Redmine

When using the autocomplete feature to list issues by typing "##", an N+1 query occurs for loading associated trackers. Each issue's tracker is queried individually.

The attached patch fixes the problem by eager-loading the tracker association.

Before:

  Issue Load (1.2ms)  SELECT `issues`.* FROM `issues` INNER JOIN `projects` ON `projects`.`id` = `issues`.`project_id` WHERE `issues`.`project_id` = 1 AND (projects.status <> 9 AND projects.status <> 10 AND EXISTS (SELECT 1 AS one FROM enabled_modules em WHERE em.project_id = projects.id AND em.name='issue_tracking')) AND (issues.subject LIKE '%c%') ORDER BY `issues`.`id` DESC LIMIT 10
  ↳ app/controllers/auto_completes_controller.rb:36:in 'AutoCompletesController#issues'
  Tracker Load (0.4ms)  SELECT `trackers`.* FROM `trackers` WHERE `trackers`.`id` = 1 LIMIT 1
  ↳ app/controllers/auto_completes_controller.rb:77:in 'block in AutoCompletesController#format_issues_json'
  CACHE Tracker Load (0.0ms)  SELECT `trackers`.* FROM `trackers` WHERE `trackers`.`id` = 1 LIMIT 1
  ↳ app/controllers/auto_completes_controller.rb:77:in 'block in AutoCompletesController#format_issues_json'
  CACHE Tracker Load (0.0ms)  SELECT `trackers`.* FROM `trackers` WHERE `trackers`.`id` = 1 LIMIT 1
  ↳ app/controllers/auto_completes_controller.rb:77:in 'block in AutoCompletesController#format_issues_json'
  CACHE Tracker Load (0.0ms)  SELECT `trackers`.* FROM `trackers` WHERE `trackers`.`id` = 1 LIMIT 1
  ↳ app/controllers/auto_completes_controller.rb:77:in 'block in AutoCompletesController#format_issues_json'
  Tracker Load (0.5ms)  SELECT `trackers`.* FROM `trackers` WHERE `trackers`.`id` = 2 LIMIT 1
  ↳ app/controllers/auto_completes_controller.rb:77:in 'block in AutoCompletesController#format_issues_json'
  CACHE Tracker Load (0.0ms)  SELECT `trackers`.* FROM `trackers` WHERE `trackers`.`id` = 1 LIMIT 1
  ↳ app/controllers/auto_completes_controller.rb:77:in 'block in AutoCompletesController#format_issues_json'

After:

  Issue Load (1.2ms)  SELECT `issues`.* FROM `issues` INNER JOIN `projects` ON `projects`.`id` = `issues`.`project_id` WHERE `issues`.`project_id` = 1 AND (projects.status <> 9 AND projects.status <> 10 AND EXISTS (SELECT 1 AS one FROM enabled_modules em WHERE em.project_id = projects.id AND em.name='issue_tracking')) ORDER BY `issues`.`id` DESC LIMIT 10
  ↳ app/controllers/auto_completes_controller.rb:39:in 'AutoCompletesController#issues'
  Tracker Load (0.6ms)  SELECT `trackers`.* FROM `trackers` WHERE `trackers`.`id` IN (1, 2)