Rails: Preserving GET query string parameters in link_to

I have a typical search facility in my app which returns a list of results that can be paginated, sorted, viewed with a different records_per_page value, etc. Each of these options is controlled by parameters in the query string. A simplified example:

/search?q=test&page=2

Now say I need to display a set of links that set records_per_page value to 10, 20, 30. Each link must include the existing query parameters, which can be a very long set, plus a new per_page parameter.

/search?q=test&page=2& ... &per_page=10
/search?q=test&page=2& ... &per_page=20
/search?q=test&page=2& ... &per_page=30

Is there an easy way to do it with just link_to helper or I need to parse and reproduce the query string from previous request somehow?

Solution 1:

link_to 'Link', request.query_parameters.merge({:per_page => 20})

Solution 2:

link_to 'Link', params.merge({:per_page => 20})

Solution 3:

The simplest way to merge the new params with the query parameters and NOT with all parameters (including those obtained through the path) is to merge with request.query_parameters

link_to 'Search', search_path(request.query_parameters.merge({ per_page: 20 }))

Otherwise you end up with query strings duplicating the path parameters, for example ?action=index&controller=products&foo=bar instead of ?foo=bar.