Question

How do I create a CHECK constraint to check for a range of possible values in Sequel. a Ruby ORM.

All attempts seem to generate CHECK (1 = 0) as seen in the output logs.

Here’s the table I’m trying to model using Sequel’s DSL:

create table memberships(  
      id integer primary key autoincrement
    , group_id integer references groups(id) on delete cascade
    , user_id integer references users(id) on delete cascade
    , role char check (role in ('u','a','o')) default 'u'
    , unique(group_id, user_id, role)   
);

and here’s the Sequel schema generation code:

db.create_table(:memberships){
    primary_key :id
    foreign_key :user_id, :users
    foreign_key :group_id, :groups  
    char :role, default: 'u'
    check{role=='u' or role=='a'} #<-----this line generates CHECK (1 = 0)
    unique [:user_id, :group_id, :role]
}

Answer 1

In Sequel, check constraints are handled just like a filter expression. The recommended way to handle your case would be:

check(:role=>%w[a o u])

I agree that more documentation would probably be better, though there are examples in http://sequel.jeremyevans.net/rdoc/files/doc/schema_modification_rdoc.html