Rails Active Record通过多个连接进行排序

Question

I have the following relationships.

AdhocBkg
  has_many :invoice_trans
InvoiceTran
  belongs_to :invoice_hdr
  belongs_to :meal
InvoiceHdr
  belongs_to :supplier
  belongs_to :client      

I need to pull out All AdhocBkgs with a 'Billed' status and then sort them by: supplier name, client name, inv no, inv tran date and meal sort sequence BUT via the last invoice transaction for each AdhocBkg.

My current code is :

#AdhocBkg Billed Status ID
abbilledstatusid = AdhocBkgStatus.find_by_abstatdesc('Billed').id
@adhocbkgs = AdhocBkg.find_all_by_abstatusid(abbilledstatusid)
@adhocbkgs.sort! {|x,y| x.invoice_trans.last.invoice_hdr.supplier.suppname + x.invoice_trans.last.invoice_hdr.client.clientname + x.invoice_trans.last.invoice_hdr.invno.to_s + x.invoice_trans.last.invtrndate.strftime('%Y%m%d') + x.invoice_trans.last.meal.mealsortseq.to_s <=> y.invoice_trans.last.invoice_hdr.supplier.suppname + y.invoice_trans.last.invoice_hdr.client.clientname + y.invoice_trans.last.invoice_hdr.invno.to_s + y.invoice_trans.last.invtrndate.strftime('%Y%m%d') + y.invoice_trans.last.meal.mealsortseq.to_s }

The above works but is VERY slow largely because of the multiple reads to the database and I suspect the actual sort. I was wondering how I could refactor the code to use either :include or :joins with an :order clause, which may help speed this up. However I can't work out what the Rails Active record 'find' statement should be for the above.

I am using Rails 3.2.1, Ruby 1.9.3p0 and MySQL 5.1 on Ubuntu 11.04.

Answer 1

What is the last transaction? Is it the one with the max ID (looking at your code, seems like it is), or the latest updated timestamp?

Let's try to figure this out:

AdHocBkg.joins(:adhoc_bkg_status, :invoice_trans => [ :meal, { :invoice_hdr => [ :supplier, :client ] } ]).
  where("adhoc_bkg_statuses.abstatdesc='Billed' and invoice_trans.id = (select max(id) from invoice_trans as it where it.ad_hoc_bkg_id=ad_hoc_bkgs.id)").
  order("suppliers.suppname desc, clients.clientname desc, invoice_hdrs.invno desc, invoice_trans.invtrndate, meals.mealsortseq desc")

I have not tested this so not sure it will work exactly like you want it to, but you can probably start from this.

EDIT

You can try using includes instead of joins if you want to access the fields you were sorting on.