Moodle foreign keys

Moodle foreign keys

i am installing moodle (2.2 or 2.5) and modified the sql generator.php to
have foreign keys and map the database for studies proposes and i get this
allways, i am using 5.5.27 - MySQL Community Server by the way
Debug info: Table 'config' already exists CREATE TABLE config ( id
BIGINT(10) NOT NULL auto_increment, name VARCHAR(255) CHARACTER SET utf8
COLLATE utf8_spanish_ci NOT NULL DEFAULT '', value LONGTEXT CHARACTER SET
utf8 COLLATE utf8_spanish_ci NOT NULL, CONSTRAINT PRIMARY KEY (id) )
ENGINE = InnoDB DEFAULT CHARACTER SET utf8 DEFAULT COLLATE =
utf8_spanish_ci Error code: ddlexecuteerror Stack trace:
line 429 of \lib\dml\moodle_database.php: ddl_change_structure_exception
thrown
line 842 of \lib\dml\mysqli_native_moodle_database.php: call to
moodle_database->query_end()
line 88 of \lib\ddl\database_manager.php: call to
mysqli_native_moodle_database->change_database_structure()
line 77 of \lib\ddl\database_manager.php: call to
database_manager->execute_sql()
line 417 of \lib\ddl\database_manager.php: call to
database_manager->execute_sql_arr()
line 369 of \lib\ddl\database_manager.php: call to
database_manager->install_from_xmldb_structure()
line 1479 of \lib\upgradelib.php: call to
database_manager->install_from_xmldb_file()
line 203 of \admin\index.php: call to install_core()
i found this is a minor bug at https://tracker.moodle.org/browse/MDL-20437
anyways its for the version 1.9 but this is not the version i try to
install
i have searched so far and no solution!. did someone actually fix this