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module ActiveRecord
module ConnectionAdapters # :nodoc:
module QueryCache
class << self
def included(base) #:nodoc:
dirties_query_cache base, :insert, :update, :delete, :rollback_to_savepoint, :rollback_db_transaction
end
def dirties_query_cache(base, *method_names)
method_names.each do |method_name|
base.class_eval <<-end_code, __FILE__, __LINE__ + 1
def #{method_name}(*)
clear_query_cache if @query_cache_enabled
super
end
end_code
end
end
end
attr_reader :query_cache, :query_cache_enabled
def initialize(*)
super
@query_cache = Hash.new { |h,sql| h[sql] = {} }
@query_cache_enabled = false
end
# Enable the query cache within the block.
def cache
old, @query_cache_enabled = @query_cache_enabled, true
yield
ensure
@query_cache_enabled = old
clear_query_cache unless @query_cache_enabled
end
def enable_query_cache!
@query_cache_enabled = true
end
def disable_query_cache!
@query_cache_enabled = false
end
# Disable the query cache within the block.
def uncached
old, @query_cache_enabled = @query_cache_enabled, false
yield
ensure
@query_cache_enabled = old
end
# 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.
def clear_query_cache
@query_cache.clear
end
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, binds) { super(sql, name, binds, preparable: preparable) }
else
super
end
end
private
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
# If arel is locked this is a SELECT ... FOR UPDATE or somesuch. Such
# queries should not be cached.
def locked?(arel)
arel.respond_to?(:locked) && arel.locked
end
end
end
end
|
