Thread: Acceptable level of over-estimation?

Is there a rule of thumb about when the planner's row estimates are too
high? In particular, when should I be concerned that planner's estimated
number of rows estimated for a nested loop is off? By a factor of 10? 100?
1000?

Carlo

"Carlo Stonebanks" <stonec.register@sympatico.ca> writes:

> Is there a rule of thumb about when the planner's row estimates are too high?
> In particular, when should I be concerned that planner's estimated number of
> rows estimated for a nested loop is off? By a factor of 10? 100? 1000?

Not really. It's a big enough difference for the planner to make a bad
decision or it isn't. But if you pressed me I would say a factor of 10 is bad.
A factor of 2 is inevitable in some cases.

--
  Gregory Stark
  EnterpriseDB          http://www.enterprisedb.com