Scheduling Conditions: results changed since last run

[Arkadi_Tereshen]

Hi,

I am looking at the clarifications on Scheduling Conditions. Here is Looker help description.
and results changed since last run : This option cuts down on unnecessary data deliveries. Looker sends the data only if the query results have changed since the last data delivery was sent. This option is not available if you want to use the All Results limit option.

The question is how exactly Looker determines results are changed?
Does it literally store the last run results and compare the new results to see if this is changed or it is down to the query still being in cache because there is a datagroup that has not triggered a refresh?

In this case if there is no datagroup at all, does it mean every 6 hours (default cache duration) results will be purged and report resent next time schedule kicks in?

Our use case is to really send the report when there any changes in it, but we do not have history in some cases and want to rely on Looker to determine the change condition.