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 17
        def dirties_query_cache(base, *method_names)
          method_names.each do |method_name|
            base.class_eval <<-end_code, __FILE__, __LINE__ + 1
              def #{method_name}(*)
                ActiveRecord::Base.clear_query_caches_for_current_thread
                super
              end
            end_code
          end
        end
new(*) click to toggle source
Calls superclass method
# File lib/active_record/connection_adapters/abstract/query_cache.rb, line 52
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 59
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 90
def clear_query_cache
  @lock.synchronize do
    @query_cache.clear
  end
end
disable_query_cache!() click to toggle source
# File lib/active_record/connection_adapters/abstract/query_cache.rb, line 71
def disable_query_cache!
  @query_cache_enabled = false
  clear_query_cache
end
enable_query_cache!() click to toggle source
# File lib/active_record/connection_adapters/abstract/query_cache.rb, line 67
def enable_query_cache!
  @query_cache_enabled = true
end
select_all(arel, name = nil, binds = [], preparable: nil) click to toggle source
Calls superclass method
# File lib/active_record/connection_adapters/abstract/query_cache.rb, line 96
def select_all(arel, name = nil, binds = [], preparable: nil)
  if @query_cache_enabled && !locked?(arel)
    arel = arel_from_relation(arel)
    sql, binds, preparable = to_sql_and_binds(arel, binds, preparable)

    cache_sql(sql, name, binds) { super(sql, name, binds, preparable: preparable) }
  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 77
def uncached
  old, @query_cache_enabled = @query_cache_enabled, false
  yield
ensure
  @query_cache_enabled = old
end

Private Instance Methods

cache_notification_info(sql, name, binds) click to toggle source

Database adapters can override this method to provide custom cache information.

# File lib/active_record/connection_adapters/abstract/query_cache.rb, line 126
def cache_notification_info(sql, name, binds)
  {
    sql: sql,
    binds: binds,
    type_casted_binds: -> { type_casted_binds(binds) },
    name: name,
    connection: self,
    cached: true
  }
end
cache_sql(sql, name, binds) { || ... } click to toggle source
# File lib/active_record/connection_adapters/abstract/query_cache.rb, line 108
def cache_sql(sql, name, binds)
  @lock.synchronize do
    result =
      if @query_cache[sql].key?(binds)
        ActiveSupport::Notifications.instrument(
          "sql.active_record",
          cache_notification_info(sql, name, binds)
        )
        @query_cache[sql][binds]
      else
        @query_cache[sql][binds] = yield
      end
    result.dup
  end
end
configure_query_cache!() click to toggle source
# File lib/active_record/connection_adapters/abstract/query_cache.rb, line 144
def configure_query_cache!
  enable_query_cache! if pool.query_cache_enabled
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 139
def locked?(arel)
  arel = arel.arel if arel.is_a?(Relation)
  arel.respond_to?(:locked) && arel.locked
end