has_many :through, with condition

rubyonrails-talk
1

I have this simple model with orders and products. Orders looks like this:

class Order < ActiveRecord::Base   has_many :orders_products, :foreign_key => :order_id   has_many :products, :through => :orders_products   has_many :priority_products, :through => :orders_products, :source => :product, :conditions => { "orders_products.priority" => true } end

The :condition on :priority_products is cause problems for me. It worked fine in Rails 2.0.2, but breaks in Rails 2.1.1 when putting the relation in a :include clause:

orders = Order.find(:all, :include => :priority_products)

This result in PostgreSQL saying: missing FROM-clause entry for table "orders_products"

for this malformed query:

SELECT * FROM "products" WHERE ("products"."id" IN (1,2,3) AND ("orders_products"."priority" = 't'))

Full working example: http://pastie.org/299592

Is this something that should work, or am I making some mistake?

2

I have this simple model with orders and products. Orders looks like this:

class Order < ActiveRecord::Base has_many :orders_products, :foreign_key => :order_id has_many :products, :through => :orders_products has_many :priority_products, :through => :orders_products, :source => :product, :conditions => { "orders_products.priority" => true } end

The :condition on :priority_products is cause problems for me. It worked fine in Rails 2.0.2, but breaks in Rails 2.1.1 when putting the relation in a :include clause:

orders = Order.find(:all, :include => :priority_products)

This is a problem with 2.1's implementation of eager loading. You should be able to force a fallback to the old code by adding something like :conditions => "some trivial condition on the priority_products or orders_products table")

Fred

3

> orders = Order.find(:all, :include => :priority_products)

This is a problem with 2.1's implementation of eager loading. You should be able to force a fallback to the old code by adding something like :conditions => "some trivial condition on the priority_products or orders_products table")

Thanks, this sovled the immediate problem. Will I need this workaround with future version of Rails or is it something being looked at?

Rgds, Lars

4

orders = Order.find(:all, :include => :priority_products)

This is a problem with 2.1's implementation of eager loading. You should be able to force a fallback to the old code by adding
something like :conditions => "some trivial condition on the priority_products or orders_products table")

Thanks, this sovled the immediate problem. Will I need this workaround with future version of Rails or is it something being looked at?

I don't think 2.2 will be any different. I did have plans to look at
it but got side tracked and didn't get it finished.

Fred

5

Frederick Cheung wrote:

I don't think 2.2 will be any different. I did have plans to look at it but got side tracked and didn't get it finished.

Does anyone know if there are any plans to allow conditions to be specified that are applied to the ON clause of a join ?

6

Frederick Cheung wrote:

I don't think 2.2 will be any different. I did have plans to look at it but got side tracked and didn't get it finished.

Does anyone know if there are any plans to allow conditions to be specified that are applied to the ON clause of a join ?

you can do that anyway - :joins accepts arbitrary sql fragments.

Fred