Rails: Can I spool off a column as a table in its own right?

Question

I'm using a model to track my dupermarket purchases. The schema of the table representing items is:

CREATE TABLE "items"
 ("id" INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL,
  "barcode" varchar,
  "brand" varchar,
  "gendesc" varchar,
  "size" float,
  "unit_id" integer,
  "created_at" datetime NOT NULL,
  "updated_at" datetime NOT NULL);

Inclusion of gendesc (generic description, as a varchar) was a modeling mistake; I should have made this a foreign key, with the text descriptions in an additional table, as different brands of the same thing are equivalent for some but not all purposes of analysis. So I want to replace the gendesc column with a gendescs_id column that is a foreign key for some gedescs table which would be equivalent to something created thus:

create table gendescs (id integer primary key, gendesc varchar);

select into gendescs(gendesc) distinct gendesc from items;

Is there a sequence of Rails migrations which does something like this?

score 1 · Accepted Answer · edited May 23 '17 at 12:30

Ideal flow should be like this:

Create gendescs table. I will prefer not to name column as same as table name.

rails g model Gendesc value:string
Add foreign key

rails g migration AddGendescToItem gendesc:references
Run rake db:migrate
If you have data in items.gendesc column then you need to create entries for them in gendescs table. Run following code in rails console.
```
Item.find_each do |i|
  g = Gendesc.find_or_create_by(value: i.gendesc)
  i.update(gendesc_id: g.id)
end
```
Remove column gendesc from items table How to remove a column from my Rails model?
add belongs_to relationship to item model

belongs_to: :gendesc

Rails: Can I spool off a column as a table in its own right?

1 Answers1