vendor/rails/activerecord/lib/active_record/connection_adapters/abstract/query_cache.rb

   1 module ActiveRecord
   2   module ConnectionAdapters # :nodoc:
   3     module QueryCache
   4       class << self
   5         def included(base)
   6           base.class_eval do
   7             alias_method_chain :columns, :query_cache
   8             alias_method_chain :select_all, :query_cache
   9           end
  10
  11           dirties_query_cache base, :insert, :update, :delete
  12         end
  13
  14         def dirties_query_cache(base, *method_names)
  15           method_names.each do |method_name|
  16             base.class_eval <<-end_code, __FILE__, __LINE__
  17               def #{method_name}_with_query_dirty(*args)
  18                 clear_query_cache if @query_cache_enabled
  19                 #{method_name}_without_query_dirty(*args)
  20               end
  21
  22               alias_method_chain :#{method_name}, :query_dirty
  23             end_code
  24           end
  25         end
  26       end
  27
  28       attr_reader :query_cache, :query_cache_enabled
  29
  30       # Enable the query cache within the block.
  31       def cache
  32         old, @query_cache_enabled = @query_cache_enabled, true
  33         @query_cache ||= {}
  34         yield
  35       ensure
  36         clear_query_cache
  37         @query_cache_enabled = old
  38       end
  39
  40       # Disable the query cache within the block.
  41       def uncached
  42         old, @query_cache_enabled = @query_cache_enabled, false
  43         yield
  44       ensure
  45         @query_cache_enabled = old
  46       end
  47
  48       # Clears the query cache.
  49       #
  50       # One reason you may wish to call this method explicitly is between queries
  51       # that ask the database to randomize results. Otherwise the cache would see
  52       # the same SQL query and repeatedly return the same result each time, silently
  53       # undermining the randomness you were expecting.
  54       def clear_query_cache
  55         @query_cache.clear if @query_cache
  56       end
  57
  58       def select_all_with_query_cache(*args)
  59         if @query_cache_enabled
  60           cache_sql(args.first) { select_all_without_query_cache(*args) }
  61         else
  62           select_all_without_query_cache(*args)
  63         end
  64       end
  65
  66       def columns_with_query_cache(*args)
  67         if @query_cache_enabled
  68           @query_cache["SHOW FIELDS FROM #{args.first}"] ||= columns_without_query_cache(*args)
  69         else
  70           columns_without_query_cache(*args)
  71         end
  72       end
  73
  74       private
  75         def cache_sql(sql)
  76           result =
  77             if @query_cache.has_key?(sql)
  78               log_info(sql, "CACHE", 0.0)
  79               @query_cache[sql]
  80             else
  81               @query_cache[sql] = yield
  82             end
  83
  84           if Array === result
  85             result.collect { |row| row.dup }
  86           else
  87             result.duplicable? ? result.dup : result
  88           end
  89         rescue TypeError
  90           result
  91         end
  92     end
  93   end
  94 end