Simple pagination solution for previous and next page navigation.

We saw some websites using will_paginate or kaminari for pagination, but they just need previous and next page navigation, will_paginate or kaminari is overqualified.

Pagination in databae sometimes is slow because

1. it sends a sql with OFFSET to get collection
2. it sends additional sql with COUNT to get total number of record.

simple_paginate eliminates the additional COUNT sql, make your pagination faster.

will_paginate and kaminari uses page and per_page to calculate offset and limit, then send 2 sqls

SELECT * FROM posts OFFSET 20 LIMIT 10;
SELECT COUNT(*) FROM posts;

after getting total count, they can calculate total pages, then render page numbers, prev, next, first and last page links.

simple_paginate also uses page and per_page to calculate offset and limit, but it only sends 1 sql

SELECT * FROM posts OFFSET 20 LIMIT 11;

it fetches one more record (11 = 10 + 1) to calculate if there is a next page records, so it doesn't need to send COUNT sql.

## perform a paginate query:
@users = User.paginate(:page => params[:page])

# or, use page and per scope:
@users = User.page(params[:page]).per(25)

## render previous page link:
<%= link_to_previous_page @users, 'Previous' %>

## render next page link:
<%= link_to_next_page @users, 'Next' %>

## render previous page link and next page link
<%= simple_paginate @users

You can configure the following default values by overriding these values using SimplePaginate.configure method.

default_per_page    # 25 by default

There's a handy generator that generates the default configuration file into config/initializers directory. Run the following generator command, then edit the generated file.

% rails g simple_paginate:config

SimplePaginate includes a handy template generator, To edit your paginator, run the generator first:

% rails g simple_paginate:views 

To run the test suite locally:

% bundle install
% rake spec:active_record_42