RedisPagination

Simple pagination for Redis lists and sorted sets.

Make sure your redis server is running! Redis configuration is outside the scope of this README, but check out the Redis documentation for more information.

Installation

Add this line to your application's Gemfile:

gem 'redis_pagination'

And then execute:

$ bundle

Or install it yourself as:

$ gem install redis_pagination

Usage

Configure redis_pagination:

RedisPagination.configure do |configuration|
  configuration.redis = Redis.new
  configuration.page_size = 25
end

Use redis_pagination:

require 'redis_pagination'

RedisPagination.configure do |configuration|
  configuration.redis = Redis.new(:db => 15)
  configuration.page_size = 25
end

# List
add_items_to_list('items', RedisPagination.page_size + 2)
 => 1
items_paginator = RedisPagination.paginate('items')
 => #<RedisPagination::Paginator::ListPaginator:0x007f8109b08ba0 @key="items">
items_paginator.total_items
 => 27
items_paginator.total_pages
 => 2
items_paginator.total_pages(5)
 => 6
items = items_paginator.page(1)
 => {:current_page=>1, :total_pages=>2, :total_items=>27, :items=>["item_1", "item_2", "item_3", "item_4", "item_5", "item_6", "item_7", "item_8", "item_9", "item_10", "item_11", "item_12", "item_13", "item_14", "item_15", "item_16", "item_17", "item_18", "item_19", "item_20", "item_21", "item_22", "item_23", "item_24", "item_25"]}
items = items_paginator.page(2)
 => {:current_page=>2, :total_pages=>2, :total_items=>27, :items=>["item_26", "item_27"]}

# Sorted Set
add_items_to_sorted_set('items', RedisPagination.page_size + 2)
 => 1
items_paginator = RedisPagination.paginate('items')
 => #<RedisPagination::Paginator::SortedSetPaginator:0x007f8109a25828 @key="items">
items_paginator.total_items
 => 27
items_paginator.total_pages
 => 2
items_paginator.total_pages(5)
 => 6
items = items_paginator.page(1)
 => {:current_page=>1, :total_pages=>2, :total_items=>27, :items=>[["item_27", 27.0], ["item_26", 26.0], ["item_25", 25.0], ["item_24", 24.0], ["item_23", 23.0], ["item_22", 22.0], ["item_21", 21.0], ["item_20", 20.0], ["item_19", 19.0], ["item_18", 18.0], ["item_17", 17.0], ["item_16", 16.0], ["item_15", 15.0], ["item_14", 14.0], ["item_13", 13.0], ["item_12", 12.0], ["item_11", 11.0], ["item_10", 10.0], ["item_9", 9.0], ["item_8", 8.0], ["item_7", 7.0], ["item_6", 6.0], ["item_5", 5.0], ["item_4", 4.0], ["item_3", 3.0]]}
items = items_paginator.page(2)
 => {:current_page=>2, :total_pages=>2, :total_items=>27, :items=>[["item_2", 2.0], ["item_1", 1.0]]}
items = items_paginator.page(1, :with_scores => false, :reverse => false)
 => {:current_page=>1, :total_pages=>2, :total_items=>27, :items=>["item_1", "item_2", "item_3", "item_4", "item_5", "item_6", "item_7", "item_8", "item_9", "item_10", "item_11", "item_12", "item_13", "item_14", "item_15", "item_16", "item_17", "item_18", "item_19", "item_20", "item_21", "item_22", "item_23", "item_24", "item_25"]}

# If the key is non-existent, the paginate call will return a RedisPagination::Paginator::NonePaginator
items_paginator = RedisPagination.paginate('unknown-key-in-redis')
 => #<RedisPagination::Paginator::NonePaginator:0x007f956b8052c0>
items_paginator.total_items
 => 0
items_paginator.total_pages
 => 0
items_paginator.total_pages(5)
 => 0
items = items_paginator.page(1)
 => {:current_page=>1, :total_pages=>0, :total_items=>0, :items=>[]}
items = items_paginator.page(2)
 => {:current_page=>2, :total_pages=>0, :total_items=>0, :items=>[]}

Retrieving All Members

The RedisPagination::Paginator::SortedSetPaginator and RedisPagination::Paginator::ListPaginator classes have an all method that can be called to retrieve all elements from these data types for a given key.

Paging Options

Valid options in the page call for paginating a Redis list are:

• :page_size controls the page size for the call. Default is RedisPagination.page_size.

Valid options in the page call for paginating a Redis sorted set are:

• :page_size controls the page size for the call. Default is RedisPagination.page_size.
• :with_scores controls whether the score is returned along with the item. Default is true.
• :reverse controls whether to return items in highest-to-lowest (true) or lowest-to-highest order (false). Default is true.

Differences in Redis Client Libraries

There is a difference between how sorted set data with scores is returned between the 2.x and the 3.x branch of the Ruby Redis client library.

If you are using the 2.x branch, you will get items returned with alternating item and score as follows:

{:current_page=>1, :total_pages=>2, :total_items=>27, :items=>["item_27", "27", "item_26", "26", "item_25", "25", "item_24", "24", "item_23", "23", "item_22", "22", "item_21", "21", "item_20", "20", "item_19", "19", "item_18", "18", "item_17", "17", "item_16", "16", "item_15", "15", "item_14", "14", "item_13", "13", "item_12", "12", "item_11", "11", "item_10", "10", "item_9", "9", "item_8", "8", "item_7", "7", "item_6", "6", "item_5", "5", "item_4", "4", "item_3", "3"]}

If you are using the 3.x branch, you will get items returned as an array of arrays, where the internal arrays are the item and score as follows:

{:current_page=>1, :total_pages=>2, :total_items=>27, :items=>[["item_27", 27.0], ["item_26", 26.0], ["item_25", 25.0], ["item_24", 24.0], ["item_23", 23.0], ["item_22", 22.0], ["item_21", 21.0], ["item_20", 20.0], ["item_19", 19.0], ["item_18", 18.0], ["item_17", 17.0], ["item_16", 16.0], ["item_15", 15.0], ["item_14", 14.0], ["item_13", 13.0], ["item_12", 12.0], ["item_11", 11.0], ["item_10", 10.0], ["item_9", 9.0], ["item_8", 8.0], ["item_7", 7.0], ["item_6", 6.0], ["item_5", 5.0], ["item_4", 4.0], ["item_3", 3.0]]}

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Added some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request