Module: Picky::Backends::Redis::Scripting

Defined in:
lib/picky/backends/redis.rb

Overview

Uses Lua scripting on Redis 2.6.

Instance Method Summary collapse

Instance Method Details

#ids(combinations, amount, offset) ⇒ Object 



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# File 'lib/picky/backends/redis.rb', line 224

def ids combinations, amount, offset
  identifiers = identifiers_for combinations

  # Assume it's using EVALSHA.
  #
  begin
    if identifiers.size > 1
      # Reuse script already installed in Redis.
      #
      # Note: This raises an error in Redis,
      # when the script is not installed.
      #
      client.evalsha @ids_script_hash,
                     identifiers,
                     [
                       generate_intermediate_result_id,
                       offset,
                       (offset + amount)
                     ]
    else
      # No complex calculation necessary.
      #
      client.zrange identifiers.first,
                    offset,
                    (offset + amount)
    end
  rescue ::Redis::CommandError => e
    # Install script in Redis.
    #
    @ids_script_hash = client.script 'load', @ids_script
    retry
  end
end