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MDL-63983 messaging: Improve the performance of non-contact searches

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When the messagingallusers setting is disabled only contacts that are
on the same course as the user should be returned as results.

We can reduce the number of candidate users significantly by
pre-filtering them by being enrolled on the same courses as the user
performing the search.

Since we must also return the user themselves sometimes, even when they
are not enrolled on a course I used a UNION as the most efficient way of
retriving them, this meant that the order by had to reference returned
columns by number to be sufficiently cross-database compatiable.
This commit is contained in:
Neill Magill 2020-10-06 10:57:36 +01:00
parent 2b2897bf10
commit a8d9b17b4b
1 changed files with 56 additions and 15 deletions
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71
message/classes/api.php
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@ -239,23 +239,64 @@ class api {
// Let's get those non-contacts.
// Because we can't achieve all the required visibility checks in SQL, we'll iterate through the non-contact records
// and stop once we have enough matching the 'visible' criteria.
// TODO: MDL-63983 - Improve the performance of non-contact searches when site-wide messaging is disabled (default).
// Use a local generator to achieve this iteration.
$getnoncontactusers = function ($limitfrom = 0, $limitnum = 0) use($fullname, $exclude, $params, $excludeparams) {
global $DB;
$sql = "SELECT u.*
FROM {user} u
WHERE u.deleted = 0
AND u.confirmed = 1
AND " . $DB->sql_like($fullname, ':search', false) . "
AND u.id $exclude
AND NOT EXISTS (SELECT mc.id
FROM {message_contacts} mc
WHERE (mc.userid = u.id AND mc.contactid = :userid1)
OR (mc.userid = :userid2 AND mc.contactid = u.id))
ORDER BY " . $DB->sql_fullname();
while ($records = $DB->get_records_sql($sql, $params + $excludeparams, $limitfrom, $limitnum)) {
$getnoncontactusers = function ($limitfrom = 0, $limitnum = 0) use (
$fullname,
$exclude,
$params,
$excludeparams,
$userid,
$selfconversation
) {
global $DB, $CFG;
$joinenrolled = '';
$enrolled = '';
$unionself = '';
$enrolledparams = [];
// Since we want to order a UNION we need to list out all the user fields individually this will
// allow us to reference the fullname correctly.
$userfields = implode(', u.', get_user_fieldnames());
$select = "u.id, " . $DB->sql_fullname() ." AS sortingname, u." . $userfields;
// When messageallusers is false valid non-contacts must be enrolled on one of the users courses.
if (empty($CFG->messagingallusers)) {
$joinenrolled = "JOIN {user_enrolments} ue ON ue.userid = u.id
JOIN {enrol} e ON e.id = ue.enrolid";
$enrolled = "AND e.courseid IN (
SELECT e.courseid
FROM {user_enrolments} ue
JOIN {enrol} e ON e.id = ue.enrolid
WHERE ue.userid = :enroluserid
)";
if ($selfconversation !== false) {
// We must include the user themselves, when they have a self conversation, even if they are not
// enrolled on any courses.
$unionself = "UNION SELECT u.id FROM {user} u
WHERE u.id = :self AND ". $DB->sql_like($fullname, ':selfsearch', false);
}
$enrolledparams = ['enroluserid' => $userid, 'self' => $userid, 'selfsearch' => $params['search']];
}
$sql = "SELECT $select
FROM (
SELECT DISTINCT u.id
FROM {user} u $joinenrolled
WHERE u.deleted = 0
AND u.confirmed = 1
AND " . $DB->sql_like($fullname, ':search', false) . "
AND u.id $exclude $enrolled
AND NOT EXISTS (SELECT mc.id
FROM {message_contacts} mc
WHERE (mc.userid = u.id AND mc.contactid = :userid1)
OR (mc.userid = :userid2 AND mc.contactid = u.id)) $unionself
) targetedusers
JOIN {user} u ON u.id = targetedusers.id
ORDER BY 2";
while ($records = $DB->get_records_sql($sql, $params + $excludeparams + $enrolledparams, $limitfrom, $limitnum)) {
yield $records;
$limitfrom += $limitnum;
}