Rails ActiveRecord::Migration what is the difference between index: true and add_index?

Question

What is the difference between

t.boolean :is_live, index: true

and

add_index :table_name, :is_live

If there is no difference, how come only the add_index is reflected in schema.rb. When I use index: true, I can't actually see the index in schema.rb. Should I only use the add_index method.

When use the add_index method, I can see this in my schema.rb

add_index "table_name", ["is_live"], name: "index_table_name_on_is_live", using: :blahblah

score 34 · Answer 1 · answered Jul 15 '14 at 06:51

34

Just found out that the :index option is for references only (t.references or t.belongs_to). For 'ordinary' column types this option is ignored (that's why indices are not reflected in your schema.db when you used the :index option).

For less verbose syntax there is an index type:

t.index :column_name # extra options may be provided also

answered Jul 15 '14 at 06:51

Alexey

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so is `t.reference :users, index: true` to same thing as `t.index :users`? – mbigras Feb 08 '17 at 17:58
I would like to know that too. Any anwser? – João Ramires Sep 25 '20 at 01:10
Absolutely not the same. The former creates a column named `user_id` and an index for it. The latter creates an index for an existing column named `users`. – Alexey Sep 26 '20 at 09:34

score 7 · Accepted Answer · answered Dec 13 '13 at 04:32

7

In short: both do the same job. ìndex: true` just saves you an additional line. Look here https://github.com/rails/rails/pull/5262#issuecomment-4329571

answered Dec 13 '13 at 04:32

cantonic

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This statement is misleading. Sure, they do the same thing, but not in all circumstances. :index option is for references only (t.references or t.belongs_to). See answer from @Alexey – karlingen Feb 10 '15 at 12:33

Rails ActiveRecord::Migration what is the difference between index: true and add_index?

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