Fix N+1 queries fetching all projects

[eduardoj]

Craft with a scope the join condition of projects and values. This prevent N+1 queries.

Also, remove the loop to render more than one value for the OBS:QualityCategory attribute. This attribute can only keep one value.

Before

The last query (SELECT attrib_values.* FROM attrib_values INNER JOIN...) is repeated 25 times.

Project Load (0.7ms)  SELECT `projects`.* FROM `projects` WHERE `projects`.`id` != 0 AND NOT (name rlike '^home:.+') ORDER BY projects.name ASC LIMIT 25 OFFSET 0
↳ app/datatables/project_datatable.rb:33:in `map'
AttribValue Load (0.5ms)  SELECT `attrib_values`.* FROM `attrib_values` INNER JOIN `attribs` ON `attribs`.`id` = `attrib_values`.`attrib_id` INNER JOIN `attrib_types` ON `attrib_types`.`id` = `attribs`.`attrib_type_id` INNER JOIN `attrib_namespaces` ON `attrib_namespaces`.`id` = `attrib_types`.`attrib_namespace_id` WHERE `attribs`.`project_id` = 10 AND `attrib_types`.`name` = 'QualityCategory' AND `attrib_namespaces`.`name` = 'OBS'
↳ app/queries/obs_quality_categories_finder.rb:8:in `map'
AttribValue Load (0.9ms)  SELECT `attrib_values`.* FROM `attrib_values` INNER JOIN `attribs` ON `attribs`.`id` = `attrib_values`.`attrib_id` INNER JOIN `attrib_types` ON `attrib_types`.`id` = `attribs`.`attrib_type_id` INNER JOIN `attrib_namespaces` ON `attrib_namespaces`.`id` = `attrib_types`.`attrib_namespace_id` WHERE `attribs`.`project_id` = 1 AND `attrib_types`.`name` = 'QualityCategory' AND `attrib_namespaces`.`name` = 'OBS'
↳ app/queries/obs_quality_categories_finder.rb:8:in `map'
[...]
AttribValue Load (0.8ms)  SELECT `attrib_values`.* FROM `attrib_values` INNER JOIN `attribs` ON `attribs`.`id` = `attrib_values`.`attrib_id` INNER JOIN `attrib_types` ON `attrib_types`.`id` = `attribs`.`attrib_type_id` INNER JOIN `attrib_namespaces` ON `attrib_namespaces`.`id` = `attrib_types`.`attrib_namespace_id` WHERE `attribs`.`project_id` = 1 AND `attrib_types`.`name` = 'QualityCategory' AND `attrib_namespaces`.`name` = 'OBS'
↳ app/queries/obs_quality_categories_finder.rb:8:in `map'

After

Project Load (2.2ms)  SELECT projects.*, attrib_values.value AS attrib_value FROM `projects` LEFT OUTER JOIN attribs ON (attribs.project_id = projects.id AND attribs.attrib_type_id = 15) LEFT OUTER JOIN attrib_values ON attribs.id = attrib_values.attrib_id WHERE `projects`.`id` != 0 AND NOT (name rlike '^home:.+') ORDER BY projects.name ASC LIMIT 25 OFFSET 0
↳ app/datatables/project_datatable.rb:36:in `map'

For reviewers

• Access http://localhost:3000/project in your local development environment
• See logs.

[obs-bot]

Review app will appear here: http://obs-reviewlab.opensuse.org/eduardoj-fixall_projects_n_plus_1_queries