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|
module ActiveRecord
module ConnectionAdapters # :nodoc:
module QueryCache
class << self
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
def dirties_query_cache(base, *method_names)
method_names.each do |method_name|
base.class_eval <<-end_code, __FILE__, __LINE__
def #{method_name}_with_query_dirty(*args)
clear_query_cache if query_cache_enabled
#{method_name}_without_query_dirty(*args)
end
alias_method_chain :#{method_name}, :query_dirty
end_code
end
end
end
def query_cache_enabled
Thread.current['query_cache_enabled']
end
def query_cache_enabled=(flag)
Thread.current['query_cache_enabled'] = flag
end
def query_cache
Thread.current['query_cache']
end
def query_cache=(cache)
Thread.current['query_cache'] = cache
end
# Enable the query cache within the block.
def cache
old, self.query_cache_enabled = query_cache_enabled, true
self.query_cache ||= {}
yield
ensure
clear_query_cache
self.query_cache_enabled = old
end
# Disable the query cache within the block.
def uncached
old, self.query_cache_enabled = query_cache_enabled, false
yield
ensure
self.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 if query_cache
end
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
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
private
def cache_sql(sql)
result =
if query_cache.has_key?(sql)
log_info(sql, "CACHE", 0.0)
query_cache[sql]
else
query_cache[sql] = yield
end
if Array === result
result.collect { |row| row.dup }
else
result.duplicable? ? result.dup : result
end
rescue TypeError
result
end
end
end
end
|
