Rails: Faster way to perform updates on many records

Question

In our Rails 3.2.13 app (Ruby 2.0.0 + Postgres on Heroku), we are often retreiving a large amount of Order data from an API, and then we need to update or create each order in o

Answer 1

You can monkey-patch ActiveRecord like this:

class ActiveRecord::Base

  #http://stackoverflow.com/questions/15317837/bulk-insert-records-into-active-record-table?lq=1
  #https://gist.github.com/jackrg/76ade1724bd816292e4e
  #  "UPDATE THIS SET   FROM  THIS  JOIN (VALUES (, ,...) VALS (  ) ON "
  def self.bulk_update(record_list)
      pk = self.primary_key
      raise "primary_key not found" unless pk.present?

      raise "record_list not an Array of Hashes" unless record_list.is_a?(Array) && record_list.all? {|rec| rec.is_a? Hash }
      return nil if record_list.empty?

      result = nil

      #test if every hash has primary keys, so we can JOIN
      record_list.each { |r|  raise "Primary Keys '#{self.primary_key.to_s}' not found on record: #{r}" unless hasAllPKs?(r) }


      #list of primary keys comparison
      pk_comparison_array = []
      if (pk).is_a?(Array)
          pk.each {|thiskey| pk_comparison_array << "THIS.#{thiskey} = VALS.#{thiskey}" }
      else
          pk_comparison_array << "THIS.#{pk} = VALS.#{pk}"
      end
      pk_comparison = pk_comparison_array.join(' AND ')

      #SQL
      (1..record_list.count).step(1000).each do |start|
        key_list, value_list = convert_record_list(record_list[start-1..start+999])
        #csv values
        csv_vals = value_list.map {|v| "(#{v.join(", ")})" }.join(", ")
        #column names
        column_names = key_list.join(", ")
        #list of columns assignments
        columns_assign_array = []
        key_list.each {|col|
          unless inPK?(col)
            columns_assign_array << "THIS.#{col} = VALS.#{col}"
          end }
        columns_assign = columns_assign_array.join(', ')

        sql = "UPDATE THIS SET #{columns_assign}  FROM #{self.table_name} THIS  JOIN ( VALUES #{csv_vals} ) VALS ( #{column_names} ) ON ( #{pk_comparison} )"
        result = self.connection.execute(sql)

        return result if result<0
      end

      return result

  end

  def self.inPK?(str)
      pk = self.primary_key

      test = str.to_s
      if pk.is_a?(Array)
            (pk.include?(test))
      else
            (pk==test)
      end
  end

  #test if given hash has primary keys included as hash keys and those keys are not empty
  def self.hasAllPKs?(hash)
      h = hash.stringify_keys
      pk = self.primary_key

      if pk.is_a?(Array)
           (pk.all? {|k| h.key?(k) and h[k].present? })
      else
           h.key?(pk) and h[pk].present?
      end
  end

  def self.convert_record_list(record_list)
    # Build the list of keys
    key_list = record_list.map(&:keys).flatten.map(&:to_s).uniq.sort

    value_list = record_list.map do |rec|
      list = []
      key_list.each {|key| list <<  ActiveRecord::Base.connection.quote(rec[key] || rec[key.to_sym]) }
      list
    end

    # If table has standard timestamps and they're not in the record list then add them to the record list
    time = ActiveRecord::Base.connection.quote(Time.now)
    for field_name in %w(created_at updated_at)
      if self.column_names.include?(field_name) && !(key_list.include?(field_name))
        key_list << field_name
        value_list.each {|rec| rec << time }
      end
    end

    return [key_list, value_list]
  end
end

Then, you can generate a array of hashes containing your models attributes (including theirs primary keys) and do something like:

ActiveRecord::Base.transaction do
   Model.bulk_update [ {attr1: val1, attr2: val2,...},  {attr1: val1, attr2: val2,...},   ... ]
end

It will be a single SQL command without Rails callbacks and validations.