How do I handle too long index names in a Ruby on Rails ActiveRecord migration?
Provide the :name option to add_index, e.g.:
add_index :studies, ["user_id", "university_id", "subject_name_id", "subject_type_id"], unique: true, name: 'my_index'If using the :index option on references in a create_table block, it takes the same options hash as add_index as its value:
t.references :long_name, index: { name: :my_index }
You can also change the index name in column definitions within a create_table block (such as you get from the migration generator).
create_table :studies do |t| t.references :user, index: {:name => "index_my_shorter_name"}end
In PostgreSQL, the default limit is 63 characters. Because index names must be unique it's nice to have a little convention. I use (I tweaked the example to explain more complex constructions):
def change add_index :studies, [:professor_id, :user_id], name: :idx_study_professor_userendThe normal index would have been:
:index_studies_on_professor_id_and_user_idThe logic would be:
indexbecomesidx- Singular table name
- No joining words
- No
_id - Alphabetical order
Which usually does the job.