Michal Politowski <mpol+pg@meep.pl> writes:
> Cannot there be a (system/hardware) setup where there is a perceptible
> performance difference between forward and backward index scans?
I think it's been reported already that backward index scans indeed can
be much slower than forward index scan, but that how to model that is
still unclear and undone in the cost estimations.
You will have to crawl the pgsql-performance list yourself, though…
Regards,
--
Dimitri Fontaine
http://2ndQuadrant.fr PostgreSQL : Expertise, Formation et Support