module ActiveRecord::ConnectionAdapters::QueryCache

Attributes

query_cache[R]
query_cache_enabled[R]

Public Class Methods

dirties_query_cache(base, *method_names) click to toggle source
# File lib/active_record/connection_adapters/abstract/query_cache.rb, line 9
        def dirties_query_cache(base, *method_names)
          method_names.each do |method_name|
            base.class_eval "              def #{method_name}(*)
                clear_query_cache if @query_cache_enabled
                super
              end
", __FILE__, __LINE__ + 1
          end
        end
new(*) click to toggle source
Calls superclass method
# File lib/active_record/connection_adapters/abstract/query_cache.rb, line 23
def initialize(*)
  super
  @query_cache         = Hash.new { |h,sql| h[sql] = {} }
  @query_cache_enabled = false
end

Public Instance Methods

cache() { || ... } click to toggle source

Enable the query cache within the block.

# File lib/active_record/connection_adapters/abstract/query_cache.rb, line 30
def cache
  old, @query_cache_enabled = @query_cache_enabled, true
  yield
ensure
  @query_cache_enabled = old
  clear_query_cache unless @query_cache_enabled
end
clear_query_cache() click to toggle source

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.

# File lib/active_record/connection_adapters/abstract/query_cache.rb, line 60
def clear_query_cache
  @query_cache.clear
end
disable_query_cache!() click to toggle source
# File lib/active_record/connection_adapters/abstract/query_cache.rb, line 42
def disable_query_cache!
  @query_cache_enabled = false
end
enable_query_cache!() click to toggle source
# File lib/active_record/connection_adapters/abstract/query_cache.rb, line 38
def enable_query_cache!
  @query_cache_enabled = true
end
select_all(arel, name = nil, binds = []) click to toggle source
Calls superclass method
# File lib/active_record/connection_adapters/abstract/query_cache.rb, line 64
def select_all(arel, name = nil, binds = [])
  if @query_cache_enabled && !locked?(arel)
    arel, binds = binds_from_relation arel, binds
    sql = to_sql(arel, binds)
    cache_sql(sql, binds) { super(sql, name, binds) }
  else
    super
  end
end
uncached() { || ... } click to toggle source

Disable the query cache within the block.

# File lib/active_record/connection_adapters/abstract/query_cache.rb, line 47
def uncached
  old, @query_cache_enabled = @query_cache_enabled, false
  yield
ensure
  @query_cache_enabled = old
end

Private Instance Methods

cache_sql(sql, binds) { || ... } click to toggle source
# File lib/active_record/connection_adapters/abstract/query_cache.rb, line 76
def cache_sql(sql, binds)
  result =
    if @query_cache[sql].key?(binds)
      ActiveSupport::Notifications.instrument("sql.active_record",
        :sql => sql, :binds => binds, :name => "CACHE", :connection_id => object_id)
      @query_cache[sql][binds]
    else
      @query_cache[sql][binds] = yield
    end
  result.dup
end
locked?(arel) click to toggle source

If arel is locked this is a SELECT … FOR UPDATE or somesuch. Such queries should not be cached.

# File lib/active_record/connection_adapters/abstract/query_cache.rb, line 90
def locked?(arel)
  arel.respond_to?(:locked) && arel.locked
end