On Sun, Jun 11, 2017 at 10:27 AM, Peter Geoghegan <pg@bowt.ie> wrote:
> Note that I introduced a new, redundant exists() in the agg_lineitem
> fact table subquery. It now takes 23 seconds for me on Tomas' 10GB
> TPC-H dataset, whereas the original query took over 90 minutes.
> Clearly we're missing a trick or two here. I think that you need a
> DAG-shaped query plan to make this work well, though, so it is
> certainly a big project.
On closer examination, this seems to be due to the number of heap
accesses required by an index-only scan that the original query plan
uses; my test case was invalid. All the same, I understand that moving
predicates into many (TPC-H) subqueries is an important optimization,
and hope that more work can be done in this area.
--
Peter Geoghegan
