module ActiveRecord::Import::MysqlAdapter

def duplicate_key_update_error?(exception)# :nodoc:

:nodoc:
return true if the statement is a duplicate key record error 
def duplicate_key_update_error?(exception)# :nodoc:
  exception.is_a?(ActiveRecord::StatementInvalid) && exception.to_s.include?('Duplicate entry')
end

def max_allowed_packet # :nodoc:

:nodoc:
in a single packet
Returns the maximum number of bytes that the server will allow 
def max_allowed_packet # :nodoc:
  @max_allowed_packet ||= begin
    result = execute( "SHOW VARIABLES like 'max_allowed_packet';" )
    # original Mysql gem responds to #fetch_row while Mysql2 responds to #first
    val = result.respond_to?(:fetch_row) ? result.fetch_row[1] : result.first[1]
    val.to_i
  end
end

def sql_for_on_duplicate_key_update( table_name, *args ) # :nodoc:

:nodoc:
in +args+.
Returns a generated ON DUPLICATE KEY UPDATE statement given the passed 
def sql_for_on_duplicate_key_update( table_name, *args ) # :nodoc:
  sql = ' ON DUPLICATE KEY UPDATE '
  arg = args.first
  if arg.is_a?( Array )
    sql << sql_for_on_duplicate_key_update_as_array( table_name, arg )
  elsif arg.is_a?( Hash )
    sql << sql_for_on_duplicate_key_update_as_hash( table_name, arg )
  elsif arg.is_a?( String )
    sql << arg
  else
    raise ArgumentError.new( "Expected Array or Hash" )
  end
  sql
end

def sql_for_on_duplicate_key_update_as_array( table_name, arr ) # :nodoc:

:nodoc: 
def sql_for_on_duplicate_key_update_as_array( table_name, arr )  # :nodoc:
  results = arr.map do |column|
    qc = quote_column_name( column )
    "#{table_name}.#{qc}=VALUES(#{qc})"
  end
  results.join( ',' )
end

def sql_for_on_duplicate_key_update_as_hash( table_name, hsh ) # :nodoc:

:nodoc: 
def sql_for_on_duplicate_key_update_as_hash( table_name, hsh ) # :nodoc:
  sql = ' ON DUPLICATE KEY UPDATE '
  results = hsh.map do |column1, column2|
    qc1 = quote_column_name( column1 )
    qc2 = quote_column_name( column2 )
    "#{table_name}.#{qc1}=VALUES( #{qc2} )"
  end
  results.join( ',')
end