Re: Proposal : Parallel Merge Join

Amit Kapila <amit.kapila16@gmail.com>

From: Amit Kapila <amit.kapila16@gmail.com>
To: Dilip Kumar <dilipbalaut@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-02-25T05:59:19Z
Lists: pgsql-hackers
On Fri, Feb 24, 2017 at 4:49 PM, Dilip Kumar <dilipbalaut@gmail.com> wrote:
> On Fri, Feb 24, 2017 at 3:04 PM, Amit Kapila <amit.kapila16@gmail.com> wrote:
>> What advantage do you see for considering such a path when the cost of
>> innerpath is more than cheapest_total_inner?  Remember the more paths
>> we try to consider, the more time we spend in the planner.  By any
>> chance are you able to generate any query where it will give benefit
>> by considering costlier innerpath?
>
> Changed
>

It seems you have forgotten to change in the below check:

+ if (innerpath != NULL &&
+ innerpath->parallel_safe &&
+ (cheapest_startup_inner == NULL ||
+ cheapest_startup_inner->parallel_safe == false ||
+ compare_path_costs(innerpath, cheapest_startup_inner,
+ STARTUP_COST) < 0))


+ /* Found a cheap (or even-cheaper) sorted parallel safer path */

typo
/safer/safe

Note - Change the patch status in CF app (to Needs Review) whenever
you post a new patch.  I could see that your other patch also needs a
similar update in CF app.

-- 
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com


Commits

  1. Consider parallel merge joins.

  2. Preparatory refactoring for parallel merge join support.

  3. Fix parallel hash join path search.