I have a very large table with 500m rows and 150 columns (I did not design the table, im simply trying to figure out what is going on here). I try to update a single statistic for this table.
I run like so
update statistics A (stat1) with sample 5000000 rows
It takes me 35 minutes for this to complete. Subsequent runs of the same task finish in less than 1 minute. I don't know what is happening here. I tried to monitor sys.dm_exec_requests and there is no other load, I did notice on the initial run that cpu_time to elapsed_time ratio was pretty low (like 1:5 vs 1:1 on subsequent runs).