minetest/src/database-sqlite3.cpp

/*
Minetest
Copyright (C) 2013 celeron55, Perttu Ahola <celeron55@gmail.com>

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/

/*
SQLite format specification:
	blocks:
		(PK) INT id
		BLOB data
*/


#include "database-sqlite3.h"

#include "log.h"
#include "filesys.h"
#include "exceptions.h"
#include "settings.h"
#include "porting.h"
#include "util/string.h"

#include <cassert>

// When to print messages when the database is being held locked by another process
// Note: I've seen occasional delays of over 250ms while running minetestmapper.
#define BUSY_INFO_TRESHOLD	100	// Print first informational message after 100ms.
#define BUSY_WARNING_TRESHOLD	250	// Print warning message after 250ms. Lag is increased.
#define BUSY_ERROR_TRESHOLD	1000	// Print error message after 1000ms. Significant lag.
#define BUSY_FATAL_TRESHOLD	3000	// Allow SQLITE_BUSY to be returned, which will cause a minetest crash.
#define BUSY_ERROR_INTERVAL	10000	// Safety net: report again every 10 seconds


#define SQLRES(s, r, m) \
	if ((s) != (r)) { \
		throw FileNotGoodException(std::string(m) + ": " +\
				sqlite3_errmsg(m_database)); \
	}
#define SQLOK(s, m) SQLRES(s, SQLITE_OK, m)

#define PREPARE_STATEMENT(name, query) \
	SQLOK(sqlite3_prepare_v2(m_database, query, -1, &m_stmt_##name, NULL),\
		"Failed to prepare query '" query "'")

#define FINALIZE_STATEMENT(statement) \
	SQLOK(sqlite3_finalize(statement), "Failed to finalize " #statement)

int Database_SQLite3::busyHandler(void *data, int count)
{
	s64 &first_time = reinterpret_cast<s64 *>(data)[0];
	s64 &prev_time = reinterpret_cast<s64 *>(data)[1];
	s64 cur_time = getTimeMs();

	if (count == 0) {
		first_time = cur_time;
		prev_time = first_time;
	} else {
		while (cur_time < prev_time)
			cur_time += s64(1)<<32;
	}

	if (cur_time - first_time < BUSY_INFO_TRESHOLD) {
		; // do nothing
	} else if (cur_time - first_time >= BUSY_INFO_TRESHOLD &&
			prev_time - first_time < BUSY_INFO_TRESHOLD) {
		infostream << "SQLite3 database has been locked for "
			<< cur_time - first_time << " ms." << std::endl;
	} else if (cur_time - first_time >= BUSY_WARNING_TRESHOLD &&
			prev_time - first_time < BUSY_WARNING_TRESHOLD) {
		warningstream << "SQLite3 database has been locked for "
			<< cur_time - first_time << " ms." << std::endl;
	} else if (cur_time - first_time >= BUSY_ERROR_TRESHOLD &&
			prev_time - first_time < BUSY_ERROR_TRESHOLD) {
		errorstream << "SQLite3 database has been locked for "
			<< cur_time - first_time << " ms; this causes lag." << std::endl;
	} else if (cur_time - first_time >= BUSY_FATAL_TRESHOLD &&
			prev_time - first_time < BUSY_FATAL_TRESHOLD) {
		errorstream << "SQLite3 database has been locked for "
			<< cur_time - first_time << " ms - giving up!" << std::endl;
	} else if ((cur_time - first_time) / BUSY_ERROR_INTERVAL !=
			(prev_time - first_time) / BUSY_ERROR_INTERVAL) {
		// Safety net: keep reporting every BUSY_ERROR_INTERVAL
		errorstream << "SQLite3 database has been locked for "
			<< (cur_time - first_time) / 1000 << " seconds!" << std::endl;
	}

	prev_time = cur_time;

	// Make sqlite transaction fail if delay exceeds BUSY_FATAL_TRESHOLD
	return cur_time - first_time < BUSY_FATAL_TRESHOLD;
}


Database_SQLite3::Database_SQLite3(const std::string &savedir) :
	m_initialized(false),
	m_savedir(savedir),
	m_database(NULL),
	m_stmt_read(NULL),
	m_stmt_write(NULL),
	m_stmt_list(NULL),
	m_stmt_delete(NULL),
	m_stmt_begin(NULL),
	m_stmt_end(NULL)
{
}

void Database_SQLite3::beginSave() {
	verifyDatabase();
	SQLRES(sqlite3_step(m_stmt_begin), SQLITE_DONE,
		"Failed to start SQLite3 transaction");
	sqlite3_reset(m_stmt_begin);
}

void Database_SQLite3::endSave() {
	verifyDatabase();
	SQLRES(sqlite3_step(m_stmt_end), SQLITE_DONE,
		"Failed to commit SQLite3 transaction");
	sqlite3_reset(m_stmt_end);
}

void Database_SQLite3::openDatabase()
{
	if (m_database) return;

	std::string dbp = m_savedir + DIR_DELIM + "map.sqlite";

	// Open the database connection

	if (!fs::CreateAllDirs(m_savedir)) {
		infostream << "Database_SQLite3: Failed to create directory \""
			<< m_savedir << "\"" << std::endl;
		throw FileNotGoodException("Failed to create database "
				"save directory");
	}

	bool needs_create = !fs::PathExists(dbp);

	SQLOK(sqlite3_open_v2(dbp.c_str(), &m_database,
			SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, NULL),
		std::string("Failed to open SQLite3 database file ") + dbp);

	SQLOK(sqlite3_busy_handler(m_database, Database_SQLite3::busyHandler,
		m_busy_handler_data), "Failed to set SQLite3 busy handler");

	if (needs_create) {
		createDatabase();
	}

	std::string query_str = std::string("PRAGMA synchronous = ")
			 + itos(g_settings->getU16("sqlite_synchronous"));
	SQLOK(sqlite3_exec(m_database, query_str.c_str(), NULL, NULL, NULL),
		"Failed to modify sqlite3 synchronous mode");
}

void Database_SQLite3::verifyDatabase()
{
	if (m_initialized) return;

	openDatabase();

	PREPARE_STATEMENT(begin, "BEGIN");
	PREPARE_STATEMENT(end, "COMMIT");
	PREPARE_STATEMENT(read, "SELECT `data` FROM `blocks` WHERE `pos` = ? LIMIT 1");
#ifdef __ANDROID__
	PREPARE_STATEMENT(write,  "INSERT INTO `blocks` (`pos`, `data`) VALUES (?, ?)");
#else
	PREPARE_STATEMENT(write, "REPLACE INTO `blocks` (`pos`, `data`) VALUES (?, ?)");
#endif
	PREPARE_STATEMENT(delete, "DELETE FROM `blocks` WHERE `pos` = ?");
	PREPARE_STATEMENT(list, "SELECT `pos` FROM `blocks`");

	m_initialized = true;

	verbosestream << "ServerMap: SQLite3 database opened." << std::endl;
}

inline void Database_SQLite3::bindPos(sqlite3_stmt *stmt, const v3s16 &pos, int index)
{
	SQLOK(sqlite3_bind_int64(stmt, index, getBlockAsInteger(pos)),
		"Internal error: failed to bind query at " __FILE__ ":" TOSTRING(__LINE__));
}

bool Database_SQLite3::deleteBlock(const v3s16 &pos)
{
	verifyDatabase();

	bindPos(m_stmt_delete, pos);

	bool good = sqlite3_step(m_stmt_delete) == SQLITE_DONE;
	sqlite3_reset(m_stmt_delete);

	if (!good) {
		warningstream << "deleteBlock: Block failed to delete "
			<< PP(pos) << ": " << sqlite3_errmsg(m_database) << std::endl;
	}
	return good;
}

bool Database_SQLite3::saveBlock(const v3s16 &pos, const std::string &data)
{
	verifyDatabase();

#ifdef __ANDROID__
	/**
	 * Note: For some unknown reason SQLite3 fails to REPLACE blocks on Android,
	 * deleting them and then inserting works.
	 */
	bindPos(m_stmt_read, pos);

	if (sqlite3_step(m_stmt_read) == SQLITE_ROW) {
		deleteBlock(pos);
	}
	sqlite3_reset(m_stmt_read);
#endif

	bindPos(m_stmt_write, pos);
	SQLOK(sqlite3_bind_blob(m_stmt_write, 2, data.data(), data.size(), NULL),
		"Internal error: failed to bind query at " __FILE__ ":" TOSTRING(__LINE__));

	SQLRES(sqlite3_step(m_stmt_write), SQLITE_DONE, "Failed to save block")
	sqlite3_reset(m_stmt_write);

	return true;
}

void Database_SQLite3::loadBlock(const v3s16 &pos, std::string *block)
{
	verifyDatabase();

	bindPos(m_stmt_read, pos);

	if (sqlite3_step(m_stmt_read) != SQLITE_ROW) {
		sqlite3_reset(m_stmt_read);
		return;
	}

	const char *data = (const char *) sqlite3_column_blob(m_stmt_read, 0);
	size_t len = sqlite3_column_bytes(m_stmt_read, 0);

	*block = (data) ? std::string(data, len) : "";

	sqlite3_step(m_stmt_read);
	// We should never get more than 1 row, so ok to reset
	sqlite3_reset(m_stmt_read);
}

void Database_SQLite3::createDatabase()
{
	assert(m_database); // Pre-condition
	SQLOK(sqlite3_exec(m_database,
		"CREATE TABLE IF NOT EXISTS `blocks` (\n"
		"	`pos` INT PRIMARY KEY,\n"
		"	`data` BLOB\n"
		");\n",
		NULL, NULL, NULL),
		"Failed to create database table");
}

void Database_SQLite3::listAllLoadableBlocks(std::vector<v3s16> &dst)
{
	verifyDatabase();

	while (sqlite3_step(m_stmt_list) == SQLITE_ROW) {
		dst.push_back(getIntegerAsBlock(sqlite3_column_int64(m_stmt_list, 0)));
	}
	sqlite3_reset(m_stmt_list);
}

Database_SQLite3::~Database_SQLite3()
{
	FINALIZE_STATEMENT(m_stmt_read)
	FINALIZE_STATEMENT(m_stmt_write)
	FINALIZE_STATEMENT(m_stmt_list)
	FINALIZE_STATEMENT(m_stmt_begin)
	FINALIZE_STATEMENT(m_stmt_end)
	FINALIZE_STATEMENT(m_stmt_delete)

	SQLOK(sqlite3_close(m_database), "Failed to close database");
}