Tom Lane wrote:
> If you have background tasks doing ANALYZEs then this explanation seems
> plausible enough. I'm willing to accept it anyway ...
Yup, there are such tasks. I could dig through logs to try to confirm
or reject it; but I think it's reasonably likely that this happened.
Basically, data gets added to that table as it becomes ready from other
systems, and after each batch a vacuum analyze is run.