A compact class which collects and inserts bulk of data into MySql. Used for inserting large data.

bulk_import.rb

# A class which collects and inserts bulk of data
# Implemented for MySQL 5
# Count of records inserted at once is configured by MAX

class BulkImporter
  
  MAX = 100
  
  # posts_writer =  BulkImporter.new( ActiveRecord::Base.connection, Post )
  def initialize(connection, klass)
    @connection = connection
    @table = klass.table_name
    @column_names = klass.column_names
    @buffer = []
  end
  
  # posts_writer.collect( { :title => 'My post', :descr => 'Description' } )
  def collect(values)
    if @buffer.size == MAX
      push_values
    end
    @buffer << values
  end
  
  # posts_writer.finalize  - should be called after data inserts' loop
  def finalize
    push_values unless @buffer.empty?
  end
  
private
  
  def push_values
    quoted_column_names = @column_names.collect {|col| "`#{ col }`" }
    rows = @buffer.collect {|row|
      quoted_attributes = @column_names.collect{|col| "#{ ActiveRecord::Base.sanitize( row[col] ) }" }
      "(#{ quoted_attributes.join(',') })"   # ('value1','value2')
    }.join(',')  # ('value1','value2'),('value1','value2'), ...
    sql = "INSERT INTO `#{@table}` (#{ quoted_column_names.join(',') }) VALUES #{rows}"
    @buffer.clear
    @connection.execute(sql)
  end

end