# 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 12
            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 47
    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 54
    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 85
    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 66
    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 62
    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 91
    def select_all(arel, name = nil, binds = [], preparable: nil)
      if @query_cache_enabled && !locked?(arel)
        arel, binds = binds_from_relation arel, binds
        sql = to_sql(arel, binds)
        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 72
    def uncached
      old, @query_cache_enabled = @query_cache_enabled, false
      yield
    ensure
      @query_cache_enabled = old
    end

### Private Instance Methods

cache_sql(sql, name, binds) { || ... } click to toggle source

    # File lib/active_record/connection_adapters/abstract/query_cache.rb, line 103
    def cache_sql(sql, name, binds)
      @lock.synchronize do
        result =
          if @query_cache[sql].key?(binds)
            ActiveSupport::Notifications.instrument(
              "sql.active_record",
              sql: sql,
              binds: binds,
              name: name,
              connection_id: object_id,
              cached: true,
            )
            @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 129
    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 125
    def locked?(arel)
      arel.respond_to?(:locked) && arel.locked
    end