Question

I have a three models: locations > hotspots > accounts

In my locations model, I have this:

has_many :hotspots
has_many :accounts, :foreign_key => :calledstationidclean, :through => :hotspots

I’m trying to show some summary data from the accounts model for each location.

The following works ok:

  scope :location_history, lambda { |id|
                               joins('INNER JOIN hotspots b ON locations.id = b.location_id INNER JOIN account ON b.mac = account.calledstationidclean')
                               .where(:id => id)
                               .select("count(locations.id) AS sessions_count, sum(account.acctoutputoctets) AS downloads, sum(account.acctinputoctets) AS uploads, count(distinct account.callingstationid) AS unique_user")
                            }

But I need to run some calculations and I can’t figure out how to do this.

Ordinarily, in the accounts model I’m able to do something like this:

 def self.session_time
   Account.sum("acctsessiontime")
 end

 def self.average_session
   self.session_time / Account.count
 end

How can I do something similar but in my location model – and display only the information for the specific location I’m viewing?? Do I actually need to run a join?

Answer 1

Yes, you will have to do the join.

  scope :location_history,
        lambda { |id| joins(:hotspots, :accounts).where(:id => id).
                      select("sum(account.acctsessiontime) as acctsessiontime, count(locations.id) AS sessions_count, sum(account.acctoutputoctets) AS downloads, sum(account.acctinputoctets) AS uploads, count(distinct account.callingstationid) AS unique_user")
               }

By the way, you can use a group and combine all these with the records from location.

  scope :with_history,
        lambda { |id| joins(:hotspots, :accounts).where(:id => id).
                      select("locations.*, sum(account.acctsessiontime) as acctsessiontime, count(locations.id) AS sessions_count, sum(account.acctoutputoctets) AS downloads, sum(account.acctinputoctets) AS uploads, count(distinct account.callingstationid) AS unique_user")
               }

This will return Location objects with all the Location fields, and the aggregations you are doing.