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482ca72089
This is an extremely dangerous query, because it includes the user
table twice, along-side two other potentially large tables,
role_assignments and user_enrolments.
The solution is to rewrite the query so that:
1. The subquery is JOINed, not WHERE ... INed. Typically query
optimisers handle the JOIN case better.
2. Before the join was role-assignments <-> users <-> subquery.
That is, everything was linked to u.id.
Now the linking is role-assignments <-> subquery <-> users,
so the SELECT DISTINT eu1_u.id FROM {enrolled users} is central.
That seems to send a strong hint to the query optimiser about
a good order to execute the query.
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| .. | ||
| classes | ||
| tests | ||
| admins.php | ||
| allow.php | ||
| assign.php | ||
| check.php | ||
| define.php | ||
| lib.php | ||
| manage.php | ||
| managetabs.php | ||
| module.js | ||
| override.php | ||
| permissions.php | ||
| role_schema.xml | ||
| usersroles.php | ||