On Thu, Oct 17, 2019 at 03:15:21PM -0600, Michael Lewis wrote:
https://explain.depesz.com/s/Caa5
I am looking at this explain analyze output and seeing a nested loop
towards the lowest levels with pretty bad estimate vs actual (2.3k vs 99k),
but the things that feed that nested loop seem like the estimates are
rather close (index scans with 11 estimated vs 30 actual and 3350 vs
3320)... why does the higher node have such a different estimate vs actual
ratio?
This is usually a sign of non-uniform distribution for the join columns,
and/or correlation between sides of the join.
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
