|From:||Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>|
|To:||David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>|
|Cc:||Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>|
|Subject:||Re: Performance improvement for joins where outer side is unique|
|Views:||Raw Message | Whole Thread | Download mbox|
On 12/17/2015 02:17 PM, David Rowley wrote:
> On 17 December 2015 at 19:11, Simon Riggs <simon(at)2ndquadrant(dot)com
> <mailto:simon(at)2ndquadrant(dot)com>> wrote:
> On 17 December 2015 at 00:17, Tomas Vondra
> <tomas(dot)vondra(at)2ndquadrant(dot)com <mailto:tomas(dot)vondra(at)2ndquadrant(dot)com>>
> I'd go with match_first_tuple_only.
> unique_inner is a state that has been detected,
> match_first_tuple_only is the action we take as a result.
> Ok great. I've made it so in the attached. This means the comment in the
> join code where we perform the skip can be a bit less verbose and all
> the details can go in where we're actually setting the
> match_first_tuple_only to true.
OK. I've looked at the patch again today, and it seems broken bv
45be99f8 as the partial paths were not passing the unique_inner to the
create_*_path() functions. The attached patch should fix that.
Otherwise I think the patch is ready for committer - I think this is a
valuable optimization and I see nothing wrong with the code.
Any objections to marking it accordingly?
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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