Module: ActiveRecord::ConnectionAdapters::QueryCache

Included in:
AbstractAdapter
Defined in:
lib/active_record/connection_adapters/abstract/query_cache.rb

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#query_cache ⇒ Object (readonly)

Returns the value of attribute query_cache.



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# File 'lib/active_record/connection_adapters/abstract/query_cache.rb', line 28

def query_cache
  @query_cache
end

#query_cache_enabled ⇒ Object (readonly)

Returns the value of attribute query_cache_enabled.



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# File 'lib/active_record/connection_adapters/abstract/query_cache.rb', line 28

def query_cache_enabled
  @query_cache_enabled
end

Class Method Details

.dirties_query_cache(base, *method_names) ⇒ Object 



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# File 'lib/active_record/connection_adapters/abstract/query_cache.rb', line 14

def dirties_query_cache(base, *method_names)
  method_names.each do |method_name|
    base.class_eval <<-end_code, __FILE__, __LINE__ + 1
      def #{method_name}_with_query_dirty(*args)        # def update_with_query_dirty(*args)
        clear_query_cache if @query_cache_enabled       #   clear_query_cache if @query_cache_enabled
        #{method_name}_without_query_dirty(*args)       #   update_without_query_dirty(*args)
      end                                               # end
                                                        #
      alias_method_chain :#{method_name}, :query_dirty  # alias_method_chain :update, :query_dirty
    end_code
  end
end

.included(base) ⇒ Object 



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# File 'lib/active_record/connection_adapters/abstract/query_cache.rb', line 5

def included(base)
  base.class_eval do
    alias_method_chain :columns, :query_cache
    alias_method_chain :select_all, :query_cache
  end

  dirties_query_cache base, :insert, :update, :delete
end

Instance Method Details

#cache ⇒ Object

Enable the query cache within the block.



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# File 'lib/active_record/connection_adapters/abstract/query_cache.rb', line 31

def cache
  old, @query_cache_enabled = @query_cache_enabled, true
  @query_cache ||= {}
  yield
ensure
  clear_query_cache
  @query_cache_enabled = old
end

#clear_query_cache ⇒ Object

Clears the query cache.

One reason you may wish to call this method explicitly is between queries that ask the database to randomize results. Otherwise the cache would see the same SQL query and repeatedly return the same result each time, silently undermining the randomness you were expecting.



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# File 'lib/active_record/connection_adapters/abstract/query_cache.rb', line 54

def clear_query_cache
  @query_cache.clear if @query_cache
end

#columns_with_query_cache(*args) ⇒ Object 



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# File 'lib/active_record/connection_adapters/abstract/query_cache.rb', line 66

def columns_with_query_cache(*args)
  if @query_cache_enabled
    @query_cache["SHOW FIELDS FROM #{args.first}"] ||= columns_without_query_cache(*args)
  else
    columns_without_query_cache(*args)
  end
end

#select_all_with_query_cache(*args) ⇒ Object 



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# File 'lib/active_record/connection_adapters/abstract/query_cache.rb', line 58

def select_all_with_query_cache(*args)
  if @query_cache_enabled
    cache_sql(args.first) { select_all_without_query_cache(*args) }
  else
    select_all_without_query_cache(*args)
  end
end

#uncached ⇒ Object

Disable the query cache within the block.



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# File 'lib/active_record/connection_adapters/abstract/query_cache.rb', line 41

def uncached
  old, @query_cache_enabled = @query_cache_enabled, false
  yield
ensure
  @query_cache_enabled = old
end