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The user_groups table maps the users in a particular MediaWiki installation to their corresponding user rights. Each group can be assigned a mixture of permissions through LocalSettings.php or via extensions; all users of a particular group have those permissions granted to them as a result of their membership in the group. As the table is separate from the user table, this allows for the creation of a shared user database with permissions that vary from wiki to wiki within a wiki farm. This table was introduced on r5648, in MediaWiki 1.5. If you are using MediaWiki 1.3 or 1.4, have a look at Manual:User rights (older versions) . Before MediaWiki 1.5, user rights were stored in the user_rights field of the user table.

All unregistered users automatically belong to the '*' group and only to that group; all registered users additionally are automatically part of the 'user' group. User groups are additive; as a result, all registered users have all the privileges assigned to the '*' group as well. Formerly there was a "sysop bit"; now, making a user a sysop adds a row to user_groups.

This field links to a given user's user_id . It is a foreign key used to link accounts with their assigned privileges.

This field stores the user's permissions, which are stored as groups. At runtime, $wgGroupPermissions will associate group keys with particular permissions; a user will have the combined permissions of any group they're explicitly in, plus the implicit '*' and 'user' groups. Example ug_group values: 'bot', 'bureaucrat', 'sysop'.

There is one row for each (explicit) group the user is in.

This field stores a user group's expiry time. It is similar to pr_expiry in the page_restrictions table and ipb_expiry in the ipblocks table.

DESCRIBE user_groups;

+-----------+------------------+------+-----+---------+-------+
| Field     | Type             | Null | Key | Default | Extra |
+-----------+------------------+------+-----+---------+-------+
| ug_user   | int(10) unsigned | NO   | PRI | 0       |       |
| ug_group  | varbinary(255)   | NO   | PRI |         |       |
| ug_expiry | varbinary(14)    | YES  | MUL | NULL    |       |
+-----------+------------------+------+-----+---------+-------+

DESCRIBE user_groups;

+----------+------------------+------+-----+---------+-------+
| Field    | Type             | Null | Key | Default | Extra |
+----------+------------------+------+-----+---------+-------+
| ug_user  | int(10) unsigned | NO   | PRI | 0       |       |
| ug_group | varbinary(255)   | NO   | PRI |         |       |
+----------+------------------+------+-----+---------+-------+

DESCRIBE user_groups;

+----------+------------------+------+-----+---------+-------+
| Field    | Type             | Null | Key | Default | Extra |
+----------+------------------+------+-----+---------+-------+
| ug_user  | int(10) unsigned | NO   | PRI | 0       |       |
| ug_group | varbinary(32)    | NO   | PRI |         |       |
+----------+------------------+------+-----+---------+-------+

DESCRIBE user_groups;

+----------+------------------+------+-----+---------+-------+
| Field    | Type             | Null | Key | Default | Extra |
+----------+------------------+------+-----+---------+-------+
| ug_user  | int(10) unsigned | NO   | PRI | 0       |       |
| ug_group | varbinary(16)    | NO   | PRI |         |       |
+----------+------------------+------+-----+---------+-------+

DESCRIBE user_groups;

+----------+-----------------+------+-----+---------+-------+
| Field    | Type            | Null | Key | Default | Extra |
+----------+-----------------+------+-----+---------+-------+
| ug_user  | int(5) unsigned | NO   | PRI | 0       |       |
| ug_group | char(16)        | NO   | PRI |         |       |
+----------+-----------------+------+-----+---------+-------+

SHOW INDEX IN user_groups;

+-------------+------------+-----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table       | Non_unique | Key_name  | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-------------+------------+-----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| user_groups |          0 | PRIMARY   |            1 | ug_user     | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
| user_groups |          0 | PRIMARY   |            2 | ug_group    | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
| user_groups |          1 | ug_group  |            1 | ug_group    | A         |           0 |     NULL | NULL   |      | BTREE      |         |               |
| user_groups |          1 | ug_expiry |            1 | ug_expiry   | A         |           0 |     NULL | NULL   | YES  | BTREE      |         |               |
+-------------+------------+-----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

In a default MediaWiki installation, ug_group can be one of the following:

SELECT DISTINCT `ug_group` FROM `user_groups`;

+------------+
| ug_group   |
+------------+
| bot        |
| bureaucrat |
| sysop      |
+------------+

• MediaWiki database tables