Redmine

SUM of time entries query loading issue
when, i remove where clause query gets executed quickly.(I know the where clause is important to validate the module is enabled for the project).
In JOIN clauses, The query validates issue_tracking module is enabled or not.
again in WHERE Clause, The validation happens for time_tracking module.
In this case, when join exec happens 4496 columns filtered
when exec move to LEFT OUTER JOIN, issue_tracking module validation. 1181 rows get filtered.
Now in where clause another 1181 again.
(4496 * 1181 * 1181) now of rows examined in query is increased.

SELECT
    SUM(`time_entries`.`hours`)
FROM
    `time_entries`
    INNER JOIN `projects` ON `projects`.`id` = `time_entries`.`project_id`
    INNER JOIN `enumerations` ON `enumerations`.`id` = `time_entries`.`activity_id`
    AND `enumerations`.`type` = 'TimeEntryActivity' 
    INNER JOIN `users` ON `users`.`id` = `time_entries`.`user_id`
    AND `users`.`type` IN ('User', 'AnonymousUser')
    LEFT OUTER JOIN issues ON issues.id = time_entries.issue_id
    AND (
        projects.status IN (1, 5)
        AND EXISTS (
            SELECT
                1 AS one
            FROM
                enabled_modules em
            WHERE
                em.project_id = projects.id
                AND em.name = 'issue_tracking'
        )
    )
WHERE 
    (
        projects.status IN (1, 5)
        AND EXISTS (
            SELECT
                1 AS one
            FROM
                enabled_modules em
            WHERE
                em.project_id = projects.id
                AND em.name = 'time_tracking'
        )
    )