`index_exists?` with `:name` checks specified columns.

[Yves Senn & Matthew Draper]

The column check was embodied in the defaul index name.
If the :name option was used, the specified columns were not verified at all.

Given:

```
assert connection.index_exists?(table_name, :foo_id, :name => :index_testings_on_yo_momma)
```

That index could have been defined on any field, not necessarily on `:foo_id`.

1 files changed, 8 insertions, 7 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 10753defc2..4957e1ac80 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
@@ -43,13 +43,14 @@ module ActiveRecord
       #   index_exists?(:suppliers, :company_id, name: "idx_company_id")
       #
       def index_exists?(table_name, column_name, options = {})
-        column_names = Array(column_name)
-        index_name = options.key?(:name) ? options[:name].to_s : index_name(table_name, :column => column_names)
-        if options[:unique]
-          indexes(table_name).any?{ |i| i.unique && i.name == index_name }
-        else
-          indexes(table_name).any?{ |i| i.name == index_name }
-        end
+        column_names = Array(column_name).map(&:to_s)
+        index_name = options.key?(:name) ? options[:name].to_s : index_name(table_name, column: column_names)
+        checks = []
+        checks << lambda { |i| i.name == index_name }
+        checks << lambda { |i| i.columns == column_names }
+        checks << lambda { |i| i.unique } if options[:unique]
+
+        indexes(table_name).any? { |i| checks.all? { |check| check[i] } }
       end
 
       # Returns an array of Column objects for the table specified by +table_name+.