Avoid problems with duplicate column names and joins

[davetron5000]

Suppose I have plans that contains a meal_id that is a foreign key into meals. Suppose further that both tables have a field external_id.

Suppose this data:

PLANS
+----------------------+
| id          | 1      |
| external_id | plan_1 |
| meal_id     | 1      |
+----------------------+

MEALS
+----------------------+
| id          | 1      |
| external_id | meal_1 |
+----------------------+

This code results in a Plan object whose external_id value is meal_id, not plan_1:

> Plan.join(:meals, id: :meal_id).first
#<Plan @values={id: 1, meal_id: 1, external_id: "meal_1"}>

The reason is that the code above generates this SQL:

SELECT * FROM plans INNER JOIN meals ON (meals.id = plans.meal_id)

Postgres does not prefix the columns with the table name, so the output dataset has two columns named external_id.

Not that I expect Sequel to act like Active Record, but it's hard to see how this behavior would ever be desired and could be extremely confusing.

I can address this like so:

> Plan.select_all(:plans).join(:meals, id: :meal_id).first
#<Plan @values={id: 1, meal_id: 1, external_id: "plan_1"}>

So my question is - is there another way to avoid the behavior without using select_all - I would love if the default behavior using joins would be to qualify the values with the table name so that the ORM would work as expected (or at least as I expect :)

Is there some setting or way to do this? If not, is there an obvious extension point where I could make an extension or plugin that provided this behavior?

[jeremyevans]

Assuming you have the appropriate meals association, Plan.association_join(:meals).first should disambiguate column names.

[davetron5000]

That didn't work - it still uses SELECT *. Of note, :meals gave an error, I had to do association_join(:meal)

Here are my models:

# Including this in case the extra class matters
AppDataModel = Class.new(Sequel::Model)
class AppDataModel
end

class Plan < AppDataModel
  many_to_one :meal
end

class Meal < AppDataModel
  one_to_one :plan
end

[adam12]

I might opt for the table_select plugin here.

[davetron5000]

That plugin worked, thanks!