| From: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, 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 |
| Date: | 2015-12-17 13:17:20 |
| Message-ID: | CAKJS1f8MpcL4_oS+n-vmnisd_8OMuZR2vyLETOF7ABSLk_iNZg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 17 December 2015 at 19:11, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> On 17 December 2015 at 00:17, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
> wrote:
>
>> I'd go with match_first_tuple_only.
>
>
> +1
>
> 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.
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
| Attachment | Content-Type | Size |
|---|---|---|
| unique_joins_18-12-2015_843fb71.patch | application/octet-stream | 76.2 KB |
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