Validating uniqueness of a particular value in Ecto

Questions / Help
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1

Hi!

I have this database table where I keep nationalities of users and I applied a unique_index between user id and the country code for its nationality so there wouldn’t be duplicates.

Then I created a citext field to determine different characteristics of these nationalities, one of them marking it being the place of birth.

So I wanted to validate making it sure you could have multiple nationalities, but only one of them having this particular field marked as a place of birth.

I this something I can (or should) achieve using changeset validations?

Thanks!

2

You can put the uniqueness validation entirely inside the DB and then you can point Ecto at the name of the DB constraint. Worked fine every time I did it.

3

You could have two association between User and Nationality. One is a many to many, while the other is a belong to (place of birth).

You can set a unique constraint on the join table for many to many… user_id, nationality_id to ensure You don’t have duplicate.

You need also to ensure place of birth is not in nationalities, with a custom validation.