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http://stackoverflow.com/questions/22667401/postgres-json-data-type-rails-query
http://stackoverflow.com/questions/40702813/query-on-postgres-json-array-field-in-rails

#payload: [{"kind"=>"person"}]
Segment.where("payload @> ?", [{kind: "person"}].to_json)

#data: {"interest"=>["music", "movies", "programming"]}
Segment.where("data @> ?",  {"interest": ["music", "movies", "programming"]}.to_json)
Segment.where("data #>> '{interest, 1}' = 'movies' ")
Segment.where("jsonb_array_length(data->'interest') > 1")

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/* delete records one by one */
cutoff_time = new Date();
removed_count = 0
/* findOne is less expensive  so its impact on live data will be minimal */
while((row = db.collection.findOne({deleted_at: null, created_at: { $lt: cutoff_time }})) != null){
  db.collection.remove({_id: row['_id']});
  removed_count += 1; 
  print('\r Deleted:'+ removed_count); 
}

bisusubedi

# Author: Pieter Noordhuis
# Description: Simple demo to showcase Redis PubSub with EventMachine
#
# Update 7 Oct 2010:
# - This example does *not* appear to work with Chrome >=6.0. Apparently,
#   the WebSocket protocol implementation in the cramp gem does not work
#   well with Chrome's (newer) WebSocket implementation.
#
# Requirements:
# - rubygems: eventmachine, thin, cramp, sinatra, yajl-ruby

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tries = 0
begin 
  raise JobNotFoundError
rescue JobNotFoundError
   tries += 1
   retry if tries <= 3
   puts "No jobs found!"
end

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class JobNotFoundError < StandardError
  attr_accessor :message
  def initialize(message = "")
    @message =  message
  end

  def to_s
    return super if message == ""
    super + ": #{message}"
  end