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## query_planner.markdown

      
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                hgmnz
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              March 23, 2011 14:14
            
              
                PostgreSQL query plan and SQL performance notes
              
          
    Types of index scans

Indexes

Sequential Scan:


Read every row in the table
No reading of index. Reading from indexes is also expensive.


## mongo_active_model_compat.rb
module ActiveModel::Compatible
  extend ActiveSupport::Concern
  extend ActiveModel::Naming

  include ActiveModel::Serializers::Xml
  include ActiveModel::Serializers::JSON

  def to_xml(options = {}, &block)
    options[:except] ||= []
    options[:except] << :_id
	module ActiveModel::Compatible
	extend ActiveSupport::Concern
	extend ActiveModel::Naming

	include ActiveModel::Serializers::Xml
	include ActiveModel::Serializers::JSON

	def to_xml(options = {}, &block)
	options[:except] \|\|= []
	options[:except] << :_id