Ruby on Rails Tuesday, April 29, 2014

Hi,

On Monday, April 28, 2014 9:31:06 PM UTC+2, Matt Jones wrote:

This doesn't make any sense to me - if I request a ReportsSubject object from the database directly (via `find`, for instance), what do I get if I ask for its subject? What would the reports_subjects table even *store*? A bare `subject_id` would be insufficient since without a class_name it's unclear what table that ID refers to.

A "report subject" (a row in the join table) doesn't carry any semantics without the report, which has further information about required details. A report also only ever has a single type of subject, so IMO it would not make sense to store a couple thousand repetitions of an STI name (although note that the subjects are not all part of a single STI hierarchy!) in a column that adds no information at all to the system.
 
And that's not even considering what should happen when this sort of code runs:

Report.joins(:subjects).where(name: 'hey wait WHAT TABLE IS THIS EVEN QUERYING')

This is not functionally different from having the polymorphic subject type specified in the join table.

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