[ci skip] docs for add_references index option

- Add link for finding the addional options for index.
- Add example for unique index as this is a common requirement.
- Add link in guide for index options.

1 files changed, 10 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
index 020d9bbdca..da0c961142 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
@@ -776,7 +776,8 @@ module ActiveRecord
       # [<tt>:type</tt>]
       #   The reference column type. Defaults to +:integer+.
       # [<tt>:index</tt>]
-      #   Add an appropriate index. Defaults to false.
+      #   Add an appropriate index. Defaults to false.  
+      #   See #add_index for usage of this option.
       # [<tt>:foreign_key</tt>]
       #   Add an appropriate foreign key constraint. Defaults to false.
       # [<tt>:polymorphic</tt>]
@@ -796,6 +797,14 @@ module ActiveRecord
       #
       #   add_reference(:products, :supplier, polymorphic: true, index: true)
       #
+      # ====== Create a supplier_id column with a unique index
+      #
+      #   add_reference(:products, :supplier, index: { unique: true })
+      #
+      # ====== Create a supplier_id column with a named index
+      #
+      #   add_reference(:products, :supplier, index: { name: "my_supplier_index" })
+      #
       # ====== Create a supplier_id column and appropriate foreign key
       #
       #   add_reference(:products, :supplier, foreign_key: true)