module DeleteInBatches

# File lib/delete_in_batches.rb, line 9
def delete_in_batches(options = {})
  batch_size = options[:batch_size] || 10000

  pk       = "#{quoted_table_name}.#{quoted_primary_key}"
  sql_proc = proc { select(pk).limit(batch_size).to_sql }
  sql      = connection.try(:unprepared_statement, &sql_proc) || sql_proc.call

  if %w(MySQL Mysql2 Mysql2Spatial).include?(connection.adapter_name)
    sql = "SELECT * FROM (#{sql}) AS t"
  end

  unless connection.adapter_name =~ /postg/i
    # TODO raise error
    warn "[delete_in_batches] Use in_batches(of: #{batch_size.to_i}).delete_all instead of this gem for non-Postgres databases"
  end

  while connection.delete("DELETE FROM #{quoted_table_name} WHERE #{pk} IN (#{sql})") == batch_size
    yield if block_given?
    sleep(options[:sleep]) if options[:sleep]
  end
end