In the docs above, it is written as below.
It doesn’t accurately describe past system behavior because it doesn’t include all completed instances.
This is because historical task statistics may be discarded by SingleStore DB at unspecified times.
I wonder about meaning of ‘unspecified times’.
Is there a way to know the approximate time or data size?
It’s liable to change, and I wouldn’t use this information for anything except deciding how much to trust the stats, but: rows with activity_type = “Query” currently have stats stretching back as long as their plan has been loaded into memory, rows with activity_type = “Database” stretch back to the creation of the database (though things like rebalance would count as “creation”), and rows with activity_type = “System” stretch back for the lifetime of a process.
Indefinitely.
For example, “The suspect is being held in jail indefinitely”. It is not known for how long the suspect will be held.