How can I disable MySQL unique constraints in a RSpec test

Question

I'm trying to run a spec for a script that will uniquify a given table.

I now have the unique constraints in my migrations so I'm having a hard time creating duplicates to test my script.

My current specs looks like that.

require 'spec_helper'

describe OneTime::UniquifyTypeDescriptorContext do

  before(:each) do
    duplicated_type_descriptor_contexts = FactoryGirl.build_list(:type_descriptor_context, 5, {:type_name => :foo})
    ActiveRecord::Base.connection.execute('SET unique_checks=0;')
    duplicated_type_descriptor_contexts.each{|tdc| tdc.save!(:validate => false)}
    ActiveRecord::Base.connection.execute('SET unique_checks=1;')
    FactoryGirl.create(:type_descriptor_context, :type_name => :bar)
  end

  context "#process!" do
    it "should remove duplicates" do
      OneTime::UniquifyTypeDescriptorContext.new.process!
      expect(TypeDescriptorContext.count).to eq 2
    end
  end
end

but It keeps on failing on

ActiveRecord::RecordNotUnique:
       ActiveRecord::JDBCError: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry 'foo' for key 'index_type_descriptor_contexts_on_type_name': INSERT INTO `type_descriptor_contexts` (`created_at`, `type_name`, `updated_at`) VALUES ('2015-10-06 18:23:39', 'foo', '2015-10-06 18:23:39')

Am I missing something?

I'd have to ask, why would you need to have/test functionality that uniquifies records in a table where duplicate records cannot be created? — Magnuss
– Magnuss, Commented Oct 6, 2015 at 19:43
Because it was not the case before. I'm adding a migration to add a constraint but I need to run the script first to remove the duplicates. My specs starts by running all migrations so they run the one that adds the constraint and that point I can't create bad data to test my script. — Paté
– Paté, Commented Oct 6, 2015 at 20:05

Magnuss · Accepted Answer · 2015-10-07 07:44:05Z

1

Someone may need to confirm this.

SET unique_checks=0; is not a global operation. If you'd want this to work then you'd have to write it like that:

ActiveRecord::Base.connection.execute <<-SQL
  SET unique_checks=0;
  INSERT INTO <table_name> VALUES ....
  SET unique_checks=1;
SQL

Or you could drop the unique index, create the records and re-create the index afterwards.

answered Oct 7, 2015 at 7:44

Magnuss

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