Join to searchable model with nested associations not including tables

[domcleal]

In Foreman, we hit an issue in the following scenario:

• host has many reports, reports belong to a host
• hostgroup has_many hosts, hosts belong to a hostgroup
• host has search definition: scoped_search :in => :hostgroup, :on => :name, :complete_value => true, :rename => :hostgroup

We then want to list reports for hosts that match a certain hostgroup, so:

Report.where(:reports => {:host_id => Host.search_for('hostgroup = One') })

This is equivalent to:

Report.where(:reports => {:host_id => Host.joins('hostgroup').where('hostgroups.name = "Foo"') })

But the resulting joined SQL query doesn't include the hostgroups table, so throws an error:

ActiveRecord::StatementInvalid: SQLite3::SQLException: no such column: hostgroups.name: SELECT "reports".* FROM "reports" WHERE "reports"."host_id" IN (SELECT "hosts"."id" FROM "hosts" WHERE (("hostgroups"."name" = 'One')))

It seems the right way to do this in Rails is:

Report.joins('host' => ['hostgroup']).where('hostgroups.name = "One"')

(http://guides.rubyonrails.org/active_record_querying.html#eager-loading-multiple-associations)

I've sort of managed to work around it by calling ScopedSearch::QueryBuilder.build_query directly and then generating an AR query with the right sequence as shown above, but it would be good to have some help building join queries in scoped_search itself - if this is the case, and I'm not missing something blindingly obvious.

In our case the scoped search queries could be querying a variety of objects associated to host depending on user configuration, so hardcoding this isn't an option. As a workaround, it's possible to make an inefficient query with IDs, but this was very slow with large numbers of hosts.

Here's a small application and unit test demonstrating it: https://github.com/domcleal/ss_join_search_issue (scoped_search 3.2.0, Rails 4.2.0, sqlite 3.8.8, Ruby 2.0.0).

[tbrisker]

I think this is caused by the Rails 4 changes to the .includes method behaviour. The :includes values generated by the query builder should be :eager_loaded or :joinsed instead.

[tbrisker]

Diving even deeper into this, looks like the issue may actually be in Rails ignoring .includes(:relation).references(:relation) inside an inner query for a where clause. However, I wonder why a LEFT JOIN is generated in this case instead of an INNER JOIN - since if we are searching on attributes of a related table, it makes no sense including rows which have no relation to it.