On 2016-10-10 17:46:22 -0700, Andres Freund wrote: > > TPC-DS (tpcds.ods) > > ------------------ > > > > In this case, I'd say the results are less convincing. There are quite a few > > queries that got slower by ~10%, which is well above - for example queries > > 22 and 67. There are of course queries that got ~10% faster, and in total > > the patched version executed more queries (so overall the result is slightly > > positive, but not significantly). > > That's interesting. I wonder whether that's plan changes just due to the > changing memory estimates, or what's causing that. I'll look into it.
Hm. Based on an initial look those queries aren't planned with any of the affected codepaths. Could this primarily be a question of randomness? Would it perhaps make sense to run the tests in a comparable order? Looking at tpcds.py and the output files, it seems that the query order differes between the runs, that can easily explain bigger difference than the above. For me a scale=1 run creates a database of approximately 4.5GB, thus with shared_buffers=1GB execution order is likely to have a significant performance impact. Greetings, Andres Freund -- Sent via pgsql-hackers mailing list (firstname.lastname@example.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers