path, const String & table_name)
{
	return base_path + (endsWith(base_path, "/") ? "" : "/") + escapeForFileName(table_name) + ".sql";
}

static void loadTable(
	Context & context,
	const String & database_metadata_path,
	DatabaseOrdinary & database,
	const String & database_name,
	const String & database_data_path,
	const String & file_name,
	bool has_force_restore_data_flag)
{
	Logger * log = &Logger::get("loadTable");

	const String table_metadata_path = database_metadata_path + "/" + file_name;

	String s;
	{
		char in_buf[METADATA_FILE_BUFFER_SIZE];
		ReadBufferFromFile in(table_metadata_path, METADATA_FILE_BUFFER_SIZE, -1, in_buf);
		readStringUntilEOF(s, in);
	}

	/** Empty files with metadata are generated after a rough restart of the server.
	  * Remove these files to slightly reduce the work of the admins on startup.
	  */
	if (s.empty())
	{
		LOG_ERROR(log, "File " << table_metadata_path << " is empty. Removing.");
		Poco::File(table_metadata_path).remove();
		return;
	}

	try
	{
		String table_name;
		StoragePtr table;
		std::tie(table_name, table) = createTableFromDefinition(
			s, database_name, database_data_path, context, has_force_restore_data_flag, "in file " + table_metadata_path);
		database.attachTable(table_name, table);
	}
	catch (const Exception & e)
	{
		throw Exception("Cannot create table from metadata file " + table_metadata_path + ", error: " + e.displayText() +
			", stack trace:\n" + e.getStackTrace().toString(),
			ErrorCodes::CANNOT_CREATE_TABLE_FROM_METADATA);
	}
}


DatabaseOrdinary::DatabaseOrdinary(
	const String & name_, const String & path_)
	: DatabaseMemory(name_), path(path_)
{
}


void DatabaseOrdinary::loadTables(Context & context, ThreadPool * thread_pool, bool has_force_restore_data_flag)
{
	log = &Logger::get("DatabaseOrdinary (" + name + ")");

	using FileNames = std::vector<std::string>;
	FileNames file_names;

	Poco::DirectoryIterator dir_end;
	for (Poco::DirectoryIterator dir_it(path); dir_it != dir_end; ++dir_it)
	{
		/// For '.svn', '.gitignore' directory and similar.
		if (dir_it.name().at(0) == '.')
			continue;

		/// There are .sql.bak files - skip them.
		if (endsWith(dir_it.name(), ".sql.bak"))
			continue;

		/// There are files .sql.tmp - delete.
		if (endsWith(dir_it.name(), ".sql.tmp"))
		{
			LOG_INFO(log, "Removing file " << dir_it->path());
			Poco::File(dir_it->path()).remove();
			continue;
		}

		/// The required files have names like `table_name.sql`
		if (endsWith(dir_it.name(), ".sql"))
			file_names.push_back(dir_it.name());
		else
			throw Exception("Incorrect file extension: " + dir_it.name() + " in metadata directory " + path,
				ErrorCodes::INCORRECT_FILE_NAME);
	}

	/** Tables load faster if they are loaded in sorted (by name) order.
	  * Otherwise (for the ext4 file system), `DirectoryIterator` iterates through them in some order,
	  *  which does not correspond to order tables creation and does not correspond to order of their location on disk.
	  */
	std::sort(file_names.begin(), file_names.end());

	size_t total_tables = file_names.size();
	LOG_INFO(log, "Total " << total_tables << " tables.");

	String data_path = context.getPath() + "/data/" + escapeForFileName(name) + "/";

	StopwatchWithLock watch;
	std::atomic<size_t> tables_processed {0};

	auto task_function = [&](FileNames::const_iterator begin, FileNames::const_iterator end)
	{
		for (FileNames::const_iterator it = begin; it != end; ++it)
		{
			const String & table = *it;

			/// Messages, so that it's not boring to wait for the server to load for a long time.
			if ((++tables_processed) % PRINT_MESSAGE_EACH_N_TABLES == 0
				|| watch.lockTestAndRestart(PRINT_MESSAGE_EACH_N_SECONDS))
			{
				LOG_INFO(log, std::fixed << std::setprecision(2) << tables_processed * 100.0 / total_tables << "%");
				watch.restart();
			}

			loadTable(context, path, *this, name, data_path, table, has_force_restore_data_flag);
		}
	};

	/** `packaged_task` is used so that exceptions are automatically passed to the main thread.
	  * Disadvantage - exceptions fall into the main thread only after the end of all tasks.
	  */

	const size_t bunch_size = TABLES_PARALLEL_LOAD_BUNCH_SIZE;
	size_t num_bunches = (total_tables + bunch_size - 1) / bunch_size;

	for (size_t i = 0; i < num_bunches; ++i)
	{
		auto begin = file_names.begin() + i * bunch_size;
		auto end = (i + 1 == num_bunches)
			? file_names.end()
			: (file_names.begin() + (i + 1) * bunch_size);

		auto task = std::bind(task_function, begin, end);

		if (thread_pool)
			thread_pool->schedule(task);
		else
			task();
	}

	if (thread_pool)
		thread_pool->wait();
}


void DatabaseOrdinary::createTable(
	const String & table_name, const StoragePtr & table, const ASTPtr & query, const String & engine, const Settings & settings)
{
	/// Create a file with metadata if necessary - if the query is not ATTACH.
	/// Write the query of `ATTACH table` to it.

	/** The code is based on the assumption that all threads share the same order of operations
	  * - creating the .sql.tmp file;
	  * - adding a table to `tables`;
	  * - rename .sql.tmp to .sql.
	  */

	/// A race condition would be possible if a table with the same name is simultaneously created using CREATE and using ATTACH.
	/// But there is protection from it - see using DDLGuard in InterpreterCreateQuery.

	{
		std::lock_guard<std::mutex> lock(mutex);
		if (tables.count(table_name))
			throw Exception("Table " + name + "." + table_name + " already exists.", ErrorCodes::TABLE_ALREADY_EXISTS);
	}

	String table_metadata_path = getTableMetadataPath(path, table_name);
	String table_metadata_tmp_path = table_metadata_path + ".tmp";
	String statement;

	{
		statement = getTableDefinitionFromCreateQuery(query);

		/// Exclusive flags guarantees, that table is not created right now in another thread. Otherwise, exception will be thrown.
		WriteBufferFromFile out(table_metadata_tmp_path, statement.size(), O_WRONLY | O_CREAT | O_EXCL);
		writeString(statement, out);
		out.next();
		if (settings.fsync_metadata)
			out.sync();
		out.close();
	}

	try
	{
		/// Add a table to the map of known tables.
		{
			std::lock_guard<std::mutex> lock(mutex);
			if (!tables.emplace(table_name, table).second)
				throw Exception("Table " + name + "." + table_name + " already exists.", ErrorCodes::TABLE_ALREADY_EXISTS);
		}

		/// If it was ATTACH query and file with table metadata already exist
		/// (so, ATTACH is done after DETACH), then rename atomically replaces old file with new one.
		Poco::File(table_metadata_tmp_path).renameTo(table_metadata_path);
	}
	catch (...)
	{
		Poco::File(table_metadata_tmp_path).remove();
		throw;
	}
}


void DatabaseOrdinary::removeTable(const String & table_name)
{
	StoragePtr res = detachTable(table_name);

	String table_metadata_path = getTableMetadataPath(path, table_name);

	try
	{
		Poco::File(table_metadata_path).remove();
	}
	catch (...)
	{
		attachTable(table_name, res);
		throw;
	}
}


static ASTPtr getCreateQueryImpl(const String & path, const String & table_name)
{
	String table_metadata_path = getTableMetadataPath(path, table_name);

	String query;
	{
		ReadBufferFromFile in(table_metadata_path, 4096);
		readStringUntilEOF(query, in);
	}

	ParserCreateQuery parser;
	return parseQuery(parser, query.data(), query.data() + query.size(), "in file " + table_metadata_path);
}


void DatabaseOrdinary::renameTable(
	const Context & context, const String & table_name, IDatabase & to_database, const String & to_table_name, const Settings & settings)
{
	DatabaseOrdinary * to_database_concrete = typeid_cast<DatabaseOrdinary *>(&to_database);

	if (!to_database_concrete)
		throw Exception("Moving tables between databases of different engines is not supported", ErrorCodes::NOT_IMPLEMENTED);

	StoragePtr table = tryGetTable(table_name);

	if (!table)
		throw Exception("Table " + name + "." + table_name + " doesn't exist.", ErrorCodes::TABLE_ALREADY_EXISTS);

	/// Notify the table that it is renamed. If the table does not support renaming, exception is thrown.
	try
	{
		table->rename(context.getPath() + "/data/" + escapeForFileName(to_database_concrete->name) + "/",
			to_database_concrete->name,
			to_table_name);
	}
	catch (const Poco::Exception & e)
	{
		/// More good diagnostics.
		throw Exception{e};
	}

	ASTPtr ast = getCreateQueryImpl(path, table_name);
	ASTCreateQuery & ast_create_query = typeid_cast<ASTCreateQuery &>(*ast);
	ast_create_query.table = to_table_name;

	/// NOTE Non-atomic.
	to_database_concrete->createTable(to_table_name, table, ast, table->getName(), settings);
	removeTable(table_name);
}


time_t DatabaseOrdinary::getTableMetadataModificationTime(const String & table_name)
{
	String table_metadata_path = getTableMetadataPath(path, table_name);
	Poco::File meta_file(table_metadata_path);

	if (meta_file.exists())
	{
		return meta_file.getLastModified().epochTime();
	}
	else
	{
		return static_cast<time_t>(0);
	}
}


ASTPtr DatabaseOrdinary::getCreateQuery(const String & table_name) const
{
	ASTPtr ast = getCreateQueryImpl(path, table_name);

	ASTCreateQuery & ast_create_query = typeid_cast<ASTCreateQuery &>(*ast);
	ast_create_query.attach = false;
	ast_create_query.database = name;

	return ast;
}


void DatabaseOrdinary::shutdown()
{
	/// You can not hold a lock during shutdown.
	/// Because inside `shutdown` function the tables can work with database, and mutex is not recursive.

	for (auto iterator = getIterator(); iterator->isValid(); iterator->next())
		iterator->table()->shutdown();

	std::lock_guard<std::mutex> lock(mutex);
	tables.clear();
}


void DatabaseOrdinary::drop()
{
	/// No additional removal actions are required.
}


void DatabaseOrdinary::alterTable(
	const Context & context,
	const String & name,
	const NamesAndTypesList & columns,
	const NamesAndTypesList & materialized_columns,
	const NamesAndTypesList & alias_columns,
	const ColumnDefaults & column_defaults,
	const ASTModifier & engine_modifier)
{
	/// Read the definition of the table and replace the necessary parts with new ones.

	String table_name_escaped = escapeForFileName(name);
	String table_metadata_tmp_path = path + "/" + table_name_escaped + ".sql.tmp";
	String table_metadata_path = path + "/" + table_name_escaped + ".sql";
	String statement;

	{
		char in_buf[METADATA_FILE_BUFFER_SIZE];
		ReadBufferFromFile in(table_metadata_path, METADATA_FILE_BUFFER_SIZE, -1, in_buf);
		readStringUntilEOF(statement, in);
	}

	ParserCreateQuery parser;
	ASTPtr ast = parseQuery(parser, statement.data(), statement.data() + statement.size(), "in file " + table_metadata_path);

	ASTCreateQuery & ast_create_query = typeid_cast<ASTCreateQuery &>(*ast);

	ASTPtr new_columns = InterpreterCreateQuery::formatColumns(columns, materialized_columns, alias_columns, column_defaults);
	auto it = std::find(ast_create_query.children.begin(), ast_create_query.children.end(), ast_create_query.columns);
	if (it == ast_create_query.children.end())
		throw Exception("Logical error: cannot find columns child in ASTCreateQuery", ErrorCodes::LOGICAL_ERROR);
	*it = new_columns;
	ast_create_query.columns = new_columns;

	if (engine_modifier)
		engine_modifier(ast_create_query.storage);

	statement = getTableDefinitionFromCreateQuery(ast);

	{
		WriteBufferFromFile out(table_metadata_tmp_path, statement.size(), O_WRONLY | O_CREAT | O_EXCL);
		writeString(statement, out);
		out.next();
		if (context.getSettingsRef().fsync_metadata)
			out.sync();
		out.close();
	}

	try
	{
		/// rename atomically replaces the old file with the new one.
		Poco::File(table_metadata_tmp_path).renameTo(table_metadata_path);
	}
	catch (...)
	{
		Poco::File(table_metadata_tmp_path).remove();
		throw;
	}
}

}