On 11 November 2015 at 14:53, Robert Haas <robertmhaas@gmail.com> wrote: > On Mon, Nov 9, 2015 at 11:15 AM, Amit Kapila <amit.kapila16@gmail.com> wrote: >> Okay, I have updated the patch to make seq scan node parallel aware. >> To make that happen we need to have parallel_aware flag both in Plan >> as well as Path, so that we can pass that information from Path to Plan. >> I think the right place to copy parallel_aware info from path to >> plan is copy_path_costsize and ideally we should change the name >> of function to something like copy_generic_path_info(), but for >> now I have retained it's original name as it is used at many places, >> let me know if you think we should goahead and change the name >> of function as well. >> >> I have changed Explain as well so that it adds Parallel for Seq Scan if >> SeqScan node is parallel_aware. >> >> I have not integrated it with consider-parallel patch, so that this and >> Partial Seq Scan version of the patch can be compared without much >> difficulity. >> >> Thoughts? > > I've committed most of this, except for some planner bits that I > didn't like, and after a bunch of cleanup. Instead, I committed the > consider-parallel-v2.patch with some additional planner bits to make > up for the ones I removed from your patch. So, now we have parallel > sequential scan! > > For those following along at home, here's a demo: > > rhaas=# \timing > Timing is on. > rhaas=# select * from pgbench_accounts where filler like '%a%'; > aid | bid | abalance | filler > -----+-----+----------+-------- > (0 rows) > > Time: 743.061 ms > rhaas=# set max_parallel_degree = 4; > SET > Time: 0.270 ms > rhaas=# select * from pgbench_accounts where filler like '%a%'; > aid | bid | abalance | filler > -----+-----+----------+-------- > (0 rows) > > Time: 213.412 ms > > This is all pretty primitive at this point - there are still lots of > things that need to be fixed and improved, and it applies to only the > very simplest cases at present, but, hey, parallel query. Check it > out.
Congratulations to both you and Amit. This is a significant landmark in PostgreSQL feature development.
