On 06/02/15 16:37, Tom Lane wrote:
Tomas Vondra <tomas.von...@2ndquadrant.com> writes:
OK, so I did the testing today - with TPC-H and TPC-DS benchmarks. The
results are good, IMHO.
I'm a bit disturbed by that, because AFAICS from the plans, these
queries did not involve any semi or anti joins, which should mean
that the patch would not have changed the planner's behavior. You
were using the second patch as-posted, right, without further hacking
on compare_path_costs_fuzzily?
Yes, no additional changes.
It's possible that the change was due to random variation in ANALYZE
statistics, in which case it was just luck.
I don't think so. I simply loaded the data, ran ANALYZE, and then simply
started either master or patched master. There should be no difference
in statistics, I believe. Also, the plans contain pretty much the same
row counts, but the costs differ.
For example look at the 'cs_ui' CTE, right at the beginning of the
analyze logs. The row counts are exactly the same, but the costs are
different. And it's not using semijoins or not nested loops ...
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
--
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers
