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# lib/tasks/pg.rake
namespace :pg do
  desc "Dumps the database to backups"
  task :dump => :environment do
    cmd = nil
    with_config do |app, host, db, user|
      cmd = "pg_dump -h #{host} -d #{db} -U #{user} -Ft -v -c -f #{Rails.root}/public/resources/duoduo/db_backup/#{Time.now.strftime("%Y%m%d%H%M%S")}_#{db}.tar"
    end
    puts cmd
    exec cmd

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require 'thread'

QUEUE_SIZE = 2
POOL_SIZE  = 5

queue = SizedQueue.new(QUEUE_SIZE)

producers = POOL_SIZE.times.map do
  Thread.new do
    item = rand(10)

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require 'logger'

# Examples
#
#   logger = DistinctFileLogger.new(STDOUT)
#   logger.set_error_path('/Users/wendi/tmp/logger/error.log')

#   logger.info "processing: 1/10"
#   logger.info "processing: 2/10"
#   logger.info "processing: 3/10"

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class MultiLevelPageTable
  PAGE_DIRECTORY_BASE_REGISTER = 108

  # Save all intermedial state in binary string
  attr_reader :pages, :virtual_address,
    :page_directory_index, :page_table_index, :offset,
    :page_directory, :page_directory_entry, :page_frame_number,
    :page_table, :page_table_entry, :physical_frame_number,
    :physical_address, :value

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?: - Non capture the group

http://stackoverflow.com/questions/3512471/non-capturing-group

str = "http://stackoverflow.com/questions/tagged/regex"
str =~ /(http|ftp):\/\/([^\/\r\n]+)(\/[^\r\n]*)?/
puts $1 # => http

# with ?:

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from http://blog.honeybadger.io/advanced-ruby-hash-techniques/

Strict fetching

h = Hash.new { |hash, key| raise ArgumentError.new("No hash key: #{ key }") }
h[:a]=1
h[:a] # 1
h[:x] # raises ArgumentError: No hash key: x

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csrf.js

var csrftk = $("meta[name='csrf-token']").attr("content");

// Ajax set
$(document).ajaxSend(function(e, xhr, options) {
  xhr.setRequestHeader("X-CSRF-Token", csrftk);
});

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# API
#
# + push
# + top
# + pop
# + empty
# + empty?

ArrayStack = Struct.new(:values) do
  def push(value)

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There is a weird situation I haven't noticed before:

class Counter
  attr_accessor :processed, :processed_names

  def initialize
    @processed = 0
    @processed_names = []
 end

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git filter-branch -f --commit-filter '
    if [ "$GIT_COMMITTER_NAME" = "<Old name>" ];
    then
        GIT_COMMITTER_NAME="<New name>";
        GIT_COMMITTER_EMAIL="<New email>";
        GIT_AUTHOR_NAME="<New name>";
        GIT_AUTHOR_EMAIL="<New email>";
    else
        git commit-tree "$@";
    fi' -- --all