gistfile1.coffee

# Uses 101 (also known as n + 1 where n = 100) queries
mergeTransactionsBad: ->

  all_transactions = []

  te_transactions = db.run "select * from te_transactions where member_id=1 order by posted_at DESC limit 100"

  for transaction in te_transactions
    network_transaction = db.run "select * from network_transactions where transaction_id=#{transaction.id}"
    transaction.member_id = network_transaction.id
    all_transactions.push transaction

  return all_transactions

# Uses 2 queries
mergeTransactionsGood: ->

  all_transactions = {} # Make sure this is an ordered data store -- Redis sorted sets serve this use case quite well 

  te_transactions = db.run "select * from te_transactions where member_id=1 order by posted_at DESC limit 100"
  network_transactions = db.run "select * from network_transactions where member_id=1 order by posted_at DESC limit 100"

  for te_transaction in te_transactions
    all_transactions[transaction.id] = te_transaction

  for network_transaction in network_transactions
    transaction = all_transactions[network_transaction.id]
    transaction.member_id = transaction
    all_transactions[transaction.id] = transaction

  return all_transactions