Ecto.Changeset.check_constraint

Questions / Help
,
1

I have an existing migration Posts

One post has many comments. It is structured as follows.

id
post_name
post_num
comments
      [  
        %{
        id
        post_num
        },
    %{
        id
        post_num
        },
       ]

I would like to add a constraint that checks if the post_num in Posts matches the post_num in comments, if not it should return an error changeset. I came across Ecto.Changeset.check_constraint from the docs. I feel this will be more suitable for my scenario here (would appreciate any other better options aswell). I would like to know how to create a migration for this case and what goes into the migration file.

2

Could you please post your Post and Comment schema and migration files? It’ll be easier to understand your intention with them, because it seems that you want post_num in comments to refer to Post’s post_num and not its primary id, which would get you the referential integrity you seem to be looking for from the DB.

3

Okay, so I rechecked my requirements and I realized I would want the post_num in Posts to match the primary id of the comments. And I do not have a post_num field in comments.