[utils] Fixed issue in clearing QueryCache When trying to add an item in a full QueryCache, the cache tries to make room. It tries to list and remove non-permanent items with a transient counter (number of times it has been requested). However, there is a pathological case where items could be non-permanent but still not have a transient counter because they were added, but never requested. In some cases, the full cache could be flushed, including the permanent items. This changeset attempts to fix this issue by only dropping the non-permanent items that did not hav a transient counter.

[statsd] add a statsd_timethis context manager This context manager allows to report to statsd the execution time of any piece of code, without the need for it to be a function or a method, like:: def some_function(): do_stuff() with statsd_timethis('some context message'): do_that() ensure_this()

[test/rset] add tests for ResultSet.first() and .last() methods