Class: Zermelo::Filters::Steps::ListStep

Inherits:
BaseStep
  • Object
show all
Defined in:
lib/zermelo/filters/steps/list_step.rb

Instance Attribute Summary

Attributes inherited from BaseStep

#attributes, #options

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from BaseStep

#initialize

Constructor Details

This class inherits a constructor from Zermelo::Filters::Steps::BaseStep

Class Method Details

.accepted_types ⇒ Object 



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# File 'lib/zermelo/filters/steps/list_step.rb', line 7

def self.accepted_types
  [:sorted_set, :list]
end

.returns_type ⇒ Object 



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# File 'lib/zermelo/filters/steps/list_step.rb', line 11

def self.returns_type
  nil # same as the source type
end

Instance Method Details

#resolve(backend, associated_class, opts = {}) ⇒ Object 



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# File 'lib/zermelo/filters/steps/list_step.rb', line 15

def resolve(backend, associated_class, opts = {})
  shortcut = opts[:shortcut]

  offset = @options[:offset]
  limit = @options[:limit]

  o = offset.to_i
  l = limit.to_i

  case backend
  when Zermelo::Backends::Redis

    source = opts[:source]
    # idx_attrs = opts[:index_attrs]
    # attr_types = opts[:attr_types]
    temp_keys = opts[:temp_keys]

    # TODO apply these transformations via a subset?
    # TODO need a guaranteed non-existing key for non-sorting 'sort'

    # TODO check if source is in temp_keys, use a generated temp_key instead if not
    r_source = backend.key_to_backend_key(source)

    result, r_result = case source.type
    when :sorted_set
      limited = associated_class.send(:temp_key, :sorted_set)
      temp_keys << limited
      r_limited = backend.key_to_backend_key(limited)

      lim = Zermelo.redis.send(
        :desc.eql?(opts[:sort_order]) ? :zrevrange : :zrange,
        r_source, o, (o + l), :with_scores => true
      )

      Zermelo.redis.zadd(r_limited, lim.collect {|li| [li[1], li[0]]} )

      [limited, r_limited]
    when :list

      l = (Zermelo.redis.llen(r_source) - o) if (l < 1)

      sort_opts = {:by => 'no_sort', :limit => [o, l]}

      # https://github.com/antirez/redis/issues/2079, fixed in redis 2.8.19
      result, r_result = if (Zermelo.redis_version.split('.') <=> ['2', '8', '18']) == 1
        sort_opts.update(:store => r_source)
        Zermelo.redis.sort(r_source, sort_opts)
        [source, r_source]
      else
        data = Zermelo.redis.sort(r_source, sort_opts)

        if data.empty?
          # TODO fix
        else
          limited = associated_class.send(:temp_key, :list)
          temp_keys << limited
          r_limited = backend.key_to_backend_key(limited)

          Zermelo.redis.rpush(r_limited, data)

          [limited, r_limited]
        end
      end
    end

    return result if shortcut.nil?

    extra_args = case source.type
    when :sorted_set
      [opts[:sort_order]]
    when :list
      []
    end

    Zermelo::Filters::Redis::SHORTCUTS[source.type][shortcut].
      call(*([r_result] + extra_args + opts[:shortcut_args]))
  end
end