Rails: Cannot add :precision or :scale options with change_column in a migration?

Question

This seems to have been asked before: rails decimal precision and scale

But when running a change_column migration for :precision or :scale they don't actually affect the schema or database, but db:migrate runs without errors.

My migration file looks like this:

class ChangePrecisionAndScaleOfPaybackPeriodInTags < ActiveRecord::Migration
  def self.up
    change_column :tags, :payback_period, :decimal, { :scale => 3, :precision => 10 }
  end

  def self.down
    change_column :tags, :payback_period, :decimal
  end
end

But my schema (and the data) remains as:

t.decimal  "payback_period"

Anybody else have this issue?

Thanks,

Josh

Answer 1

Had a related (but not same) problem. I was just changing scale, so when changing the :scale you need the full line:

change_column :something, :weight, :decimal, :precision => 10, :scale => 2

omitting :decimal (which it already was) and :precision (which already was 10) will cause the migration to fail.