Rails : migration for creating a fixed-length char(12) column

sql ruby-on-rails rails-migrations
manu_v picture manu_v · Apr 4, 2011 · Viewed 29.8k times · Source

What is the best way to define a fixed-length SQL column (CHAR(12) for instance) through a Rails migration ?

Why this should not handled by the model is because of the performance of char() vs varchar(), and I'd like to avoid injecting raw SQL in the database.

Edit : I know the :limit modifier, however the field is still varchar (which is bad for performance) and does not allow a minimum size.

Answer

KenB picture KenB · May 6, 2011

If Rails doesn’t understand the column type, it’ll pass it straight through to the database. So if you want a char instead of varchar, just replace:

t.column :token, :string

With:

t.column :token, "char(12)"

Of course, this may or may not make your migrations non-portable to another database.

(credit to http://laurelfan.com/2010/1/26/special-mysql-types-in-rails-migrations)

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