On 11 November 2015 at 14:53, Robert Haas <robertmh...@gmail.com> wrote:
> On Mon, Nov 9, 2015 at 11:15 AM, Amit Kapila <amit.kapil...@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;
> 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.


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