TMXCredit/pg_power — pull request #26 by ermolaev (2013-04-05 13:21:43+00:00)
Title: simple detect functional index

I want to create the following index
```ruby
add_index :products, '(price_usual-price_retail)'
```
and have this error
```
PG::Error: ERROR: column "(price_usual-price_retail)" does not exist
```

I think, detected a functional index should be easier
```ruby

def quoted_columns_for_index(column_names, options = {})
column_names.map do |name|
if name.to_s.include?('(')
name
else
quote_column_name(name)
end
end
end

```