Index improvements on oc_preferences

[juliusknorr]

IConfig methods may issue queries which are causing a full table scan on oc_preferences with using the existing primary key as an index as it is only partially filtered for in the where clause, as the order seems to be relevant (userid,appid,configkey)

server/lib/private/AllConfig.php

Lines 485 to 490 in c92ac34

	public function getUsersForUserValue($appName, $key, $value) {
	// TODO - FIXME
	$this->fixDIInit();
	$sql = 'SELECT `userid` FROM `*PREFIX*preferences` ' .
	'WHERE `appid` = ? AND `configkey` = ? ';

server/lib/private/AllConfig.php

Lines 387 to 392 in c92ac34

	public function deleteAppFromAllUsers($appName) {
	// TODO - FIXME
	$this->fixDIInit();
	$sql = 'DELETE FROM `*PREFIX*preferences` '.
	'WHERE `appid` = ?';

• Partial index after Always store and compare the email address as lower case #30197

CREATE INDEX prefix_configvalue_index on oc_preferences (configvalue(80));