Export ActiveRecord Tables to CSV

exporter.rb

require 'csv'

class Exporter
  DEFAULT_EXPORT_TABLES = [ Invoice, InvoiceItem, Item, Merchant, Transaction, User ]
  DESTINATION_FOLDER = "tmp/"

  def self.export_tables_to_csv(tables = DEFAULT_EXPORT_TABLES)
    tables.each { |klass| export_table_to_csv(klass) }
  end

  def self.export_table_to_csv(klass)
    output_file = CSV.open(filename_for_class(klass), "w")
    output_file << klass.headers
    klass.data.each{ |row| output_file << row }
    output_file.close
  end

  def self.filename_for_class(klass)
    DESTINATION_FOLDER + klass.to_s.underscore + '.csv'
  end
end

class ActiveRecord::Base
  def self.data
    find(:all).map{ |i| i.data}
  end
  
  def self.headers
    columns.map(&:name)
  end
  
  def data
    self.class.headers.map { |column| self.send(column) }
  end
end

If you have a reasonable amount of data it's much faster and easier to drop down a level and just use the command-line switches provided by mysqldump and friends:

mysqldump -u [username] -p -t -T/path/to/directory [database] --fields-enclosed-by=\" --fields-terminated-by=,
psql -c "COPY foo_table TO stdout DELIMITER ',' CSV HEADER"

Line 25, I recommend you don't call find(:all) but instead use find_in_batches or find_each(:batch_size => 500) to show that you can totally blow the process memory if you have too many records.

SELECT INTO OUTFILE BRO

I note that two of the three comments assume that the database is MySQL.

@ccalvert my comment includes the command for Postgres, so no, I didn't assume that.

@norman, wow, I read your code too fast, didn't I? Sorry about that. Comment retracted.